Radio Frequency (RF) energy transfer and harvesting techniques have recently become alternative methods to empower the next generation wireless networks. As this emerging technology enables proactive energy replenishment of wireless devices, it is advantageous in supporting applications with quality of service requirements. In this paper, some wireless power transfer methods, RF energy harvesting networks, various receiver architectures and existing applications are presented. Finally, some open research directions are envisioned.
This document provides an overview of dielectric resonator antennas (DRAs) and their design. It discusses:
1) Common DRA characteristics such as resonant frequencies defined by material properties and dimensions. Multiple modes can be excited and radiation patterns depend on the excited mode.
2) Common feeding methods for DRAs including coaxial probes, microstrip lines, coplanar waveguides, and apertures. These determine the excited mode and coupling.
3) A case study of a cylindrical DRA analyzing modes using analytical equations and simulations. For a dielectric constant of 30, the HE11δ mode resonates at 503.6 MHz and is excited using a coaxial probe.
This document discusses key concepts related to antennas including:
1. It defines radiation power density as the power radiated per unit surface area from the antenna surface.
2. It explains that directivity is a measure of the directional properties of an antenna and is defined as the ratio of radiation intensity in a given direction compared to an isotropic source.
3. Gain accounts for both the directional properties and efficiency of an antenna, defined as the ratio of intensity in a given direction compared to an isotropic source radiating the same total power.
4. Additional concepts covered include beamwidth, radiation patterns, and parameters related to receiving performance such as effective length and capture area.
MicroStrip Antenna
Introduction .
Micro-Strip Antennas Types .
Micro-Strip Antennas Shapes .
Types of Substrates (Dielectric Media) .
Comparison of various types of flat profile printed antennas .
Advantages & DisAdvantages of MSAs .
Applications of MSAs .
Radiation patterns of MSAs .
How to Optimizing the Substrate Properties for Increased Bandwidth ?
Comparing the different feed techniques .
The document discusses key concepts related to antennas and electromagnetic waves. It defines that radio waves have electric and magnetic fields that are perpendicular to each other and the direction of wave propagation. It also describes how antennas can transmit electromagnetic waves by converting electrical energy to radio waves and receive waves by converting radio waves back to electrical energy. Antenna size is inversely proportional to frequency, with higher frequencies requiring smaller antennas. Antenna radiation patterns and near/far field regions are also discussed.
Design & Study of Microstrip Patch Antenna.The project here provides a detailed study of how to design a probe-fed Square Micro-strip Patch Antenna using HFSS, v11.0 software and study the effect of antenna dimensions Length (L), and substrate parameters relative Dielectric constant (εr), substrate thickness (t) on the Radiation parameters of Bandwidth and Beam-width.
This document provides information on fundamental antenna parameters and concepts. It discusses:
1. How antennas convert guided waves into radiating waves and vice versa.
2. Key antenna parameters including radiation pattern, directivity, radiation resistance, efficiency, gain, bandwidth, reciprocity, effective aperture, beamwidth, and polarization matching.
3. The Friis transmission formula for calculating received power between two antennas in free space based on their gains, wavelength, and distance.
hello readers i give my PPT presentation for about antenna and ther properties and working explain in this ppt
i hope you like it THANK YOU.......!!!!!!!
This document provides an overview of dielectric resonator antennas (DRAs) and their design. It discusses:
1) Common DRA characteristics such as resonant frequencies defined by material properties and dimensions. Multiple modes can be excited and radiation patterns depend on the excited mode.
2) Common feeding methods for DRAs including coaxial probes, microstrip lines, coplanar waveguides, and apertures. These determine the excited mode and coupling.
3) A case study of a cylindrical DRA analyzing modes using analytical equations and simulations. For a dielectric constant of 30, the HE11δ mode resonates at 503.6 MHz and is excited using a coaxial probe.
This document discusses key concepts related to antennas including:
1. It defines radiation power density as the power radiated per unit surface area from the antenna surface.
2. It explains that directivity is a measure of the directional properties of an antenna and is defined as the ratio of radiation intensity in a given direction compared to an isotropic source.
3. Gain accounts for both the directional properties and efficiency of an antenna, defined as the ratio of intensity in a given direction compared to an isotropic source radiating the same total power.
4. Additional concepts covered include beamwidth, radiation patterns, and parameters related to receiving performance such as effective length and capture area.
MicroStrip Antenna
Introduction .
Micro-Strip Antennas Types .
Micro-Strip Antennas Shapes .
Types of Substrates (Dielectric Media) .
Comparison of various types of flat profile printed antennas .
Advantages & DisAdvantages of MSAs .
Applications of MSAs .
Radiation patterns of MSAs .
How to Optimizing the Substrate Properties for Increased Bandwidth ?
Comparing the different feed techniques .
The document discusses key concepts related to antennas and electromagnetic waves. It defines that radio waves have electric and magnetic fields that are perpendicular to each other and the direction of wave propagation. It also describes how antennas can transmit electromagnetic waves by converting electrical energy to radio waves and receive waves by converting radio waves back to electrical energy. Antenna size is inversely proportional to frequency, with higher frequencies requiring smaller antennas. Antenna radiation patterns and near/far field regions are also discussed.
Design & Study of Microstrip Patch Antenna.The project here provides a detailed study of how to design a probe-fed Square Micro-strip Patch Antenna using HFSS, v11.0 software and study the effect of antenna dimensions Length (L), and substrate parameters relative Dielectric constant (εr), substrate thickness (t) on the Radiation parameters of Bandwidth and Beam-width.
This document provides information on fundamental antenna parameters and concepts. It discusses:
1. How antennas convert guided waves into radiating waves and vice versa.
2. Key antenna parameters including radiation pattern, directivity, radiation resistance, efficiency, gain, bandwidth, reciprocity, effective aperture, beamwidth, and polarization matching.
3. The Friis transmission formula for calculating received power between two antennas in free space based on their gains, wavelength, and distance.
hello readers i give my PPT presentation for about antenna and ther properties and working explain in this ppt
i hope you like it THANK YOU.......!!!!!!!
This thesis focuses on mobile phones antenna design with brief description about the historical development, basic parameters and the types of antennas which are used in mobile phones. Mobile phones antenna design section consists of two proposed PIFA antennas. The first design concerns a single band antenna with resonant frequency at GPS frequency (1.575GHz). The first model is designed with main consideration that is to have the lower possible PIFA single band dimensions with reasonable return loss (S11) and the efficiencies. Second design concerns in a wideband PIFA antenna which cover the range from 1800MHz to 2600MHz. This range covers certain important bands: GSM (1800MHz & 1900MHz), UMTS (2100MHz), Bluetooth & Wi-Fi (2.4GHz) and LTE system (2.3GHz, 2.5GHz, and 2.6GHz). The wideband PIFA design is achieved by using slotted ground plane technique. The simulations for both models are performed in COMSOL Multiphysics.
The last two parts of the thesis present the problems of mobile phones antenna. Starting with Specific absorption rate (SAR) problem, efficiency of Mobile phones antenna, and hand-held environment.
This document provides an introduction to the High Frequency Structure Simulator (HFSS), a finite element method simulation tool for complex 3D geometries. It discusses the background, requirements, features, and procedure for using HFSS to simulate electromagnetic fields. Examples are given of modeling microstrip lines, waveguide components, antennas, and other applications. The document also provides an overview of Agilent and Ansoft's HFSS software.
1. Cavity resonators confine electromagnetic waves inside hollow structures such as rectangular boxes or cylindrical cans through resonance.
2. The resonant modes inside the cavity depend on its geometry and are determined by solving Maxwell's equations with the appropriate boundary conditions.
3. Common modes include TE and TM, where the electric and magnetic fields are transverse to the axis of propagation.
4. Coupling mechanisms such as wires or loops are used to input and output power to selectively excite specific resonant modes within the cavity.
Link Power Budget Calculation and Propagation Factors for Satellite COmmunica...THANDAIAH PRABU
- Antenna Pointing Loss
- Free Space Loss
- Atmospheric Loss
(gaseous, clouds, rain)
- Rx Antenna Pointing Loss
Reception:
+ Antenna gain
- Reception Losses
(cables & connectors)
- Noise Temperature
Contribution
Rx
Pr
1) The document discusses various propagation factors that affect radio wave transmission in satellite systems including atmospheric absorption, attenuation, and traveling ionospheric disturbances.
2) It provides details on calculating a link power budget including defining equivalent isotropic radiated power (EIRP), transmitter power, antenna gains, losses from free space path, the atmosphere, and other sources.
The document discusses microstrip patch antennas and defected ground structures (DGS). It provides an overview of microstrip antenna design including patch geometries and feeding techniques. It also discusses the advantages and disadvantages of microstrip antennas. Next, it introduces DGS, describing various DGS unit cell shapes and their applications in delay lines and antennas. The document concludes by presenting the design and performance analysis of a rectangular microstrip patch antenna with a dumbbell-shaped DGS cell for size reduction and efficiency improvement.
An antenna converts radio frequency electric current into electromagnetic waves that are radiated into space. The same antenna can transmit and receive signals. Key antenna concepts include reciprocity, radiation patterns, gain, and polarization. Antenna gain compares its power output to an isotropic antenna. Common antennas include dipole, parabolic reflective, and types are optimized for propagation modes like ground wave, sky wave, and line-of-sight. Signal strength is reduced by factors like free space loss, noise, multipath, and fading over the transmission path.
By completing this presentation will be have a clear idea about Antenna's working principles, Antenna's Types & Antenna's Parameters. At the end to this document you'll have a brief idea about Antenna's Tilt vs Distance Calculation & Cluster wise optimum Antenna Selection procedure. Impact of antenna PIM & VSWR have been described elaborately in this document as well.
This document describes the design of an equal split Wilkinson power divider with the following specifications: frequency of 2.4 GHz, source and load impedances of 50 ohms, substrate permittivity of 3.38, substrate thickness of 1.524 mm, and conductor thickness of 0.15 mm. It provides background on Wilkinson power dividers, describes the calculation of microstrip line widths and lengths, shows the simulated circuit schematic and layout, and plots the resulting S-parameters which achieve the desired 3 dB power split with good port matching and isolation as expected.
This document outlines an RF fundamentals course taught in 3 modules. Module 1 covers basics of RF including frequency, amplitude, wavelength, phase, and polarization. It also discusses transmission line fundamentals. Module 2 discusses RF communication systems, modulation techniques, and RF design. Module 3 covers wireless technologies like Bluetooth, WiFi, and cellular standards. The course provides assignments on topics like wavelength calculation and transmission line speed calculation in different materials. It also explains dBm calculations and concepts like signal to noise ratio, gain and loss.
Hello everyone. This is a short presentation on path loss and shadowing. I have not covered all the topics but a brief idea is given on path loss and wireless channel propagation models.
Hope you find it useful.
Thanks
1) The document presents information about a magic tee, which is a waveguide component used in microwave engineering systems.
2) A magic tee has four ports and is able to split or combine signals passing through in specific ways depending on which port is used.
3) The document discusses the working, operation, and S-matrix of a magic tee. It also provides examples of how magic tees can be used for applications like impedance measurement, duplexing, and mixing.
The document discusses the design of a microstrip patch antenna (MPA) resonating in the K-band frequency range (18-26GHz) using HFSS software. It provides an introduction to antennas and describes the basic structure of an MPA including the radiating patch, dielectric substrate, and ground plane. Design considerations for the MPA include selecting the rectangular patch shape and FR4 epoxy substrate material. The document outlines the design process in HFSS and lists some advantages and applications of MPAs for mobile/satellite communication systems. It concludes that the designed MPA exhibits good impedance matching at the center frequency and can be easily fabricated on an FR4 substrate.
A loop antenna is a radio antenna consisting of a loop or coil of wire, tubing, or other electrical conductor with its ends connected to a balanced transmission line (or possibly a balun). There are two distinct antenna designs: the small loop (or magnetic loop) with a size much smaller than a wavelength, and the much larger resonant loop antenna with a circumference close to the intended wavelength of operation. Small loops have low radiation resistance and thus poor efficiency and are mainly used as receiving antennas at low frequencies. To increase the magnetic field in the loop and thus the efficiency, the coil of wire is often wound around a ferrite rod magnetic core; this is called a ferrite loop antenna. The ferrite loop is the antenna used in many AM broadcast receivers, with the exception of external loops used with AV Amplifier-Receivers and car radios; the antenna is often contained inside the radio's case. These antennas are also used for radio direction finding. In amateur radio, loop antennas are often used for low profile operating where larger antennas would be inconvenient, unsightly.
(c) WIkipedia
RF energy harvesting involves capturing wireless signals like Wi-Fi and converting them into usable electrical energy. It consists of an antenna that receives RF signals, rectification circuits that convert AC to DC, energy storage components like capacitors, and power management circuitry that regulates voltage and current delivery. RF energy harvesting shows potential to power wireless devices without batteries and supports growing applications in sensor networks and IoT. Ongoing research aims to improve efficiency, allow multi-band harvesting, further miniaturize components, and integrate the technology into more devices.
This document provides an overview of microwave tubes, including their components and operating principles. It discusses cavity resonators, rectangular cavity resonators, limitations of conventional vacuum tubes at high frequencies, and types of microwave tubes like klystrons, traveling wave tubes (TWTs), and magnetrons. Magnetrons are used in microwave ovens and produce hundreds of watts of microwave power by directing an electron beam in a circular pattern using a strong magnetic field. TWTs amplify signals in the microwave frequency range from 500 MHz to 300 GHz using an electron beam interacting with a slow-wave structure.
The document discusses various aspects of radio wave propagation. It explains that radio waves travel through the ionosphere and can be refracted back to Earth, allowing long distance communication. The ionosphere consists of several layers (D, E, F1, F2) that reflect radio waves of different frequencies depending on factors like solar activity and time of day. Radio propagation involves line-of-sight transmission as well as skywave propagation via reflection/refraction from ionospheric layers, which can allow signals to hop or skip distances beyond the horizon through multiple reflections. Absorption, fading, and noise affect signal strength over distance.
- Antennas convert electric currents into radio waves and vice versa. They are used in various technologies including radio, television, mobile phones, WiFi, and radar.
- The first antennas were built in 1888 by Heinrich Hertz to transmit and receive electromagnetic waves. Modern antennas come in different types for applications like broadcasting, communications, and space exploration.
- Antennas work by using an oscillating current to generate oscillating electric and magnetic fields that propagate as radio waves. During reception, the antenna intercepts some power from incoming radio waves to produce a voltage for the receiver.
This document discusses wireless power transmission (WPT) and compares microwave and laser transmission methods. It describes how a rectenna works to receive microwaves with 85% efficiency within 5km. Solar power satellites that transmit power via microwaves from space are also discussed, including their advantages over earth-based solar like constant sunlight. Current development of a low-cost Japanese demonstration project by 2025 and potential applications of WPT like electric vehicles are mentioned.
Design and Simulation Microstrip patch Antenna using CST Microwave StudioAymen Al-obaidi
The document describes the design and simulation of a microstrip patch antenna in CST Microwave Studio. It begins with an introduction to microstrip patch antennas and their applications. Then, it outlines the theoretical design of a rectangular patch antenna for 2.4 GHz WiFi using transmission line equations. Finally, it details the simulation process in CST Microwave Studio, including adding the patch, feedline, substrate and ground plane, assigning materials and frequencies, setting up the port and monitors, and solving to obtain results like the bandwidth and radiation pattern.
The document discusses RF energy harvesting, which involves collecting ambient radio frequency energy from sources like TV and cell phone towers to power devices. It describes the concept of using a receiver to collect RF energy and convert it to DC power. The harvesting unit is explained as consisting of an antenna, impedance matching, rectifier to convert RF to DC, and storage components. Different types of antennas and considerations for impedance matching networks are also covered. The document concludes by noting advantages of RF energy harvesting like free wireless power but also challenges of low ambient power levels and conversion efficiency.
Powercast - RF Energy Harvesting for Controllable Wireless Power SystemsHarry Ostaffe
This document discusses RF energy harvesting and wireless power transmission for low-power applications. It describes how microwatts of power transmitted over radio waves can be collected by receiver devices to trickle charge batteries or power devices. Key advantages of this technology include extended battery life, reduced operating costs, and improved product design flexibility. Example applications shown include wireless sensors, RFID tags, and wirelessly charged consumer electronics.
This thesis focuses on mobile phones antenna design with brief description about the historical development, basic parameters and the types of antennas which are used in mobile phones. Mobile phones antenna design section consists of two proposed PIFA antennas. The first design concerns a single band antenna with resonant frequency at GPS frequency (1.575GHz). The first model is designed with main consideration that is to have the lower possible PIFA single band dimensions with reasonable return loss (S11) and the efficiencies. Second design concerns in a wideband PIFA antenna which cover the range from 1800MHz to 2600MHz. This range covers certain important bands: GSM (1800MHz & 1900MHz), UMTS (2100MHz), Bluetooth & Wi-Fi (2.4GHz) and LTE system (2.3GHz, 2.5GHz, and 2.6GHz). The wideband PIFA design is achieved by using slotted ground plane technique. The simulations for both models are performed in COMSOL Multiphysics.
The last two parts of the thesis present the problems of mobile phones antenna. Starting with Specific absorption rate (SAR) problem, efficiency of Mobile phones antenna, and hand-held environment.
This document provides an introduction to the High Frequency Structure Simulator (HFSS), a finite element method simulation tool for complex 3D geometries. It discusses the background, requirements, features, and procedure for using HFSS to simulate electromagnetic fields. Examples are given of modeling microstrip lines, waveguide components, antennas, and other applications. The document also provides an overview of Agilent and Ansoft's HFSS software.
1. Cavity resonators confine electromagnetic waves inside hollow structures such as rectangular boxes or cylindrical cans through resonance.
2. The resonant modes inside the cavity depend on its geometry and are determined by solving Maxwell's equations with the appropriate boundary conditions.
3. Common modes include TE and TM, where the electric and magnetic fields are transverse to the axis of propagation.
4. Coupling mechanisms such as wires or loops are used to input and output power to selectively excite specific resonant modes within the cavity.
Link Power Budget Calculation and Propagation Factors for Satellite COmmunica...THANDAIAH PRABU
- Antenna Pointing Loss
- Free Space Loss
- Atmospheric Loss
(gaseous, clouds, rain)
- Rx Antenna Pointing Loss
Reception:
+ Antenna gain
- Reception Losses
(cables & connectors)
- Noise Temperature
Contribution
Rx
Pr
1) The document discusses various propagation factors that affect radio wave transmission in satellite systems including atmospheric absorption, attenuation, and traveling ionospheric disturbances.
2) It provides details on calculating a link power budget including defining equivalent isotropic radiated power (EIRP), transmitter power, antenna gains, losses from free space path, the atmosphere, and other sources.
The document discusses microstrip patch antennas and defected ground structures (DGS). It provides an overview of microstrip antenna design including patch geometries and feeding techniques. It also discusses the advantages and disadvantages of microstrip antennas. Next, it introduces DGS, describing various DGS unit cell shapes and their applications in delay lines and antennas. The document concludes by presenting the design and performance analysis of a rectangular microstrip patch antenna with a dumbbell-shaped DGS cell for size reduction and efficiency improvement.
An antenna converts radio frequency electric current into electromagnetic waves that are radiated into space. The same antenna can transmit and receive signals. Key antenna concepts include reciprocity, radiation patterns, gain, and polarization. Antenna gain compares its power output to an isotropic antenna. Common antennas include dipole, parabolic reflective, and types are optimized for propagation modes like ground wave, sky wave, and line-of-sight. Signal strength is reduced by factors like free space loss, noise, multipath, and fading over the transmission path.
By completing this presentation will be have a clear idea about Antenna's working principles, Antenna's Types & Antenna's Parameters. At the end to this document you'll have a brief idea about Antenna's Tilt vs Distance Calculation & Cluster wise optimum Antenna Selection procedure. Impact of antenna PIM & VSWR have been described elaborately in this document as well.
This document describes the design of an equal split Wilkinson power divider with the following specifications: frequency of 2.4 GHz, source and load impedances of 50 ohms, substrate permittivity of 3.38, substrate thickness of 1.524 mm, and conductor thickness of 0.15 mm. It provides background on Wilkinson power dividers, describes the calculation of microstrip line widths and lengths, shows the simulated circuit schematic and layout, and plots the resulting S-parameters which achieve the desired 3 dB power split with good port matching and isolation as expected.
This document outlines an RF fundamentals course taught in 3 modules. Module 1 covers basics of RF including frequency, amplitude, wavelength, phase, and polarization. It also discusses transmission line fundamentals. Module 2 discusses RF communication systems, modulation techniques, and RF design. Module 3 covers wireless technologies like Bluetooth, WiFi, and cellular standards. The course provides assignments on topics like wavelength calculation and transmission line speed calculation in different materials. It also explains dBm calculations and concepts like signal to noise ratio, gain and loss.
Hello everyone. This is a short presentation on path loss and shadowing. I have not covered all the topics but a brief idea is given on path loss and wireless channel propagation models.
Hope you find it useful.
Thanks
1) The document presents information about a magic tee, which is a waveguide component used in microwave engineering systems.
2) A magic tee has four ports and is able to split or combine signals passing through in specific ways depending on which port is used.
3) The document discusses the working, operation, and S-matrix of a magic tee. It also provides examples of how magic tees can be used for applications like impedance measurement, duplexing, and mixing.
The document discusses the design of a microstrip patch antenna (MPA) resonating in the K-band frequency range (18-26GHz) using HFSS software. It provides an introduction to antennas and describes the basic structure of an MPA including the radiating patch, dielectric substrate, and ground plane. Design considerations for the MPA include selecting the rectangular patch shape and FR4 epoxy substrate material. The document outlines the design process in HFSS and lists some advantages and applications of MPAs for mobile/satellite communication systems. It concludes that the designed MPA exhibits good impedance matching at the center frequency and can be easily fabricated on an FR4 substrate.
A loop antenna is a radio antenna consisting of a loop or coil of wire, tubing, or other electrical conductor with its ends connected to a balanced transmission line (or possibly a balun). There are two distinct antenna designs: the small loop (or magnetic loop) with a size much smaller than a wavelength, and the much larger resonant loop antenna with a circumference close to the intended wavelength of operation. Small loops have low radiation resistance and thus poor efficiency and are mainly used as receiving antennas at low frequencies. To increase the magnetic field in the loop and thus the efficiency, the coil of wire is often wound around a ferrite rod magnetic core; this is called a ferrite loop antenna. The ferrite loop is the antenna used in many AM broadcast receivers, with the exception of external loops used with AV Amplifier-Receivers and car radios; the antenna is often contained inside the radio's case. These antennas are also used for radio direction finding. In amateur radio, loop antennas are often used for low profile operating where larger antennas would be inconvenient, unsightly.
(c) WIkipedia
RF energy harvesting involves capturing wireless signals like Wi-Fi and converting them into usable electrical energy. It consists of an antenna that receives RF signals, rectification circuits that convert AC to DC, energy storage components like capacitors, and power management circuitry that regulates voltage and current delivery. RF energy harvesting shows potential to power wireless devices without batteries and supports growing applications in sensor networks and IoT. Ongoing research aims to improve efficiency, allow multi-band harvesting, further miniaturize components, and integrate the technology into more devices.
This document provides an overview of microwave tubes, including their components and operating principles. It discusses cavity resonators, rectangular cavity resonators, limitations of conventional vacuum tubes at high frequencies, and types of microwave tubes like klystrons, traveling wave tubes (TWTs), and magnetrons. Magnetrons are used in microwave ovens and produce hundreds of watts of microwave power by directing an electron beam in a circular pattern using a strong magnetic field. TWTs amplify signals in the microwave frequency range from 500 MHz to 300 GHz using an electron beam interacting with a slow-wave structure.
The document discusses various aspects of radio wave propagation. It explains that radio waves travel through the ionosphere and can be refracted back to Earth, allowing long distance communication. The ionosphere consists of several layers (D, E, F1, F2) that reflect radio waves of different frequencies depending on factors like solar activity and time of day. Radio propagation involves line-of-sight transmission as well as skywave propagation via reflection/refraction from ionospheric layers, which can allow signals to hop or skip distances beyond the horizon through multiple reflections. Absorption, fading, and noise affect signal strength over distance.
- Antennas convert electric currents into radio waves and vice versa. They are used in various technologies including radio, television, mobile phones, WiFi, and radar.
- The first antennas were built in 1888 by Heinrich Hertz to transmit and receive electromagnetic waves. Modern antennas come in different types for applications like broadcasting, communications, and space exploration.
- Antennas work by using an oscillating current to generate oscillating electric and magnetic fields that propagate as radio waves. During reception, the antenna intercepts some power from incoming radio waves to produce a voltage for the receiver.
This document discusses wireless power transmission (WPT) and compares microwave and laser transmission methods. It describes how a rectenna works to receive microwaves with 85% efficiency within 5km. Solar power satellites that transmit power via microwaves from space are also discussed, including their advantages over earth-based solar like constant sunlight. Current development of a low-cost Japanese demonstration project by 2025 and potential applications of WPT like electric vehicles are mentioned.
Design and Simulation Microstrip patch Antenna using CST Microwave StudioAymen Al-obaidi
The document describes the design and simulation of a microstrip patch antenna in CST Microwave Studio. It begins with an introduction to microstrip patch antennas and their applications. Then, it outlines the theoretical design of a rectangular patch antenna for 2.4 GHz WiFi using transmission line equations. Finally, it details the simulation process in CST Microwave Studio, including adding the patch, feedline, substrate and ground plane, assigning materials and frequencies, setting up the port and monitors, and solving to obtain results like the bandwidth and radiation pattern.
The document discusses RF energy harvesting, which involves collecting ambient radio frequency energy from sources like TV and cell phone towers to power devices. It describes the concept of using a receiver to collect RF energy and convert it to DC power. The harvesting unit is explained as consisting of an antenna, impedance matching, rectifier to convert RF to DC, and storage components. Different types of antennas and considerations for impedance matching networks are also covered. The document concludes by noting advantages of RF energy harvesting like free wireless power but also challenges of low ambient power levels and conversion efficiency.
Powercast - RF Energy Harvesting for Controllable Wireless Power SystemsHarry Ostaffe
This document discusses RF energy harvesting and wireless power transmission for low-power applications. It describes how microwatts of power transmitted over radio waves can be collected by receiver devices to trickle charge batteries or power devices. Key advantages of this technology include extended battery life, reduced operating costs, and improved product design flexibility. Example applications shown include wireless sensors, RFID tags, and wirelessly charged consumer electronics.
Powercast Overview - RF Energy Harvesting and Wireless Power for Micro-Power ...Powercast Corporation
This document discusses RF energy harvesting and wireless power transmission for low-power applications. It describes how microwatts of power transmitted over radio waves can be used to trickle charge batteries or power battery-free devices. Key factors that determine the received power are the power of the RF source, distance from the source, size of the receiving antenna, and transmission frequency. Examples of applications that could benefit from this technology include wireless sensors for industrial monitoring and smart buildings.
These slides use concepts from my (Jeff Funk) course entitled analyzing hi-tech opportunities to show how energy harvesters are becoming more economically feasible for the Internet of Things (IoT). Small amounts of energy can be harvested from vibrations, temperature differences, and radio frequencies using various types of electronic devices such as piezoelectric, MEMS, thermo-electric power generators, and other devices. As improvements in them occur and as the energy requirements of accelerometers, pressure sensors, gas detectors, bio-sensors, and readout circuits fall from microwatts to hundreds of nano-watts, energy harvesters become cheaper and better than are batteries. Improvements in energy harvesting are occurring in the form of higher power per area or higher power per temperature difference and improvements of about five times are expected to occur in the next 5 to 10 years. The market for energy harvesters is expected to reach $2.5 Billion by 2024. In addition to their impact on buildings and the other usual applications for IoT, they will also impact on agriculture, aircraft, and medical implants.
This document describes an elective on energy harvesting that will discuss harnessing renewable energy from the environment, including an overview of energy harvesting, applications, and a hands-on activity where students will characterize solar panels and use the energy to power loads like LEDs, motors, and buzzers. Students will also design a scenario to power a 3 room apartment using solar energy under constraints set by the owner.
RF MEMS have potential for energy harvesting by converting electromagnetic energy into electrical charge. The proposed RF MEMS design aims to be scalable and easily integrated in microsystems, unlike existing MEMS energy harvesters that have low efficiency, scaling issues, and high costs. RF MEMS can be fabricated using processes like co-planar waveguide deposition, lithography, aluminum deposition and patterning, and sacrificial layer removal. When activated, the RF MEMS structure can store up to 35 pC of charge per cycle that is generated from the membrane's overlap with the signal isolation layer. However, reliability issues from electrostatic discharge still need to be addressed for practical applications in wireless sensors.
DESIGN & ANALYSIS OF RF ENERGY HARVESTING SYSTEM FOR CHARGING LOW POWER DEVICESJournal For Research
Finite electrical battery life is encouraging the companies and researchers to come up with new ideas and technologies to drive wireless mobile devices for an infinite or enhance period of time. Common resource constrained wireless devices when they run out of battery they should be recharged. For that purpose main supply & charger are needed to charge drained mobile phone batteries or any portable devices. Practically it is not possible to carry charger wherever we go and also to expect availability of power supply everywhere. To avoid such disadvantages some sort of solution should be given and that can be wireless charging of mobile phones.[4] If the mobile can receive RF power signals from the mobile towers, why can’t we extract the power from the received signals? This can be done by the method or technology called RF energy harvesting. RF energy harvesting holds a promise able future for generating a small amount of electrical power to drive partial circuits in wirelessly communicating electronics devices. RF power harvesting is one of the diverse fields where still research continues. The energy of RF waves used by devices can be harvested and used to operate in more effective and efficient way.
Wireless & Energy Harvesting Technologies for Energy Inefficient BuildingsDan Wright, MBA
This document discusses how energy harvesting and wireless technologies can enable more energy efficient buildings through building automation. It provides an overview of these technologies, including how they work and their benefits. Energy harvesting sensors can power wireless controls without batteries by harvesting small amounts of energy from motion, light, or electromagnetic switching. This allows retrofitting buildings with lighting and HVAC controls to reduce energy use by 20-28% through occupancy-based control. Demonstrations show how energy harvesting switches and sensors communicate wirelessly to automatically control lights.
The slides for a presentation on Energy harvesting and the state off the art designs currently taking advantage of the energy around us.
Energy harvesting (also known as power harvesting or energy scavenging) is the process by which energy is derived from external sources (e.g.solar power, thermal energy, wind energy, salinity gradients, and kinetic energy), captured, and stored for small, wireless autonomous devices, like those used in wearable electronics and wireless sensor networks.
Credits: A thanks go out to Johan Pedersen for introducing me to the subject a great workshop and use of some of his slides.
The document describes energy harvesting trees, also known as solar botanic trees. These trees harness renewable energy from the sun, wind, and rain through advanced nano-technologies. The trees consist of nanoleaves, a long tower, LEDs, batteries, and stems connecting the nanoleaves. Nanoleaves generate power from sunlight and wind via the flapping motion, while piezoelectric ribbons in the stems create energy from wind-induced vibrations. Compared to traditional solar panels, these trees require less land for equivalent power generation and provide an efficient, eco-friendly renewable energy solution especially for densely populated areas.
The document summarizes the development of an energy harvesting wireless sensor node powered by piezoelectric, thermoelectric, and solar techniques. It describes the design of a demo board with energy harvesting capabilities including an RF communication module and temperature sensor. The node is intended to operate with low power consumption in sleep mode and integrate energy from multiple ambient sources to power wireless transmission of sensor data for long-term remote monitoring applications.
Development of a Wireless Sensors Network powered by Energy Harvesting techni...Daniele Costarella
Develer Workshop:
A workshop focused on the principles and benefits of applying the Energy Harvesting techniques on Wireless Sensor Networks. The contents come from my Better Embedded 2013 talk.
The document discusses the design of an RF MEMS switch using COMSOL Multiphysics and Intellisuite simulation software. A cantilever beam switch structure is designed with dimensions and materials specified. Simulation results show the switch has a low actuation voltage of 4V, insertion loss of -8dB, and isolation of -40dB at 1.5GHz. To reduce the high resistance of a single switch, 10 switches are placed in parallel, lowering the effective resistance to 5.9 ohms. The switch performance is better at lower frequencies.
Linda Drabik - Energy harvesting for IoTWithTheBest
As sensors and actuators are deployed in increasing numbers across greater distances, autonomous devices will become more ubiquitous. For systems that require longer life than a primary battery can deliver, Energy Harvesting offers a promising solution.
Energy Harvesting (EH) is the process by which ambient energy is captured from one or more energy sources and stored for later use. It enables autonomous sensors or switches to perpetually run with little to no maintenance, eliminating the need for connection to an electric grid and overcoming limitations of a battery-only power source with limited energy storage.
While the cost of buying and disposing batteries is a significant consideration, it’s the operational drain of maintenance that makes Energy Harvesting a particularly attractive solution for IoT.
In this presentation:
- Energy Harvesting solutions, including those that convert sources such as light, vibration, and heat into electricity (solar cells, piezoelectric devices, and thermoelectric generators).
- Key considerations for an Energy Harvesting terminal, including optimal capacitor size.
Linda Brabik, Founder/Organizer, IoT NY Meetup
The document discusses a booklet published by the DMK party about the Setu project. It provides a critical analysis and raises several questions about the booklet. It notes that the booklet does not address important issues regarding national security, coastline security, or tsunami protection. It also points out that the booklet does not reference or explain important aspects of the history and culture associated with Rama Setu, despite the author being the Chief Minister. Overall, the document questions the validity and completeness of the arguments made in the DMK party's booklet.
RF-based energy harvesting involves capturing ambient radio frequency (RF) energy from sources like cell phones, WiFi networks, and television broadcasts. This energy can then be converted into direct current (DC) power to charge or operate low-power electronic devices without needing batteries. For example, one system harvests RF energy from nearby iPhones using an RF receiver and converts it to power tiny wireless sensor nodes for applications like health monitoring. This technology could eliminate the need for batteries in many small devices.
This document provides instructions for building a Solar Joule Bracelet that combines a solar battery and a Joule Thief circuit. The solar battery is made from a series of photodiodes connected to a supercapacitor. The Joule Thief circuit uses a common-mode choke, transistor, resistor and capacitor to convert the low voltage from the solar battery into bursts of voltage that light up an LED. The document outlines the steps to assemble these components and connect them together. It also provides troubleshooting tips in case the circuit does not light the LED as expected. The final step is to mount the solar battery and Joule Thief circuit onto a fabric bracelet.
JOULE THIEF WHICH GIVES LIFE TO DEAD BATTERIES!!!Sanjay4502
It is very important that buying a set of batteries for household purposes. How about draining the last drop of energy from a battery which you have declared dead? This slideshare does that. See to it!!!!!!!!!
In modern days, the use of energy consumption increasing very rapidly. Fossil fuels are finite and environmentally costly. Sustainable, environmentally benign energy can be derived from nuclear fission or captured from ambient sources. Large-scale ambient energy (eg. solar, wind and tide), is widely available and large-scale technologies are being developed to efficiently capture it. At the other end of the scale, there are small amounts of ‘wasted’ energy that could be useful if captured. Recovering even a fraction of this energy would have a significant economic and environmental impact. This is where energy harvesting (EH) comes in.
IC Design of Power Management Circuits (IV)Claudia Sin
by Wing-Hung Ki
Integrated Power Electronics Laboratory
ECE Dept., HKUST
Clear Water Bay, Hong Kong
www.ee.ust.hk/~eeki
International Symposium on Integrated Circuits
Singapore, Dec. 14, 2009
The wireless Power Transmission is a useful and proper technology is used in various fields like electronic devices, implantable medical devices, industry and other fields, and has become a research hotspot at home and abroad. Because it enables the transmission of electrical energy from a power source to an electrical load across an air gap without interconnecting wires. This paper reviews the methods used in the wireless power transmission system, recent technologies, future and its application, merits as well as demerits. Mrs. Yogita Shailesh Kadam "Wireless Power Transmission System- A Review" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-7 | Issue-3 , June 2023, URL: https://www.ijtsrd.com.com/papers/ijtsrd57380.pdf Paper URL: https://www.ijtsrd.com.com/engineering/electrical-engineering/57380/wireless-power-transmission-system-a-review/mrs-yogita-shailesh-kadam
This document discusses wireless recharging/transmission technology. It begins with an introduction to the concept of wirelessly transmitting electricity without physical connection. It then provides a brief history of wireless transmission technology and discusses current techniques like inductive charging, evanescent wave coupling, and capacitive induction. The document also discusses far field electricity transmission using radio/microwave waves or lasers. Currently, induction-based wireless chargers have achieved 80-90% efficiency and are commercially available, while evanescent wave coupling research continues. Far field transmission is still inefficient and not economically viable.
This document discusses wireless recharging/transmission technology. It begins with an introduction to the concept of wirelessly transmitting electricity without physical connection. It then provides a brief history of wireless transmission technology and discusses current techniques like inductive charging, evanescent wave coupling, and capacitive induction. The document also discusses far field electricity transmission using radio/microwave waves or lasers. Currently, induction-based wireless chargers have achieved 80-90% efficiency and are commercially available, while evanescent wave coupling research continues. Far field transmission is still not economically viable due to low efficiency.
World cannot be imagined without electrical
power. Generally the power is transmitted through
transmission networks. This paper describes an original
idea to eradicate the hazardous usage of electrical wires
which involve lot of confusion in particularly organizing
them. Imagine a future in which wireless power transfer is
feasible: cell phones, household robots, mp3 players,
laptop computers and other portable electronic devices
capable of charging themselves without ever being plugged
in freeing us from that final ubiquitous power wire. This
paper includes the techniques of transmitting power
without using wires with an efficiency of about 95% with
non-radioactivemethods. In this paper wireless power
transfer technique have been implemented on test system.
Keywords : power, ubiquitous, efficiency
No Wire is the brief description of the wireless technology and wireless power transmission. this presentation gives the overview of the wireless power transmission and also you can found the different types of the methods used to transfer the power wirelessly i mean the types of the wireless power transmission. ...................................................................................................................................................................................................................................................................
STUDY ON IMPROVED RADIATION PERFORMANCE CHARACTERISTICS OF FRACTAL ANTENNA FO...vnktrjr
This document discusses a study on improving the radiation performance of fractal antennas for wireless applications. It begins with an introduction to wireless communication systems and the importance of antennas. It then discusses the basics of antenna theory, including key properties like gain, directivity, efficiency, input impedance, polarization, return loss, radiation patterns and beamwidth. Finally, it briefly describes common antenna types such as dipoles, monopoles, corner reflectors and Yagi antennas. The overall aim is to analyze how the performance of a microstrip fractal antenna can be improved by using an array configuration and electromagnetic band gap structure.
Add more information to your upload Tip: Better titles and descriptions lead ...ZaiAssociate
This document summarizes a project on wireless power transmission using inductive coupling between two coils. The system transmits power from a transmitting coil connected to an AC power source to a receiving coil connected to a load. At the transmitter, AC power is converted to a magnetic flux using an oscillator and primary coil. This magnetic flux induces an EMF in the secondary coil at the receiver, transmitting power wirelessly. The system provides advantages over wired transmission like eliminating wires and allowing power transmission over distances without connections. Various applications are discussed including charging devices and electric vehicles wirelessly.
Review Paper on Wireless Power Transmission by using Inductive Coupling for D...IRJET Journal
This document summarizes wireless power transmission using inductive coupling for different applications. It discusses how an alternating current in a transmitter coil generates a magnetic field which induces a voltage in a receiver coil. This induced voltage can be used to power mobile devices or charge batteries wirelessly. The document then reviews inductive coupling technology and compares various wireless power transfer methods. It presents practical results of a wireless mobile phone charger, LED lighting, and a DC fan operating without wires by using inductive coupling to transmit power. The document concludes that wireless power transmission through inductive coupling is an efficient means of transferring power without wires and has many potential applications.
This project report discusses wireless power transmission techniques. It begins by introducing wireless power transmission and some of its advantages over wired transmission. It then describes various near-field techniques like inductive coupling and resonant inductive coupling. Far-field techniques like microwave power transmission and laser power transmission are also summarized. Key differences between various techniques are highlighted. The report provides examples and diagrams to illustrate wireless power transmission concepts.
This document discusses wireless power transmission using microwaves as an alternative to wired power transmission. It describes how microwaves can be used to transmit power over long distances without wires, using a transmitting antenna to broadcast the power and a receiving rectenna to convert it back to electricity. The key components of wireless power transmission systems using microwaves are described, including microwave generators, transmitting antennas, and rectennas. Applications like powering homes and electric vehicles are discussed. Advantages include reduced transmission losses and costs, while concerns relate to efficiency and potential health effects of microwave exposure.
This document discusses wireless charging of mobile devices using microwaves. It describes three types of wireless charging - inductive, radio, and resonance charging. It then focuses on using microwaves for wireless charging. Microwaves with frequencies between 300MHz to 300GHz can transfer energy over short distances. The document proposes using the 2.45GHz ISM band to wirelessly charge mobiles. It provides block diagrams of the transmitter and receiver sections, describing the use of a magnetron to generate microwaves at the transmitter and a rectenna circuit to convert microwaves to DC power at the receiver.
Ramesh Kumar Maurya presented on wireless power transmission techniques for his fourth year electrical engineering seminar. He discussed three main wireless power transmission types: microwave, inductive coupling, and laser. For microwave transmission, power is transmitted through free space using antennas, while inductive coupling uses magnetic fields between coils for near-field transmission. Laser transmission involves converting solar or electrical power to a laser beam and receiving it with photovoltaic cells. Maurya provided an example system operating at 40kHz and benefits of wireless including reduced infrastructure costs and enabling power where wires cannot reach. Applications include solar power satellites and wireless vehicles, robots, and sensors.
wireless electricity and power transmissionStudent
The document discusses various techniques for wireless transmission of energy including near field techniques like inductive coupling and resonant inductive coupling, and far field techniques like laser power transmission, microwave power transmission, and solar power satellites. It provides details on how inductive coupling, resonant inductive coupling, microwave power transmission, and solar power satellites work. The document also discusses advantages and disadvantages of near field and far field techniques as well as applications of wireless power transmission including electric vehicle charging, consumer electronics, and industrial uses.
This document discusses wireless power transmission (WPT), including its history, types, techniques, advantages, and applications. WPT involves transmitting energy from one place to another without wires. There are two main types - near-field techniques like inductive coupling and resonant inductive coupling, and far-field techniques like microwave power transmission and laser power transmission. Some advantages of WPT are that it is reliable, efficient, fast, and has low maintenance costs. Applications include electric vehicle charging, consumer electronics, solar power satellites, and transmitting energy to remote areas.
This document discusses wireless power transfer (WPT), where electrical energy is transmitted through electromagnetic fields without physical connections like wires. WPT works by using a transmitter device powered by electricity to generate a time-varying electromagnetic field that transmits power through space to a receiver device, which extracts the power. The technology eliminates wires and batteries and increases mobility and safety of electronic devices. Common WPT methods include inductive coupling using coils, resonant inductive coupling using coils and capacitors, and far-field techniques like microwave and laser beam transmission.
This document discusses wireless power transfer (WPT), where electrical energy is transmitted through electromagnetic fields without physical connections like wires. WPT works by using a transmitter device powered by electricity to generate a time-varying electromagnetic field that transmits power through space to a receiver device, which extracts the power. The technology eliminates wires and batteries and increases mobility and safety of electronic devices. Common WPT methods include inductive coupling using coils, resonant inductive coupling using coils and capacitors, and far-field techniques like microwave and laser beam transmission.
This document discusses wireless power transfer (WPT), where electrical energy is transmitted through electromagnetic fields without physical connections like wires. WPT works by using a transmitter device powered by electricity to generate a time-varying electromagnetic field that transmits power through space to a receiver device, which extracts the power. The key technologies discussed are inductive coupling using coils, resonant inductive coupling (RIC) which improves efficiency, and microwave and laser systems for far-field wireless power transmission. WPT has applications for powering devices where wires are inconvenient as well as for transmitting solar power from satellites.
This document discusses wireless power transfer (WPT), where electrical energy is transmitted through electromagnetic fields without physical connections like wires. WPT works by using a transmitter device powered by electricity to generate a time-varying electromagnetic field that transmits power through space to a receiver device, which extracts the power. The technology eliminates wires and batteries and increases mobility and safety of electronic devices. Common WPT methods include inductive coupling using coils, resonant inductive coupling using coils and capacitors, and far-field techniques like microwave and laser beam transmission.
wireless charging of mobile phones using microwave full seminar reportHarish N Nayak
This document discusses wireless charging of mobile devices using microwaves. It describes three types of wireless charging - inductive, radio, and resonance charging. It then focuses on using microwaves for wireless charging. The electromagnetic spectrum is introduced, with microwaves described as radio waves between 1mm-1m wavelengths. A general block diagram shows the transmitting and receiving parts, with the transmitter using a magnetron to produce microwaves and a slotted waveguide antenna to transmit them, and the receiver using an impedance matching circuit and rectenna to convert the microwaves to DC power.
Similar to RF Energy Harvesting for Wireless Devices (20)
A Novel Method for Prevention of Bandwidth Distributed Denial of Service AttacksIJERD Editor
Distributed Denial of Service (DDoS) Attacks became a massive threat to the Internet. Traditional
Architecture of internet is vulnerable to the attacks like DDoS. Attacker primarily acquire his army of Zombies,
then that army will be instructed by the Attacker that when to start an attack and on whom the attack should be
done. In this paper, different techniques which are used to perform DDoS Attacks, Tools that were used to
perform Attacks and Countermeasures in order to detect the attackers and eliminate the Bandwidth Distributed
Denial of Service attacks (B-DDoS) are reviewed. DDoS Attacks were done by using various Flooding
techniques which are used in DDoS attack.
The main purpose of this paper is to design an architecture which can reduce the Bandwidth
Distributed Denial of service Attack and make the victim site or server available for the normal users by
eliminating the zombie machines. Our Primary focus of this paper is to dispute how normal machines are
turning into zombies (Bots), how attack is been initiated, DDoS attack procedure and how an organization can
save their server from being a DDoS victim. In order to present this we implemented a simulated environment
with Cisco switches, Routers, Firewall, some virtual machines and some Attack tools to display a real DDoS
attack. By using Time scheduling, Resource Limiting, System log, Access Control List and some Modular
policy Framework we stopped the attack and identified the Attacker (Bot) machines
Hearing loss is one of the most common human impairments. It is estimated that by year 2015 more
than 700 million people will suffer mild deafness. Most can be helped by hearing aid devices depending on the
severity of their hearing loss. This paper describes the implementation and characterization details of a dual
channel transmitter front end (TFE) for digital hearing aid (DHA) applications that use novel micro
electromechanical- systems (MEMS) audio transducers and ultra-low power-scalable analog-to-digital
converters (ADCs), which enable a very-low form factor, energy-efficient implementation for next-generation
DHA. The contribution of the design is the implementation of the dual channel MEMS microphones and powerscalable
ADC system.
Influence of tensile behaviour of slab on the structural Behaviour of shear c...IJERD Editor
-A composite beam is composed of a steel beam and a slab connected by means of shear connectors
like studs installed on the top flange of the steel beam to form a structure behaving monolithically. This study
analyzes the effects of the tensile behavior of the slab on the structural behavior of the shear connection like slip
stiffness and maximum shear force in composite beams subjected to hogging moment. The results show that the
shear studs located in the crack-concentration zones due to large hogging moments sustain significantly smaller
shear force and slip stiffness than the other zones. Moreover, the reduction of the slip stiffness in the shear
connection appears also to be closely related to the change in the tensile strain of rebar according to the increase
of the load. Further experimental and analytical studies shall be conducted considering variables such as the
reinforcement ratio and the arrangement of shear connectors to achieve efficient design of the shear connection
in composite beams subjected to hogging moment.
Gold prospecting using Remote Sensing ‘A case study of Sudan’IJERD Editor
Gold has been extracted from northeast Africa for more than 5000 years, and this may be the first
place where the metal was extracted. The Arabian-Nubian Shield (ANS) is an exposure of Precambrian
crystalline rocks on the flanks of the Red Sea. The crystalline rocks are mostly Neoproterozoic in age. ANS
includes the nations of Israel, Jordan. Egypt, Saudi Arabia, Sudan, Eritrea, Ethiopia, Yemen, and Somalia.
Arabian Nubian Shield Consists of juvenile continental crest that formed between 900 550 Ma, when intra
oceanic arc welded together along ophiolite decorated arc. Primary Au mineralization probably developed in
association with the growth of intra oceanic arc and evolution of back arc. Multiple episodes of deformation
have obscured the primary metallogenic setting, but at least some of the deposits preserve evidence that they
originate as sea floor massive sulphide deposits.
The Red Sea Hills Region is a vast span of rugged, harsh and inhospitable sector of the Earth with
inimical moon-like terrain, nevertheless since ancient times it is famed to be an abode of gold and was a major
source of wealth for the Pharaohs of ancient Egypt. The Pharaohs old workings have been periodically
rediscovered through time. Recent endeavours by the Geological Research Authority of Sudan led to the
discovery of a score of occurrences with gold and massive sulphide mineralizations. In the nineties of the
previous century the Geological Research Authority of Sudan (GRAS) in cooperation with BRGM utilized
satellite data of Landsat TM using spectral ratio technique to map possible mineralized zones in the Red Sea
Hills of Sudan. The outcome of the study mapped a gossan type gold mineralization. Band ratio technique was
applied to Arbaat area and a signature of alteration zone was detected. The alteration zones are commonly
associated with mineralization. The alteration zones are commonly associated with mineralization. A filed check
confirmed the existence of stock work of gold bearing quartz in the alteration zone. Another type of gold
mineralization that was discovered using remote sensing is the gold associated with metachert in the Atmur
Desert.
Reducing Corrosion Rate by Welding DesignIJERD Editor
This document summarizes a study on reducing corrosion rates in steel through welding design. The researchers tested different welding groove designs (X, V, 1/2X, 1/2V) and preheating temperatures (400°C, 500°C, 600°C) on ferritic malleable iron samples. Testing found that X and V groove designs with 500°C and 600°C preheating had corrosion rates of 0.5-0.69% weight loss after 14 days, compared to 0.57-0.76% for 400°C preheating. Higher preheating reduced residual stresses which decreased corrosion. Residual stresses were 1.7 MPa for optimal X groove and 600°C
Router 1X3 – RTL Design and VerificationIJERD Editor
Routing is the process of moving a packet of data from source to destination and enables messages
to pass from one computer to another and eventually reach the target machine. A router is a networking device
that forwards data packets between computer networks. It is connected to two or more data lines from different
networks (as opposed to a network switch, which connects data lines from one single network). This paper,
mainly emphasizes upon the study of router device, it‟s top level architecture, and how various sub-modules of
router i.e. Register, FIFO, FSM and Synchronizer are synthesized, and simulated and finally connected to its top
module.
Active Power Exchange in Distributed Power-Flow Controller (DPFC) At Third Ha...IJERD Editor
This paper presents a component within the flexible ac-transmission system (FACTS) family, called
distributed power-flow controller (DPFC). The DPFC is derived from the unified power-flow controller (UPFC)
with an eliminated common dc link. The DPFC has the same control capabilities as the UPFC, which comprise
the adjustment of the line impedance, the transmission angle, and the bus voltage. The active power exchange
between the shunt and series converters, which is through the common dc link in the UPFC, is now through the
transmission lines at the third-harmonic frequency. DPFC multiple small-size single-phase converters which
reduces the cost of equipment, no voltage isolation between phases, increases redundancy and there by
reliability increases. The principle and analysis of the DPFC are presented in this paper and the corresponding
simulation results that are carried out on a scaled prototype are also shown.
Mitigation of Voltage Sag/Swell with Fuzzy Control Reduced Rating DVRIJERD Editor
Power quality has been an issue that is becoming increasingly pivotal in industrial electricity
consumers point of view in recent times. Modern industries employ Sensitive power electronic equipments,
control devices and non-linear loads as part of automated processes to increase energy efficiency and
productivity. Voltage disturbances are the most common power quality problem due to this the use of a large
numbers of sophisticated and sensitive electronic equipment in industrial systems is increased. This paper
discusses the design and simulation of dynamic voltage restorer for improvement of power quality and
reduce the harmonics distortion of sensitive loads. Power quality problem is occurring at non-standard
voltage, current and frequency. Electronic devices are very sensitive loads. In power system voltage sag,
swell, flicker and harmonics are some of the problem to the sensitive load. The compensation capability
of a DVR depends primarily on the maximum voltage injection ability and the amount of stored
energy available within the restorer. This device is connected in series with the distribution feeder at
medium voltage. A fuzzy logic control is used to produce the gate pulses for control circuit of DVR and the
circuit is simulated by using MATLAB/SIMULINK software.
Study on the Fused Deposition Modelling In Additive ManufacturingIJERD Editor
Additive manufacturing process, also popularly known as 3-D printing, is a process where a product
is created in a succession of layers. It is based on a novel materials incremental manufacturing philosophy.
Unlike conventional manufacturing processes where material is removed from a given work price to derive the
final shape of a product, 3-D printing develops the product from scratch thus obviating the necessity to cut away
materials. This prevents wastage of raw materials. Commonly used raw materials for the process are ABS
plastic, PLA and nylon. Recently the use of gold, bronze and wood has also been implemented. The complexity
factor of this process is 0% as in any object of any shape and size can be manufactured.
Spyware triggering system by particular string valueIJERD Editor
This computer programme can be used for good and bad purpose in hacking or in any general
purpose. We can say it is next step for hacking techniques such as keylogger and spyware. Once in this system if
user or hacker store particular string as a input after that software continually compare typing activity of user
with that stored string and if it is match then launch spyware programme.
A Blind Steganalysis on JPEG Gray Level Image Based on Statistical Features a...IJERD Editor
This paper presents a blind steganalysis technique to effectively attack the JPEG steganographic
schemes i.e. Jsteg, F5, Outguess and DWT Based. The proposed method exploits the correlations between
block-DCTcoefficients from intra-block and inter-block relation and the statistical moments of characteristic
functions of the test image is selected as features. The features are extracted from the BDCT JPEG 2-array.
Support Vector Machine with cross-validation is implemented for the classification.The proposed scheme gives
improved outcome in attacking.
Secure Image Transmission for Cloud Storage System Using Hybrid SchemeIJERD Editor
- Data over the cloud is transferred or transmitted between servers and users. Privacy of that
data is very important as it belongs to personal information. If data get hacked by the hacker, can be
used to defame a person’s social data. Sometimes delay are held during data transmission. i.e. Mobile
communication, bandwidth is low. Hence compression algorithms are proposed for fast and efficient
transmission, encryption is used for security purposes and blurring is used by providing additional
layers of security. These algorithms are hybridized for having a robust and efficient security and
transmission over cloud storage system.
Application of Buckley-Leverett Equation in Modeling the Radius of Invasion i...IJERD Editor
A thorough review of existing literature indicates that the Buckley-Leverett equation only analyzes
waterflood practices directly without any adjustments on real reservoir scenarios. By doing so, quite a number
of errors are introduced into these analyses. Also, for most waterflood scenarios, a radial investigation is more
appropriate than a simplified linear system. This study investigates the adoption of the Buckley-Leverett
equation to estimate the radius invasion of the displacing fluid during waterflooding. The model is also adopted
for a Microbial flood and a comparative analysis is conducted for both waterflooding and microbial flooding.
Results shown from the analysis doesn’t only records a success in determining the radial distance of the leading
edge of water during the flooding process, but also gives a clearer understanding of the applicability of
microbes to enhance oil production through in-situ production of bio-products like bio surfactans, biogenic
gases, bio acids etc.
Gesture Gaming on the World Wide Web Using an Ordinary Web CameraIJERD Editor
- Gesture gaming is a method by which users having a laptop/pc/x-box play games using natural or
bodily gestures. This paper presents a way of playing free flash games on the internet using an ordinary webcam
with the help of open source technologies. Emphasis in human activity recognition is given on the pose
estimation and the consistency in the pose of the player. These are estimated with the help of an ordinary web
camera having different resolutions from VGA to 20mps. Our work involved giving a 10 second documentary to
the user on how to play a particular game using gestures and what are the various kinds of gestures that can be
performed in front of the system. The initial inputs of the RGB values for the gesture component is obtained by
instructing the user to place his component in a red box in about 10 seconds after the short documentary before
the game is finished. Later the system opens the concerned game on the internet on popular flash game sites like
miniclip, games arcade, GameStop etc and loads the game clicking at various places and brings the state to a
place where the user is to perform only gestures to start playing the game. At any point of time the user can call
off the game by hitting the esc key and the program will release all of the controls and return to the desktop. It
was noted that the results obtained using an ordinary webcam matched that of the Kinect and the users could
relive the gaming experience of the free flash games on the net. Therefore effective in game advertising could
also be achieved thus resulting in a disruptive growth to the advertising firms.
Hardware Analysis of Resonant Frequency Converter Using Isolated Circuits And...IJERD Editor
-LLC resonant frequency converter is basically a combo of series as well as parallel resonant ckt. For
LCC resonant converter it is associated with a disadvantage that, though it has two resonant frequencies, the
lower resonant frequency is in ZCS region[5]. For this application, we are not able to design the converter
working at this resonant frequency. LLC resonant converter existed for a very long time but because of
unknown characteristic of this converter it was used as a series resonant converter with basically a passive
(resistive) load. . Here, it was designed to operate in switching frequency higher than resonant frequency of the
series resonant tank of Lr and Cr converter acts very similar to Series Resonant Converter. The benefit of LLC
resonant converter is narrow switching frequency range with light load[6] . Basically, the control ckt plays a
very imp. role and hence 555 Timer used here provides a perfect square wave as the control ckt provides no
slew rate which makes the square wave really strong and impenetrable. The dead band circuit provides the
exclusive dead band in micro seconds so as to avoid the simultaneous firing of two pairs of IGBT’s where one
pair switches off and the other on for a slightest period of time. Hence, the isolator ckt here is associated with
each and every ckt used because it acts as a driver and an isolation to each of the IGBT is provided with one
exclusive transformer supply[3]. The IGBT’s are fired using the appropriate signal using the previous boards
and hence at last a high frequency rectifier ckt with a filtering capacitor is used to get an exact dc
waveform .The basic goal of this particular analysis is to observe the wave forms and characteristics of
converters with differently positioned passive elements in the form of tank circuits.
Simulated Analysis of Resonant Frequency Converter Using Different Tank Circu...IJERD Editor
LLC resonant frequency converter is basically a combo of series as well as parallel resonant ckt. For
LCC resonant converter it is associated with a disadvantage that, though it has two resonant frequencies, the
lower resonant frequency is in ZCS region [5]. For this application, we are not able to design the converter
working at this resonant frequency. LLC resonant converter existed for a very long time but because of
unknown characteristic of this converter it was used as a series resonant converter with basically a passive
(resistive) load. . Here, it was designed to operate in switching frequency higher than resonant frequency of the
series resonant tank of Lr and Cr converter acts very similar to Series Resonant Converter. The benefit of LLC
resonant converter is narrow switching frequency range with light load[6] . Basically, the control ckt plays a
very imp. role and hence 555 Timer used here provides a perfect square wave as the control ckt provides no
slew rate which makes the square wave really strong and impenetrable. The dead band circuit provides the
exclusive dead band in micro seconds so as to avoid the simultaneous firing of two pairs of IGBT’s where one
pair switches off and the other on for a slightest period of time. Hence, the isolator ckt here is associated with
each and every ckt used because it acts as a driver and an isolation to each of the IGBT is provided with one
exclusive transformer supply[3]. The IGBT’s are fired using the appropriate signal using the previous boards
and hence at last a high frequency rectifier ckt with a filtering capacitor is used to get an exact dc
waveform .The basic goal of this particular analysis is to observe the wave forms and characteristics of
converters with differently positioned passive elements in the form of tank circuits. The supported simulation
is done through PSIM 6.0 software tool
Amateurs Radio operator, also known as HAM communicates with other HAMs through Radio
waves. Wireless communication in which Moon is used as natural satellite is called Moon-bounce or EME
(Earth -Moon-Earth) technique. Long distance communication (DXing) using Very High Frequency (VHF)
operated amateur HAM radio was difficult. Even with the modest setup having good transceiver, power
amplifier and high gain antenna with high directivity, VHF DXing is possible. Generally 2X11 YAGI antenna
along with rotor to set horizontal and vertical angle is used. Moon tracking software gives exact location,
visibility of Moon at both the stations and other vital data to acquire real time position of moon.
“MS-Extractor: An Innovative Approach to Extract Microsatellites on „Y‟ Chrom...IJERD Editor
Simple Sequence Repeats (SSR), also known as Microsatellites, have been extensively used as
molecular markers due to their abundance and high degree of polymorphism. The nucleotide sequences of
polymorphic forms of the same gene should be 99.9% identical. So, Microsatellites extraction from the Gene is
crucial. However, Microsatellites repeat count is compared, if they differ largely, he has some disorder. The Y
chromosome likely contains 50 to 60 genes that provide instructions for making proteins. Because only males
have the Y chromosome, the genes on this chromosome tend to be involved in male sex determination and
development. Several Microsatellite Extractors exist and they fail to extract microsatellites on large data sets of
giga bytes and tera bytes in size. The proposed tool “MS-Extractor: An Innovative Approach to extract
Microsatellites on „Y‟ Chromosome” can extract both Perfect as well as Imperfect Microsatellites from large
data sets of human genome „Y‟. The proposed system uses string matching with sliding window approach to
locate Microsatellites and extracts them.
Importance of Measurements in Smart GridIJERD Editor
- The need to get reliable supply, independence from fossil fuels, and capability to provide clean
energy at a fixed and lower cost, the existing power grid structure is transforming into Smart Grid. The
development of a smart energy distribution grid is a current goal of many nations. A Smart Grid should have
new capabilities such as self-healing, high reliability, energy management, and real-time pricing. This new era
of smart future grid will lead to major changes in existing technologies at generation, transmission and
distribution levels. The incorporation of renewable energy resources and distribution generators in the existing
grid will increase the complexity, optimization problems and instability of the system. This will lead to a
paradigm shift in the instrumentation and control requirements for Smart Grids for high quality, stable and
reliable electricity supply of power. The monitoring of the grid system state and stability relies on the
availability of reliable measurement of data. In this paper the measurement areas that highlight new
measurement challenges, development of the Smart Meters and the critical parameters of electric energy to be
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RF Energy Harvesting for Wireless Devices
1. International Journal of Engineering Research and Development
e-ISSN: 2278-067X, p-ISSN: 2278-800X, www.ijerd.com
Volume 11, Issue 04 (April 2015), PP.39-52
39
RF Energy Harvesting for Wireless Devices
R. Sandhya Lakshmi
R.V. College of Engineering, Bangalore.
Abstract:- Radio Frequency (RF) energy transfer and harvesting techniques have recently become alternative
methods to empower the next generation wireless networks. As this emerging technology enables proactive
energy replenishment of wireless devices, it is advantageous in supporting applications with quality of service
requirements. In this paper, some wireless power transfer methods, RF energy harvesting networks, various
receiver architectures and existing applications are presented. Finally, some open research directions are
envisioned.
Keywords:- RF Energy Harvesting, Simultaneous wireless information and power transfer (SWIPT), Receiver
power, Wireless power transfer, Power management module.
I. INTRODUCTION
Energy harvesting is a process in which energy from external sources like solar power, thermal energy,
wind energy etc., is captured and stored for small, wireless devices like those used in wearable electronics and
wireless sensor networks[1]. It is also called power harvesting or energy scavenging. The ambient energy may
come from stray electric or magnetic fields or radio waves from nearby electrical equipment, light, thermal
energy or kinetic energy such as vibration or motion of the device. The efficiency of conversion is usually low
and the power gathered is often in milli-watts or in microwatts but it is enough to recharge small micro-power
devices such as remote sensors. This technology is being developed to eliminate the need for battery
replacement or charging of such wireless devices.
Wireless power transmission is a collective term that refers to a number of different technologies for
transmitting power by means of time-varying electro-magnetic fields [5]. The technologies, listed in the table,
differ in a number of aspects like directivity, efficient power transmission, type of electromagnetic energy they
use. The current focus is to develop wireless systems to charge mobile and handheld computing devices such as
cell phones, digital music player and portable computers without being connected to a wall plug.
Wireless power uses much of the same fields and waves as wireless communication devices like radio,
which involves power transmitted without wires by electromagnetic fields, used in cell phones, radio, television
broadcasting, and Wi-Fi. In radio communication, the goal is to transmit information, so that the amount of
power reaching the receiver is unimportant as long as it maintains the required signal to noise ratio. In wireless
communication technologies, only tiny amounts of power reach the receiver. By contrast, in wireless power, the
amount of power received is the important thing, so the efficiency i.e., fraction of transmitted power that is
received, is a significant parameter [9]. For this reason wireless power technologies are more limited by
distance than wireless communication technologies.
Types of Field Regions
Electric and magnetic fields are created by charged particles in matter such as electrons. A Stationary
charge creates an electrostatic field in the space around it. A steady current of charges creates a static magnetic
field around it. These fields contain energy but they cannot carry power because they are static, but time-varying
fields can. Accelerating electric charges, such as are found in an alternating current of electrons in a wire, create
time-varying electric and magnetic fields in the space around them. These fields can exert oscillating forces on
the electrons in a receiving antenna, causing them to move back and forth which represents alternating current
which can be used to power a load.
The oscillating electric and magnetic fields surrounding moving electric charges in an antenna device
can be divided into two regions depending on distance from the antenna. The fields have different characteristics
in these regions, and different technologies are used for transmitting power.
2. RF Energy Harvesting for Wireless Devices
40
Table 1.1 Different wireless power technologies
Technology Range Directivity Frequency Devices Applications
Inductive
Coupling
Short Low Hz – MHz Wire Coils Induction Stove tops
Resonant
Inductive
Coupling
Mid Low MHz– GHz Tuned Wire
Coils, lumped
elements
resonators
RFID, Smart Cards
Capacitive
Coupling
Short Low KHz –MHz Electrodes Power routing in large scale
integrated circuits
Magneto
dynamic
Short Hz Rotating Magnets Charging electric vehicles
Microwaves Long High GHz Parabolic Dishes,
Phased Arrays,
Rectannas
Solar power satellite
Light Waves Long High THz Lasers,
Photocells, lenses,
Telescopes
Power drone aircraft,
Powering space elevator
climbers
Near-field or non-radiative region – The area within about 1 wavelength of the antenna is the near field
region. In this region the oscillating electric and magnetic fields are separate and power can be transferred via
electric fields by capacitive coupling between metal electrodes, or via magnetic fields by inductive coupling
between coils of the wire. These fields are not radiative, that is the energy stays within a short distance of the
transmitter. If there is no receiving device or absorbing material within their limited range, no power leaves the
transmitter. The range of these fields is short, and depends on the size and shape of the antenna devices, which
are usually coils of wire. The fields, and thus the power transmitted, decrease exponentially with distance, so if
the distance between the two antennas is much larger than the diameter of the antennas, very little power will be
received. Therefore, these techniques cannot be used for long distance power transmission.
Resonance, such as resonant inductive coupling, can increase the coupling between the antennas
greatly, allowing efficient transmission at somewhat greater distances, although the fields still decrease
exponentially. Therefore the range of near-field devices can be divided into two categories:
Short range - up to about one antenna diameter. This is the range over which ordinary non-resonant
capacitive or inductive coupling can transfer practical amounts of power.
Mid-range - up to 10 times the antenna diameter. This is the range over which resonant capacitive or
inductive coupling can transfer practical amounts of power.
Far-field or radiative region - Beyond about 1 wavelength of the antenna, the electric and magnetic
fields are perpendicular to each other and propagate as an electromagnetic wave such as radio waves,
microwaves or light waves. This part of the energy is radiative, that is it leaves the antenna whether or not there
is a receiver to absorb it. The portion of energy which does not strike the receiving antenna is dissipated and lost
to the system. The amount of power emitted as electromagnetic waves by an antenna depends on the ratio of the
antenna's size to the wavelength of the waves. Antennas about the same size as the wavelength such as
monopole or dipole antennas, radiate power efficiently, but the electromagnetic waves are radiated in all
directions, so if the receiving antenna is far away, only a small amount of the radiation will hit it. Therefore
these can be used for short range, inefficient power transmission but not for long range transmission.
II. NEAR-FIELD OR NON-RADIATIVE TECHNIQUES
The near-field components of electric and magnetic fields die out quickly beyond a distance of about
one diameter of the antenna. Since power is proportional to the square of the field strength, the power
transferred decreases with the sixth power of the distance or 60 dB per decade. In other words, doubling the
distance between transmitter and receiver causes the power received to decrease by a factor of 26
= 64.
Inductive coupling
The electrodynamic induction wireless transmission technique relies on the use of a magnetic field
generated by an electric current to induce a current in a second conductor. This effect occurs in the
electromagnetic near field, with the secondary in close proximity to the primary. As the distance from the
3. RF Energy Harvesting for Wireless Devices
41
primary is increased, more and more of the primary's magnetic field misses the secondary. Even over a
relatively short range the inductive coupling is grossly inefficient, wasting much of the transmitted energy [3].
Fig 1.1: Inductive wireless power system
This action of an electrical transformer is the simplest form of wireless power transmission. The
primary coil and secondary coil of a transformer are not directly connected; each coil is part of a separate
circuit. Energy transfer takes place through mutual induction. Principal functions are stepping the primary
voltage either up or down and electrical isolation. Mobile phone and electric toothbrush battery chargers,
Induction cookers are examples of this principle. The main drawback to this basic form of wireless transmission
is short range. The receiver must be directly adjacent to the transmitter or induction unit in order to efficiently
couple with it.
Common uses of resonance-enhanced electrodynamic induction are charging the batteries of portable
devices such as laptop computers and cell phones, medical implants and electric vehicles. A localized charging
technique selects the appropriate transmitting coil in a multilayer winding array structure. Resonance is used in
both the wireless charging pad and the receiver module to maximize energy transfer efficiency. Battery-powered
devices fitted with a special receiver module can then be charged simply by placing them on a wireless charging
pad.
This technology is also used for powering devices with very low energy requirements, such as RFID
patches and contactless smartcards. Instead of relying on each of the many thousands or millions of RFID
patches or smartcards to contain a working battery, electrodynamic induction can provide power only when the
devices are needed.
CAPACITIVE COUPLING
In capacitive coupling, the dual of inductive coupling, power is transmitted by electric
fields between electrodes such as metal plates. The transmitter and receiver electrodes form a capacitor, with the
intervening space as the dielectric. An alternating voltage generated by the transmitter is applied to the
transmitting plate, and the oscillating electric field induces an alternating potential on the receiver plate
by electrostatic induction, which causes an alternating current to flow in the load circuit. The amount of power
transferred increases with the frequency and the capacitance between the plates, which is proportional to the
area of the smaller plate and (for short distances) inversely proportional to the separation.
Capacitive coupling has only been used practically in a few low power applications, because the very
high voltages on the electrodes required to transmit significant power can be hazardous, and can cause
unpleasant side effects such as noxious ozone production [5]. In addition, in contrast to magnetic fields, electric
fields interact strongly with most materials, including the human body, due to dielectric
polarization. Intervening materials between or near the electrodes can absorb the energy, in the case of humans
possibly causing excessive electromagnetic field exposure. However capacitive coupling has a few advantages
over inductive. The field is largely confined between the capacitor plates, reducing interference, which in
inductive coupling requires heavy ferrite flux confinement cores. Also, alignment requirements between the
transmitter and receiver are less critical. Capacitive coupling has recently been applied to charging battery
powered portable devices and is being considered as a means of transferring power between substrate layers in
integrated circuits.
MAGNETO-DYNAMIC COUPLING
In this method, power is transmitted between two rotating armatures, one in the transmitter and one in
the receiver, which rotate synchronously, coupled together by a magnetic field generated by permanent
4. RF Energy Harvesting for Wireless Devices
42
magnets on the armatures. The transmitter armature is turned either by or as the rotor of an electric motor, and
its magnetic field exerts torque on the receiver armature, turning it. The magnetic field acts like a mechanical
coupling between the armatures. The receiver armature produces power to drive the load, either by turning
an electric generator or by using the receiver armature as the rotor in an induction generator [3].
This device has been proposed as an alternative to inductive power transfer for noncontact charging
of electric vehicles. A rotating armature embedded in a garage floor or curb would turn a receiver armature in
the underside of the vehicle to charge its batteries. It is claimed that this technique can transfer power over
distances of 10 to 15 cm with high efficiency, over 90%. Also, the low frequency stray magnetic fields
produced by the rotating magnets produce less electromagnetic interference to nearby electronic devices than
the high frequency magnetic fields produced by inductive coupling systems.
III. FAR-FIELD OR RADIATIVE TECHNIQUES
Far field methods achieve longer ranges, often multiple kilometer ranges, where the distance is much
greater than the diameter of the device. The main reason for longer ranges with radio wave and optical devices
is the fact that electromagnetic radiation in the far-field can be made to match the shape of the receiving area
using high directivity antennas or well-collimated laser beams. The maximum directivity for antennas is
physically limited by diffraction [12].
In general, visible light and microwaves are the forms of electromagnetic radiation best suited to
energy transfer. The dimensions of the components may be dictated by the distance from transmitter to receiver,
the wavelength and the Rayleigh criterion or diffraction limit, used in standard radio frequency antenna design,
which also applies to lasers. Electromagnetic radiation experiences less diffraction at shorter wavelengths
(higher frequencies).
Microwave power beaming can be more efficient than lasers, and is less prone toatmospheric attenuation caused
by dust or water vapor.
Microwaves
Power transmission via radio waves can be made more directional, allowing longer distance power
beaming, with shorter wavelengths of electromagnetic radiation, typically in
the microwave range. A rectanna may be used to convert the microwave energy back into electricity. Rectenna
conversion efficiencies exceeding 95% have been realized. Power beaming using microwaves can be used to
transmit the energy from orbiting solar power satellites to Earth [5].
Power beaming by microwaves has the difficulty that for most space applications the required aperture
sizes are very large due to diffraction limiting antenna directionality. These sizes can be somewhat decreased by
using shorter wavelengths, although short wavelengths may have difficulties with atmospheric absorption and
beam blockage by rain or water droplets [13].
Lasers
In the case of electromagnetic radiation closer to the visible region of the spectrum (tens
of micrometers to tens of nanometers), power can be transmitted by converting electricity into a laser beam that
is then pointed at a photovoltaic cell. This mechanism is generally known as "power beaming" because the
power is beamed at a receiver that can convert it to electrical energy.
Compared to other wireless methods:
Collimated monochromatic wavefront propagation allows narrow beam cross-section area for
transmission over large distances.
Compact size: solid state lasers fit into small products.
No radio frequency interference to existing radio communication such as Wi-Fi and cell phones.
Access control: only receivers hit by the laser receive power.
Drawbacks include:
Laser radiation is hazardous. Low power levels can blind humans and other animals. High power levels can
kill through localized spot heating.
Conversion between electricity and light is inefficient. Photovoltaic cells achieve only 40%–50% efficiency.
Atmospheric absorption, and absorption and scattering by clouds, fog, rain, etc., cause up to 100% losses.
Requires a direct line of sight with the target.
Laser power beaming technology has been mostly explored in military weapons and aerospace applications
and is now being developed for commercial and consumer electronics [5].
5. RF Energy Harvesting for Wireless Devices
43
IV. RF ENERGY HARVESTING NETWORKS
2.1 Architecture:
A typical centralized architecture of an RF-EHN, as shown in Fig.2.1, has three major components, i.e.,
information gateways, the RF energy sources and the network nodes/devices. The information gateways are
generally known as base stations, wireless routers and relays. The RF energy sources can be either dedicated RF
energy transmitters or ambient RF sources (e.g., TV towers). The network nodes are the user equipment that
communicates with the information gateways. Typically, the information gateways and RF energy sources have
continuous and fixed electric supply, while the network nodes harvest energy from RF sources to support their
operations. In some cases, the information gateway and RF energy source can be the same. As shown in Fig.2,
the solid arrow lines represent information flows, while the dashed arrow lines mean energy flows [14].
The information gateway has an energy harvesting zone and an information transmission zone
represented by the dashed circles in Fig. 2.1. The devices in the energy harvesting zone are able to harvest RF
energy from the information gateway. The devices in the information transmission zone can successfully decode
information transmitted from the gateway. Generally, the operating power of the energy harvesting component
is much higher than that of the information decoding component. Therefore, the energy harvesting zone is
smaller than the information transmission zone.
Fig. 2.1. A general architecture of an RF energy harvesting network.
Figure 2.2 also shows the block diagram of a network node with RF energy harvesting capability. An
RF energy harvesting node consists of the following major components:
• The application,
• A low-power microcontroller, to process data from the application,
• A low-power RF transceiver, for information transmission or reception,
• An energy harvester, composed of an RF antenna, an impedance matching, a voltage multiplier and a capacitor,
to collect RF signals and convert them into electricity,
• A power management module, which decides whether to store the electricity obtained from the RF energy
harvester or to use it for information transmission immediately, and
• An energy storage or battery.
The power management module can adopt two methods to control the incoming energy flow, i.e.,
harvest-use and harvest-store-use. In the harvest-use method, the harvested energy is immediately used to
power the network node. Therefore, for the network node to operate normally, the converted electricity has to
constantly exceed the minimum energy demand of the network node. Otherwise, the node will be disabled. In
the harvest-store-use method, the network node is equipped with energy storage or a rechargeable battery that
stores the converted electricity. Whenever the harvested energy is more than that of the node’s consumption, the
excess energy will be stored in the battery for future use.
Figure 2.2 illustrates the block diagram of an RF energy harvester.
6. RF Energy Harvesting for Wireless Devices
44
• The antenna can be designed to work on either single frequency or multiple frequency bands, in which the
network node can harvest from a single or multiple sources simultaneously. Nevertheless, the RF energy
harvester typically operates over a range of frequencies since energy density of RF signals is diverse in
frequency.
• The impedance matching is a resonator circuit operating at the designed frequency to maximize the power
transfer between the antenna and the multiplier. The efficiency of the impedance matching is high at the
designed frequency.
• The main component of the voltage multiplier is diodes of the rectifying circuit which converts RF signals (AC
signals in nature) into DC voltage. Generally, higher conversion efficiency can be achieved by diodes with
lower built-in voltage. The capacitor ensures to deliver power smoothly to the load. Additionally, when RF
energy is unavailable, the capacitor can also serve as a reserve for a short duration.
The efficiency of the RF energy harvester depends on the efficiency of the antenna, the accuracy of the
impedance matching between the antenna and the voltage multiplier, and the power efficiency of the voltage
multiplier that converts the received RF signals to DC voltage.
For the general node architecture introduced above, the network node has the separate RF energy
harvester and RF transceiver. Therefore, the node can perform energy harvesting and data communication
simultaneously. In other words, this architecture supports both in-band and out-of-band RF energy harvesting.
In the in-band RF energy harvesting, the network node can harvest RF energy from the same frequency band as
that of data communication. By contrast, in the out-of-band RF energy harvesting, the network node harvests RF
energy from the different frequency band from that used for data communication. Since RF signals can carry
energy as well as information, theoretically RF energy harvesting and information reception can be performed
from the same RF signal input. This is referred to as the simultaneous wireless information and power transfer
(SWIPT) concept. This concept allows the information receiver and RF energy harvester to share the same
antenna or antenna array [16].
Fig. 2.2. A general architecture of an RF energy harvesting device
2.2 RF Energy Propagation Models:
In RF energy harvesting, the amount of energy that can be harvested depends on the transmit power,
wavelength of the RF signals and the distance between an RF energy source and the harvesting node. The
harvested RF power from a transmitter in free space can be calculated based on the Friis equation as follows:
= (2.1)
Where PR is the received power, PT is the transmitted power, L is the path loss factor, GT is the transmit antenna
gain, GR is the receive antenna gain, λ is the wavelength emitted, and d is the distance between the transmit
antenna and the receiver antenna.
The free-space model has the assumption that there is only one single path between a transmitter and a
receiver. However, due to RF scattering and reflection, a receiver may collect RF signals from a transmitter
from multiple paths. The two ray ground model captures this phenomenon by considering the received RF
signals pass through a line-of-sight path and a reflected path separately. The harvested RF power from a
transmitter according to the two ray ground model is given by
= (2.2)
Where ht and hr are the heights of the transmit and receive antennas, respectively.
7. RF Energy Harvesting for Wireless Devices
45
The above two deterministic models characterize RF propagation based on determinate parameters. By
contrast, probabilistic models draw parameters from a distribution, while allows a more realistic modeling. A
practical and widely adopted probabilistic model is a Rayleigh model, which represents the situation when there
is no line-of-sight channel between a transmitter and receiver. In the Rayleigh model, we have
PR = PR
det
* 10L
* log(1 – unif(0,1)) (2.3)
Where PR
det
represents the received RF power calculated by a deterministic model. The path loss factor L is
defined as L = −α log 10(d/d0), where d0 is a reference distance. unif(0, 1) denotes a random number generated
following uniform distribution between 0 and 1.
The aggregated harvested RF energy can be calculated based on the adoption of the network model and
RF propagation model.
2.3 RF Energy Harvesting Technique:
Unlike energy harvesting from other sources, such as solar, wind and vibrations, RF energy harvesting
has the following characteristics:
• RF sources can provide controllable and constant energy transfer over distance for RF energy harvesters.
• In a fixed RF-EHN, the harvested energy is predictable and relatively stable over time due to fixed distance.
• Since the amount of harvested RF energy depends on the distance from the RF source, the network nodes in
the different locations can have significant difference in harvested RF energy.
The RF sources can mainly be classified into two types, i.e. dedicated RF sources and ambient RF
sources.
1) Dedicated RF sources: Dedicated RF sources can be deployed to provide energy to network nodes when
more predictable energy supply is needed. The dedicated RF sources can use the license-free ISM frequency
bands for RF energy transfer. The Power caster transmitter operating on 915MHz with 1W or 3W transmit
power is an example of a dedicated RF source, which has been commercialized. However, deploying the
dedicated RF sources can incur high cost for the network. Moreover, the output power of RF sources must be
limited by regulations, such as Federal Communications Commission (FCC) due to safety and health concern of
RF radiations. For example, in the 900MHz band, the maximum threshold is 4W. Even at this highest setting,
the received power at a moderate distance of 20m is attenuated down to only 10 μW. Due to this limitation,
many dedicated RF sources may need to be deployed to meet the user demand. As the RF energy harvesting
process with dedicated RF sources is fully controllable, it is more suitable to support applications with QoS
constraints. The dedicated RF sources could be mobile, which can periodically move and transfer RF energy to
network nodes.
2) Ambient RF sources: Ambient RF sources refer to the RF transmitters that are not intended for RF energy
transfer. This RF energy is essentially free. The transmit power of ambient RF sources varies significantly, from
around 106W for TV tower, to about 10W for cellular and RFID systems, to roughly 0.1W for mobile
communication devices and WiFi systems. Ambient RF sources can be further classified into static and dynamic
ambient RF sources [2].
• Static ambient RF sources: Static ambient RF sources are the transmitters which release relatively stable
power over time, such as TV and radio towers. Although the static ambient RF sources can provide predictable
RF energy, there could be long-term and short-term fluctuations due to service schedule (e.g., TV and radio) and
fading, respectively. Normally, the power density of ambient RF sources at different frequency bands is small.
As a result, a high gain antenna for all frequency bands is required. Moreover, the rectifier must also be
designed for wideband spectrum. When the distribution of ambient RF sources exhibits stronger repulsion,
larger RF energy harvesting rate can be achieved at the sensor [2].
• Dynamic ambient RF sources: Dynamic ambient RF sources are the RF transmitters that work periodically or
use time-varying transmit power (e.g., a WiFi access point and licensed users in a cognitive radio network). The
RF energy harvesting from the dynamic ambient RF sources has to be adaptive and possibly intelligent to search
for energy harvesting opportunities in a certain frequency range. An example is the energy harvesting from
dynamic ambient RF sources in a cognitive radio network. A secondary user can harvest RF energy from nearby
transmitting primary users, and can transmit data when it is sufficiently far from primary users or when the
nearby primary users are idle [2].
The energy harvesting rate varies significantly depending on the source power and distance. Typically,
the amount of harvested energy is in order of micro-watts, which is sufficient for powering small devices [10].
8. RF Energy Harvesting for Wireless Devices
46
2.4 Applications of RF Energy Harvesting:
Wireless sensor networks have become one of the most widely applied applications of RF-EHNs. An
RF energy harvester can be used in a sensor node to supply energy. The RF-powered devices also have
attractive healthcare and medical applications such as wireless body network. Benefiting from RF energy
harvesting, low-power medical devices can achieve real-time work-on-demand power from dedicated RF
sources, which further enables a battery-free circuit with reduced size [11]. The antenna of a body device circuit
dual-band operating at GSM 900 and GSM 1800 achieves gains of the order 1.8-2.06 dBi and efficiency of
77.6−84%. Another RF energy harvesting application that has caught intensive research investigation is RFID,
widely used for identification, tracking, and inventory management. Recent developments in low-power circuit
and RF energy harvesting technology can extend the lifetime and operation range of conventional RFID tags. In
particular, RFID tags, instead of relying on the readers to activate their circuits passively, can harvest RF energy
and perform communication actively. Consequently, RFID technology has evolved from simple passive tags to
smart tags with newly introduced features such as sensing, on-tag data processing and intelligent power
management. Other than these applications, devices powered by ambient RF energy are attracting increasingly
research attention. For example, an information rate of 1 kbps can be achieved between two prototype devices
powered by ambient RF signals, at the distance of up to 2.5 feet and 1.5 feet for outdoors and indoors,
respectively. Many implementations of battery-free devices can be powered by ambient energy from WiFi,
GSM and DTV bands as well as ambient mobile electronic devices.
Additionally, RF energy harvesting can be used to provide charging capability for a wide variety of
low-power mobile devices such as electronic watches, hearing aids, and MP3 players, wireless keyboard and
mouse, as most of them consume only micro-watts to milli-watts range of power [11].
V. CIRCUIT DESIGNS OF RF ENERGY HARVESTING DEVICES
This section introduces some background related to the hardware circuit designs of RF energy
harvesting devices.
3.1. Circuitry Implementations
There have been a large number RF energy harvester implementations based on various different
technologies such as CMOS, HSMS and SMS. Most of the implementations are based on the CMOS technology.
Generally, to achieve 1V DC output, -22 dBm to -14 dBm harvested RF power is required. Though CMOS
technology allows a lower minimum RF input power, the peak RF-to-DC conversion efficiency is usually
inferior to that of HSMS technology. The efficiency above 70% can be achieved when the harvested power is
above -10 dBm. For RF energy harvesting at a relatively high power (e.g., 40 dBm/10W), SMS technology can
be adopted. In particular, 30V output voltage is achieved at 40 dBm input RF power with 85% conversion
efficiency. However, when the harvested RF power is low, the conversion efficiency is low. For example, only
10% as input power is -10 dBm [15].
3.2. Antenna Design
An antenna is responsible for capturing RF signals. Miniaturised size and high antenna gain are the
main aims of antenna technology. Antenna arrays are effective in increasing the capability for low input power.
However, a tradeoff exists between antenna size and performance [4].
3.3. Matching Network
The crucial task of matching network is to reduce the transmission loss from an antenna to a rectifier
circuit and increase the input voltage of a rectifier circuit. To this end, a matching network is usually made with
reactive components such as coils and capacitors that are not dissipative. Maximum power transfer can be
realized when the impedance at the antenna output and the impedance of the load are conjugates of each other.
This procedure is known as impedance matching. Currently, there exist three main matching network circuits
designed for RF energy harvesting, i.e., transformer, shunt inductor, LC network [4].
3.4. Rectifier
The function of a rectifier is to convert the input RF signals (AC type) captured by an antenna into DC
voltage. A major challenge of the rectifier design is to generate a battery-like voltage from very low input RF
power. Generally, there are three main options for a rectifier, which are a diode, a bridge of diodes and a voltage
rectifier multiplier.
The diode is the main component of a rectifier circuit. The rectification performance of a rectifier
mainly depends on the saturation current, junction capacitance and its conduction resistance of the diode. The
circuit of a rectifier, especially the diode, determines the RF-to-DC conversion efficiency. The most commonly
used diode for rectennas is silicon Schottky barrier diodes. Generally, a diode with a lower built-in voltage can
9. RF Energy Harvesting for Wireless Devices
47
achieve a higher rectifying efficiency. This is because larger voltage will result in significantly more harmonic
signals due to the nonlinear characteristics of the diode, thus notably decreasing the rectifying efficiency [15].
3.5. Receiver Architecture Design
The traditional information receiver architecture designed for information reception may not be optimal
for SWIPT [6]. The reason is because information reception and RF energy harvesting works on very different
power sensitivity (e.g., -10 dBm for energy harvesters versus -60 dBm for information receivers). Currently,
there are four typical types of receiver architectures.
• Separated Receiver Architecture: Separated receiver architecture, also known as antenna-switching, equips an
energy harvester and information receiver with independent antennas so that they observe different channels.
Figure 3.1 shows the model for the separated receiver architecture. The antenna array is divided into two sets
with each connected to the energy harvester or the information receiver. Consequently, the architecture allows
performing energy harvesting and information decoding independently and concurrently. The antenna-switching
scheme can be used to optimize the performance of the separated receiver architecture.
Fig. 3.1. Seperated Receiver Architecture
• Co-located Receiver Architecture: The co-located receiver architecture lets an energy harvester and an
information receiver share the same antenna so that they observe the same channel. As a single antenna can be
adopted, the co-located receiver architecture is able to enable a smaller size compared to the separated receiver
architecture. This architecture can be categorized into two models, i.e., time-switching and power-splitting
architectures. The time-switching architecture, as shown in Fig. 3.2, allows the network node to switch and use
either the information receiver or the RF energy harvester for the received RF signals at a time. When a time
switching receiver j is working in the energy harvesting mode, the power harvested from source i can be
calculated as follows:
Pj,i = ηPi│hi,j│2
(3.1)
where η denotes the energy harvesting efficiency factor, Pi is the transmit power at source i, and hi,j denotes the
channel gain between the source i and receiver j. Let W and σ2
denote the transmission bandwidth and noise
power, respectively. When the time-switching receiver j working in the information decoding mode, the
maximum information decoding rate from source i is
Rj,i = W log(1 + Pi|hi,j|2
/σ2
) (3.2)
Fig. 3.2. Time Switching Architecture
10. RF Energy Harvesting for Wireless Devices
48
In the power-splitting architecture, as shown in Fig. 3.3, the received RF signals are split into two
streams for the information receiver and RF energy harvester with different power levels [7]. Let θj ϵ [0, 1]
denote the power-splitting coefficient for receiver j, i.e., θj is the fraction of RF signals used for energy
harvesting. Similarly, the power of harvested RF energy at a power-splitting receiver j from source i can be
calculated as follows:
Pj,i = _Pi|hi,j|2
θj (3.3)
Let σ2
sp denote the power of signal processing noise. The maximum information decoding rate at the
power splitting receiver j decoded from source i is
Rj,i = W log(1 + (1 – θi)Pi|hi,j |2
/(σ2
+ σ2
sp)) (3.4)
In practice, power splitting is based on a power splitter and time switching requires a simpler switcher.
Power-splitting achieves better tradeoffs between information rate and amount of RF energy transferred.
Fig. 3.3. Power Splitting Architecture
• Integrated Receiver Architecture: In the integrated receiver architecture, the implementation of RF-to-
baseband conversion for information decoding, is integrated with the energy harvester via the rectifier.
Therefore, this architecture allows a smaller form factor. Figure 3.4 demonstrates the model for integrated
receiver architecture. The RF flow controller can also adopt a switcher or power splitter, like in the co-located
receiver architecture. However, the difference is that the switcher and power splitter are adopted in the
integrated receiver architecture.
Fig. 3.4. Integrated Receiver Architecture
• Ideal Receiver Architecture: The ideal receiver architecture assumes that the receiver is able to extract the RF
energy from the same signals used for information decoding. However, this assumption is not realistic in
practice. The current circuit designs are not yet able to extract RF energy directly from the decoded information
carrier. In other words, any energy carried by received RF signals sent for an information receiver is lost during
the information decoding processing. When the circuit power consumptions are relatively small compared with
the received signal power, the integrated receiver architecture outperforms the co-located receiver architecture at
high harvested energy region, whereas the co-located receiver architecture is superior at low harvested energy
region. When the circuit power consumption is high, the integrated receiver architecture performs better. For a
11. RF Energy Harvesting for Wireless Devices
49
system without minimum harvested energy requirement, the integrated receiver achieves higher information rate
than that of the separated receiver at short transmission distances.
With an antenna array, the dual-antenna receiver architecture can be adopted. As shown in Fig.3.5, a
combiner is adopted to coherently combine the input RF signals for enhancement of the received power. This
architecture can be easily extended to the case with a larger number of antennas and the case with time-
switching operation.
Fig. 3.5. An architecture for Dual antenna Receiver
VI. FUTURE DIRECTIONS AND PRACTICAL CHALLENGES
A. Distributed Energy Beamforming
Distributed energy beamforming enables a cluster of distributed energy sources to cooperatively
emulate an antenna array by transmitting RF energy simultaneously in the same direction to an intended energy
harvester for better diversity gains. The potential energy gains at the receiver from distributed energy
beamforming are expected to be the same as that from the well-known information beamforming. However,
challenges arise in the implementation, e.g., time synchronization among energy sources and coordination of
distributed carriers in phase and frequency so that RF signals can be combined constructively at the receiver
[20].
B. Interference Management
Some of the existing interference management techniques are interference alignment and interference
cancellation, attempt to avoid or mitigate interference through spectrum scheduling. However, with RF energy
harvesting, harmful interference can be turned into useful energy through a scheduling policy. In this context,
how to mitigate interference as well as facilitate energy transfer, which may be conflicting, is the problem to be
addressed. Furthermore, the scheduling policy can be combined with power management schemes for further
improvement in energy efficiency.
C. Energy Trading
In RF-EHNs, RF energy becomes a valuable resource. The RF energy market can be established to
economically manage this energy resource jointly with radio resource. For example, wireless charging service
providers may act as RF energy suppliers to meet the energy demand from network nodes. The wireless energy
service providers can decide on pricing and guarantee the quality of charging service. One of the efficient
approaches in this dynamic market is to develop demand side management, which allows the service providers
and network nodes to interact like in smart grid, to guarantee energy efficiency and reliability. However, the
issues related to the amount of RF energy and price at which they are willing to trade while optimizing the
trade-off between the revenue and cost must be investigated.
D. Effect of Mobility
Network nodes, RF sources, and information gateway can be mobile. Therefore, mobility becomes an
important factor for RF energy harvesting and information transmission. The major issue is due to the fact that
the energy harvesting and information transmission performances become time-varying, and resource allocation
has to be dynamic and adaptive.
When compared, impact of mobile RF source under two different mobility models, namely center-
tocenter mobility (CM) model and around edges moving (EM) model with the focus on the energy gain at
12. RF Energy Harvesting for Wireless Devices
50
receivers. The trade-off between transmit power and distance is explored, taking the energy loss during
movement into account. It is found that CM yields better network performance in small networks with high
node density. By contrast, EM yields better performance in large networks with low node density.
E. Network Coding
Network coding is well-known to be energy efficient in information transmission. With network coding,
senders are allowed to transmit information simultaneously. This property, especially in large-scale network,
increases the amount of RF energy that can be harvested. During the time slots when relays or senders are not
transmitting, they can harvest ambient RF signals. The lifetime of the network for a two-way relay network with
network coding can be increased up to 70% by enabling RF energy harvesting. From the perspective of network
lifetime, more diverse network models and network coding schemes, such as physical-layer network coding and
analogy network coding, are worth to be explored. Intuitively, taking advantage of the broadcast nature of RF
signals to reuse some of the dissipated energy can lead to energy saving. However, theoretically, whether RF
energy harvesting will increase the upper bound of energy gain or not and how much exactly the bound will
increase still require further investigation.
F. Impact on Health
It has long been recognized that intense RF exposure can cause heating of materials with finite
conductivity, including biological tissues. Some effects to genes are noticed when the RF power reaches the
upper bound of international security levels. Although there are many existing studies on the health risks of
mobile phones, little effort has been made for investigation on health effect caused by a dedicated RF charger,
which can release much higher power. Thus, there is a need to address the safety concerns on deploying RF
chargers [18].
G. Practical Challenges
Due to the inverse-square law that the power density of RF waves decreases proportionally to the
inverse of the square of the propagation distance, practical RF energy transfer and harvesting that complies to
FCC regulations is limited to a local area. For example, the FCC allows operation up to 4W equivalent
isotropically radiated power. However, to realize 5.5μW energy transfer rate with a 4W power source, only the
distance of 15 meters is possible.
Other than transfer distance, RF energy harvesting rate is also largely affected by the direction and gain
of the receive antennas. Therefore, to improve the energy harvesting efficiency, devising a high gain antenna
(e.g., based on materials and geometry) for a wide range of frequency is an important research issue [19].
Impedance mismatching occurs when the input resistance and reactance of the rectifier do not equal to
that of the antenna. In this context, the antenna is not able to deliver all the harvested power to the rectifier. Thus,
impedance variations (e.g., introduced by on-body antennas) can severely degrade the energy conversion
efficiency. There is a need to develop circuit design techniques that automatically tune the parameters to
minimize impedance mismatch.
The RF-to-DC conversion efficiency depends on the density of harvested RF power. Improving the RF-
to-DC conversion efficiency at low harvested power input is important. Moreover, realizing a high-efficient low
power DC-to-DC converter, which converts a source of DC from a voltage level to another would be another
effort to achieve highly efficient RF energy harvesting.
RF energy harvesting components need to be small enough to be embedded in low-power devices. For
example, the size of an RF-powered sensor should be smaller than or comparable to that of a battery-power
sensor. An RF energy harvesting component may require an independent antenna, matching network and
rectifier. The antenna size has a crucial impact on an energy harvesting rate. Additionally, high voltage at the
output of a rectifier requires very high impedance loads (e.g., 5M), which is a function of the length of the
impedance. Thus, it is challenging to reduce the size of embedded devices while maintaining high energy
harvesting efficiency.
Without line-of-sight for RF waves from an RF source to an energy harvester, the considerable energy
transfer loss is expected. Therefore, the RF energy source must be optimally placed to support multiple receivers
to be charged. Moreover, in a mobile environment, the mobility of receivers and energy sources can affect the
RF energy transfer significantly.
The sensitivity of an information receiver is typically much higher than that of an RF energy harvester.
Consequently, a receiver located at a distance away from an RF transmitter may be able only to decode
information and fail to extract energy from the RF signals. In this case, any SWIPT scheme cannot be used
efficiently. Therefore, improving the sensitivity of RF energy harvesting circuit is crucial.
For RF-powered devices, as the transmit power is typical low, multiple antennas can be adopted to
improve the transmission efficiency. However, larger power consumption comes along when the number of
13. RF Energy Harvesting for Wireless Devices
51
antennas increases. Thus, there exists a trade off between the transmission efficiency and power consumption.
The scheme to optimize this trade-off needs to be developed. This issue becomes more complicated in a
dynamic environment, e.g., with varying energy harvesting rate.
As RF-powered devices typically have a strict operation power constraint, it is not practical to support
high computation algorithms. Any schemes, such as modulation and coding, receiver operation policy and
routing protocol, to be adopted need to be energy-efficient and low-power. Hence, power consumption is always
a serious concern in RF-powered devices, which may require the re-design of existing schemes and algorithms
for conventional networks.
VII. CONCLUSIONS
The RF-EHNs is a far field or radiative technique which uses harvest-use or harvest-store-use method
for managing the power. The RF Sources for energy harvesting are dedicated RF Sources and dynamic ambient
RF sources. Different receiver architectures like separated receiver, co-located receivers, integrated receiver
architectures can be used for receiving the power depending on the application. Some of the applications of RF-
EHNs are Wireless sensor networks, wireless body network, RFID tags and charging for a wide variety of low
power mobile devices. Some of the open design issues are Distributed Energy beamforming, interference
management, network coding etc. Impedance matching, Sensitivity of the receiver, transmission efficiency are
the practical challenges that are to be looked up on when designing RF energy harvester.
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