This document discusses electromagnetic radiation and antenna fundamentals. It begins by defining an antenna as a transducer between transmission lines and the surrounding medium that allows efficient launching of electromagnetic waves. The key characteristics of antennas like frequency, mounting location, gain, polarization, and efficiency are discussed. The document then covers topics such as radiation patterns, directivity, power gain, near fields, far fields, and polarization. Dipole antennas and the Friis transmission equation are also summarized.
This document discusses various types of antennas and antenna arrays. It begins by describing common antenna types including helical antennas, horn antennas, and parabolic reflector antennas. It then discusses how antenna arrays work, noting that they are composed of multiple similar radiating elements whose spacing and excitation determine the array's properties. Examples of linear and 2D arrays are provided. The document also summarizes different array configurations and beamforming techniques as well as applications such as smart antennas and adaptive arrays. Key benefits of arrays like controlling radiation patterns electronically are highlighted.
The Yagi-Uda antenna consists of a driven element connected to a transmission line and one or more passive parasitic elements. The reflector element is longer than the driven element to make it inductive, while the director elements are shorter than the driven element to make them capacitive. Together the elements produce a unidirectional beam with moderate directivity and gains of around 8dB. Adding more director elements increases the directivity. It has advantages of simple construction, low cost, and ease of feeding but has limitations of limited bandwidth and requiring additional elements for higher gains over longer distances.
In radio and electronics, an antenna (plural antennae or antennas), or aerial, is an electrical device which converts electric power into radio waves, and vice versa.[1] It is usually used with a radio transmitter or radio receiver. In transmission, a radio transmitter supplies an electric current oscillating at radio frequency (i.e. a high frequency alternating current (AC)) to the antenna's terminals, and the antenna radiates the energy from the current as electromagnetic waves (radio waves). In reception, an antenna intercepts some of the power of an electromagnetic wave in order to produce a tiny voltage at its terminals, that is applied to a receiver to be amplified.
This document provides lecture notes on antennas and wave propagation. It begins with a brief history of antennas from Heinrich Hertz's experiments in the late 1800s to modern applications. It then covers key topics in the first unit, including different types of antennas like dipoles, monopoles, loops, horns and arrays. The document discusses the basic principles of electromagnetic radiation from antennas and conditions required for radiation. It also introduces important antenna parameters and the different types of dimensions and units used to measure antennas.
This document summarizes information about spiral antennas. It begins with an introduction and history, noting that spiral antennas were first developed in 1954 by Edwin Turner. It then discusses key aspects of spiral antennas such as their very large bandwidth of up to 30:1, circular polarization, gains typically between 2-8dB, and the two main types - Archimedean and log-periodic spirals. Parameters for designing spiral antennas and their applications are also covered, along with conclusions about their advantages for wideband operation and disadvantages related to their complex geometric forms.
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
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.
This document discusses various types of antennas and antenna arrays. It begins by describing common antenna types including helical antennas, horn antennas, and parabolic reflector antennas. It then discusses how antenna arrays work, noting that they are composed of multiple similar radiating elements whose spacing and excitation determine the array's properties. Examples of linear and 2D arrays are provided. The document also summarizes different array configurations and beamforming techniques as well as applications such as smart antennas and adaptive arrays. Key benefits of arrays like controlling radiation patterns electronically are highlighted.
The Yagi-Uda antenna consists of a driven element connected to a transmission line and one or more passive parasitic elements. The reflector element is longer than the driven element to make it inductive, while the director elements are shorter than the driven element to make them capacitive. Together the elements produce a unidirectional beam with moderate directivity and gains of around 8dB. Adding more director elements increases the directivity. It has advantages of simple construction, low cost, and ease of feeding but has limitations of limited bandwidth and requiring additional elements for higher gains over longer distances.
In radio and electronics, an antenna (plural antennae or antennas), or aerial, is an electrical device which converts electric power into radio waves, and vice versa.[1] It is usually used with a radio transmitter or radio receiver. In transmission, a radio transmitter supplies an electric current oscillating at radio frequency (i.e. a high frequency alternating current (AC)) to the antenna's terminals, and the antenna radiates the energy from the current as electromagnetic waves (radio waves). In reception, an antenna intercepts some of the power of an electromagnetic wave in order to produce a tiny voltage at its terminals, that is applied to a receiver to be amplified.
This document provides lecture notes on antennas and wave propagation. It begins with a brief history of antennas from Heinrich Hertz's experiments in the late 1800s to modern applications. It then covers key topics in the first unit, including different types of antennas like dipoles, monopoles, loops, horns and arrays. The document discusses the basic principles of electromagnetic radiation from antennas and conditions required for radiation. It also introduces important antenna parameters and the different types of dimensions and units used to measure antennas.
This document summarizes information about spiral antennas. It begins with an introduction and history, noting that spiral antennas were first developed in 1954 by Edwin Turner. It then discusses key aspects of spiral antennas such as their very large bandwidth of up to 30:1, circular polarization, gains typically between 2-8dB, and the two main types - Archimedean and log-periodic spirals. Parameters for designing spiral antennas and their applications are also covered, along with conclusions about their advantages for wideband operation and disadvantages related to their complex geometric forms.
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
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.
- Antennas are devices used for radiating and receiving electromagnetic waves and are essential for wireless communication technologies like mobile phones, WiFi, and satellite communications.
- The radiation pattern of an antenna shows its radiation properties as a function of position and is usually represented by the electric field magnitude over a spherical surface. Common patterns include isotropic, directional, and omnidirectional.
- Key antenna parameters include the main beam direction, half power beamwidth (-3dB beamwidth), beamwidth between first nulls, and side lobe level. These characteristics help describe the antenna's radiation properties.
This document discusses dipole and monopole antennas. It notes that dipoles and monopoles are widely used across radio frequencies for applications like mobile communications. An infinitesimal dipole is introduced as a theoretical construct to model antennas like top-loaded designs. The document also provides an example calculation for determining the power density and radiation resistance of a 1 cm Hertzian dipole antenna operating at 100 MHz from a distance of 1 km. Key parameters for dipole antennas like their radiation patterns and the properties of half-wave dipoles are additionally summarized.
- 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.
Frequency Independent Antennas:
Wide band antennas
Frequency independent bandwidth in octave range
Broadband antennas
Frequency independent bandwidth in the range 40:1
Multiband antennas
Antenna resonate at different frequencies.
The document discusses horn antennas, which consist of a flaring metal shape like a horn. Horn antennas were first constructed in 1897 and became widely used in the 1960s as feed horns for satellite dishes and radio telescopes. They work by converting electric power to radio waves and vice versa, providing a gradual impedance transition between a waveguide and free space to efficiently radiate waves. Common types include rectangular, sectoral, pyramidal, and conical horns. Horn antennas are used for applications like radar guns and satellite communications due to properties like high directivity, gain, and bandwidth.
1) MIMO systems use multiple antennas at both the transmitter and receiver to improve wireless communication capabilities. This allows for increased data rates and signal strength.
2) Traditional wireless systems use a single antenna at both ends (SISO) while MIMO can have multiple at both, known as MISO, SIMO, or fully multiple-input multiple-output (MIMO).
3) MIMO provides higher capacity through spatial multiplexing and increases spectrum efficiency. The Shannon capacity can increase linearly with the number of antennas or data streams.
An Antenna is a transducer, which converts electrical power into electromagnetic waves and vice versa.
An Antenna can be used either as a transmitting antenna or a receiving antenna.
A transmitting antenna is one, which converts electrical signals into electromagnetic waves and radiates them.
A receiving antenna is one, which converts electromagnetic waves from the received beam into electrical signals.
In two-way communication, the same antenna can be used for both transmission and reception.
Basic Parameters
Frequency
Wavelength
Impedance matching
VSWR & reflected power
Bandwidth
Percentage bandwidth
Radiation intensity.
The document discusses concepts of antenna arrays and their applications. It provides an overview of antenna arrays, including their need, types, parameters that influence their radiation patterns, and applications. The key points are:
1) An antenna array consists of multiple antenna elements arranged to form a single antenna with controllable radiation patterns. This allows for increased directivity, narrower beams, and electronic beam steering.
2) Common array types include linear, circular, and planar arrays. Parameters like element spacing, excitation amplitudes and phases shape the overall radiation pattern.
3) Applications of antenna arrays include radar systems, wireless communications, and radio astronomy due to their ability to focus signals in desired directions without mechanical movement.
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.
A dipole antenna is the simplest antenna but its radiation characteristics are very good. The main drawback of a dipole antenna is very narrow bandwidth. The analysis of a dipole antenna can be performed with integration of Hertzian dipoles.
The document discusses limitations of vacuum tubes at microwave frequencies. Key limitations include increased parasitic inductance and capacitance from electrode leads, which reduce efficiency. Transit time effects also limit bandwidth as electrons oscillate between electrodes. Gain-bandwidth product remains constant, requiring alternative designs like reentrant cavities. Overall, vacuum tubes face challenges amplifying signals above 1 GHz due to these inherent timescale limitations. Solid state devices like transistors addressed these issues and enabled widespread microwave applications.
Lens antenna is a microwave antenna in which a dielectric lens is placed in front of the dipole or horn radiator to concentrate the radiated energy into a narrow beam or to focus received energy on the receiving dipole or horn.
The attached narrated power point presentation attempts to explain the methods of computation of total power loss and system rise time in a fiber optic link. The material will be useful for KTU final year B Tech students who prepare for the subject EC 405, Optical Communications.
The document summarizes key components and concepts in basic microwave engineering. It discusses waveguides and their operating frequencies based on dimensions. It also describes electric and magnetic fields in rectangular waveguides. Additional components summarized include coaxial to waveguide transitions, choke joints, coupling loops, phase shifters, junctions, tuners, mixers, isolators, circulators, directional couplers, and cavity resonators. Isolators, circulators, and directional couplers are multi-port devices that control the direction of signal propagation with differing levels of attenuation.
The document discusses different types of antennas used for radio transmission and reception. It categorizes antennas into several groups: log periodic antennas, wire antennas, travelling wave antennas, microwave antennas, and reflector antennas. Within each category, specific antenna types are described, including their basic design and purpose. Key antenna types mentioned include dipole antennas, monopole antennas, Yagi-Uda arrays, parabolic reflectors, horn antennas, and slot antennas.
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 electromagnetic radiation, antenna fundamentals, and wave propagation. It discusses antennas as the linkage between circuits and electromagnetic fields. Key concepts covered include the electromagnetic spectrum, frequency-wavelength relationships, antenna radiation patterns, gain, directivity, polarization, and near, intermediate, and far field regions. Common antenna types for mobile communication like dipoles, monopoles, and arrays are also mentioned. Baluns are described as devices that convert between balanced and unbalanced signals.
An antenna converts electric energy to radio waves and vice versa. It consists of a transmitter and receiver. There are different types of antennas including Yagi-Uda antennas, helix antennas, parabolic antennas, loop antennas, and horn antennas. Each antenna type has distinct characteristics like directionality, frequency range, and applications. For example, Yagi-Uda antennas have high gain and directivity for frequencies from 300MHz to 3GHz, while helix antennas are omni-directional for VHF and UHF bands.
The document discusses antennas and their electrical size relative to wavelength. An electrically small antenna has dimensions small compared to the wavelength, while an electrically large antenna has dimensions large compared to the wavelength. It then discusses the fields radiated by an infinitesimal dipole antenna, including near fields when kr is small, radiating near fields when kr is around 1, and far fields when kr is large. The fields of an arbitrarily oriented infinitesimal dipole are also derived using coordinate transformations. Finally, Poynting's theorem relating to conservation of power in radiating antennas is presented.
- Antennas are devices used for radiating and receiving electromagnetic waves and are essential for wireless communication technologies like mobile phones, WiFi, and satellite communications.
- The radiation pattern of an antenna shows its radiation properties as a function of position and is usually represented by the electric field magnitude over a spherical surface. Common patterns include isotropic, directional, and omnidirectional.
- Key antenna parameters include the main beam direction, half power beamwidth (-3dB beamwidth), beamwidth between first nulls, and side lobe level. These characteristics help describe the antenna's radiation properties.
This document discusses dipole and monopole antennas. It notes that dipoles and monopoles are widely used across radio frequencies for applications like mobile communications. An infinitesimal dipole is introduced as a theoretical construct to model antennas like top-loaded designs. The document also provides an example calculation for determining the power density and radiation resistance of a 1 cm Hertzian dipole antenna operating at 100 MHz from a distance of 1 km. Key parameters for dipole antennas like their radiation patterns and the properties of half-wave dipoles are additionally summarized.
- 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.
Frequency Independent Antennas:
Wide band antennas
Frequency independent bandwidth in octave range
Broadband antennas
Frequency independent bandwidth in the range 40:1
Multiband antennas
Antenna resonate at different frequencies.
The document discusses horn antennas, which consist of a flaring metal shape like a horn. Horn antennas were first constructed in 1897 and became widely used in the 1960s as feed horns for satellite dishes and radio telescopes. They work by converting electric power to radio waves and vice versa, providing a gradual impedance transition between a waveguide and free space to efficiently radiate waves. Common types include rectangular, sectoral, pyramidal, and conical horns. Horn antennas are used for applications like radar guns and satellite communications due to properties like high directivity, gain, and bandwidth.
1) MIMO systems use multiple antennas at both the transmitter and receiver to improve wireless communication capabilities. This allows for increased data rates and signal strength.
2) Traditional wireless systems use a single antenna at both ends (SISO) while MIMO can have multiple at both, known as MISO, SIMO, or fully multiple-input multiple-output (MIMO).
3) MIMO provides higher capacity through spatial multiplexing and increases spectrum efficiency. The Shannon capacity can increase linearly with the number of antennas or data streams.
An Antenna is a transducer, which converts electrical power into electromagnetic waves and vice versa.
An Antenna can be used either as a transmitting antenna or a receiving antenna.
A transmitting antenna is one, which converts electrical signals into electromagnetic waves and radiates them.
A receiving antenna is one, which converts electromagnetic waves from the received beam into electrical signals.
In two-way communication, the same antenna can be used for both transmission and reception.
Basic Parameters
Frequency
Wavelength
Impedance matching
VSWR & reflected power
Bandwidth
Percentage bandwidth
Radiation intensity.
The document discusses concepts of antenna arrays and their applications. It provides an overview of antenna arrays, including their need, types, parameters that influence their radiation patterns, and applications. The key points are:
1) An antenna array consists of multiple antenna elements arranged to form a single antenna with controllable radiation patterns. This allows for increased directivity, narrower beams, and electronic beam steering.
2) Common array types include linear, circular, and planar arrays. Parameters like element spacing, excitation amplitudes and phases shape the overall radiation pattern.
3) Applications of antenna arrays include radar systems, wireless communications, and radio astronomy due to their ability to focus signals in desired directions without mechanical movement.
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.
A dipole antenna is the simplest antenna but its radiation characteristics are very good. The main drawback of a dipole antenna is very narrow bandwidth. The analysis of a dipole antenna can be performed with integration of Hertzian dipoles.
The document discusses limitations of vacuum tubes at microwave frequencies. Key limitations include increased parasitic inductance and capacitance from electrode leads, which reduce efficiency. Transit time effects also limit bandwidth as electrons oscillate between electrodes. Gain-bandwidth product remains constant, requiring alternative designs like reentrant cavities. Overall, vacuum tubes face challenges amplifying signals above 1 GHz due to these inherent timescale limitations. Solid state devices like transistors addressed these issues and enabled widespread microwave applications.
Lens antenna is a microwave antenna in which a dielectric lens is placed in front of the dipole or horn radiator to concentrate the radiated energy into a narrow beam or to focus received energy on the receiving dipole or horn.
The attached narrated power point presentation attempts to explain the methods of computation of total power loss and system rise time in a fiber optic link. The material will be useful for KTU final year B Tech students who prepare for the subject EC 405, Optical Communications.
The document summarizes key components and concepts in basic microwave engineering. It discusses waveguides and their operating frequencies based on dimensions. It also describes electric and magnetic fields in rectangular waveguides. Additional components summarized include coaxial to waveguide transitions, choke joints, coupling loops, phase shifters, junctions, tuners, mixers, isolators, circulators, directional couplers, and cavity resonators. Isolators, circulators, and directional couplers are multi-port devices that control the direction of signal propagation with differing levels of attenuation.
The document discusses different types of antennas used for radio transmission and reception. It categorizes antennas into several groups: log periodic antennas, wire antennas, travelling wave antennas, microwave antennas, and reflector antennas. Within each category, specific antenna types are described, including their basic design and purpose. Key antenna types mentioned include dipole antennas, monopole antennas, Yagi-Uda arrays, parabolic reflectors, horn antennas, and slot antennas.
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 electromagnetic radiation, antenna fundamentals, and wave propagation. It discusses antennas as the linkage between circuits and electromagnetic fields. Key concepts covered include the electromagnetic spectrum, frequency-wavelength relationships, antenna radiation patterns, gain, directivity, polarization, and near, intermediate, and far field regions. Common antenna types for mobile communication like dipoles, monopoles, and arrays are also mentioned. Baluns are described as devices that convert between balanced and unbalanced signals.
An antenna converts electric energy to radio waves and vice versa. It consists of a transmitter and receiver. There are different types of antennas including Yagi-Uda antennas, helix antennas, parabolic antennas, loop antennas, and horn antennas. Each antenna type has distinct characteristics like directionality, frequency range, and applications. For example, Yagi-Uda antennas have high gain and directivity for frequencies from 300MHz to 3GHz, while helix antennas are omni-directional for VHF and UHF bands.
The document discusses antennas and their electrical size relative to wavelength. An electrically small antenna has dimensions small compared to the wavelength, while an electrically large antenna has dimensions large compared to the wavelength. It then discusses the fields radiated by an infinitesimal dipole antenna, including near fields when kr is small, radiating near fields when kr is around 1, and far fields when kr is large. The fields of an arbitrarily oriented infinitesimal dipole are also derived using coordinate transformations. Finally, Poynting's theorem relating to conservation of power in radiating antennas is presented.
This document discusses antennas and propagation in wireless communication systems. It covers topics such as antenna characteristics, radiation patterns, polarization, Maxwell's equations, far-field approximation, Hertzian dipole antenna model, radiated power flux density, normalized radiation intensity, antenna gain, directivity, radiation resistance, and different antenna types including dipole and Yagi antennas. Examples are provided to analyze antenna properties such as radiated power, resistance, directionality, and beamwidth for dipole antennas of different lengths.
Electromagnetic waves are an essential aspect of the study of physics, particularly in the realm of electromagnetism. These waves are characterized by their ability to propagate through space without the need for a medium, unlike mechanical waves such as sound waves. At the heart of electromagnetic theory lies the groundbreaking work of James Clerk Maxwell, who formulated a set of equations that unified the phenomena of electricity and magnetism.
Radio waves are electromagnetic waves that propagate through free space as transverse electromagnetic waves, with the electric field, magnetic field, and direction of propagation being mutually perpendicular. When emitted by an antenna, radio waves travel through space and are affected by objects they encounter, with the signal strength decreasing with distance from the transmitter due to the inverse square law. Radio waves can be reflected, refracted, diffracted, and focused similar to light waves.
The document discusses band theory of solids, which explains the electrical, thermal, and magnetic properties of solids. It begins by covering classical and quantum free electron theories, before introducing band theory. Band theory states that the motion of free electrons in solids is characterized by allowed energy bands separated by forbidden bands. The width of bands and size of gaps depends on factors like the periodic potential of the lattice and strength of scattering. Semiconductors have a small forbidden band gap, allowing electrical conductivity to be controlled by doping with impurities.
1. The document discusses radiation from a two-wire transmission line connected to an antenna. It explains how electric and magnetic fields are created between the conductors when a voltage is applied. Electromagnetic waves travel along the transmission line and enter the antenna.
2. When part of the antenna structure is removed, free space waves are formed by connecting the open ends of the electric field lines. The constant phase point of these waves moves outward at the speed of light.
3. Key terms related to antennas like radial power flow, radiation resistance, uniform current distribution, principle planes, beam width, polarization, effective aperture area, directive gain, power gain, and dual characteristics are defined in the document.
The document discusses magnetic fields produced by electric currents. It begins by introducing the Biot-Savart law, which describes the magnetic field generated by a straight wire carrying a current. It then examines the magnetic field of a circular current loop, noting that the field depends on the current I, distance R from the loop, and radius a. At large distances R compared to the radius a, the field approximates that of a magnetic dipole with a magnetic dipole moment m proportional to the current I and area A of the loop.
Electronic and Optical Properties of Materials-1.pptxAkashMaurya104959
This document discusses electronic and optical properties of materials including band structure, free electron theory, energy gaps in solids, intrinsic and extrinsic semiconductors. Specifically, it covers how the band structure relates to atomic bonding and electron mobility. It also explains free electron theory, diffraction phenomenon, energy gaps that occur at critical electron wavelengths, Brillouin zones, intrinsic conduction via thermal excitation, and extrinsic doping to create n-type or p-type semiconductors by adding donor or acceptor impurities.
1. The document discusses fundamentals of electromagnetic radiation and antennas. It describes how accelerated charges radiate electromagnetic waves according to Poynting's theorem.
2. It then analyzes the radiation pattern and fields of an infinitesimal electric dipole antenna. The electric and magnetic fields are derived in the far-field region and shown to depend on angle with maxima at 90 degrees to the dipole axis.
3. Properties of a finite electric dipole antenna with a sinusoidally driven current are also examined, with the current assumed to have a sinusoidal distribution along the antenna rods.
ir spectroscopy: introduction modes of vibration, selection rule, factor, influcing of vibration, scaning of ir spectroscopy(instrumentation) vibration frequency of organic and inorganic compound
Propagation of ELF Radiation from RS-LC System and Red Sprites in Earth- Iono...degarden
This document compares the propagation of extremely low frequency (ELF) radiation from return stroke-lateral corona (RS-LC) systems and red sprites in the Earth-ionosphere waveguide. It finds that red sprites contribute more greatly to Schumann resonances than RS-LC systems. The document derives mathematical expressions to model the velocity, current, and current moment of RS-LC systems and red sprites. It then uses these expressions to calculate the electric and magnetic fields generated by RS-LC systems and red sprites, finding that red sprites produce fields on the order of 10-5 V/m and 10-8 A/m, peaking at Schumann resonance frequencies.
Propagation of ELF Radiation from RS-LC System and Red Sprites in Earth- Iono...degarden
This document compares the propagation of extremely low frequency (ELF) radiation from return stroke-lateral corona (RS-LC) systems and red sprites in the Earth-ionosphere waveguide. It finds that red sprites contribute more greatly to Schumann resonances than RS-LC systems. The document derives mathematical expressions to model the velocity, current, and current moment of RS-LC systems and red sprites. It then uses these expressions to calculate the electric and magnetic fields generated by RS-LC systems and red sprites and compares their contributions to Schumann resonances.
The document discusses various parameters related to antennas including:
1. Radians and steradians which are units used to measure plane angles and solid angles respectively.
2. Radiation power density and radiation intensity which describe the power associated with electromagnetic waves.
3. Directivity and gain which are measures of an antenna's directional capabilities compared to an isotropic radiator.
4. Other parameters like efficiency, bandwidth, polarization, radiation resistance, and effective length/aperture which characterize an antenna's performance.
The document describes an experiment to measure the refractive index of HCl gas using a Michelson interferometer. A HeNe laser beam is split into two paths, with one path passing through an evacuated glass cell. As the cell is pumped out, the interference fringes shift due to the changing optical path length. Counting the number of fringe shifts allows calculating the refractive index from the changing wavelength of light in the gas versus vacuum. The experiment is performed at varying HCl pressures and temperatures, with results corrected to standard temperature and pressure for comparison to literature values of the molar refractivity and effective molecular radius of HCl.
This document provides an overview of antenna parameters and types. It discusses basic parameters like radiation pattern, beamwidth, gain and directivity. It also covers antenna arrays, measurement techniques, and different antenna types. Key antenna concepts are defined, such as radiation pattern lobes, field regions, radian, steradian, radiation power density, radiation intensity, effective length, aperture and polarization. Common antenna parameters and their calculations are presented. Examples of antenna problems involving these concepts are provided.
This document discusses various propagation models used in wireless communications. It begins by introducing the free space propagation model and 2-ray ground reflection model. It then describes the key propagation mechanisms of reflection, diffraction, and scattering. Reflection from smooth surfaces and conductors is explained. Fresnel zone geometry and knife edge diffraction models are used to analyze diffraction. Buildings can help diffraction by providing some gain, with the amount of diffracted energy dependent on factors like height and frequency. Propagation effects must be considered for accurate wireless system design and performance prediction.
This document provides an introduction to basic antenna parameters and concepts. It discusses how antennas convert between guided waves on transmission lines and free-space electromagnetic waves. Antennas radiate energy through accelerated or decelerated charge and currents. Key concepts covered include radiation resistance, patterns, beam area, directivity, gain, apertures, and polarization. The document aims to provide foundational knowledge of antennas and their language and parameters.
This document discusses different types of antenna jobs and areas of research. It describes three main sectors for antenna jobs: private sector working for consumer electronics companies, defense department/government jobs, and university/research jobs. It provides details on the responsibilities for each type of private sector job and notes that defense and government jobs focus more on research and integration. University/research jobs primarily involve publishing research and involve some teaching. Active areas of antenna research mentioned include meta-materials, electromagnetic solvers, miniaturization, and array optimization.
The document discusses radio wave propagation through the ionosphere. It describes the three main layers of the ionosphere - the D layer, E layer, and F layer. The D layer absorbs lower radio frequencies during the day. The E layer supports short-range propagation during the day. The F layer, divided into F1 and F2, is responsible for long-distance high frequency propagation, especially at night when the layers merge. Ground wave propagation travels along the ground, while skywave propagation involves reflection from the ionosphere.
This document discusses different types of antennas and their characteristics, including whips, loops, helicals, Yagis, log periodic, horns, and parabolic antennas. It also covers topics like antenna radiation pattern measurement systems, gain and loss calculations, antenna design considerations, and the differences between EIRP and ERP.
This document discusses wire antennas and antenna arrays. It begins by categorizing radiation patterns from an engineering, analytical, and technical perspective. It then covers basic wire antenna structures like dipoles and loops. The document focuses on linear, planar and array types including properties like radiation patterns, array factors, and design considerations for arrays like element spacing, progressive phase shifts and different array geometries. Specific array examples covered include uniform, broadside, endfire, binomial and filled disk arrays.
The document discusses various types of aperture antennas including slot antennas, horn antennas, and corrugated horns. It explains key concepts such as Babinet's principle, which relates the fields of an antenna to its complement, and how this allows the fields of a slot antenna to be understood based on a dipole antenna. The document also discusses how horns are commonly used as feeds for large satellite and radio astronomy dishes due to their simplicity, versatility, and ability to produce a uniform phase front. Corrugated horns are highlighted as a type of horn that can improve the aperture efficiency of large reflectors.
This lab document outlines 5 experiments: 1) Resistor colour coding and measuring AC signal parameters using an oscilloscope, 2) Studying logic gates like AND, OR, EOR and NOT, 3) Generating a clock signal, 4) Soldering practice on a breadboard, and 5) Measuring the ripple factor of half-wave and full-wave rectifiers. The experiments cover topics like resistor color coding, logic gates, signal generation and measurement, soldering skills, and power electronics measurements.
Null Bangalore | Pentesters Approach to AWS IAMDivyanshu
#Abstract:
- Learn more about the real-world methods for auditing AWS IAM (Identity and Access Management) as a pentester. So let us proceed with a brief discussion of IAM as well as some typical misconfigurations and their potential exploits in order to reinforce the understanding of IAM security best practices.
- Gain actionable insights into AWS IAM policies and roles, using hands on approach.
#Prerequisites:
- Basic understanding of AWS services and architecture
- Familiarity with cloud security concepts
- Experience using the AWS Management Console or AWS CLI.
- For hands on lab create account on [killercoda.com](https://killercoda.com/cloudsecurity-scenario/)
# Scenario Covered:
- Basics of IAM in AWS
- Implementing IAM Policies with Least Privilege to Manage S3 Bucket
- Objective: Create an S3 bucket with least privilege IAM policy and validate access.
- Steps:
- Create S3 bucket.
- Attach least privilege policy to IAM user.
- Validate access.
- Exploiting IAM PassRole Misconfiguration
-Allows a user to pass a specific IAM role to an AWS service (ec2), typically used for service access delegation. Then exploit PassRole Misconfiguration granting unauthorized access to sensitive resources.
- Objective: Demonstrate how a PassRole misconfiguration can grant unauthorized access.
- Steps:
- Allow user to pass IAM role to EC2.
- Exploit misconfiguration for unauthorized access.
- Access sensitive resources.
- Exploiting IAM AssumeRole Misconfiguration with Overly Permissive Role
- An overly permissive IAM role configuration can lead to privilege escalation by creating a role with administrative privileges and allow a user to assume this role.
- Objective: Show how overly permissive IAM roles can lead to privilege escalation.
- Steps:
- Create role with administrative privileges.
- Allow user to assume the role.
- Perform administrative actions.
- Differentiation between PassRole vs AssumeRole
Try at [killercoda.com](https://killercoda.com/cloudsecurity-scenario/)
Discover the latest insights on Data Driven Maintenance with our comprehensive webinar presentation. Learn about traditional maintenance challenges, the right approach to utilizing data, and the benefits of adopting a Data Driven Maintenance strategy. Explore real-world examples, industry best practices, and innovative solutions like FMECA and the D3M model. This presentation, led by expert Jules Oudmans, is essential for asset owners looking to optimize their maintenance processes and leverage digital technologies for improved efficiency and performance. Download now to stay ahead in the evolving maintenance landscape.
Design and optimization of ion propulsion dronebjmsejournal
Electric propulsion technology is widely used in many kinds of vehicles in recent years, and aircrafts are no exception. Technically, UAVs are electrically propelled but tend to produce a significant amount of noise and vibrations. Ion propulsion technology for drones is a potential solution to this problem. Ion propulsion technology is proven to be feasible in the earth’s atmosphere. The study presented in this article shows the design of EHD thrusters and power supply for ion propulsion drones along with performance optimization of high-voltage power supply for endurance in earth’s atmosphere.
Rainfall intensity duration frequency curve statistical analysis and modeling...bijceesjournal
Using data from 41 years in Patna’ India’ the study’s goal is to analyze the trends of how often it rains on a weekly, seasonal, and annual basis (1981−2020). First, utilizing the intensity-duration-frequency (IDF) curve and the relationship by statistically analyzing rainfall’ the historical rainfall data set for Patna’ India’ during a 41 year period (1981−2020), was evaluated for its quality. Changes in the hydrologic cycle as a result of increased greenhouse gas emissions are expected to induce variations in the intensity, length, and frequency of precipitation events. One strategy to lessen vulnerability is to quantify probable changes and adapt to them. Techniques such as log-normal, normal, and Gumbel are used (EV-I). Distributions were created with durations of 1, 2, 3, 6, and 24 h and return times of 2, 5, 10, 25, and 100 years. There were also mathematical correlations discovered between rainfall and recurrence interval.
Findings: Based on findings, the Gumbel approach produced the highest intensity values, whereas the other approaches produced values that were close to each other. The data indicates that 461.9 mm of rain fell during the monsoon season’s 301st week. However, it was found that the 29th week had the greatest average rainfall, 92.6 mm. With 952.6 mm on average, the monsoon season saw the highest rainfall. Calculations revealed that the yearly rainfall averaged 1171.1 mm. Using Weibull’s method, the study was subsequently expanded to examine rainfall distribution at different recurrence intervals of 2, 5, 10, and 25 years. Rainfall and recurrence interval mathematical correlations were also developed. Further regression analysis revealed that short wave irrigation, wind direction, wind speed, pressure, relative humidity, and temperature all had a substantial influence on rainfall.
Originality and value: The results of the rainfall IDF curves can provide useful information to policymakers in making appropriate decisions in managing and minimizing floods in the study area.
Optimizing Gradle Builds - Gradle DPE Tour Berlin 2024Sinan KOZAK
Sinan from the Delivery Hero mobile infrastructure engineering team shares a deep dive into performance acceleration with Gradle build cache optimizations. Sinan shares their journey into solving complex build-cache problems that affect Gradle builds. By understanding the challenges and solutions found in our journey, we aim to demonstrate the possibilities for faster builds. The case study reveals how overlapping outputs and cache misconfigurations led to significant increases in build times, especially as the project scaled up with numerous modules using Paparazzi tests. The journey from diagnosing to defeating cache issues offers invaluable lessons on maintaining cache integrity without sacrificing functionality.
Embedded machine learning-based road conditions and driving behavior monitoringIJECEIAES
Car accident rates have increased in recent years, resulting in losses in human lives, properties, and other financial costs. An embedded machine learning-based system is developed to address this critical issue. The system can monitor road conditions, detect driving patterns, and identify aggressive driving behaviors. The system is based on neural networks trained on a comprehensive dataset of driving events, driving styles, and road conditions. The system effectively detects potential risks and helps mitigate the frequency and impact of accidents. The primary goal is to ensure the safety of drivers and vehicles. Collecting data involved gathering information on three key road events: normal street and normal drive, speed bumps, circular yellow speed bumps, and three aggressive driving actions: sudden start, sudden stop, and sudden entry. The gathered data is processed and analyzed using a machine learning system designed for limited power and memory devices. The developed system resulted in 91.9% accuracy, 93.6% precision, and 92% recall. The achieved inference time on an Arduino Nano 33 BLE Sense with a 32-bit CPU running at 64 MHz is 34 ms and requires 2.6 kB peak RAM and 139.9 kB program flash memory, making it suitable for resource-constrained embedded systems.
Electric vehicle and photovoltaic advanced roles in enhancing the financial p...IJECEIAES
Climate change's impact on the planet forced the United Nations and governments to promote green energies and electric transportation. The deployments of photovoltaic (PV) and electric vehicle (EV) systems gained stronger momentum due to their numerous advantages over fossil fuel types. The advantages go beyond sustainability to reach financial support and stability. The work in this paper introduces the hybrid system between PV and EV to support industrial and commercial plants. This paper covers the theoretical framework of the proposed hybrid system including the required equation to complete the cost analysis when PV and EV are present. In addition, the proposed design diagram which sets the priorities and requirements of the system is presented. The proposed approach allows setup to advance their power stability, especially during power outages. The presented information supports researchers and plant owners to complete the necessary analysis while promoting the deployment of clean energy. The result of a case study that represents a dairy milk farmer supports the theoretical works and highlights its advanced benefits to existing plants. The short return on investment of the proposed approach supports the paper's novelty approach for the sustainable electrical system. In addition, the proposed system allows for an isolated power setup without the need for a transmission line which enhances the safety of the electrical network
Applications of artificial Intelligence in Mechanical Engineering.pdfAtif Razi
Historically, mechanical engineering has relied heavily on human expertise and empirical methods to solve complex problems. With the introduction of computer-aided design (CAD) and finite element analysis (FEA), the field took its first steps towards digitization. These tools allowed engineers to simulate and analyze mechanical systems with greater accuracy and efficiency. However, the sheer volume of data generated by modern engineering systems and the increasing complexity of these systems have necessitated more advanced analytical tools, paving the way for AI.
AI offers the capability to process vast amounts of data, identify patterns, and make predictions with a level of speed and accuracy unattainable by traditional methods. This has profound implications for mechanical engineering, enabling more efficient design processes, predictive maintenance strategies, and optimized manufacturing operations. AI-driven tools can learn from historical data, adapt to new information, and continuously improve their performance, making them invaluable in tackling the multifaceted challenges of modern mechanical engineering.
3. Antenna: Linkage Between Circuits and Fields
• Steady-state time-varying signals (e.g., RF CW)
• Transient signals (e.g. Electromagnetic pulses)
• Knowledge of basic RF concepts needed.
3
Circuits Fields
V, I, Z, P E, H,h, S
Antenna
4. Electromagnetic Spectrum
4
• The Electromagnetic Spectrum covers a very wide range of frequency,
from almost DC to gamma rays.
• Radio frequency (RF) is a subset of the EM spectrum and is loosely
defined as:
“The frequency in the portion of the electromagnetic spectrum that is
between the audio-frequency portion and the infrared portion. The present
practical limits of radio frequency are roughly 10 kHz to 100 GHz.” [IEEE
Std 100-1988 Standard Dictionary of Electrical and Electronic Terms]
• EM (Electromagnetic) waves can propagate in vacuum but not acoustic
waves.
5. 5
Frequency – Wavelength Relationship
• The wavelength l of an electromagnetic wave is related to its frequency f
by:
• Conveniently in practice, we can quickly estimate the wavelength of a
frequency given in MHz or GHz by:
f
c
=l where c = 3x108 m/s (speed of light in vacuum)
)m(
fMHz
300
=l
)mm(
fGHz
300
=l
5
e.g., l of 100 MHz is 3 m.
e.g., l of 10 GHz is 30 mm.
6. what is an antenna ?
(everything can radiate)
- antenna is a filter in frequency
and spatial domain
7. Antenna as an Interface/Transducer
Antennas are conducting or dielectric structures that allow efficient launching or
radiating of electromagnetic waves into space. (Theoretically, any structure can
radiate EM waves but not all structures can do it efficiently.)
An antenna can be viewed as a transducer between a transmission line (or
directly from an electrical or electronic circuit) and the surrounding medium. It
can be used for either transmitting or receiving.
7
RF Generator
(including
Transmission Line)
EM wave
radiating
into space
Antenna
wave front of EM
wave
8. Hertzian Dipole
• A Hertzian Dipole is an infinitesimal current element Idl (i.e.,
current I flowing in a conductor dl long). The current I is
assumed to be constant along the whole length of dl.
• Such a current element does not exist in real life in isolation.
• It forms the basic building block of a practical antenna – e.g. a
dipole is made up of many of these current elements connected
together end to end, each with a different current I.
8
~
I
dl
16. The principles of radiation of electromagnetic energy are
based on two laws:
1. A MOVING ELECTRIC FIELD CREATES A MAGNETIC (H)
FIELD.
2. A MOVING MAGNETIC FIELD CREATES AN ELECTRIC (E)
FIELD.
In space, these two fields will be in phase and perpendicular
to each other at any given point
Charge in Motion Gives Rise to a Magnetic Field the
magnitude of the resulting magnetic field depends
upon the velocity of the charge and the amount of
charge
17.
18.
19.
20.
21. Choosing Antennas
• Frequency – Dictates size
• Mounting location – Base or mobile
• Omni or directional – Coverage or gain
• Polarization – Horizontal, vertical, circular
• Resonant or non-resonant – Tuner required?
• Power available
• Feedline length and type
• Cost
49. Polarization
Polarization is a description of how the direction of the electric field vector changes
with time at a fixed point in space. If the wave is propagating in the positive z-
direction, the electric field vector at a fixed point, say z=0, can be expressed in the
following general form:
Then, the polarization can be categorized using the two real
quantities A and .
( ) ( ) ( ) ++== tAEatEatzE yx cosˆcosˆ,0 00
50. Polarization
If the locus of the tip of the E-field is a straight line, linear polarization.
Circular locus → Circular polarization.
Elliptical locus → Elliptical polarization.
The polarization is called right-handed, if the fingers of the right hand follow the
direction of rotation of the E-vector while the thumb points in the direction of
propagation. Otherwise, left-handed.
Linear Circular Elliptical
60. The E- and H-fields for the infinitesimal dipole, as
represented by equations derived and shown in previous
slide are valid everywhere (except on the source itself).
At a distance r = λ/2π (or kr = 1), which is referred to as the
radian distance, the magnitude of the first and second
terms within the brackets of
are same.
61.
62. Also at the radian distance the
magnitude of all three terms within the
brackets of
is identical; the only term that
contributes to the total field is the
second, because the first and third
terms cancel each other. This is
illustrated in Figure in the following
slides
63. At distances less than the radian distance r < λ/2π (kr <1), the magnitude of the second
term within the brackets of
is greater than the first term and begins to dominate as r <λ/2π.
For
and r < λ/2π, the magnitude of the third term within the brackets is greater than the
magnitude of the first and second terms while the magnitude of the second term is
greater than that of the first one; each of these terms begins to dominate as r < λ/2π.
64. Magnitude variation, as a function of the radial distance, of the
field terms radiated by an infinitesimal dipole.
This is illustrated in this Figure .
The region r < λ/2π (kr <1) is
referred to as the near-field
region, and the energy in that
region is basicallyimaginary
(stored).
65. Magnitude variation, as a function of the radial distance, of the
field terms radiated by an infinitesimal dipole.
At distances greater than the radian distance r >
λ/2π (kr >1), the first term within the brackets
is greater than the magnitude of the second
term and begins to dominate as r> λ/2π (kr >
1). For
and r > λ/2π, the first term withinthe brackets
is greater than the magnitude of the second
and third terms while the magnitude of the
second term is greater than that of the third;
each of these terms begins to dominate as
r >> λ/ 2π. This is illustrated inFigure . The
region r > λ/2π (kr >1) is referred to as the
intermediate-field regionwhile that forr>> λ/2π
(kr >> 1) is referred to as the far-field region,
and the energy in that region is basically real
(radiated).
66. Magnitude variation, as a function of the radial distance, of the
field terms radiated by an infinitesimal dipole.
The sphere with radius equal to the radiandistan ce
(r = λ/2π) is referred as the radian sphere, and it
defines the region within which the reactive power
density is greater than the radiated power density .
For an antenna, the radian sphere represents the
volume occupied mainly by the stored energy of the
antenna’s electric and magnetic fields. Outside the
radian sphere the radiated power density is greater
than the reactive power density and begins to
dominate as r > λ/2π. Therefore the radian sphere
can be used as a reference, and it defines the
transition between stored energy pulsating
primarily in the ±θ direction and energy radiating in
the radial (r) direction [represented by the first term
the second term represents stored energy pulsating
inwardly and outwardly in the radial (r) direction].
Similar behavior, where the power density near the
antenna is primarily reactive and far away is
primarily real, is exhibited by all antennas, although
not exactly at the radiandistance.
68. An inspection of
reveals that for kr << λ or r <<λ/2π they can be reduced in much simpler form and can
be approximated by
The E-field components, Er and Eθ , are intime-phase but they are intime-phase
quadrature with the H-field component Hφ; therefore there is no time-average
power flow associated with them. The condition of kr << 1 can be satisfied at moderate
distances away from the antenna provided that the frequency of operation is very low.
70. As the values of kr begin to increase and become greater than unity, the terms
that were dominant for kr << 1 become smaller and eventually vanish.
For moderate values of kr the E-field components lose their in-phase
condition and approach time-phase quadrature. Since their magnitude is not
the same, in general, they form a rotating vector whose extremity traces an
ellipse.
At intermediate values of kr, the Eθ and Hφ components approach time-phase,
which is an indication of the formation of time-average power flow in the
outward (radial) direction (radiation phenomenon).
As the values of kr become moderate (kr > 1), the field expressions can be
approximated againbut ina different form.
71. In con trast to the region where kr << 1, the first term within the brackets in
becomes more dominant and the second term can be neglected.
73. The ratio of Eθ to Hφ is equal to
Where Zw = wave impedance
η = intrinsic impedance (377 120π ohms for free-space)
The E- an dH-field components are perpendicular to each
other, transverse to the radial direction of propagation, and
the r variations are separable from those of θ and φ. The
shape of the pattern is not a function of the radial distance
r, and the fields form a T ransverse ElectroMagnetic (TEM)
wave whose wave impedance is equal to the intrinsic
impedance of the medium
75. The average power density radiated by the dipole is
Integrating the above equation over a closed sphere of radius r reduces it to .
Associated with the average power density is the radiation intensity U which
is given by
The maximum value occurs at θ = π/2 and it is equal to
So the the directivity is
the maximum effective aperture is
80. ➢The dipole and monopole are two of the most widely used
antennas for wireless mobile communication systems
➢An array of dipole elements is extensively used as an
antenna at the base station of a land mobile system
➢The monopole, because of its broadband characteristics
and simple construction, is perhaps to most common
antenna element for portable equipment, such as cellular
telephones, cordless telephones, automobiles, trains, etc.
➢An alternative to the monopole for the handheld unit is the
loop.Other elements include the inverted F, planar inverted F
antenna (PIFA), microstrip (patch), spiral, etc…
81. TYPICAL ANTENNA PROBLEMS
• Radio Interference to nearby devices.
• Transmission line radiation.
• The above are due to “common mode
currents” on the transmission line.
• Loss of power to antenna due to mismatch
between coax and antenna.
• BALUNS can address these problems.
82. BALUN – A Coined Word
• Balun formed from BALance – UNbalance.
• Name suggest device converts between
“Balance <> Unbalance”.
• BALUN is name of device that can be many
things like a common mode choke, unbalance
to balance transformer, and a step up or down
transformer.
84. What is a balun?
• A Balun is special type of transformer that performs
two functions:
– Impedance transformation
– Balanced to unbalanced transformation
• The word balun is a contraction of “balanced to
unbalanced transformer”
85. Why do we need a balun?
• Baluns are important because many types of antennas
(dipoles, yagis, loops) are balanced loads, which are fed with
an unbalanced transmission line (coax).
• Baluns are required for proper connection of parallel line to a
transceiver with a 50 ohm unbalanced output
• The antenna’s radiation pattern changes if the currents in the
driven element of a balanced antenna are not equal and
opposite.
• Baluns prevent unwanted RF currents from flowing in the
“third” conductor of a coaxial cable.
86. Gain/Loss Calculations
• ERP (Effective Radiated Power) is the real
number to consider
• Gain uses a Log-10 scale
▪ 3dB = 2-fold improvement
▪ 6dB = 4-fold improvement
▪ 10dB = 10-fold improvement
▪ 20dB = 100-fold improvement
• ERP=Power x (Gain - Feedline Loss)
87. Antenna Design Considerations
• Gain, SWR, Bandwidth, Front/Back ratio are
related and optimum values are not achieved
simultaneously for each
• Does antenna have power going in desired
direction? Gain/Beamwidth
88. EIRP and ERP
• EIRP = effective isotropic radiated power
– Equal to the amount of power that would have to
be applied to an isotropic radiator to give the
same power density at a given point
• ERP = effective radiated power
– Equal to the amount of power that would have to
be applied to a half-wave dipole, oriented in
direction of maximum gain, to give the same
power density at a given point
89. EIRP/ERP Conversion
• EIRP = ERP + 2.14 dB
• EIRP is used in all our equations
• Sometimes government regulations specify
ERP for transmitting installations
• Conversion is easy (see above)