1) The document discusses thin linear wire antennas and their properties like radiation from small electric dipoles, quarter wave monopoles and half wave dipoles.
2) It describes the calculation of electromagnetic fields using retarded potentials for time-varying sources like electric and magnetic dipoles.
3) Key concepts discussed include the vector and scalar potentials, derivation of wave equations from Maxwell's equations, and calculation of power radiated from a current element.
The document provides an overview of microwave engineering and rectangular waveguides. It defines microwave frequencies as ranging from 1 GHz to 300 GHz. Rectangular waveguides transmit electromagnetic waves through successive reflections from inner walls. Modes in waveguides include transverse electric (TE) and transverse magnetic (TM) modes. The document analyzes the TM and TE modes in rectangular waveguides through solving Maxwell's equations with boundary conditions. Cut-off frequencies above which modes can propagate are determined. Examples demonstrate calculating waveguide parameters and resonant frequencies of cavity resonators.
This document discusses the half-wave dipole antenna. It describes how a half-wave dipole antenna works by converting electric power to electromagnetic waves and vice versa using two conductive elements that are half the wavelength of the operating frequency. It resonates when the inductive and capacitive reactances cancel each other out. The document outlines the key parameters of directivity, SWR bandwidth, polarization, and self-impedance. It lists common applications and the advantages of receiving balanced signals from multiple frequencies with lower loss closer to the horizon. The disadvantages are that outdoor antennas are large and difficult to install.
This document provides an overview of basic electronics topics including transmission lines, waveguides, and antenna fundamentals. It discusses the characteristics and applications of transmission lines, advantages of using them to reduce electromagnetic interference, and examples of different types of transmission lines. Waveguides are introduced as an alternative to transmission lines at higher frequencies. Key concepts around waveguides such as applications and the expression for cutoff wavelength are summarized. Finally, the document outlines fundamental concepts relating to antennas such as radiation patterns, efficiency, and gain.
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.
Directional couplers are four-port waveguide junctions that allow power transmission between ports 1 and 2 without transmission between ports 1 and 3 or 2 and 4. The coupling factor and directivity quantify the power coupling between ports. Common directional coupler types include two-hole, four-hole, and reverse-coupling designs. Hybrid couplers consist of interdigitated microstrip lines and have applications in circuits like balanced amplifiers. Circulators and isolators use ferrite materials to achieve non-reciprocal transmission, allowing wave propagation from port n to port n+1 in circulators and blocking reverse transmission in isolators.
The document discusses FM demodulation using a phase-locked loop (PLL). A PLL consists of a phase detector, loop filter, and voltage-controlled oscillator (VCO) connected in a feedback loop. It works by using the phase detector to compare the input signal frequency to the VCO output frequency. Any difference or error signal is fed through the loop filter to control the VCO frequency, adjusting it until the two frequencies are synchronized and phase-locked. In this way, a PLL can track the frequency and phase of an incoming FM signal to demodulate it.
A PLL or phase-locked loop is a control system that generates an output signal whose phase is related to the phase of an input signal. It consists of three basic elements: a phase detector that compares the phase of two signals and generates an error signal, a loop filter that filters the error signal, and a voltage-controlled oscillator whose frequency is controlled by the filtered error signal. PLLs are commonly used in applications such as frequency synthesis, signal demodulation, and motor speed control.
This document discusses different types of traveling wave antennas, including long wire antennas and V antennas. It provides definitions of traveling wave antennas as non-resonant antennas where standing waves do not exist along the length. Long wire antennas are classified as having a length between 1-many wavelengths. Their current distribution attenuates along the length due to losses. V antennas consist of two wire antennas arranged horizontally to form a V shape. They can be resonant or non-resonant. Rhombic antennas are formed from two connected V antennas in a diamond shape and are highly directional but require large spaces. The document provides examples of their usage and concludes with designing a rhombic antenna.
The document provides an overview of microwave engineering and rectangular waveguides. It defines microwave frequencies as ranging from 1 GHz to 300 GHz. Rectangular waveguides transmit electromagnetic waves through successive reflections from inner walls. Modes in waveguides include transverse electric (TE) and transverse magnetic (TM) modes. The document analyzes the TM and TE modes in rectangular waveguides through solving Maxwell's equations with boundary conditions. Cut-off frequencies above which modes can propagate are determined. Examples demonstrate calculating waveguide parameters and resonant frequencies of cavity resonators.
This document discusses the half-wave dipole antenna. It describes how a half-wave dipole antenna works by converting electric power to electromagnetic waves and vice versa using two conductive elements that are half the wavelength of the operating frequency. It resonates when the inductive and capacitive reactances cancel each other out. The document outlines the key parameters of directivity, SWR bandwidth, polarization, and self-impedance. It lists common applications and the advantages of receiving balanced signals from multiple frequencies with lower loss closer to the horizon. The disadvantages are that outdoor antennas are large and difficult to install.
This document provides an overview of basic electronics topics including transmission lines, waveguides, and antenna fundamentals. It discusses the characteristics and applications of transmission lines, advantages of using them to reduce electromagnetic interference, and examples of different types of transmission lines. Waveguides are introduced as an alternative to transmission lines at higher frequencies. Key concepts around waveguides such as applications and the expression for cutoff wavelength are summarized. Finally, the document outlines fundamental concepts relating to antennas such as radiation patterns, efficiency, and gain.
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.
Directional couplers are four-port waveguide junctions that allow power transmission between ports 1 and 2 without transmission between ports 1 and 3 or 2 and 4. The coupling factor and directivity quantify the power coupling between ports. Common directional coupler types include two-hole, four-hole, and reverse-coupling designs. Hybrid couplers consist of interdigitated microstrip lines and have applications in circuits like balanced amplifiers. Circulators and isolators use ferrite materials to achieve non-reciprocal transmission, allowing wave propagation from port n to port n+1 in circulators and blocking reverse transmission in isolators.
The document discusses FM demodulation using a phase-locked loop (PLL). A PLL consists of a phase detector, loop filter, and voltage-controlled oscillator (VCO) connected in a feedback loop. It works by using the phase detector to compare the input signal frequency to the VCO output frequency. Any difference or error signal is fed through the loop filter to control the VCO frequency, adjusting it until the two frequencies are synchronized and phase-locked. In this way, a PLL can track the frequency and phase of an incoming FM signal to demodulate it.
A PLL or phase-locked loop is a control system that generates an output signal whose phase is related to the phase of an input signal. It consists of three basic elements: a phase detector that compares the phase of two signals and generates an error signal, a loop filter that filters the error signal, and a voltage-controlled oscillator whose frequency is controlled by the filtered error signal. PLLs are commonly used in applications such as frequency synthesis, signal demodulation, and motor speed control.
This document discusses different types of traveling wave antennas, including long wire antennas and V antennas. It provides definitions of traveling wave antennas as non-resonant antennas where standing waves do not exist along the length. Long wire antennas are classified as having a length between 1-many wavelengths. Their current distribution attenuates along the length due to losses. V antennas consist of two wire antennas arranged horizontally to form a V shape. They can be resonant or non-resonant. Rhombic antennas are formed from two connected V antennas in a diamond shape and are highly directional but require large spaces. The document provides examples of their usage and concludes with designing a rhombic antenna.
1) Rectangular waveguides can transmit electromagnetic waves above a certain cutoff frequency, acting as a high-pass filter. They support transverse electric (TE) and transverse magnetic (TM) modes of propagation.
2) For TM modes, the electric field is transverse to the direction of propagation, while the magnetic field has a longitudinal component. The modes are denoted TMmn, with m and n indicating the number of half-wavelength variations across the width and height.
3) For TE modes, the magnetic field is entirely transverse, while the electric field has a longitudinal component. These modes are denoted TEmn, with m and n having the same meaning as in the TM case.
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.
This document discusses different types of avalanche transit time devices (ATTDs) used to generate microwaves, including IMPATT diodes and TRAPATT diodes. It provides details on:
1) The basics of how ATTDs like IMPATT and TRAPATT diodes utilize the avalanche breakdown effect across a reverse-biased p-n junction to produce carriers and negative resistance at microwave frequencies.
2) The different modes of ATTD oscillators, including the IMPATT mode where typical efficiency is 5-10% and frequencies can reach 100 GHz, and the TRAPATT mode with higher typical efficiency of 20-60%.
3) The physical structures and operating principles of IMPATT diodes
Optical fiber communication Part 2 Sources and DetectorsMadhumita Tamhane
For optical fiber communication, major light sources are hetero-junction-structured semiconductor laser diode and light emitting diodes. Heterojunction consists of two adjoining semiconductor materials with different bandgap energies. They have adequate power for wide range of applications. Detectors used are PiN diode and Avalanche Photodiode. Being very small in size and feeding to small core optical fiber, it is very important to study emission characteristics of sources and their coupling to fiber. As it can operate for low power over a long distance, received power is very small, hence study of noise characteristics of detectors is very essential...
This document provides information about light propagation through optical fibers. It begins by defining an optical fiber as a cylindrical waveguide made of glass that uses total internal reflection to transmit light. It then discusses the fiber's core and cladding layers and the conditions needed for total internal reflection. The key points covered include:
- Light propagation is guided through the fiber core by total internal reflection at the core-cladding interface.
- Only rays entering the fiber core within the acceptance angle will continue propagating through total internal reflection.
- Electromagnetic mode theory is needed to fully understand light propagation in fibers. Discrete modes exist that are solutions to Maxwell's equations.
- The evanescent field that penetrates the cl
Waveguide tees are used in microwave technologies to split or extract power in a waveguide. There are several types of waveguide tees that affect the energy in different ways, including H-type, E-type, magic T, and hybrid ring tees. E-type tees produce outputs that are 180 degrees out of phase, while H-type tees produce in-phase outputs. Magic T tees combine properties of H-type and E-type tees. Hybrid ring tees overcome power limitations of magic T tees using a circular waveguide design.
Classification of signals and systems as well as their properties are given in the PPT .Examples related to types of signals and systems are also given .
Antennas are used for transmitting and receiving electromagnetic waves in wireless communication systems. They work by converting electrical energy into electromagnetic waves that propagate through space. There are different types of antennas suited for different applications, but they all share fundamental properties like radiation pattern, gain, directivity, and polarization. Antennas must be designed to direct radiation in the desired direction and impedance match the transmission line to prevent reflections. Key antenna types are directional antennas like Yagi, parabolic, and sector antennas which achieve longer ranges but less coverage, versus omni-directional antennas which provide wider coverage over shorter ranges.
Transmission line, single and double matchingShankar Gangaju
This document discusses different types of transmission lines used for transmitting energy and signals over long distances. It describes common transmission line media like twisted pair, coaxial cable and optical fiber. It covers their applications in telephone networks, buildings and computer networks. It also discusses their transmission characteristics and limitations. The document compares properties of unshielded and shielded twisted pair. It provides details on utilizing different wavelengths in optical fiber for various applications.
A Gunn diode is a type of diode that uses the Gunn effect to generate microwave frequencies when a voltage above a threshold is applied. It consists of a single piece of N-type semiconductor like gallium arsenide and has a negative differential resistance region in its current-voltage characteristics that allows it to function as an oscillator. Gunn diodes are used to generate microwave signals from 10 GHz to THz and have applications in radar, sensors, and microwave transmission.
This document discusses microwave junctions and S-parameters. It provides information on:
1) Power dividers and directional couplers which are passive microwave components used for power division or combining. S-parameters are used to define the power relationships between ports.
2) The scattering matrix (S-matrix) is a matrix that defines the power relationships between ports in terms of incident and reflected voltage waves. It is commonly used for microwave analysis since direct voltage and current measurements are difficult at high frequencies.
3) Examples are provided to demonstrate calculating S-matrix coefficients for different microwave junction configurations like E-plane and H-plane tee junctions. Properties of reciprocal and lossless networks in relation to the S
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.
The document discusses equalization techniques used to mitigate inter-symbol interference (ISI) in digital communication systems. Equalization aims to remove ISI and noise effects from the channel. It is located at the receiver and uses techniques like linear equalizers, decision feedback equalization, and maximum likelihood sequence estimation to estimate the channel response and minimize the error between transmitted and received symbols while balancing noise. As the wireless channel changes over time, adaptive equalization is used where the equalizer periodically trains and tracks the changing channel response.
The receiver structure consists of four main components:
1. A matched filter that maximizes the SNR by matching the source impulse and channel.
2. An equalizer that removes intersymbol interference.
3. A timing component that determines the optimal sampling time using an eye diagram.
4. A decision component that determines whether the received bit is a 0 or 1 based on a threshold.
The performance of the receiver depends on factors like noise, equalization technique used, and timing accuracy. The bit error rate can be estimated using tools like error functions.
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 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.
This document discusses amplitude modulation (AM) as a type of modulation used to transmit information signals. Modulation involves varying a high frequency carrier signal by an information signal in order to transmit the information signal over long distances. In AM, the amplitude of the carrier signal is varied in accordance with the instantaneous amplitude of the modulating or information signal. This creates two new sideband frequencies above and below the carrier frequency equal to the modulation frequency. The carrier and sidebands together make up the modulated signal. Only a portion of the transmitted power is present in the sidebands containing the information, while the rest is wasted in the carrier.
This document discusses voltage standing wave ratio (VSWR) meters, which are used to measure impedance matching and standing waves in microwave systems. It describes the principles of VSWR meters, including their construction with normal, expanded, and dB scales. Two common types are directional VSWR meters and SWR bridge circuits. Applications include laboratories, live broadcast systems, and medical equipment. Problems with VSWR meters are also noted, such as their inability to measure reactance and sensitivity to signal attenuation.
This document discusses microwave devices, specifically directional couplers and isolators. It begins by defining microwaves and their applications such as telecommunications and radar. It then describes how directional couplers are passive devices that divide power through four ports and discusses their key figures of merit like coupling factor, isolation, and directivity. Isolators are also covered as two-port non-reciprocal devices that allow high power transmission in one direction while providing high attenuation in the opposite direction using Faraday rotation in a ferrite rod.
The document discusses different types of antenna arrays, including broadside arrays, end-fire arrays, and collinear arrays. It provides details on 2-element arrays with currents of equal magnitude and phase, equal magnitude and opposite phase, and unequal magnitude and opposite phase. It also discusses properties of n-element uniform linear arrays, including expressions for directivity, beamwidth, maximum radiation direction, and null directions for broadside arrays.
The document discusses magnetostatics and provides definitions and explanations of key concepts including magnetic field, magnetic flux, Biot-Savart law, Ampere's law, solenoids, ballistic galvanometers, and damping conditions. Specific topics covered include the magnetic field produced by steady currents, magnetic field lines, curl and divergence of magnetic fields, theory and operation of ballistic galvanometers, and current and charge sensitivity of galvanometers. Examples and derivations of equations for magnetic fields and forces on conductors in fields are also provided.
1) Rectangular waveguides can transmit electromagnetic waves above a certain cutoff frequency, acting as a high-pass filter. They support transverse electric (TE) and transverse magnetic (TM) modes of propagation.
2) For TM modes, the electric field is transverse to the direction of propagation, while the magnetic field has a longitudinal component. The modes are denoted TMmn, with m and n indicating the number of half-wavelength variations across the width and height.
3) For TE modes, the magnetic field is entirely transverse, while the electric field has a longitudinal component. These modes are denoted TEmn, with m and n having the same meaning as in the TM case.
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.
This document discusses different types of avalanche transit time devices (ATTDs) used to generate microwaves, including IMPATT diodes and TRAPATT diodes. It provides details on:
1) The basics of how ATTDs like IMPATT and TRAPATT diodes utilize the avalanche breakdown effect across a reverse-biased p-n junction to produce carriers and negative resistance at microwave frequencies.
2) The different modes of ATTD oscillators, including the IMPATT mode where typical efficiency is 5-10% and frequencies can reach 100 GHz, and the TRAPATT mode with higher typical efficiency of 20-60%.
3) The physical structures and operating principles of IMPATT diodes
Optical fiber communication Part 2 Sources and DetectorsMadhumita Tamhane
For optical fiber communication, major light sources are hetero-junction-structured semiconductor laser diode and light emitting diodes. Heterojunction consists of two adjoining semiconductor materials with different bandgap energies. They have adequate power for wide range of applications. Detectors used are PiN diode and Avalanche Photodiode. Being very small in size and feeding to small core optical fiber, it is very important to study emission characteristics of sources and their coupling to fiber. As it can operate for low power over a long distance, received power is very small, hence study of noise characteristics of detectors is very essential...
This document provides information about light propagation through optical fibers. It begins by defining an optical fiber as a cylindrical waveguide made of glass that uses total internal reflection to transmit light. It then discusses the fiber's core and cladding layers and the conditions needed for total internal reflection. The key points covered include:
- Light propagation is guided through the fiber core by total internal reflection at the core-cladding interface.
- Only rays entering the fiber core within the acceptance angle will continue propagating through total internal reflection.
- Electromagnetic mode theory is needed to fully understand light propagation in fibers. Discrete modes exist that are solutions to Maxwell's equations.
- The evanescent field that penetrates the cl
Waveguide tees are used in microwave technologies to split or extract power in a waveguide. There are several types of waveguide tees that affect the energy in different ways, including H-type, E-type, magic T, and hybrid ring tees. E-type tees produce outputs that are 180 degrees out of phase, while H-type tees produce in-phase outputs. Magic T tees combine properties of H-type and E-type tees. Hybrid ring tees overcome power limitations of magic T tees using a circular waveguide design.
Classification of signals and systems as well as their properties are given in the PPT .Examples related to types of signals and systems are also given .
Antennas are used for transmitting and receiving electromagnetic waves in wireless communication systems. They work by converting electrical energy into electromagnetic waves that propagate through space. There are different types of antennas suited for different applications, but they all share fundamental properties like radiation pattern, gain, directivity, and polarization. Antennas must be designed to direct radiation in the desired direction and impedance match the transmission line to prevent reflections. Key antenna types are directional antennas like Yagi, parabolic, and sector antennas which achieve longer ranges but less coverage, versus omni-directional antennas which provide wider coverage over shorter ranges.
Transmission line, single and double matchingShankar Gangaju
This document discusses different types of transmission lines used for transmitting energy and signals over long distances. It describes common transmission line media like twisted pair, coaxial cable and optical fiber. It covers their applications in telephone networks, buildings and computer networks. It also discusses their transmission characteristics and limitations. The document compares properties of unshielded and shielded twisted pair. It provides details on utilizing different wavelengths in optical fiber for various applications.
A Gunn diode is a type of diode that uses the Gunn effect to generate microwave frequencies when a voltage above a threshold is applied. It consists of a single piece of N-type semiconductor like gallium arsenide and has a negative differential resistance region in its current-voltage characteristics that allows it to function as an oscillator. Gunn diodes are used to generate microwave signals from 10 GHz to THz and have applications in radar, sensors, and microwave transmission.
This document discusses microwave junctions and S-parameters. It provides information on:
1) Power dividers and directional couplers which are passive microwave components used for power division or combining. S-parameters are used to define the power relationships between ports.
2) The scattering matrix (S-matrix) is a matrix that defines the power relationships between ports in terms of incident and reflected voltage waves. It is commonly used for microwave analysis since direct voltage and current measurements are difficult at high frequencies.
3) Examples are provided to demonstrate calculating S-matrix coefficients for different microwave junction configurations like E-plane and H-plane tee junctions. Properties of reciprocal and lossless networks in relation to the S
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.
The document discusses equalization techniques used to mitigate inter-symbol interference (ISI) in digital communication systems. Equalization aims to remove ISI and noise effects from the channel. It is located at the receiver and uses techniques like linear equalizers, decision feedback equalization, and maximum likelihood sequence estimation to estimate the channel response and minimize the error between transmitted and received symbols while balancing noise. As the wireless channel changes over time, adaptive equalization is used where the equalizer periodically trains and tracks the changing channel response.
The receiver structure consists of four main components:
1. A matched filter that maximizes the SNR by matching the source impulse and channel.
2. An equalizer that removes intersymbol interference.
3. A timing component that determines the optimal sampling time using an eye diagram.
4. A decision component that determines whether the received bit is a 0 or 1 based on a threshold.
The performance of the receiver depends on factors like noise, equalization technique used, and timing accuracy. The bit error rate can be estimated using tools like error functions.
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 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.
This document discusses amplitude modulation (AM) as a type of modulation used to transmit information signals. Modulation involves varying a high frequency carrier signal by an information signal in order to transmit the information signal over long distances. In AM, the amplitude of the carrier signal is varied in accordance with the instantaneous amplitude of the modulating or information signal. This creates two new sideband frequencies above and below the carrier frequency equal to the modulation frequency. The carrier and sidebands together make up the modulated signal. Only a portion of the transmitted power is present in the sidebands containing the information, while the rest is wasted in the carrier.
This document discusses voltage standing wave ratio (VSWR) meters, which are used to measure impedance matching and standing waves in microwave systems. It describes the principles of VSWR meters, including their construction with normal, expanded, and dB scales. Two common types are directional VSWR meters and SWR bridge circuits. Applications include laboratories, live broadcast systems, and medical equipment. Problems with VSWR meters are also noted, such as their inability to measure reactance and sensitivity to signal attenuation.
This document discusses microwave devices, specifically directional couplers and isolators. It begins by defining microwaves and their applications such as telecommunications and radar. It then describes how directional couplers are passive devices that divide power through four ports and discusses their key figures of merit like coupling factor, isolation, and directivity. Isolators are also covered as two-port non-reciprocal devices that allow high power transmission in one direction while providing high attenuation in the opposite direction using Faraday rotation in a ferrite rod.
The document discusses different types of antenna arrays, including broadside arrays, end-fire arrays, and collinear arrays. It provides details on 2-element arrays with currents of equal magnitude and phase, equal magnitude and opposite phase, and unequal magnitude and opposite phase. It also discusses properties of n-element uniform linear arrays, including expressions for directivity, beamwidth, maximum radiation direction, and null directions for broadside arrays.
The document discusses magnetostatics and provides definitions and explanations of key concepts including magnetic field, magnetic flux, Biot-Savart law, Ampere's law, solenoids, ballistic galvanometers, and damping conditions. Specific topics covered include the magnetic field produced by steady currents, magnetic field lines, curl and divergence of magnetic fields, theory and operation of ballistic galvanometers, and current and charge sensitivity of galvanometers. Examples and derivations of equations for magnetic fields and forces on conductors in fields are also provided.
1. The document discusses conductors, dielectrics, current density, polarization, and electric susceptibility. It defines key concepts like current, current density, polarization field, dielectric constant, and boundary conditions for electric fields.
2. Conductors allow free electron flow while insulators have a large band gap; semiconductors have a small gap allowing electron excitation. Current density relates to charge velocity and conductivity.
3. Dielectrics have bound electric dipoles that contribute to polarization. The polarization field depends on dipole density and alignment with the electric field. Boundary conditions require continuous tangential E and normal D fields.
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 report describes two experiments measuring equipotential lines and electric fields between parallel plate conductors and concentric cylindrical electrodes. In both experiments, equipotential lines were marked on conducting paper connected to an 8V power supply. The electric potential and estimated field were measured and plotted against the predictions of relevant equations. For parallel plates, the potential graph matched predictions linearly but the field graph was less accurate. For concentric cylinders, both graphs matched predictions closely except for points near the disc due to measurement limitations. The experiments supported the theoretical relationships between electric potential and field.
This document provides an overview of electrostatics. It defines key concepts like electric field, electric flux density, Gauss's law, capacitance, and more. Applications of electrostatics include electric power transmission, X-ray machines, solid-state electronics, medical devices, industrial processes, and agriculture. Coulomb's law describes the electric force between point charges. Gauss's law relates the electric flux through a closed surface to the enclosed charge. Capacitance is the ratio of stored charge on conductors to the potential difference between them.
The document describes concepts from a lecture on electric fields, including:
1. The electric field E at a point is defined as the electric force F on a test charge divided by the charge q. Field lines depict the direction and strength of the field.
2. The electric field due to a point charge is directed away from a positive charge and toward a negative charge.
3. The field of a dipole is non-uniform, exerting a torque and giving the dipole a potential energy depending on its orientation in the field.
4. Continuous charge distributions are treated by summing the contributions of small charge elements to the electric field.
The document describes concepts from a lecture on electric fields, including:
1. The electric field E at a point is defined as the electric force F on a test charge divided by the test charge q. Field lines depict the direction and strength of the electric field.
2. The electric field due to a point charge is directed away from a positive charge and toward a negative charge.
3. The field due to a dipole can be determined by treating it as two point charges. A dipole experiences a torque and potential energy in an external electric field based on its orientation.
1. An antenna acts as a transducer that converts electromagnetic waves between free space and a transmission line. It is an integral part of any radio communication system.
2. Maxwell's equations relate the electric and magnetic fields through vector and scalar potentials. For time-varying electromagnetic waves, the vector potential A and scalar potential φ are defined in terms of the current and charge densities using retarded potentials.
3. Radiation from an infinitesimal current element called a Hertzian dipole is analyzed. The vector potential at a point due to a constant current element of length dl is derived in terms of the current moment dlI0.
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The document discusses different types of polarization that can occur in dielectric materials when an external electric field is applied. It defines polarization as the electric dipole moment per unit volume induced by the field. There are four main types of polarization discussed: (1) electronic polarization due to displacement of electrons and nuclei, (2) atomic polarization involving displacement of whole atoms or groups, (3) orientation polarization where the field aligns permanent dipoles, and (4) ionic polarization in ionic materials caused by displacement of positive and negative ions in opposite directions. The polarization is proportional to the applied electric field strength.
The document discusses different types of polarization that can occur in dielectric materials when an external electric field is applied. It defines polarization as the electric dipole moment per unit volume induced by the field. There are four main types of polarization discussed: electron polarization due to displacement of electrons within an atom; atomic polarization involving displacement of whole atoms or groups; orientation polarization where the field aligns permanent dipoles in the material; and ionic polarization that results from displacement of ions in an ionic lattice. The different polarization mechanisms contribute to the overall polarization of dielectric materials in electric fields.
The document discusses dielectric materials and their properties. It introduces dielectric materials and defines electric dipoles as systems of charges with zero net charge. It describes permanent dipole moments that give rise to polarization in materials and induced dipole moments that arise in external electric fields. It then discusses different types of polarization including electronic, atomic, orientation and ionic polarization.
The document discusses dielectric materials and their properties. It introduces dielectric materials and defines electric dipoles as systems of charges with zero net charge. It describes permanent dipole moments that give rise to polarization in materials and induced dipole moments that arise in external electric fields. It then discusses different types of polarization including electronic, atomic, orientation and ionic polarization.
The document discusses electric fields and electrostatics. It explains that when objects are rubbed together, electrons are transferred causing objects to become charged. It then discusses Coulomb's law which states that the force between two charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between them. It provides equations for calculating electric field strength, potential, and force experienced by charges in fields.
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Antennas and Wave Propagation
1. ANTENNA AND WAVE PROPAGATION
B.TECH (III YEAR – I SEM)
Prepared by:
Mr. P.Venkata Ratnam.,M.Tech., (Ph.D)
Associate Professor
Department of Electronics and Communication Engineering
RAJAMAHENDRI INSTITUTE OF ENGINEERING & TECHNOLOGY
(Affiliated to JNTUK, Kakinada, Approved by AICTE - Accredited by NAAC )
Bhoopalapatnam, Rajamahendravaram, E.G.Dt, Andhra Pradesh
2. Unit-II
THIN LINEAR WIRE ANTENNAS
Introduction
Retarded Potentials
Radiation from Small Electric Dipole
Quarter wave Monopole and Half wave Dipole
Current Distributions.
Evaluation of Field Components.
Power Radiated.
Radiation Resistance.
Beam widths.
Directivity.
Effective Area and Effective Height.
3. Natural current distributions.
Fields and patterns of Thin Linear Center-fed
Antennas of different lengths.
Radiation Resistance at a point which is not current
maximum.
Antenna Theorems – Applicability and Proofs for
equivalence of directional characteristics.
Loop Antennas: Small Loops - Field Components.
Comparison of far fields of small loop and short
dipole.
Concept of short magnetic dipole.
D and Rr relations for small loops.
4. Introduction :
The electric charges are the sources of the
electromagnetic (EM) fields.
When these sources are time varying, the EM waves
propagate away from the sources and radiation takes
place.
Radiation can be considered as a process of
transmitting electric energy.
The radiation of the waves into space is effectively
achieved with the help of conducting or dielectric
structures called antennas or radiators.
5. An antenna is a means of radiating or receiving the
EM waves.
An antenna may be used for either transmitting or
receiving EM energy.
In the design of antenna systems, we must consider
important requirements such as the antenna pattern,
the total power radiated, the input impedance of the
radiator, the radiation efficiency etc.
The direct solution for these requirements can be
obtained by solving Maxwell's equations with
appropriate boundary conditions of the radiator and at
infinity.
6. Potential Functions and Electromagnetic Fields :
In case of the electrostatic field or the steady magnetic
field, the electric field or the magnetic field can be
obtained easily by setting the potentials in terms of the
charges or currents.
The potentials are obtained in terms of the charges or
currents and the electric or magnetic fields are
obtained from these potentials.
For obtaining the potentials for the electromagnetic
field there are different approaches
7. In the first approach, using trial and error, the
potentials for the electric and magnetic field are
generalized.
Then it is shown that these potentials satisfy the
Maxwell's equations.
This approach is called heuristic approach.
The second approach is to start with the Maxwell's
equations and then derive the differential equations
that the potentials satisfy.
The third approach is to obtain directly the solutions
of the derived equations for the potentials.
8. Retarded Potentials :
Heuristic Approach :
Consider a uniform volume charge
density ρv over the given volume
as shown in Fig.
Consider the differential volume at a point distance r
from origin, where the charge density is ρv(r’)
Then the Scalar electric potential V at point P can be
expressed in terms of a static charge distribution as
…… 1
9. Then the fundamental electric field
can be obtained by finding the
gradient of a scalar potential V as
……. 2
Similarly for a steady magnetic field,
in a homogeneous medium, the vector
magnetic potential A can be expressed interms of
current distribution at constant with time as
…. 3
10. Then the fundamental magnetic field can be obtained
by finding the curl of the vector magnetic potential A
as
…… 4
The potentials V(r) and A(r) represent the potentials
for the static electric and Magnetic fields respectively
where the charge and current distributions do not vary
with time.
But the charge and current distributions producing the
electromagnetic field vary with time.
11. Thus the time varying fields, the potentials are given
by
Where R = |r – r’ |
In general, the velocity of the electromagnetic
field can be described in terms of μ and ε as
v= 1/√ με .
12. Then the potentials at the same point with at a finite
velocity. Hence it is necessary to accomplish this finite
propagation time, the equations can be expressed by
introducing a time delay R/v as
The potentials are delayed or retarded by time R/v,
Hence the potentials are called retarded potentials
13. Maxwell’s Equation Approach :
In this approach, starting from Maxwell’s equations,
the differential equations are derived.
For time varying fields ,Maxwell’s equations are given
by
14. From Equation.12, It is clear that the divergence of H
is zero.
But from the vector identity the divergence of a Curl of
a vector is zero.
This clearly indicates that to satisfy, H must be
expressed as a Curl of vector potential A as
Now, putting the value of μH in the Equation 9, We
get,
15. Interchanging the operators on RHS of the above
equation, We get,
From vector identity Curl of a gradient of scalar is
always zero, So equation .14 will be satisfied only if
the term is defined as gradient of scalar.
16. Now, introduce a scalar potential V such that
Then the electric field strength is given by
So from equations 13 and 16, It is clear, the electric
and magnetic fields E and H can be expressed interms
of scalar potential V and vector potential A
Now substitute the values E and H from Eq 16 and 13
in Eq. 10, We get
17. Interchanging the operators, We have
From the vector identity
Rewrite the equation 17 using above identity
18. Now, Substitute E from Eq. 16 into Eq .11, We get
The equations 18 and 19 are called Coupled
equations.
These are not sufficient enough to define A and E
completely. Using Helmholtz Theorem we get the
unique solution.
19. The Helmholtz theorem states that Any vector field
can defined uniquely if the curl and divergence of the
field both are known at any point.
Now we may choose divergence of A from equation 18
as
Thus selection divergence of A as given in equations
18,19,20 become un coupled.
The relationship between the divergence of A and V is
know as Lorentz gauge condition or Lorentz gauge for
potentials.
22. The equations 21 and 22 are the standard wave
equations including source terms.
The solutions of the equations 21 and 22 are given by
23. Potential Functions for Time Periodic Fields.
The potential functions obtained using Lorentz gauge
condition are given by,
In the sinusoidal steady state,we can rewrite these by
replacing ( ∂/∂t ) with ( jω ) ,Thus the equation 1 can
be written as,
24. Similarly equation 2 can be written as
Similarly, for the wave travelling in R direction with
phase variation represented by e-jβR. So the potential
functions for sinusoidal oscillations are given by
25. Radiation from Alternating Current Element :
To calculate the electromagnetic field radiation from
short dipole, the retarded potential is used.
A short dipole is an alternating current element. It is
also called an oscillating current element.
An alternating current element is consider as the basic
source of radiation.
In generally, a current element IdL is nothing but an
element length dL carrying current I.
This length of wire is assume to be very short.
26. To calculate the electromagnetic field due to alternating
current element, consider Spherical co-ordinate system
and the current through is IdL cosωt , locate at centre
is shown in fig.
The electromagnetic is calculate at a point P placed at a
distance R from origin.
The element is IdL cosωt is place along the z-axis.
27. Let, the vector potential A is given by
As the current element is placed along z-axis. Hence
the vector potential can be write as
28. From the equation 2, it is clear that the vector potential
Az can be obtained by integrating the current density J
over the volume.
• Now , the current is assumed to be constant along the
length dL, the integration of J over the length dL gives
value IdL .
• Thus mathematically we can write,
29. Substitute the integration of equation 3 in equation2,
the vector potential in z-axis is given by
Now , the magnetic field is given by
Using spherical co-ordinate system, to find curl A in r,
θ, ɸ direction, we have
30. Hence A is given by
Now, Aɸ = 0 and because of symmetry ∂/∂ɸ = 0. Thus
the first two terms of equation 7 can be neglected.
31. Now ,Putting values of Ar and Aθ from equation 5,
We get
Substitute the Az value in above equation, We have,
32.
33. Therefore
Hence the magnetic field H is given by
Substitute the value of , We get,
34. From equation 10, It is clear that the magnetic field H
only in ɸ direction.
Now substitute , We get,
35. Let us now calculating electric field
Now, Integrating on both sides w.r.t variable, We get,
36. Let us calculate each term of separately
The component in ar direction is given by
46. Power Radiated from Current Element :
Consider a current element placed at a centre of a
spherical co-ornate systems.
Then the power radiated per unit area at point P can
be calculated by using Poynting theorem .
The components of the Poynting vector are given by
Pr = Eθ Hɸ
Pθ = - Er Hɸ
Pɸ = Eθ Hr
But we know that, the current element is at orgin, then
the Eɸ = 0
47. Let the field components of Er , Eθ , Hɸ and replacing
v by c are given by
55. Therefore the total power radiated by current element
can be obtained by integrating the radial pointing
vector over a spherical surface.
The element area ds is given by
ds = 2πr2sinθ dθ
The total power radiated is given by
56. In Spherical coordinate system θ varies from 0 to π.
Hence
57.
58. Substitute this value, we get,
The power represented in terms of Maximum or Peak
current
59.
60.
61. Therefore the power radiated from the current
element is given by
Generally the power is expressed as
P = I2 R
So, the Radiation resistance of current element is given
by
62. Short Linear Antenna:
The current element that we have considered previously
is not a practical, but it is hypothetical.
It is useful in the theoretical calculations such as the
components of the fields, radiation of power etc.
The practical example of the centre-fed antenna is an
elementary dipole.
The length of such centre-fed antenna is very short in
wavelength.
63. The current amplitude on such antenna is maximum
at the center and it decreases uniformly to zero at the
ends.
If we consider same current I flowing through the
hypothetical current element and the practical short
dipole, both of same length.
Then the practical short dipole radiate only one-
quarter of the power that is radiated by the current
element.
64. The radiation resistance of short dipole is ¼ times of
that the current element
Hence the radiation resistance of short dipole is given
by
65. Monopole or Short vertical Antenna :
Consider the current I flows through a monopole of
length h and short dipole of length l =2h.
Then the field strength produced by both are same
above the reflecting plane.
66. The radiated power of monopole is half of that
radiated by short dipole.
Hence the radiation resistance of monopole is half of
the radiation resistance of short dipole
68. Half wave dipole and The Monopole :
A very commonly used antenna is the half wave dipole
with a length one half of the free space wavelength of
the radiated wave.
It is found the linear current distribution is not suitable
for this antenna.
But when such antenna is fed at its centre with the
help of a transmission line,
It gives a current distribution which is approximately
sinusoidal, with maximum at the centre and zero at the
ends.
69. The half wave clippie can be considered as a chain of
Hertzian dipoles.
70. Power Radiated by the Half Wave Dipole and Monopole
A dipole antenna is a vertical radiator fed in the centre.
It produces maximum is the overall length.
The vertical antenna of height H =L/2 produces the
radiation characteristics above the plane which is similar
to that produced by the dipole antenna of length L =
2H.
The vertical antenna is referred as a monopole.
The practically used antennas are half wave dipole
(λ / 2) and quarter wave monopole (λ / 4).
71. The half wave dipole consists two legs each of length
L/2.
The physical length of the half wave dipole at the
frequency of operation is λ/2 in free space.
72. The quarter wave mono pole consists of single vertical
leg erected on the perfect ground.
The length of the leg of the quarter wave monopole is
λ/4.
73. Now consider the current element I dz is placed at
distance z from z=0.
Then the sinusoidal current distribution is given by
Now consider a point P located far distance R from
current element I dz. The vector potential Az is given
by
74. Now substitute I value in the above equation, we get
We have certain assumptions to calculate radiation
field, assume R = r, replace R in denominator only
with r and
R = r - z cosθ in numerator term .
90. The total radiated power from dipole antenna is
91. Therefore
The value of integral by the Simpsons rule is given by
92. Hence the radiated power is given by
Hence the radiation resistance of the quarter wave
Monopole is
Therefore the radiation resistance of the Half wave
dipole is given by
93.
94.
95. Antenna Theorems :
An antenna can be used as both transmitting antenna
and receiving antenna.
While using so, we may come across a question
whether the properties of the antenna might change as
its operating mode is changed.
The properties of antenna being unchangeable is
called as the property of reciprocity.
96. The properties of transmitting and receiving antenna
that exhibit the reciprocity are −
Equality of Directional patterns.
Equality of Directivities.
Equality of Effective lengths.
Equality of Antenna impedances.
97. Equality of Directional patterns :
The radiation pattern of transmitting antenna 1, which
transmits to the receiving antenna 2 is equal to the
radiation pattern of antenna 2, if it transmits and
antenna1 receives the signal.
Equality of Directivities :
Directivity is same for both transmitting and receiving
antennas, if the value of directivity is same for both the
cases.
The directivities are same whether calculated from
transmitting antenna’s power or receiving antenna’s
power.
98. Equality of Effective lengths :
The value of maximum effective aperture is same for
both transmitting and receiving antennas.
Equality in the lengths of both transmitting and
receiving antennas is maintained according to the value
of the wavelength.
Equality in Antenna Impedances :
The output impedance of a transmitting antenna and
the input impedance of a receiving antenna are equal
in an effective communication.
99. Loop Antennas:
An RF current carrying coil is given a single turn into a
loop, can be used as an antenna called as loop
antenna.
The currents through this loop antenna will be in
phase.
The magnetic field will be perpendicular to the whole
loop carrying the current.
It may be in any shape such as circular, rectangular,
triangular, square or hexagonal according to the
designer’s convenience.
100. Loop antennas are of two types.
Large loop antennas
Small loop antennas
Large loop antennas are also called as resonant antennas.
They have high radiation efficiency. These antennas
have length nearly equal to the intended wavelength(L=λ).
Small loop antennas are also called as magnetic loop
antennas. These are mostly used as receivers.
These antennas are of the size of one-tenth of the
wavelength ( L = λ/10 )
101. Field Components :
Consider that the square loop is located at the centre
of the Spherical coordinate system.
Then the far field of the square loop will have only EΦ
Component.
102. Now the far field radiation due to two point sources with
reference to centre O can be represented as
EΦ = Field component + Field component
due to dipole 1,4 due to dipole 2, 3
The path difference between
from point L to M
Path difference = d cos( 900 – θ )
Then the path difference is
expressed interms of wavelength as
Path difference = d cos ( 900 – θ ) / λ
103. Let ψ is the phase angle and it is relate with path
difference is given by
Phase angle = ψ = 2π x path difference
The field component for any dipole is given by
Field component = Magnitude x ej( phase angle )
Let the field component due to dipole 1,4 is given by
104. Similarly field component due to dipole 2,3 is
given by
Hence the far field radiation due to square
loop is given by
105. We have
Hence we can write
Now substitute phase angle, we get,
106. The other field components can be given by the
following relation
107. Comparison of far fields of small loop and short dipole :
A small loop can be consider as equivalent to short
magnetic dipole.
Thus a small loop of area A carrying current I can be
replaced by a short magnetic dipole length L and
carrying fictitious magnetic current Im
108. The magnetic moment of the loop is I . A is the small
loop area, current I is the uniform phase current
throughout loop
Hence equating this magnetic moment with the
magnetic moment of short dipole is given by qm. L
Hence we can write,
The above equation represent the equivalence of
magnetic dipole of length L carrying fictitious current
Im with small loop of area A and carrying current I.
109. Radiation Resistance of Loop antenna :
To find the radiation resistance of the loop antenna, the
poynting vector is integrated over large sphere.
The power radiated is given by
P = I2
rms Rrad = ½ IM Rrad
The average poynting power
is given by
110. The total power radiated over a large sphere is given
by
Now, equate this quation with power equation, we get,
111. But πa2 is the area A of loop. Hence the radiation
resistance is given by
The above expression can be written as
112. For circular loop antenna, the radiation resistance is
given by
Where C is the Circumference ( C= 2πa )
113. When C/ λ>5, the loop consider large loop, then the
radiation resistance is given by
114. The directivity of circular Loop Antenna :
The directivity of an antenna is defined as the ratio of
maximum radiation intensity to the average radiation
intensity
Let us consider two cases one for small loop antenna
and other for large loop antenna
115.
116.
117. Application of loop antennas :
A small loop antenna is used as source for
paraboloid in many applications
Large loop antenna can be used as direction
finder.
Used in line of sight communication