This document contains 52 multiple choice questions about antennas and wave propagation. The questions cover topics such as:
- Key people and dates in the history of antennas and radio
- Fundamental dimensions and units used in antennas and waves
- Properties of electromagnetic waves like wavelength and polarization
- Maxwell's equations and their application to antennas
- Antenna parameters like directivity, gain, radiation patterns
- Near and far field regions of antennas
The questions test knowledge across the fundamental theoretical concepts and practical applications of antennas and electromagnetic wave propagation. Answering the questions would demonstrate understanding of this technical subject area.
A horn antenna or microwave horn is an antenna that consists of a flaring metal waveguide shaped like a horn to direct radio waves in a beam. Horns are widely used as antennas at UHF and microwave frequencies, above 300 MHz.
The document discusses vestigial sideband modulation (VSB) and the Hilbert transform. VSB is a type of amplitude modulation where portions of one redundant sideband are removed, leaving a "vestige" of the sideband. This reduces bandwidth compared to double sideband modulation while being easier to implement than single sideband. VSB transmission became a standard for television signals due to the large bandwidth needs of video. The Hilbert transform produces a 90 degree phase shift between positive and negative frequencies, leaving signal amplitudes unchanged. It defines the inverse transform and its properties include signals having the same amplitude spectrum and being orthogonal.
S-parameters are a useful method for representing a circuit as a "black box" whose external behavior can be predicted without knowledge of its internal contents. S-parameters are measured by sending a signal into the black box and detecting the waves that exit each port. They depend on the network, source and load impedances, and measurement frequency. Common S-parameters include S11 for the reflected signal at port 1 and S21 for the signal exiting port 2 due to a signal entering port 1.
Hello everyone. This is a short presentation on path loss and shadowing. I have not covered all the topics but a brief idea is given on path loss and wireless channel propagation models.
Hope you find it useful.
Thanks
1. An integrated circuit is a circuit constructed on a single semiconductor wafer or chip that contains transistors, resistors, and capacitors interconnected to perform a given function.
2. Integrated circuits are classified as either digital or linear. Digital ICs operate using discrete voltage levels while linear ICs have a continuously variable output.
3. Some key characteristics of operational amplifiers include very high open loop gain, very high input impedance, very low output impedance, and the ability to invert or non-invert the input signal depending on the feedback configuration. Operational amplifiers are examples of linear integrated circuits.
Radio waves can propagate between two points through four main ways: directly, following the curvature of the Earth, becoming trapped in the atmosphere, or refracting off the ionosphere. Propagation modes include ground-wave, sky-wave, and space-wave propagation. Mobile radio propagation is influenced by factors like reflections, scattering, diffraction, and the electromagnetic properties of materials. Proper propagation modeling is important for wireless system design and performance.
This document discusses various digital modulation techniques. It begins by defining modulation as adding information to a carrier signal. It then distinguishes between analog and digital modulation. Digital modulation modulates an analog carrier signal with a discrete signal, and can be considered as converting digital-to-analog and vice versa. Some key digital modulation techniques discussed include amplitude shift keying (ASK), frequency shift keying (FSK), phase shift keying (PSK), quadrature amplitude modulation (QAM), and differential phase shift keying (DPSK). Metrics for comparing digital modulation techniques include power efficiency, bandwidth efficiency, and implementation cost-effectiveness.
The document discusses sampling theory and its applications. It introduces key concepts such as:
1. Signals can be represented by discrete sample values taken at regular intervals, and reconstructed using an ideal low-pass filter, as described by the sampling theorem.
2. The sampling theorem states that a band-limited signal with no frequencies above B Hz can be uniquely determined by samples taken at least every 1/(2B) seconds.
3. Anti-aliasing filters are used to limit the bandwidth of signals before sampling to avoid aliasing when the sampling rate is lower than predicted by the sampling theorem.
A horn antenna or microwave horn is an antenna that consists of a flaring metal waveguide shaped like a horn to direct radio waves in a beam. Horns are widely used as antennas at UHF and microwave frequencies, above 300 MHz.
The document discusses vestigial sideband modulation (VSB) and the Hilbert transform. VSB is a type of amplitude modulation where portions of one redundant sideband are removed, leaving a "vestige" of the sideband. This reduces bandwidth compared to double sideband modulation while being easier to implement than single sideband. VSB transmission became a standard for television signals due to the large bandwidth needs of video. The Hilbert transform produces a 90 degree phase shift between positive and negative frequencies, leaving signal amplitudes unchanged. It defines the inverse transform and its properties include signals having the same amplitude spectrum and being orthogonal.
S-parameters are a useful method for representing a circuit as a "black box" whose external behavior can be predicted without knowledge of its internal contents. S-parameters are measured by sending a signal into the black box and detecting the waves that exit each port. They depend on the network, source and load impedances, and measurement frequency. Common S-parameters include S11 for the reflected signal at port 1 and S21 for the signal exiting port 2 due to a signal entering port 1.
Hello everyone. This is a short presentation on path loss and shadowing. I have not covered all the topics but a brief idea is given on path loss and wireless channel propagation models.
Hope you find it useful.
Thanks
1. An integrated circuit is a circuit constructed on a single semiconductor wafer or chip that contains transistors, resistors, and capacitors interconnected to perform a given function.
2. Integrated circuits are classified as either digital or linear. Digital ICs operate using discrete voltage levels while linear ICs have a continuously variable output.
3. Some key characteristics of operational amplifiers include very high open loop gain, very high input impedance, very low output impedance, and the ability to invert or non-invert the input signal depending on the feedback configuration. Operational amplifiers are examples of linear integrated circuits.
Radio waves can propagate between two points through four main ways: directly, following the curvature of the Earth, becoming trapped in the atmosphere, or refracting off the ionosphere. Propagation modes include ground-wave, sky-wave, and space-wave propagation. Mobile radio propagation is influenced by factors like reflections, scattering, diffraction, and the electromagnetic properties of materials. Proper propagation modeling is important for wireless system design and performance.
This document discusses various digital modulation techniques. It begins by defining modulation as adding information to a carrier signal. It then distinguishes between analog and digital modulation. Digital modulation modulates an analog carrier signal with a discrete signal, and can be considered as converting digital-to-analog and vice versa. Some key digital modulation techniques discussed include amplitude shift keying (ASK), frequency shift keying (FSK), phase shift keying (PSK), quadrature amplitude modulation (QAM), and differential phase shift keying (DPSK). Metrics for comparing digital modulation techniques include power efficiency, bandwidth efficiency, and implementation cost-effectiveness.
The document discusses sampling theory and its applications. It introduces key concepts such as:
1. Signals can be represented by discrete sample values taken at regular intervals, and reconstructed using an ideal low-pass filter, as described by the sampling theorem.
2. The sampling theorem states that a band-limited signal with no frequencies above B Hz can be uniquely determined by samples taken at least every 1/(2B) seconds.
3. Anti-aliasing filters are used to limit the bandwidth of signals before sampling to avoid aliasing when the sampling rate is lower than predicted by the sampling theorem.
This presentation covers:
Different types of antennas used in satellite communication
Role of an antenna
Antenna temperature
Cassegrain feed Antenna
Parabolic antenna
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
The aperture is defined as the area, oriented perpendicular to the direction of an incoming radio wave, which would intercept the same amount of power from that wave as is produced by the antenna receiving it. A horn antenna or microwave horn is an antenna that consists of a flaring metal waveguide shaped like a horn to direct radio waves in a beam. Horns are widely used as antennas at UHF and microwave frequencies, above 300 MHz.
The document describes matched filter detection using LabVIEW. It involves generating a chirp signal, adding noise to create a noisy waveform, and then using a matched filter to detect the chirp signal in the presence of noise. Specifically, it generates a chirp signal, adds white Gaussian noise, and uses a filter with an impulse response that is the time-reversed version of the chirp signal to maximize the signal-to-noise ratio and detect the chirp signal in the noisy waveform. It provides examples detecting chirp signals of different lengths in the presence of noise.
This document summarizes the helical antenna. The helical antenna is a broadband VHF and UHF antenna that provides circular polarization. It consists of a helix of thick copper wire wound in a screw thread shape around a metal plate ground plane. The helix is fed by a coaxial cable connected to the inner conductor, while the outer conductor connects to the ground plane. The antenna can operate in two modes - normal mode and axial mode - depending on the helix diameter, turn spacing, and other dimensions. The normal mode radiates perpendicularly to the axis for circular polarization. The axial ratio and other parameters must meet certain conditions for effective circular polarization.
This document discusses cavity resonators and ultra-wideband (UWB) systems. It begins with an introduction to cavity resonators and mentions that they are useful microwave devices. It then discusses different types of cavity resonators, including rectangular and circular cavity resonators. The document also covers applications of cavity resonators and UWB systems. For UWB systems, it notes that they use very short sub-nanosecond pulses across a wide bandwidth and have features like unlicensed spectrum use, high data rates, and immunity to multipath fading. It also discusses UWB antennas and their requirements like operating across the entire frequency band simultaneously with minimal pulse distortion.
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.
The document discusses amplitude modulation (AM), which is the simplest and earliest form of modulation. AM involves varying the amplitude of a carrier signal based on the instantaneous amplitude of an information signal. It describes the basic principles of AM, including modulation index and different types of AM such as double sideband suppressed carrier AM and single sideband AM. Advantages of AM include its simplicity of implementation, while disadvantages include inefficiency in power and bandwidth usage and susceptibility to noise.
A periodic signal repeats its pattern over a specific time interval and can be represented by a mathematical equation, while an aperiodic signal does not repeat over time and cannot be determined with certainty at any given point or represented by an equation. Examples of periodic signals include sine, cosine, and square waves, while aperiodic signals include sound from radios and noise.
The document describes experiments performed on three digital modulation techniques: amplitude shift keying (ASK), frequency shift keying (FSK), and phase shift keying (PSK). MATLAB and Simulink were used to generate ASK, FSK, and M-PSK modulated signals. For ASK, the amplitude of the carrier signal is varied to represent binary 1 and 0. For FSK, the frequency of the carrier signal is varied. For PSK, the phase of the carrier signal is varied to represent the data bits. Troubleshooting was required to produce the correct modulated signals. Higher carrier frequencies can cause distortion for ASK and FSK. M-PSK modulation using 8-ary PSK was also implemented in Sim
This ppt contains information about concepts of wireless communication, signal propagation effects, spread spectrum, cellular systems, multiple access systems.
This document provides an overview of communication basics and amplitude modulation. It discusses how communication involves transmitting and receiving information, and how modulation translates signals to higher frequencies for long-distance transmission. It then describes various amplitude modulation techniques like AM, DSB, and SSB. Key aspects covered include the AM envelope, frequency spectrum of AM waves, AM modulation indexes, and different AM modulation and demodulation methods.
This document discusses various topics related to antennas and propagation, including:
- The basic functions of antennas for transmission and reception of signals
- Types of radiation and reception patterns that characterize antenna performance
- Common types of antennas like dipole, vertical, and parabolic reflective antennas
- Factors that influence signal propagation over distance like free space loss, noise, multipath interference, and atmospheric effects
- Techniques to improve reliability like diversity combining, adaptive equalization, and forward error correction coding.
1. Power dividers are microwave components that divide input power between output ports. Common types include T-junction, Wilkinson, and multi-section broadband dividers. T-junction dividers can be lossless or lossy. Wilkinson dividers provide isolation between output ports.
2. Directional couplers are 4-port networks that divide power between through and coupled ports. They use quarter-wave length lines and even-odd mode analysis. Voltage ratios define coupling factors. Multisection designs provide broadband operation.
3. Hybrids like the quadrature and ring hybrids are 90 or 180 degree hybrids based on symmetric/asymmetric port designs and even-odd mode analysis to provide specific scattering
This document discusses the process of sampling in signal processing. It defines key terms like analog and digital signals, sampling frequency, and samples. It explains how sampling works by taking regular measurements of a continuous signal's amplitude over time. This converts it into a discrete-time signal. It discusses applications of sampling like audio sampling, where signals are typically sampled above 20 kHz. It also discusses video sampling rates and speech sampling rates. The document contains examples and diagrams to illustrate these concepts.
Reflector antennas use a reflecting surface to direct the radiation pattern of a feeding element. Parabolic reflectors provide highly directional beams by reflecting waves from a feed at the focus into a parallel beam. Reflectors can have different shapes like flat sheets, corners, parabolas, ellipses, and hyperbolas. Parabolic reflectors are widely used in applications like television, communication, and radio astronomy due to their ability to produce a narrow beam. The feed is a key component and common options include dipoles, horns, and Cassegrain feeds which place the feed behind the reflector. Design factors like the focal length to diameter ratio determine properties like beamwidth and efficiency.
The document discusses Module 02 which covers the uniform plane wave equation and power balance. It is a lecture by Awab Sir who can be contacted at www.awabsir.com or by phone at 8976104646. The document contains repetitive text promoting the instructor's website and contact information.
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.
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.
Description above the horn antenna, that what is it , how its work and what are the types of it and also its descriptions.
for a student that is easy to them to learning (like a easy solution)
This document provides an overview of a nonresident training course on electronics technician volume 7, which covers antennas and wave propagation. Specifically, it will discuss wave propagation with regards to how the earth's atmosphere affects it and how to optimize equipment performance. It will also cover identifying communications and radar antennas by physical characteristics, installation locations, radiation patterns and power/frequency capabilities. The course is self-paced and organized into chapters covering the topics. It is designed to help electronics technicians study for advancement and improve their knowledge of relevant military topics.
This document contains the details of an exam on the subject of Antenna and Wave Propagation for students in their third year of an Electronics and Communication Engineering program. The exam contains short answer questions worth 2 marks each, one question worth 10 marks, and two 15 mark questions from which students can choose one. The questions cover topics like defining an antenna, radiation patterns, polarization, beam solid angle, bandwidth, antenna temperature, gain and directivity, radiation from a Hertzian dipole, retarded vector potential, effective aperture, reciprocity theorem, and effective length.
This presentation covers:
Different types of antennas used in satellite communication
Role of an antenna
Antenna temperature
Cassegrain feed Antenna
Parabolic antenna
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
The aperture is defined as the area, oriented perpendicular to the direction of an incoming radio wave, which would intercept the same amount of power from that wave as is produced by the antenna receiving it. A horn antenna or microwave horn is an antenna that consists of a flaring metal waveguide shaped like a horn to direct radio waves in a beam. Horns are widely used as antennas at UHF and microwave frequencies, above 300 MHz.
The document describes matched filter detection using LabVIEW. It involves generating a chirp signal, adding noise to create a noisy waveform, and then using a matched filter to detect the chirp signal in the presence of noise. Specifically, it generates a chirp signal, adds white Gaussian noise, and uses a filter with an impulse response that is the time-reversed version of the chirp signal to maximize the signal-to-noise ratio and detect the chirp signal in the noisy waveform. It provides examples detecting chirp signals of different lengths in the presence of noise.
This document summarizes the helical antenna. The helical antenna is a broadband VHF and UHF antenna that provides circular polarization. It consists of a helix of thick copper wire wound in a screw thread shape around a metal plate ground plane. The helix is fed by a coaxial cable connected to the inner conductor, while the outer conductor connects to the ground plane. The antenna can operate in two modes - normal mode and axial mode - depending on the helix diameter, turn spacing, and other dimensions. The normal mode radiates perpendicularly to the axis for circular polarization. The axial ratio and other parameters must meet certain conditions for effective circular polarization.
This document discusses cavity resonators and ultra-wideband (UWB) systems. It begins with an introduction to cavity resonators and mentions that they are useful microwave devices. It then discusses different types of cavity resonators, including rectangular and circular cavity resonators. The document also covers applications of cavity resonators and UWB systems. For UWB systems, it notes that they use very short sub-nanosecond pulses across a wide bandwidth and have features like unlicensed spectrum use, high data rates, and immunity to multipath fading. It also discusses UWB antennas and their requirements like operating across the entire frequency band simultaneously with minimal pulse distortion.
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.
The document discusses amplitude modulation (AM), which is the simplest and earliest form of modulation. AM involves varying the amplitude of a carrier signal based on the instantaneous amplitude of an information signal. It describes the basic principles of AM, including modulation index and different types of AM such as double sideband suppressed carrier AM and single sideband AM. Advantages of AM include its simplicity of implementation, while disadvantages include inefficiency in power and bandwidth usage and susceptibility to noise.
A periodic signal repeats its pattern over a specific time interval and can be represented by a mathematical equation, while an aperiodic signal does not repeat over time and cannot be determined with certainty at any given point or represented by an equation. Examples of periodic signals include sine, cosine, and square waves, while aperiodic signals include sound from radios and noise.
The document describes experiments performed on three digital modulation techniques: amplitude shift keying (ASK), frequency shift keying (FSK), and phase shift keying (PSK). MATLAB and Simulink were used to generate ASK, FSK, and M-PSK modulated signals. For ASK, the amplitude of the carrier signal is varied to represent binary 1 and 0. For FSK, the frequency of the carrier signal is varied. For PSK, the phase of the carrier signal is varied to represent the data bits. Troubleshooting was required to produce the correct modulated signals. Higher carrier frequencies can cause distortion for ASK and FSK. M-PSK modulation using 8-ary PSK was also implemented in Sim
This ppt contains information about concepts of wireless communication, signal propagation effects, spread spectrum, cellular systems, multiple access systems.
This document provides an overview of communication basics and amplitude modulation. It discusses how communication involves transmitting and receiving information, and how modulation translates signals to higher frequencies for long-distance transmission. It then describes various amplitude modulation techniques like AM, DSB, and SSB. Key aspects covered include the AM envelope, frequency spectrum of AM waves, AM modulation indexes, and different AM modulation and demodulation methods.
This document discusses various topics related to antennas and propagation, including:
- The basic functions of antennas for transmission and reception of signals
- Types of radiation and reception patterns that characterize antenna performance
- Common types of antennas like dipole, vertical, and parabolic reflective antennas
- Factors that influence signal propagation over distance like free space loss, noise, multipath interference, and atmospheric effects
- Techniques to improve reliability like diversity combining, adaptive equalization, and forward error correction coding.
1. Power dividers are microwave components that divide input power between output ports. Common types include T-junction, Wilkinson, and multi-section broadband dividers. T-junction dividers can be lossless or lossy. Wilkinson dividers provide isolation between output ports.
2. Directional couplers are 4-port networks that divide power between through and coupled ports. They use quarter-wave length lines and even-odd mode analysis. Voltage ratios define coupling factors. Multisection designs provide broadband operation.
3. Hybrids like the quadrature and ring hybrids are 90 or 180 degree hybrids based on symmetric/asymmetric port designs and even-odd mode analysis to provide specific scattering
This document discusses the process of sampling in signal processing. It defines key terms like analog and digital signals, sampling frequency, and samples. It explains how sampling works by taking regular measurements of a continuous signal's amplitude over time. This converts it into a discrete-time signal. It discusses applications of sampling like audio sampling, where signals are typically sampled above 20 kHz. It also discusses video sampling rates and speech sampling rates. The document contains examples and diagrams to illustrate these concepts.
Reflector antennas use a reflecting surface to direct the radiation pattern of a feeding element. Parabolic reflectors provide highly directional beams by reflecting waves from a feed at the focus into a parallel beam. Reflectors can have different shapes like flat sheets, corners, parabolas, ellipses, and hyperbolas. Parabolic reflectors are widely used in applications like television, communication, and radio astronomy due to their ability to produce a narrow beam. The feed is a key component and common options include dipoles, horns, and Cassegrain feeds which place the feed behind the reflector. Design factors like the focal length to diameter ratio determine properties like beamwidth and efficiency.
The document discusses Module 02 which covers the uniform plane wave equation and power balance. It is a lecture by Awab Sir who can be contacted at www.awabsir.com or by phone at 8976104646. The document contains repetitive text promoting the instructor's website and contact information.
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.
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.
Description above the horn antenna, that what is it , how its work and what are the types of it and also its descriptions.
for a student that is easy to them to learning (like a easy solution)
This document provides an overview of a nonresident training course on electronics technician volume 7, which covers antennas and wave propagation. Specifically, it will discuss wave propagation with regards to how the earth's atmosphere affects it and how to optimize equipment performance. It will also cover identifying communications and radar antennas by physical characteristics, installation locations, radiation patterns and power/frequency capabilities. The course is self-paced and organized into chapters covering the topics. It is designed to help electronics technicians study for advancement and improve their knowledge of relevant military topics.
This document contains the details of an exam on the subject of Antenna and Wave Propagation for students in their third year of an Electronics and Communication Engineering program. The exam contains short answer questions worth 2 marks each, one question worth 10 marks, and two 15 mark questions from which students can choose one. The questions cover topics like defining an antenna, radiation patterns, polarization, beam solid angle, bandwidth, antenna temperature, gain and directivity, radiation from a Hertzian dipole, retarded vector potential, effective aperture, reciprocity theorem, and effective length.
This document discusses various topics related to antennas and propagation. It begins by defining an antenna and its roles in transmission and reception of electromagnetic energy. It then describes common antenna types including dipole antennas, quarter-wave vertical antennas, and parabolic reflective antennas. The document also covers propagation modes such as ground-wave, sky-wave, and line-of-sight propagation. Additional topics discussed include antenna gain and effective area, various sources of noise and signal impairments like multipath propagation and fading, and techniques to compensate for errors.
The document provides the study scheme and course details for the 3rd through 8th semesters of the B.Tech Electronics and Communication Engineering program at Punjab Technical University, Jalandhar, India. It includes the course codes, titles, credit hours, internal and external assessment breakdown, and total marks for each semester. The core courses cover topics in applied mathematics, network analysis, electronic devices and circuits, instrumentation, programming, and labs. Department electives are offered in areas like communication systems, VLSI design, and computer networks. Students also complete industrial training in their 4th and 7th semesters.
This document summarizes research on conformal antennas. Conformal antennas are designed to conform to non-planar surfaces for aerodynamic or stealth purposes. Examples of conformal antenna designs discussed include microstrip arrays on cylinders and spheres. Parameters like gain are calculated based on satellite communication system requirements. Various conformal antenna designs are presented, including phased arrays on aircraft and ships to provide electronic beam steering. References discuss additional conformal antenna research.
The document describes the design, construction, and working of a Yagi-Uda antenna, noting that it consists of a series of parallel dipole elements with spacing of about a quarter wavelength that boosts signal strength through mutual inductance, with the reflector element placed half a wavelength behind the driven element to further focus incoming radio waves. It also lists the advantages of Yagi-Uda antennas as being easy to design, capable of high gain, and relatively low cost.
Am Radio Receiver And Amplifier Experiment And Am Transmission Demonstrationguestb0bbf0
The document summarizes two experiments conducted by Jessica McCall, Fouzia Chuta and Martin Mills for their media technology course: 1) building an AM radio receiver with audio amplifier, and 2) demonstrating AM transmission. For the first experiment, they explain the aims, equipment used including a diagram, construction method, and results which was that the radio successfully received BBC radio stations. For the second experiment on AM transmission demonstration, they explain the aims, equipment such as an oscilloscope and function generator, method of using this equipment to generate and receive AM signals, and results being that the radio made a buzzing sound when tuned to the transmission frequency.
This chapter provides an overview of fundamental antenna concepts and properties including polarization, radiation pattern, gain, bandwidth, and voltage standing wave ratio (VSWR). It then discusses microstrip patch antennas, including their structure and advantages. Finally, it introduces metamaterials and defected ground structures (DGS), which can be used to reduce antenna size by providing a negative refractive index substrate. The chapter establishes the background knowledge needed to understand the goals of developing a miniaturized antenna using metamaterial substrates with DGS.
The document discusses various topics related to mobile communication systems:
1. Different categories of antennas and examples of each including wire antennas, microstrip antennas, reflector antennas, travelling wave antennas, and aperture antennas.
2. Types of handover in mobile networks - hard handoff and soft handoff.
3. Ionospheric bending which is the phenomenon of radio wave refraction in the ionospheric layer causing the waves to bend.
This document discusses Maxwell's equations and electromagnetic waves through conceptual problems and examples.
Some key points:
1) Maxwell's equations apply to both time-independent and time-dependent electric and magnetic fields. The electromagnetic wave equation can be derived from Maxwell's equations.
2) Electromagnetic waves are transverse waves where the electric and magnetic fields oscillate perpendicular to the direction of propagation.
3) The momentum of an electromagnetic wave depends on its intensity, so waves of equal intensity have equal momentum regardless of frequency.
4) Radiation pressure from sunlight was determined to be causing changes to the orbit of one of the first U.S. satellites, something not accounted for in its design. Estimates
AP PGECET Electrical Engineering 2016 question paperEneutron
This document provides instructions for a 120-question, 120-minute multiple choice exam. Each question has 4 answer choices marked A, B, C or D. Questions must be answered on the provided OMR answer sheet using a blue or black pen. The exam booklet and answer sheet should be returned to the invigilator before leaving the exam hall. No additional materials like calculators are allowed.
Electromagnetism ap multiplechoiceanswers2011 _1_Vladimir Morote
This document contains multiple choice questions about circuits and electricity concepts. It includes questions about:
- Equivalent resistances of circuits with resistors in series and parallel
- Current, voltage, and power calculations in circuits
- Capacitors and capacitance
- Kirchhoff's laws and circuit analysis
- Electromagnetism, magnetic fields, and induced currents
This document contains solutions to multiple physics problems involving electromagnetic waves. Problem 1 involves calculating the conductivity and penetration depth of graphite at different frequencies. Problem 2 involves propagating an electromagnetic wave in seawater and calculating various parameters like attenuation constant and phase velocity. It provides the solutions and steps for parts a, b, and c of this problem. Problem 3 involves analyzing the behavior of electromagnetic waves on a finite transmission line terminated by a load impedance and derives relevant equations.
1. The document contains 25 multiple choice questions in Section A of a mechanical engineering exam. It tests knowledge of topics including matrices, fluid mechanics, thermodynamics, heat transfer, and more.
2. It also contains 25 additional multiple choice questions testing further mechanical engineering topics. These questions cover areas such as dynamics, differential equations, stress analysis, and aerodynamics.
3. The examinee is asked to answer each question by selecting one or more correct answer choices and writing the corresponding letter(s) in the answer column. This examines their understanding of fundamental mechanical engineering concepts.
This document defines and describes various fundamental properties of antennas including radiation patterns, field regions, directivity, gain, bandwidth, polarization, input impedance, and the Friis transmission equation. It provides definitions and equations for quantifying properties like radiation intensity, directive gain, half power beamwidth, radar cross section, and more. Diagrams are included to illustrate concepts like radiation lobes, coordinate systems, and the geometrical arrangements for defining a radian and steradian.
This document defines and describes various fundamental properties of antennas including radiation patterns, field regions, directivity, gain, bandwidth, polarization, input impedance, and the Friis transmission equation. It provides definitions and equations for quantifying properties like radiation intensity, directive gain, directivity, beamwidth, radar cross section, and the radar range equation. Diagrams are included to illustrate concepts such as radiation lobes, coordinate systems, and geometries used in transmission equations.
This document provides instructions for a physics exam. It describes the format and sections of the exam paper. Section 1 contains multiple choice questions with one or more correct answers. Section 2 contains paragraphs followed by related questions, each with a single correct answer. Section 3 has multiple choice questions with matching lists. The marking scheme awards marks for correct answers and deducts marks for incorrect answers. The document then provides sample exam questions in physics.
This document discusses line integrals and Green's theorem. It defines line integrals as integrals of scalar or vector fields along a curve, parameterized by arc length. Line integrals may depend on the path taken between two points, but are path-independent for conservative vector fields. Green's theorem relates line integrals around a closed curve to a double integral over the enclosed region, equating the line integral to the curl of the vector field integrated over the region. An example demonstrates using Green's theorem to evaluate a line integral as a double integral.
This document contains a past paper for the GATE electrical engineering exam from 2009. It consists of 30 multiple choice questions testing concepts in areas like circuits, electronics, power systems, control systems, and digital electronics. The questions cover topics such as dynamometer wattmeters, error analysis in measurement systems, circuit analysis, characteristics of generators and motors, properties of semiconductors, logic gates, transformers, stability analysis, and more.
1. The document discusses concepts related to antenna gain, beamwidth, and efficiency. It provides equations to calculate gain based on an antenna's beamwidth and aperture area.
2. Two models for approximating an antenna pattern are presented: an elliptical model and a rectangular model. Equations are given for calculating gain using each model based on the antenna's azimuth and elevation beamwidths.
3. Factors like wavelength, aperture size, and efficiency determine an antenna's beamwidth and gain. The 3dB beamwidth is roughly half the angle between the main lobe peak and first null. Gain increases with smaller beamwidths or apertures concentrated in a sector.
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1. SHORT ANSWER QUESTIONS (ANTENNAS AND WAVE PROPAGATION)
SECTION – A
GENERAL
1 The first antenna was built by:
(a) J. D. Kraus (b) Guglielmo Marconi (c) Heinrich Hertz (d) R. J. Marhefka
2 The regular transatlantic message service started in:
(a) 1899 (b) 1900 (c) 1901 (d) 1902
3 Broadcasting began and the word radio was introduced in about:
(a) 1901 (b) 1910 (c) 1920 (d) 1930
4 If L, M, t, I, T and i represent Length, mass, time, electric current, temperature and
luminous intensity respectively the fundamental dimensions include:
(a) L, M and t only (b) L, M, t and I only
(c) L, M, t, I and T only (d) All L, M, t, I, T and i
5 The unit of electric flux density is:
(a) Coulombs per cubic meter (b) Coulombs per square meter
(c) Coulombs per meter (d) Coulombs
6 The wavelength of 2-GHz wave is:
(a) 15 cm (b) 15 mm (c) 1.5 cm (d) 1.5 mm
7 The relevant human dimension in terms of frequency is:
(a) KHz (b) Hundreds of KHz (c) MHz (d) Hundreds of MHz
8 The vector magnetic potential can be defined where:
(a) charge density is zero (b) current density is zero
(c) flux density is zero (d) for all time variant fields
9 The relation E = -V is not adequate for time varying fields and need to be modified to the
form E = - V + N, where N equals;
(a) – v / t (b) – A / t (c) – 2
v/ t2
(d) – 2
A/ t2
10 The inadequacy of the relation E = -V is realized on the application of the curl operation
to each side, since curl of the gradient is identically zero. But, from Faraday's’ Law E is
not generally zero. To effect an improvement the equation is modified to E =
(a) -V - D/t (b) -V - /t (c) -V - B/t (d) -V - A/t
11 Let the axial ratio (AR) of a polarization ellipse is defined in terms of the ratio of electric
field intensity E. If E2 is the value of E along major axis and E1 along minor axes AR = E2/E1.
Circular polarization is an extreme case of elliptic polarization which corresponds to:
(a) E1 = E2 and AR = 1 (b) E1 = 0 and AR = 1
(c) E1 = E2 and AR = (d) E1 = 0 and AR =
2. 12 Let the axial ratio (AR) of a polarization ellipse is defined in terms of the ratio of electric
field intensity E. If E2 is the value of E along major axis and E1 along minor axes AR = E2/E1.
Linear polarization is an extreme case of elliptic polarization which corresponds to:
(a) E1 = E2 and AR = 1 (b) E1 = 0 and AR = 1
(c) E1 = E2 and AR = (d) E1 = 0 and AR =
13 The polarization loss factor F for perfect match is:
(a) 1 (b) 10 (c) (d) 0
14 The polarization loss factor F for total mismatch is:
(a) 1 (b) 10 (c) (d) 0
15 If in a network Si is the input signal Ni is the input noise, So is the output signal and No is
the output noise the noise figure is given by:
(a) Si/So (b) Si+Ni / So+No (c) So/Si (d) So+No / Si+Ni
16 In general cosmic noise decreases with the increase in frequency and is of considerable
importance in:
(a) LF and MF bands (b) MF and HF bands
(c) HF and lower VHF bands (d) VHF and lower UHF bands.
17 The brightness “B” is related to the brightness temperature TB by the Rayleigh-Jeans
formula given by:
(a) B = (2 k TB) / 2
(b) B = 2
/ (2 k TB)
(c) B = / (2 k TB) (d) B = (2 k TB) /
18 Which of the following represents one of the Maxwell’s equations in correct form?
(a) E dl = - [B/ t] dv (b) § H dl = I + § [D/ t] ds
(c) § D ds = dv (d) B ds = J dv OR = 0
19 If ES is the field intensity vector identified as a phasor by its subscript s, and k0 is the
wave number, the equation 2
ES = - k0
2
ES is called:
(a) Poisson’s equation (b) Coulomb’s gauge condition
(c) Vector Helmholtz equation (d) Diffusion equation
20 Identify the correct equation:
(a) A = - 2
v/ t2
(b) A = - v/ t
(c) V = - + 2
v/ t2
(d) V = - E – A2
/ t2
21. The Lorentz gauge condition is given by A =:
(a) -2
V/t2
(b) -V/t (c) -V (d) 0
22. The Coulombs gauge condition is given by A =:
(a) -2
V/t2
(b) -V/t (c) -V (d) 0
23. The free space wave number k0 is equal to:
(a) 0(00) (b) 0/(00) (c) 0(0/0) (d) 0/(0/0)
3. 24 If E is a function of & t and has only Er component B will have
(a) Only Br component (b) only B component
(c) only B component (d) B & B components
25 The induction and radiation fields of an oscillating electric dipole become approximately
equal at a distance r, where r =:
(a) /6 (b) /4 (c) /3 (d) /2
26 An antenna can be assumed to have sinusoidal current distribution provided its length is:
(a) /10 (b) /5 (c) /2 (d)
27 If the radiated power of a quarter wave mono-pole is given by (1/2 ) 0.609 Im2
(eff) /
2 the radiation resistance (in Ohms) of a half wave dipole is obtained to be:
(a) 36.5 (b) 18.25 (c) 73 (d) 146
28 A dipole antenna is a straight radiator, usually fed in the center. It produces a maximum
of radiation:
(a) in the plane parallel to its axis (b) in the plane normal to its axis
(c) at the place of feed (d) at its extreme ends
29. The vertical radiation pattern of a center fed vertical dipole shown in fig. (A) is for the
dipole length:
(a) 2 (b) 3/2 (c) (d) 3/4
30. The combined radiation pattern of two non-directional radiators with separation d, fed
with equal currents and with phase shift , (shown in FIG. A) belongs to:
(a) d = /2, =00
(b) d = /2, = -900
(c) d = /4, = -900
(d) d = /4, =00
FIG. A FIG. B
31. The combined radiation pattern of two non-directional radiators with separation d, fed
with equal currents and with phase shift , (shown in FIG. B) belongs to:
(a) d =, =00
(b) d = /2, = -900
(c) d = /4, = -900
(d) d = /4, =00
32. An ungrounded antenna near the ground:
(a) acts as a single antenna of twice the height (b) is unlikely to need an earth mat
(b) acts as an antenna array (d) must be horizontally polarized.
33. The standard reference antenna for the directivity is:
(a) Infinitesimal dipole (b) elementary doublet
(c) isotropic antenna (d) half wave dipole
4. 34 A pure sinusoidal continuous variation results in:
(a) Infinite bandwidth (b) Wide bandwidth
(c) Narrow bandwidth (d) Zero bandwidth
35 If Rr is the radiation resistance, T is the antenna temperature, RP indicates the radiation
pattern and f denotes the frequency of operation, identify the correct statement.
(a) All parameters Rr, T and RP are functions of f. (b) Only Rr and T are functions of f.
(c) Only Rr and RP are functions of f. (d) Only RP and T are functions of f.
36 An ungrounded antenna near the ground acts as:
(a) a point source (b) a single antenna of twice of its actual length
(c) an antenna array (d) a single antenna of half of its actual length
37 The directive gain may have a numerical value between:
(a) 0 to 1 (b) 0 to 10 (c) 0 to (d) –1 to +1
38 The quality factor of an antenna is
(a) Directly proportional to bandwidth (b) Directly proportional to square of bandwidth
(c) Inversely proportional to bandwidth (d) Inversely proportional to square of bandwidth
39 Identify the correct statement:
(a) Time changing current radiates but accelerated charge does not radiate
(b) Time changing current does not radiate but accelerated charge radiates
(c) Both, time changing current and accelerated charge radiate
(d) Both time changing current and accelerated charge do not radiate
40 From the circuit point of view an antenna appears to the transmission line as:
(a) input resistance (b) radiation resistance
(c) mutual impedance (d) coupling impedance
41 If S(, ) is the Poynting vector and S(, )max represents its maximum value the
normalized power pattern is given by:
(a) S(, ) / S(, )max (b) S(, )max / S(, )
(c) S(, )max - S(, ) (d) S(, )max + S(, )
42 The Poynting vector is given by S(, ) = [E2
() + E2
()] / Z0 where Z0 is:
(a) input impedance of the Tx- line (b) input impedance of the antenna
(c) intrinsic impedance of the space (d) combined impedance of Tx-line and antenna
43 If the (total) beam area A (or beam solid angle) consists of the main beam area M plus
the minor-lobe area m (i.e. A = M + m) beam efficiency is given by:
(a) A / M (b) M / A (c) A / m (d) m / A
44 The directivity in terms of beam area A can be written as:
(a) A / 4 (b) 4 / A (c) A / 2 (d) 2 / A
45 If G is the gain k is the efficiency factor and D is the directivity of an antenna these are
related by:
5. (a) G = k2
D (b) G = D / k2
(c) G = D / k (d) G = k D
46 The directivity D of antenna and the number N of the point sources in the sky that can be
resolved by the are related by the equation:
(a) D = N2
(b) D = N (c) D = 1/ N (d) D = 1 / N2
47 The directivity D is given in terms of the antenna aperture Ae by the following relation:
(a) D = 4Ae/2
(b) D = 42
/Ae (c) D = Ae/42
(d) D = Ae/4
48 The field around an antenna may be divided into two principal regions called the near
field or Fresnel zone and far field or Fraunhofer zone. The boundary between the two
regions may be arbitrarily taken at a radius R for an antenna of maximum dimension L,
where R and L are related by:
(a) R = 2L2
/2
(b) R = 2L/2
(c) R = 2L2
/ (d) R = 2L/
49 Antennas act as reflection-less transducers over wide range frequencies if the
discontinuities are:
(a) large and abrupt (b) small and abrupt (c) large and gradual (d) small and
gradual
50 The ratio of the distance between antenna and point of observation of field to the physical
size of an antenna is the deciding factor for considering an antenna to be a point source.
Thus an antenna may be regarded as a point source if this ratio is:
(a) > 1 (b) >> 1 (c) << 1 (d) = 1
51 The standard reference antenna for the directivity is:
(a) Infinitesimal dipole (b) elementary doublet
(c) isotropic antenna (d) half wave dipole
6. SECTION – B
52 The vertical radiation pattern of a center fed vertical dipole shown in fig. (A) is for the
dipole length:
(a) 2 (b) 3/2 (c) (d) 3/4
53 A dipole antenna is a straight radiator, usually fed in the center. It produces a maximum
of radiation:
(a) in the plane parallel to its axis (b) in the plane normal to its axis
(c) at the place of feed (d) at its extreme ends
54 The bandwidth of a folded dipole in comparison to that of an unfolded dipole is:
(a) About 50% more (b) About 10% more (c) About 50% less (d) About
10% less
55 In relation to the directional characteristics of the dipole antennas the terms ‘theta’ and
‘phi’ polarizations are synonymous with and replace the respective older terms of:
(a) Horizontal and vertical polarizations (b) Vertical and horizontal polarizations
(c) Circular and elliptical polarizations (d) Elliptical and circular polarizations
56 If ‘z’ is the input impedance of a simple dipole, the impedance of n folded dipole is:
(a) n z (b) n2
z (c) z / n (d) z / n2
57 Wire antennas are commonly termed as dipoles provided the wire length is:
(a) (b) 3/4 (c) /2 (d) /4
58 Identify the correct statement:
(a) The location of feed determines the direction of lobe and orientation of wire determines
the polarization.
(a) The location of feed determines the Polarization and orientation of wire determines the
direction of lobe.
(a) The location of feed determines the direction of lobe and the polarization.
(a) The orientation of wire determines the direction of lobe and the polarization.
59 The thickness of wire influences the characteristics of an antenna particularly its:
(a) Radiation pattern (b) Field pattern (c) Input impedance (d) Radiation
resistance
60 The following terms assigned to an antenna bears the same meaning:
(a) Terminated/standing wave/non-resonant (b) Terminated/traveling wave/resonant
(c) Un-terminated/traveling wave/non-resonant (d) Un-terminated/Standing
wave/resonant
61 Front to back ratio of an antenna can be increased by:
(a) Sacrificing its gain (b) Increasing its size
(c) Using material of high conductivity (d) None of the above
62 An ungrounded antenna near the ground:
7. (a) acts as a single antenna of twice the height (b) is unlikely to need an earth mat
(c) acts as an antenna array (d) must be horizontally polarized.
63 At a sufficient distance R at point O on the observation circle in the far field region of an
antenna:
(a) The radiated fields are radial and the power flow is transverse.
(b) The radiated fields are transverse and power flow is radial.
(c) Both the radiated fields and power floware transverse.
(d) Both the radiated fields and power floware radial
64 A diffracted ray is one that follows a path that:
(a) cannot be interpreted as either reflection or refraction
(b) can be interpreted as either reflection or refraction
(c) can be interpreted as reflection but not as refraction
(d) can be interpreted as refraction but not as reflection
65 The Huygens principle:
(a) Neglects the vector nature of electromagnetic field.
(b) Neglects the effects of current flow at the edges of slot.
(c) Neglects the effects of current flow at the edges of horn.
(d) Neglects all aspects listed in (a, b & c) above.
SECTION – C
ANTENNA ARRAYAS
66 Side lobes in a broad side array will be entirely eliminated provided the spacing between
elements does not exceed:
(a) /4 (b) /2 (c) 3/4 (d)
67 An array consisting of a number of equidistant dipoles of equal size, fed with the currents
having same amplitude and same phase is:
(a) an end fire array (b) a back fire array (c) a broadside array (d) a
binomial array
68 Select the correct statement.
(a) The end fire directivity is proportional to the square of the array length while the
directivity of the broadside square array is proportional to the side length.
(b) The end fire directivity is proportional to the array length while the directivity of the
broadside square array is proportional to the square of the side length.
(c) The directivity of both end fire and broadside array is proportional to the array
length.
(d) The directivity of both end fire and broadside array is proportional to the square of side
length.
8. 69 Width of principal lobe for uniform BSA with array length nd is reciprocal to:
(a) nd (b) n2
d (c) n2
d2
(d) nd2
70 When the current ratios and phases are properly chosen sharp directivity with an array of
fixed length but sufficiently large number of elements can be obtained. With this phasing and
close spacing between elements the radiation resistance:
(a) Reduces to extremely low value (b) Increases to extremely high value
(c) Remains unaffected (d) Changes slightly
71 The Chebyshev polynomial Tm(x) is commonly used in design and synthesis problems.
For m = 0 and m = 1 its respective values are:
(a) 1 and 0 (b) 0 and 1 (c) 1 and (d) and 1
72 An array consisting a no. of equidistant dipoles of equal size, fed with the same currents
and phase is called:
(a) end fire array (b) back fire array (c) broad side array (d) binomial array
73. The width of the major lobe is almost exactly inversely proportional to the array length l, if
(a) l (b) < l 3 /2 (c) 3 /2 < l 2 (d) l > 2
74 Side lobes in a broad side array will be entirely eliminated provided the spacing between
adjacent antennas does not exceed
(a) / 4 (b) / 2 (c) 3 / 4 (d)
75 The directional pattern of an end fire array using isotropic radiators is substantially
independent of the spacing of the antenna radiators provided this spacing does not exceed
(a) / 8 (b) / 4 (c) 3 / 8 (d) / 2
76 Choose the correct statement:
(a) Both Binomial and uniform amplitude distributions are special cases of Dolph-
Tchebyscheff distribution.
(b) Both edge and uniform amplitude distributions are special cases of Dolph-
Tchebyscheff distribution.
(c) Both Binomial and edge distributions are special cases of the Dolph-Tchebyscheff
(D-T) distribution.
(d) All the three distributions listed in (a, b & c) above are special cases of Dolph-
Tchebyscheff distribution.
9. SECTION – C
DIFFERENT TYPES OF ANTENNAS
77 The parabola reflects the wave originating from a source at the focus and transforms:
(a) A plane wave front from the feed at focus into spherical wave front
(b) A plane wave front from the feed at focus into cylindrical wave front
(c) Any curved wave front from the feed at focus into a plane wave front
(d) A cylindrical wave front from the feed at focus into a spherical wave front
78 For large parabola of many aperture a practical choice for feed can be corner reflector
with a corner angle of (depending on F/D ratio of parabola):
(a) 0 - 450
(b) 450
-900
(c) 600
-1200
(d) 900
- 1800
79 Beam widths for corner reflector are approximately equal in both principal planes
provided corner angle =:
(a) 1200
(b) 900
(c) 600
(d) 450
80 When the field across the mouth of the parabola is everywhere of the same phase the
beam generated
(a) is omni-directional (b) is sharply unidirectional
(c) has main beam with two minor side lobes (d) is bifurcated into two major beams.
81 Antennas commonly used for microwave links are:
(a) Loop antennas (b) Log periodic antennas
(c) Rhombic antennas (d) Paraboloidal dishes
82 Identify the correct statement:
(a) The feed pattern is called primary pattern and the pattern of reflector as secondary
pattern.
(b) The pattern of reflector is the primary pattern and that of feed is termed as secondary
pattern.
(c) Only rear feed pattern is called primary pattern.
(d) Only front feed pattern is called primary pattern.
83 Zoning is used with a dielectric antenna mainly to:
(a) Increase the bandwidth of the antenna (b) Reduce the bulk of the lens
(c) Permit pin pointed focusing (d) Correct the curvature of the wave front from a
short horn
84 The delay lenses wherein the electrical path length is increased or wave is retarded by
the lens medium include:
(a) E-plane metal lenses (b) H-plane metal lenses
(c) Dielectric and H-plane metal lenses (d) E-plane and H-plane metal
lenses.
85 The fast lenses wherein the electrical path length is decreased by the lens medium
include:
(a) Dielectric and E-plane metal lenses (b) E-plane metal lenses
(c) H-plane metal lenses (d) E-plane and H-plane metal
10. lenses.
86 Refraction in the lenses may involve one or two surfaces. The use of lenses having
refraction through two surface is not very common but it offers better performance, prevents
refocusing of energy into the feed and provides wide angle scanning when r is of the order
of:
(a) 3.5 (b) 2.5 (c) 1.5 (d) 0.5
87 Lenses with n > 1 are non-dispersive, their thickness decreases as n increases,
mismatch between lens and free space increases and energy loss due to refraction
increases. The bandwidth of such a lenses in terms of the frequency of operation is about: of
the frequency of operation.
(a) 50% (b) 30% (c) 20% (d) 10%
88 The zoning makes the lens frequency sensitive, increases the energy loss, side lobe level
and the shadowing effect. These effects can be minimized by using a design with:
(a) Large f/D ratio keeping it = 1 (b) Large f/D ratio keeping it 1
(c) Less f/D ratio keeping it = 0.5 (d) Less f/D ratio keeping it < 0.5
89 Identify the correct statement:
(a) In comparison to reflector gain of lens antenna is 1 or 2 dB less, but tolerance on
surfaces is more.
(b) In comparison to reflectors gain and tolerance on surfaces of lens antenna is little more.
(c) In comparison to reflectors gain and tolerance on surfaces of lens antenna is little less.
(d) In comparison to reflectors their gain is 1 or 2 dB more and also have less lenient
tolerance on surfaces.
90 The small loop and short dipole (with loop axis parallel to the dipole) have identical field
patterns for:
(a) E (b) H (c) both E and H (d) E and H interchanged
91 The circular loop of diameter d is generally regarded as small loops if:
(a) d < /2 (b) d < /4 (c) d < /8 (d) d < /10
92 A small rectangular loop with area A satisfies the condition:
(a) A < /10 (b) A < /100 (c) A < 2
/100 (d) A < 2
/10
93 A longitudinal slot in a cylinder has a radiation pattern is practically circular in plane
perpendicular to the axis provided the cylinder diameter in terms of is of the order of
(a) / 10 (b) / 8 (c) / 4 (d) / 2
94 The slot and dipole have the same field patterns for:
(a) E alone (b) H alone (c) E as well as H (d) interchanged E and H
95 Identify the correct statement:
(a) The Horizontal slots may result in horizontal polarization and vertical slots in vertical
polarization.
(b) The vertical slots may result in horizontal polarization and horizontal slots in vertical
polarization.
(c) Both vertical and horizontal slots may result in horizontal polarization.
11. (d) Both vertical and horizontal slots may result in vertical polarization.
96 A properly designed slot antenna may have bandwidth of about:
(a) 10 % of center frequency (b) 5 % of center frequency
(c) 2 % of center frequency (d) 1 % of center frequency
97 The sharpest beam and highest gain for a given mouth size of a horn are obtained by
(a) very small flare angles (b) small flare angles
(c) large flare angles (d) very large flare angles
98 A longitudinal slot in a cylinder has a radiation pattern is practically circular in plane
perpendicular to the axis provided the cylinder diameter in terms of is of the order of
(a) / 10 (b) / 8 (c) / 4 (d) / 2
99 In an optimum horn the difference in path length along the edge and the center in E plane is:
(a) /4 (b) /2 (c) 3/4 (d)
100 Helical Antennas combine the geometry of a straight line, a circle and a cylinder. These
antennas are:
(a) Circularly polarized with high gain (b) Circularly polarized with low gain
(c) Linearly polarized with high gain (d) Linearly polarized with low gain
101 The axial (end fire) mode of helical antenna is most practical because it can achieve
over a wide band:
(a) Linear Polarization (b) Circular Polarization
(c) Elliptical Polarization (d) All the above
102 In mono-filar helices the term transmission mode is used to describe the manner in
which the electromagnetic wave is propagated along:
(a) A very short helix (b) A medium length helix
(c) A long helix (d) An infinite helix
YAGI-UDA ANTENNA
103 A Yagi antenna may have:
(a) A single director and multiple reflector (b) A single reflector and multiple
directors
(c) Multiple directors and multiple reflectors (d) All the above combinations
WAVE PROPAGATION
104 With vertical polarization the magnitude of reflection coefficient for space wave is
commonly:
(a) quite large at moderately small angles of incidence
(b) quite small at moderately small angles of incidence
(c) quite small at moderately large angles of incidence
(d) quite large at moderately large angles of incidence
105 The conductivity and dielectric constant of earth vary greatly with conditions. At
broadcast band and lower frequencies, the earth can be regarded (approximately) as:
12. (a) pure capacitive (b) pure resistive (c) pure inductive (d) a combination of
R & C
106 At Brewster’s angle the reflection coefficient “Rv” for vertically polarized wave is:
(a) >>1 (b) 1 (c) <<1 (d) 0
107 At Brewster’s angle for vertically polarized wave the phase of reflected wave, from the
earth surface with finite conductivity will differ from the phase of reflected wave from a
surface with infinite conductivity by:
(a) 1800
(b) 900
(c) 450
(d) 00
108 The earth is normally considered to be flat if the distance (d, in miles) between Tx and
Rx does not exceed:
(a) 50/(fMHz)1/4
(b) 50/(fMHz)1/2
(c) 50/(fMHz)1/3
(d) 50/(fMHz)
109 The roughness of earth is generally estimated in terms of conductivity , angle of
incidence and wavelength by the Raleigh criterion given by:
(a) R = 4 sin / (b) R = 4 sin / (c) R = 4 sin (d) R = 4 sin /
110 The ionosphere and the earth both act as good reflectors especially in the lower range
of:
(a) VHF (b) HF (c) MF (d) VLF
111 The troposphere extends from earth surface to a height of:
(a) 5 Km (b) 15 Km (c) 50 Km (d) 90 Km
112 Radiated energy in the UHF range propagate by means of:
(a) ground waves (b) sky waves (c) surface waves (d) space
waves
113 Tropospheric scatter is used with frequency in the range of:
(a) VLF (b) HF (c) VHF (d) UHF
114 The temperature of troposphere decreases with height at an average rate of:
(a) 2 degree/km (b) 4 degree/km (c) 6 degree/km (d) 8
degree/km
115 The phenomenon of super refraction occurs only when dM/dh is:
(a) Negative (b) Zero (c) Positive (d) infinite
116 In FIG.C four different paths are adopted by rays for different refractive index variations.
The ray for the condition dM / dh = 0 is:
(a) a (b) b (c) c (d) d
FIG.C
13. 117 The modified refractive index is defined by the relation M =
(a) (n + 1 – h / a) 106
(b) (n + 1 + h / a) 106
(c) (n - 1 – h / a) 106
(d) (n - 1 + h / a) 106
118 When microwave signal follows the curvature of the earth, the phenomenon is called:
(a) Faraday’s effect (b) ducting (c) Tropospheric scatter (d) ionospheric reflection
119 VLF waves are used for some specific applications because:
(a) they easily penetrate ionosphere (b) they require low power
(c) they are very reliable (d) the transmitting antennas are of convenient size
120 The day time broadcasting in 535-1600 kHz range:
(a) completely depends on tropospheric waves (b) ionospheric waves
(c) ground waves (d) does not depend on mode of propagation (listed in a, b, c
above) at all
121 The skip distance for radio wave increases with:
(a) Increase in frequency (b) Decrease in frequency
(c) Atmospheric disturbances (d) Temperature of atmosphere
122 High frequency waves are:
(a) absorbed by F2 layer (b) capable of use for long distance communication on
moon
(c) affected by solar cycle (d) reflected by D layer
123. If wave of critical frequency 30 MHz is departing at an angle of 600
, then the MUF is:
(a) 10 MHz (b) 15 MHz (c) 40 MHz (d) 60 MHz
124 If 0 is the angle of incidence, d is the distance between transmitter and receiver and R
is the radius of earth, the take-off angle is given by the relation:
(a) = 90 - 0 - 57.3 d / 2R (b) = 90 - 0 + 57.3 d / 2R
(c) = 90 + 0 - 57.3 d / 2R (d) = 90 + 0 + 57.3 d / 2R