Reflector antennas use reflecting surfaces and a feed antenna to achieve high gains for long-distance radio communications. The simplest design uses a single parabolic reflector with the feed at the focal point, while more complex dual-reflector designs position a secondary reflector at the focal point. Parabolic reflectors collimate rays from the feed into a directional beam, with path lengths from the feed equalizing phase. Dual reflectors like the Cassegrain design position the feed at the main reflector's apex for a more robust structure. The gain of reflector antennas depends on the aperture efficiency accounting for losses from tapering, spillover, surface errors and phase deviations reducing the directivity.
The document provides an overview of antennas, including their history and uses. It discusses the basics of how dipole antennas work to transmit and receive electromagnetic signals. Specifically, it explains that a dipole antenna was developed in 1886 and works by efficiently radiating radio waves into space using electric and magnetic fields. It also describes different types of dipole antennas like short dipoles, quarter-wave antennas, and half-wave antennas, and how their length relates to the transmitted wavelength.
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.
Design & Study of Microstrip Patch Antenna.The project here provides a detailed study of how to design a probe-fed Square Micro-strip Patch Antenna using HFSS, v11.0 software and study the effect of antenna dimensions Length (L), and substrate parameters relative Dielectric constant (εr), substrate thickness (t) on the Radiation parameters of Bandwidth and Beam-width.
This document provides training materials on calculating wireless link budgets to determine the feasibility and optimal configuration of radio links. It defines key concepts like free space loss, link budget, antenna gain and Fresnel zone. An example link budget calculation is shown for a 5km link. It also introduces the Radio Mobile software tool, which can automatically simulate radio links and calculate the required Fresnel zone clearance by considering terrain profiles. The document concludes with an example of using Radio Mobile to analyze a potential link in Chuuk and poses questions about configuring the masts, transmit power and antennas.
This document discusses the Yagi-Uda antenna, which was invented in 1926 by Shintaro Uda and Hidesugu Yagi. It explains that the Yagi-Uda antenna is a directional antenna system consisting of an array of coupled parallel dipoles. The document covers the principle, construction, working, advantages, disadvantages, and applications of the Yagi-Uda antenna. It is commonly used as a terrestrial TV antenna and is usually used at frequencies between 30MHz and 3GHz.
Its a good presentation on Antenna topic because every one is know that in electrical engineering antenna is a complete subject & its too much difficult subject of electrical engineering....I hope this ppt slides helpful in your future...Thanks A lot guys.......
KINDLY REGARDS
KHAWAJA SHAHBAZ IQBAL
ELECTRICAL ENGINEER
UNIVERSITY OF CENTRAL PUNJAB ,LAHORE ,PAKISTAN
+923360690272
The document provides an overview of antennas, including their history and uses. It discusses the basics of how dipole antennas work to transmit and receive electromagnetic signals. Specifically, it explains that a dipole antenna was developed in 1886 and works by efficiently radiating radio waves into space using electric and magnetic fields. It also describes different types of dipole antennas like short dipoles, quarter-wave antennas, and half-wave antennas, and how their length relates to the transmitted wavelength.
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.
Design & Study of Microstrip Patch Antenna.The project here provides a detailed study of how to design a probe-fed Square Micro-strip Patch Antenna using HFSS, v11.0 software and study the effect of antenna dimensions Length (L), and substrate parameters relative Dielectric constant (εr), substrate thickness (t) on the Radiation parameters of Bandwidth and Beam-width.
This document provides training materials on calculating wireless link budgets to determine the feasibility and optimal configuration of radio links. It defines key concepts like free space loss, link budget, antenna gain and Fresnel zone. An example link budget calculation is shown for a 5km link. It also introduces the Radio Mobile software tool, which can automatically simulate radio links and calculate the required Fresnel zone clearance by considering terrain profiles. The document concludes with an example of using Radio Mobile to analyze a potential link in Chuuk and poses questions about configuring the masts, transmit power and antennas.
This document discusses the Yagi-Uda antenna, which was invented in 1926 by Shintaro Uda and Hidesugu Yagi. It explains that the Yagi-Uda antenna is a directional antenna system consisting of an array of coupled parallel dipoles. The document covers the principle, construction, working, advantages, disadvantages, and applications of the Yagi-Uda antenna. It is commonly used as a terrestrial TV antenna and is usually used at frequencies between 30MHz and 3GHz.
Its a good presentation on Antenna topic because every one is know that in electrical engineering antenna is a complete subject & its too much difficult subject of electrical engineering....I hope this ppt slides helpful in your future...Thanks A lot guys.......
KINDLY REGARDS
KHAWAJA SHAHBAZ IQBAL
ELECTRICAL ENGINEER
UNIVERSITY OF CENTRAL PUNJAB ,LAHORE ,PAKISTAN
+923360690272
A loop antenna is a radio antenna consisting of a loop or coil of wire, tubing, or other electrical conductor with its ends connected to a balanced transmission line (or possibly a balun). There are two distinct antenna designs: the small loop (or magnetic loop) with a size much smaller than a wavelength, and the much larger resonant loop antenna with a circumference close to the intended wavelength of operation. Small loops have low radiation resistance and thus poor efficiency and are mainly used as receiving antennas at low frequencies. To increase the magnetic field in the loop and thus the efficiency, the coil of wire is often wound around a ferrite rod magnetic core; this is called a ferrite loop antenna. The ferrite loop is the antenna used in many AM broadcast receivers, with the exception of external loops used with AV Amplifier-Receivers and car radios; the antenna is often contained inside the radio's case. These antennas are also used for radio direction finding. In amateur radio, loop antennas are often used for low profile operating where larger antennas would be inconvenient, unsightly.
(c) WIkipedia
This document provides an overview of types of antennas and propagation modes. It discusses how antennas work to transmit and receive radio waves, and describes common types of antennas including omnidirectional antennas that radiate in all directions and directional antennas that preferentially radiate in a particular direction. It also summarizes the three main propagation modes: ground waves that hug the Earth's surface, space waves that travel in straight lines, and sky waves that reflect off the ionosphere. Key factors that determine the propagation path are frequency, atmospheric conditions, and time of day.
The Yagi-Uda antenna consists of a driven element connected to a transmission line and one or more passive parasitic elements. The reflector element is longer than the driven element to make it inductive, while the director elements are shorter than the driven element to make them capacitive. Together the elements produce a unidirectional beam with moderate directivity and gains of around 8dB. Adding more director elements increases the directivity. It has advantages of simple construction, low cost, and ease of feeding but has limitations of limited bandwidth and requiring additional elements for higher gains over longer distances.
Parabolic antennas use a curved parabolic reflector to direct radio waves into a narrow beam. They work by reflecting radio waves from a feed antenna located at the focal point of the parabolic dish into a parallel beam when transmitting, and focusing incoming plane waves to the feed antenna when receiving. Parabolic antennas provide high gain and directivity due to their large reflector sizes. They find applications in satellite communication, microwave links, radio astronomy, and direct broadcast television due to their ability to direct signals over long distances with strong reception.
This document discusses key concepts related to antennas including:
1. It defines radiation power density as the power radiated per unit surface area from the antenna surface.
2. It explains that directivity is a measure of the directional properties of an antenna and is defined as the ratio of radiation intensity in a given direction compared to an isotropic source.
3. Gain accounts for both the directional properties and efficiency of an antenna, defined as the ratio of intensity in a given direction compared to an isotropic source radiating the same total power.
4. Additional concepts covered include beamwidth, radiation patterns, and parameters related to receiving performance such as effective length and capture area.
This document discusses 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) The document provides lecture notes on basic antenna parameters and wire antennas. It covers topics such as classification of antennas by size and type, radiation integrals used to calculate electromagnetic fields from antenna sources, and properties of Hertzian dipoles including their radiation patterns and directivity.
2) Key concepts discussed include how antenna size relates to the operating wavelength, radiation from electric surface currents using integral equations, derivation of the electric field for an infinitesimal dipole, and definitions of directivity, gain, and beamwidth for simple antenna models.
3) Formulas are presented for calculating the electric and magnetic fields, power flow, and directivity of Hertzian dipoles based on the antenna theory and properties of spherical waves.
This document discusses various types of antennas and antenna arrays. It begins by describing common antenna types including helical antennas, horn antennas, and parabolic reflector antennas. It then discusses how antenna arrays work, noting that they are composed of multiple similar radiating elements whose spacing and excitation determine the array's properties. Examples of linear and 2D arrays are provided. The document also summarizes different array configurations and beamforming techniques as well as applications such as smart antennas and adaptive arrays. Key benefits of arrays like controlling radiation patterns electronically are highlighted.
Radar Systems- Unit-II : CW and Frequency Modulated RadarVenkataRatnam14
This document provides information about continuous wave (CW) and frequency modulated (FM-CW) radar systems. It discusses the Doppler effect and how CW radar uses the frequency shift caused by the Doppler effect to detect moving targets. The key components of a CW radar like the transmitter, receiver, and Doppler filter are described. Issues like isolation between the transmitter and receiver, limitations of zero intermediate frequency receivers, and receiver bandwidth requirements are also covered. Finally, the document introduces the concept of FM-CW radar and its use of frequency modulation to measure target range and velocity.
The document discusses the design of a microstrip patch antenna (MPA) resonating in the K-band frequency range (18-26GHz) using HFSS software. It provides an introduction to antennas and describes the basic structure of an MPA including the radiating patch, dielectric substrate, and ground plane. Design considerations for the MPA include selecting the rectangular patch shape and FR4 epoxy substrate material. The document outlines the design process in HFSS and lists some advantages and applications of MPAs for mobile/satellite communication systems. It concludes that the designed MPA exhibits good impedance matching at the center frequency and can be easily fabricated on an FR4 substrate.
This thesis focuses on mobile phones antenna design with brief description about the historical development, basic parameters and the types of antennas which are used in mobile phones. Mobile phones antenna design section consists of two proposed PIFA antennas. The first design concerns a single band antenna with resonant frequency at GPS frequency (1.575GHz). The first model is designed with main consideration that is to have the lower possible PIFA single band dimensions with reasonable return loss (S11) and the efficiencies. Second design concerns in a wideband PIFA antenna which cover the range from 1800MHz to 2600MHz. This range covers certain important bands: GSM (1800MHz & 1900MHz), UMTS (2100MHz), Bluetooth & Wi-Fi (2.4GHz) and LTE system (2.3GHz, 2.5GHz, and 2.6GHz). The wideband PIFA design is achieved by using slotted ground plane technique. The simulations for both models are performed in COMSOL Multiphysics.
The last two parts of the thesis present the problems of mobile phones antenna. Starting with Specific absorption rate (SAR) problem, efficiency of Mobile phones antenna, and hand-held environment.
This document provides an overview of microstrip patch antennas, also known as patch antennas. It defines patch antennas as consisting of a metal patch on top of a grounded dielectric substrate, which are useful at microwave frequencies above 1 GHz. The document discusses the geometry, advantages, disadvantages, feeding techniques, basic properties including resonance frequency and bandwidth, radiation pattern, and applications of microstrip patch antennas. The main applications mentioned are in mobiles, satellites, GPS, WiMAX, medical devices, and radar.
Ultra-wideband (UWB) antennas must transmit very short pulse signals accurately and efficiently. The document discusses various types of UWB antennas including traveling-wave antennas like horn antennas, frequency-independent antennas whose radiation patterns do not change with frequency, self-complementary antennas with constant input impedance regardless of frequency or shape, multiple resonance antennas made of multiple narrowband elements, and electrically small antennas. Key antenna characterization parameters in time and frequency domains are also presented.
This document discusses different types of antennas used for transmitting and receiving electromagnetic waves. It describes log-periodic antennas, which work over a wide frequency range using a logarithmic size progression of elements. Specific types are described, including bow-tie antennas and log-periodic dipole arrays. Wire antennas like dipoles, monopoles, and loops are also covered. Travelling wave antennas transmit signals along their length, represented by helical and Yagi-Uda antennas. Microwave antennas and reflector antennas are used at higher frequencies for applications like communication and radar. Key antenna properties and a variety of applications are also summarized.
An Antenna is a transducer, which converts electrical power into electromagnetic waves and vice versa.
An Antenna can be used either as a transmitting antenna or a receiving antenna.
A transmitting antenna is one, which converts electrical signals into electromagnetic waves and radiates them.
A receiving antenna is one, which converts electromagnetic waves from the received beam into electrical signals.
In two-way communication, the same antenna can be used for both transmission and reception.
Basic Parameters
Frequency
Wavelength
Impedance matching
VSWR & reflected power
Bandwidth
Percentage bandwidth
Radiation intensity.
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 different types of antennas and their properties. It describes how antennas convert radio frequency energy into electromagnetic waves and how their physical size relates to wavelength. It then summarizes the main types of antennas including directional antennas like Yagi, panel and parabolic, and omni-directional antennas. It provides examples of common antenna radiation patterns and discusses concepts like polarization, reflector optics, aperture efficiency, and Cassegrain feeds.
By completing this presentation will be have a clear idea about Antenna's working principles, Antenna's Types & Antenna's Parameters. At the end to this document you'll have a brief idea about Antenna's Tilt vs Distance Calculation & Cluster wise optimum Antenna Selection procedure. Impact of antenna PIM & VSWR have been described elaborately in this document as well.
The document describes the design and simulation of a basic half-wave dipole antenna. Key points:
1) The aim is to design a dipole antenna for a given frequency of 3.3 GHz and study the effects of varying the dielectric constant and substrate thickness on the radiation properties and frequency response.
2) Important antenna characteristics to consider include radiation patterns, gain, and frequency response.
3) The half-wave dipole antenna is designed with each arm measuring 22.725mm to operate at the target frequency, and each arm width is 4.545mm.
4) Simulation shows the antenna operates at 2.8GHz with a return loss of -14.50dB and gain of
This document discusses aperture antennas. It begins by defining an aperture antenna as an antenna that uses an opening or closed surface as the radiating element. It then lists the main types of aperture antennas like horn antennas, reflector antennas, slot antennas, and microstrip antennas. The document focuses on analyzing aperture antennas using techniques like the current distribution method, aperture analysis, and the Fourier transform method. It explains key principles used in aperture analysis like the field equivalence principle, Huygens' principle, and Babinet's principle. The document provides examples of analyzing specific aperture antenna types and their radiation patterns.
A parabolic reflector is a device that collects or projects energy such as light, sound, or radio waves by altering incoming plane waves traveling along the same axis as the parabola into a spherical wave focused at a single point. Parabolic reflectors have been used since antiquity and Archimedes is said to have used one to set fire to enemy ships. They work based on the geometric properties of the parabolic shape and the principle that any ray parallel to the dish is reflected to the central focus point. Common applications include satellite dishes, telescopes, microphones, and solar cookers.
This project is about conducting an experimental study on solar heated pipe with parabolic trough reflector. The effect of different parameters on the solar heated pipe will be analyzed for optimum design. Design and construction of the experimental setup for the above study is discussed.
Different parameters which are analyses as follows: Size and thickness of the pipe, size of the casing, flow rate of the fluid, type of fluid, angle of inclination of rim, design parameters etc. These variables will be compared by the efficiency of the solar heated pipe.
A loop antenna is a radio antenna consisting of a loop or coil of wire, tubing, or other electrical conductor with its ends connected to a balanced transmission line (or possibly a balun). There are two distinct antenna designs: the small loop (or magnetic loop) with a size much smaller than a wavelength, and the much larger resonant loop antenna with a circumference close to the intended wavelength of operation. Small loops have low radiation resistance and thus poor efficiency and are mainly used as receiving antennas at low frequencies. To increase the magnetic field in the loop and thus the efficiency, the coil of wire is often wound around a ferrite rod magnetic core; this is called a ferrite loop antenna. The ferrite loop is the antenna used in many AM broadcast receivers, with the exception of external loops used with AV Amplifier-Receivers and car radios; the antenna is often contained inside the radio's case. These antennas are also used for radio direction finding. In amateur radio, loop antennas are often used for low profile operating where larger antennas would be inconvenient, unsightly.
(c) WIkipedia
This document provides an overview of types of antennas and propagation modes. It discusses how antennas work to transmit and receive radio waves, and describes common types of antennas including omnidirectional antennas that radiate in all directions and directional antennas that preferentially radiate in a particular direction. It also summarizes the three main propagation modes: ground waves that hug the Earth's surface, space waves that travel in straight lines, and sky waves that reflect off the ionosphere. Key factors that determine the propagation path are frequency, atmospheric conditions, and time of day.
The Yagi-Uda antenna consists of a driven element connected to a transmission line and one or more passive parasitic elements. The reflector element is longer than the driven element to make it inductive, while the director elements are shorter than the driven element to make them capacitive. Together the elements produce a unidirectional beam with moderate directivity and gains of around 8dB. Adding more director elements increases the directivity. It has advantages of simple construction, low cost, and ease of feeding but has limitations of limited bandwidth and requiring additional elements for higher gains over longer distances.
Parabolic antennas use a curved parabolic reflector to direct radio waves into a narrow beam. They work by reflecting radio waves from a feed antenna located at the focal point of the parabolic dish into a parallel beam when transmitting, and focusing incoming plane waves to the feed antenna when receiving. Parabolic antennas provide high gain and directivity due to their large reflector sizes. They find applications in satellite communication, microwave links, radio astronomy, and direct broadcast television due to their ability to direct signals over long distances with strong reception.
This document discusses key concepts related to antennas including:
1. It defines radiation power density as the power radiated per unit surface area from the antenna surface.
2. It explains that directivity is a measure of the directional properties of an antenna and is defined as the ratio of radiation intensity in a given direction compared to an isotropic source.
3. Gain accounts for both the directional properties and efficiency of an antenna, defined as the ratio of intensity in a given direction compared to an isotropic source radiating the same total power.
4. Additional concepts covered include beamwidth, radiation patterns, and parameters related to receiving performance such as effective length and capture area.
This document discusses 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) The document provides lecture notes on basic antenna parameters and wire antennas. It covers topics such as classification of antennas by size and type, radiation integrals used to calculate electromagnetic fields from antenna sources, and properties of Hertzian dipoles including their radiation patterns and directivity.
2) Key concepts discussed include how antenna size relates to the operating wavelength, radiation from electric surface currents using integral equations, derivation of the electric field for an infinitesimal dipole, and definitions of directivity, gain, and beamwidth for simple antenna models.
3) Formulas are presented for calculating the electric and magnetic fields, power flow, and directivity of Hertzian dipoles based on the antenna theory and properties of spherical waves.
This document discusses various types of antennas and antenna arrays. It begins by describing common antenna types including helical antennas, horn antennas, and parabolic reflector antennas. It then discusses how antenna arrays work, noting that they are composed of multiple similar radiating elements whose spacing and excitation determine the array's properties. Examples of linear and 2D arrays are provided. The document also summarizes different array configurations and beamforming techniques as well as applications such as smart antennas and adaptive arrays. Key benefits of arrays like controlling radiation patterns electronically are highlighted.
Radar Systems- Unit-II : CW and Frequency Modulated RadarVenkataRatnam14
This document provides information about continuous wave (CW) and frequency modulated (FM-CW) radar systems. It discusses the Doppler effect and how CW radar uses the frequency shift caused by the Doppler effect to detect moving targets. The key components of a CW radar like the transmitter, receiver, and Doppler filter are described. Issues like isolation between the transmitter and receiver, limitations of zero intermediate frequency receivers, and receiver bandwidth requirements are also covered. Finally, the document introduces the concept of FM-CW radar and its use of frequency modulation to measure target range and velocity.
The document discusses the design of a microstrip patch antenna (MPA) resonating in the K-band frequency range (18-26GHz) using HFSS software. It provides an introduction to antennas and describes the basic structure of an MPA including the radiating patch, dielectric substrate, and ground plane. Design considerations for the MPA include selecting the rectangular patch shape and FR4 epoxy substrate material. The document outlines the design process in HFSS and lists some advantages and applications of MPAs for mobile/satellite communication systems. It concludes that the designed MPA exhibits good impedance matching at the center frequency and can be easily fabricated on an FR4 substrate.
This thesis focuses on mobile phones antenna design with brief description about the historical development, basic parameters and the types of antennas which are used in mobile phones. Mobile phones antenna design section consists of two proposed PIFA antennas. The first design concerns a single band antenna with resonant frequency at GPS frequency (1.575GHz). The first model is designed with main consideration that is to have the lower possible PIFA single band dimensions with reasonable return loss (S11) and the efficiencies. Second design concerns in a wideband PIFA antenna which cover the range from 1800MHz to 2600MHz. This range covers certain important bands: GSM (1800MHz & 1900MHz), UMTS (2100MHz), Bluetooth & Wi-Fi (2.4GHz) and LTE system (2.3GHz, 2.5GHz, and 2.6GHz). The wideband PIFA design is achieved by using slotted ground plane technique. The simulations for both models are performed in COMSOL Multiphysics.
The last two parts of the thesis present the problems of mobile phones antenna. Starting with Specific absorption rate (SAR) problem, efficiency of Mobile phones antenna, and hand-held environment.
This document provides an overview of microstrip patch antennas, also known as patch antennas. It defines patch antennas as consisting of a metal patch on top of a grounded dielectric substrate, which are useful at microwave frequencies above 1 GHz. The document discusses the geometry, advantages, disadvantages, feeding techniques, basic properties including resonance frequency and bandwidth, radiation pattern, and applications of microstrip patch antennas. The main applications mentioned are in mobiles, satellites, GPS, WiMAX, medical devices, and radar.
Ultra-wideband (UWB) antennas must transmit very short pulse signals accurately and efficiently. The document discusses various types of UWB antennas including traveling-wave antennas like horn antennas, frequency-independent antennas whose radiation patterns do not change with frequency, self-complementary antennas with constant input impedance regardless of frequency or shape, multiple resonance antennas made of multiple narrowband elements, and electrically small antennas. Key antenna characterization parameters in time and frequency domains are also presented.
This document discusses different types of antennas used for transmitting and receiving electromagnetic waves. It describes log-periodic antennas, which work over a wide frequency range using a logarithmic size progression of elements. Specific types are described, including bow-tie antennas and log-periodic dipole arrays. Wire antennas like dipoles, monopoles, and loops are also covered. Travelling wave antennas transmit signals along their length, represented by helical and Yagi-Uda antennas. Microwave antennas and reflector antennas are used at higher frequencies for applications like communication and radar. Key antenna properties and a variety of applications are also summarized.
An Antenna is a transducer, which converts electrical power into electromagnetic waves and vice versa.
An Antenna can be used either as a transmitting antenna or a receiving antenna.
A transmitting antenna is one, which converts electrical signals into electromagnetic waves and radiates them.
A receiving antenna is one, which converts electromagnetic waves from the received beam into electrical signals.
In two-way communication, the same antenna can be used for both transmission and reception.
Basic Parameters
Frequency
Wavelength
Impedance matching
VSWR & reflected power
Bandwidth
Percentage bandwidth
Radiation intensity.
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 different types of antennas and their properties. It describes how antennas convert radio frequency energy into electromagnetic waves and how their physical size relates to wavelength. It then summarizes the main types of antennas including directional antennas like Yagi, panel and parabolic, and omni-directional antennas. It provides examples of common antenna radiation patterns and discusses concepts like polarization, reflector optics, aperture efficiency, and Cassegrain feeds.
By completing this presentation will be have a clear idea about Antenna's working principles, Antenna's Types & Antenna's Parameters. At the end to this document you'll have a brief idea about Antenna's Tilt vs Distance Calculation & Cluster wise optimum Antenna Selection procedure. Impact of antenna PIM & VSWR have been described elaborately in this document as well.
The document describes the design and simulation of a basic half-wave dipole antenna. Key points:
1) The aim is to design a dipole antenna for a given frequency of 3.3 GHz and study the effects of varying the dielectric constant and substrate thickness on the radiation properties and frequency response.
2) Important antenna characteristics to consider include radiation patterns, gain, and frequency response.
3) The half-wave dipole antenna is designed with each arm measuring 22.725mm to operate at the target frequency, and each arm width is 4.545mm.
4) Simulation shows the antenna operates at 2.8GHz with a return loss of -14.50dB and gain of
This document discusses aperture antennas. It begins by defining an aperture antenna as an antenna that uses an opening or closed surface as the radiating element. It then lists the main types of aperture antennas like horn antennas, reflector antennas, slot antennas, and microstrip antennas. The document focuses on analyzing aperture antennas using techniques like the current distribution method, aperture analysis, and the Fourier transform method. It explains key principles used in aperture analysis like the field equivalence principle, Huygens' principle, and Babinet's principle. The document provides examples of analyzing specific aperture antenna types and their radiation patterns.
A parabolic reflector is a device that collects or projects energy such as light, sound, or radio waves by altering incoming plane waves traveling along the same axis as the parabola into a spherical wave focused at a single point. Parabolic reflectors have been used since antiquity and Archimedes is said to have used one to set fire to enemy ships. They work based on the geometric properties of the parabolic shape and the principle that any ray parallel to the dish is reflected to the central focus point. Common applications include satellite dishes, telescopes, microphones, and solar cookers.
This project is about conducting an experimental study on solar heated pipe with parabolic trough reflector. The effect of different parameters on the solar heated pipe will be analyzed for optimum design. Design and construction of the experimental setup for the above study is discussed.
Different parameters which are analyses as follows: Size and thickness of the pipe, size of the casing, flow rate of the fluid, type of fluid, angle of inclination of rim, design parameters etc. These variables will be compared by the efficiency of the solar heated pipe.
This document defines and describes parabolic antennas. It discusses the key components of a parabolic antenna including the focus, vertex, focal length, and aperture. It then explains how parabolic and hyperbolic reflectors work to direct radio waves. The document outlines different types of parabolic antennas and their applications. Parabolic antennas are commonly used for point-to-point communication, microwave relay links, wireless networks, satellite communication, radio telescopes, and radar due to their high directivity and gain.
The document discusses the benefits of exercise for mental health. Regular physical activity can help reduce anxiety and depression and improve mood and cognitive functioning. Exercise boosts blood flow, releases endorphins, and promotes changes in the brain which help regulate emotions and stress levels.
Microwave antennas can take several forms. Horn antennas are popular and can achieve gains up to 25 dB, with directional patterns. Parabolic antennas, like satellite dishes, typically have very high gain between 30-40 dB and low cross polarization. Slot antennas are often used instead of line antennas for greater pattern control and are found in radar and cell antennas. Dipole antennas are half wave resonant conductors that radiate omnidirectionally at right angles to their axis. Their gain is approximately 2 dBi. Dielectric antennas use a traveling surface wave along a dielectric rod to radiate maximally along the rod axis.
This document discusses different types of antennas, including horn antennas, slot antennas, microstrip or patch antennas, quad-helix antennas, and notch antennas. It provides details on the purpose, design, and applications of each antenna type. Horn antennas are used to direct radio waves in a beam from a waveguide and have high gain. Slot antennas consist of a metal surface with a cut-out hole or slot that radiates waves similarly to a dipole antenna. Microstrip antennas can be printed on circuit boards and are widely used in mobile devices due to their low cost. Quad-helix antennas have four connected helix antennas and transmit measurements from remote areas. Notch antennas operate based on a cut-out section similar to
MicroStrip Antenna
Introduction .
Micro-Strip Antennas Types .
Micro-Strip Antennas Shapes .
Types of Substrates (Dielectric Media) .
Comparison of various types of flat profile printed antennas .
Advantages & DisAdvantages of MSAs .
Applications of MSAs .
Radiation patterns of MSAs .
How to Optimizing the Substrate Properties for Increased Bandwidth ?
Comparing the different feed techniques .
This document describes different types of antennas used for transmitting and receiving electromagnetic waves. It discusses transmitter and receiver antennas. Specific antenna types covered include Yagi-Uda antennas, log-periodic antennas, helix antennas, parabolic antennas, loop antennas, and antenna arrays. Each antenna type has distinct characteristics that make it suitable for different frequency ranges and applications.
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 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.
Log periodic antennas are broadband antennas with multiple dipole elements of varying lengths arranged logarithmically. This allows them to radiate across a wide frequency range. They have moderate directivity compared to other directional antennas. The individual dipole elements are excited through cross connections, and the point of excitation can be varied to change the radiation pattern. Log periodic antennas are used when both wide frequency coverage and some directivity are needed, such as in television antennas.
The Yagi-Uda antenna was invented in 1926 by Shintaro Uda and Hidetsugu Yagi in Japan. It consists of a driven element connected to a transmitter or receiver, along with additional parasitic reflector and director elements that help direct the antenna's radiation pattern. Yagi-Uda antennas see widespread use where high gain and directivity are needed, such as in television antennas, radar systems, and point-to-point communication links. They provide moderate gains of up to around 17 dBi through interference of signals from the different elements.
A slotted antenna array uses slots cut into a metal waveguide to radiate electromagnetic waves. The slots are typically thin and about half the wavelength of the center frequency. As waves propagate through the waveguide, the slots disturb the current and cause it to radiate linearly polarized waves with low cross-polarization. Slotted antenna arrays are commonly used in aircraft and other applications because they can conform to surfaces and are simple and efficient to fabricate. Multiple slots can be cut into the waveguide in a periodic pattern to form an antenna array. The position and size of the slots determine the radiation pattern produced.
The document discusses different types of antennas including wire antennas like dipole antennas, monopole antennas, and broadband dipoles. It also briefly mentions loop antennas, travelling wave antennas like helical and Yagi antennas, reflector antennas like corner reflectors and parabolic dishes, microstrip patch antennas, planar inverted-F antennas, aperture antennas like slot and horn antennas.
A presentation on the physical layer basics of ADSL. I presented this to a couple of colleges in the southeast as a guest lecturer, and to the local chapter of the IEEE Signal Processing Society.
Second lesson of my introduction to antennas for space applications - Space Challenges - Sofia 2015
Topics: satellite orbits, global coverage, spot beams, multi-beam coverage, contoured coverage, reflector antennas, parabolic reflectors, phased-array antennas.
1. Wireless communication has existed for millennia using smoke signals, light signals, and flags but long-distance wireless communication was not possible until the 19th century.
2. In the late 19th century, scientific discoveries by Maxwell, Hertz, Tesla, and Marconi laid the foundation for modern radio-based wireless communication using electromagnetic waves.
3. The 20th century saw rapid advances including the first radio broadcasts, development of cell phone networks beginning in the late 1940s-1950s, and the introduction of digital cellular standards like GSM in the 1980s-1990s that enabled international roaming.
This document provides an overview and instructions for a CRCST certification preparation course. It outlines class logistics like location, times, and materials needed. It emphasizes creating a positive learning environment and explains that the course will follow the textbook and allow for adjustments. Students will participate in lectures, interactive sessions, self-study assignments, and exams. Regular attendance is required and students must achieve a 70% pass rate. The document discusses the benefits of certification and different certification options available through IAHCSMM. It provides tips for successful studying and reducing test anxiety.
A broadband antenna means the antenna with wideband radiation characteristics. To make a broadband antenna, we can use a helical, a biconical, a sleeve, a spiral, and a log-periodic antenna.
This document describes the design and simulation of a helical antenna for naval communication at 18.6 MHz. Key details include the antenna dimensions such as monopole height of 595mm, helix pitch length of 20mm, and 25 turns. Simulation results show a resonance frequency of 18.6MHz and S11 of -9.5dB. Radiation patterns are also presented. Additionally, the document discusses cylindrical strip antennas designed and simulated in HFSS, including resonance frequencies and radiation patterns.
Designing geometric parameters of axisymmetrical cassegrain antenna and corru...Editor Jacotech
Early detection of faults occurring in three-phase induction motors can appreciably reduce the costs of maintenance, which could otherwise be too much costly to repair. Internal faults in three phase induction motors can result in significant performance degradation and eventual system failures. Artificial intelligence techniques have numerous advantages over conventional Model-based and Signal Processing fault diagnostic approaches; therefore, in this paper, a soft-computing system was studied through Neural Network Analysis to detect and diagnose the stator and rotor faults. The fault diagnostic system for three-phase induction motors samples the fault symptoms and then uses a Neural Network model to first train and then identify the fault which gives fast accurate diagnostics. This approach can also be extended to other applications.
Reflector antennas use a reflector surface to modify and direct the radiation pattern of a primary antenna. Parabolic reflectors are commonly used as they focus radiated or incoming waves to/from a focal point, producing a strong, concentrated beam along the axis. The parabolic shape ensures that rays reflected from any part of the surface travel the same distance and remain in phase, resulting in a uniform wavefront at the aperture and high directivity of the beam.
The document discusses the history and innovations of L-Acoustics, a manufacturer of professional audio systems. Some key points:
- L-Acoustics invented modern line source arrays in 1992 with the V-DOSC system and Wavefront Sculpture Technology (WST), which revolutionized the industry.
- Their systems are considered the top choice worldwide for concerts, sports, performing arts, worship, and corporate events due to exceptional quality, rider friendliness, and durability.
- L-Acoustics develops its systems based on theoretical research and prioritizes a "total system approach" with dedicated controllers to ensure consistent, predictable sound performance for clients.
This document discusses the square microstrip patch antenna. It describes the basic construction and working of the antenna, which consists of a thin metallic patch placed on a ground plane with dielectric material in between. The patch can be square, circular, or rectangular in shape. The document lists some disadvantages of microstrip antennas, such as low efficiency and gain. It also outlines some advantages, including small size, easy fabrication, and ability to support multiple frequencies. Applications mentioned include use in spacecraft, aircraft, telemedicine, and mobile/satellite communication. The document provides details on simulating a square patch antenna model.
this discusses reflectarray antena and the difference between reflectarray and parabolic antenna , refelctarray antenna types,equation and applications and it's elements
Reflector antennas take various shapes like plane, corner, and parabolic reflectors. Parabolic reflectors are most widely used as they focus incoming parallel rays to a focal point, producing a high-gain pencil beam. Their analysis involves determining the induced current density on the surface using ray tracing and aperture distribution methods. The radiation characteristics of parabolic reflectors make them well suited for applications like radio astronomy, communication systems, and satellite tracking.
A Study on Reflector Antennas and Design of Reflector Antenna for 5GHz BandIRJET Journal
This document summarizes a study on reflector antennas and the design of a reflector antenna for the 5GHz band. It begins with an introduction to reflector antennas and their advantages. It then describes various feeding techniques for reflector antennas including focal feed systems, offset feeds, Gregorian feeds, and Cassegrain feeds. The document discusses using a cylindrical horn ("coffee can") as a feed antenna and presents the design of a horn for 5.5GHz. It concludes by describing the simulation and design of a parabolic reflector antenna for 5.5GHz including the reflector and horn dimensions.
This document describes the design and study of a portable solar dish concentrator. Key points:
- A 1.6 meter diameter parabolic dish concentrator was fabricated from galvanized steel with a reflective coating. It achieved a concentration ratio of 30% at midday.
- A receiver located at the focal point of the dish was able to heat water up to 80 degrees Celsius.
- The system was equipped with a two-axis tracking system to follow the sun and maximize concentration of sunlight on the receiver.
- The portable solar dish concentrator demonstrated the ability to effectively concentrate sunlight and increase thermal energy collection compared to a fixed system without tracking.
This technical report discusses the components and system design of radar systems. It describes some key subsystems including antennas, duplexers, and the radio frequency subsystem. It also discusses digital waveform generators and frequency synthesizers/oscillators. Antennas are the interface between the radar system and free space, transmitting energy in beams and collecting echo signals. Duplexers use circulators to switch the radar between transmit and receive modes. The radio frequency subsystem includes antennas, duplexers, and filters to transmit signals and filter received signals. Digital waveform generators store and output signals using digital memories and D/A converters. Frequency synthesizers and oscillators generate the radio frequencies used.
Parabolic reflector antennas use the shape of a parabola to focus electromagnetic waves onto a feed or from a feed. They operate by reflecting waves in such a way that the distance from the fixed focus point plus the distance from the directrix line is constant. This causes the waves to reflect as a collimated beam. Common types include simple parabolic reflectors and cassegrain feed parabolic reflectors, where a secondary hyperbolic reflector is used to improve directivity and reduce power loss. Key applications are in satellite communications and wireless telecommunications systems.
This document discusses various types of antennas. It begins by outlining the learning objectives, which are to classify antennas, analyze antenna parameters, and compare different antenna types. It then defines an antenna as a structure that converts electrical signals to radio waves and vice versa. Key parameters discussed include polarization, radiation pattern, directivity, impedance, bandwidth, and electrical/physical length. Standard antenna types like isotropic radiators and dipoles are introduced. Specific antenna designs covered include half-wave and folded dipoles, and quarter-wave monopoles. Near-field and far-field regions are also defined.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
- The document describes several large radio telescopes around the world, including their key design features and specifications.
- Some of the telescopes discussed are the Big Ear radio telescope in Ohio with a curved reflector of 110x21m and flat reflector of 104x31m, the Five College Radio Astronomy Observatory with a 14m dish enclosed in a geodesic dome, and the Very Large Array in New Mexico consisting of 27 steerable 25m dishes.
- The document also mentions the demolition of Big Ear in 1998 and a funding dispute around rebuilding the collapsed 91m Green Bank telescope.
IRJET- Simulation Results of Circular Horn AntennaIRJET Journal
1. The document discusses the simulation results of circular horn antennas. A conical horn antenna and elliptical horn antenna were designed and simulated using HFSS.
2. For the conical horn antenna, the return loss, field distribution, directivity, gain and radiation patterns were calculated. The resonance frequency was found to be 10.95GHz.
3. An elliptical horn antenna was also designed and its return loss, field distribution and radiation pattern were obtained through simulation. The resonance frequency of the elliptical horn antenna was 9.05GHz.
Reflector antenna design in different frequencies using frequency selective s...TELKOMNIKA JOURNAL
In this study, it is aimed to obtain two different asymmetric radiation patterns obtained from antennas in the shape of the cross-section of a parabolic reflector (fan blade type antennas) and antennas with cosecant-square radiation characteristics at two different frequencies from a single antenna. For this purpose, firstly, a fan blade type antenna design will be made, and then the reflective surface of this antenna will be completed to the shape of the reflective surface of the antenna with the cosecant-square radiation characteristic with the frequency selective surface designed to provide the characteristics suitable for the purpose. The frequency selective surface designed and it provides the perfect transmission as possible at 4 GHz operating frequency, while it will act as a band-quenching filter for electromagnetic waves at 5 GHz operating frequency and will be a reflective surface. Thanks to this frequency selective surface to be used as a reflective surface in the antenna, a fan blade type radiation characteristic at 4 GHz operating frequency will be obtained, while a cosecant-square radiation characteristic at 5 GHz operating frequency will be obtained.
The horn antenna is a simple tapered pipe that is widely used as a feed element for large satellite and radio astronomy dishes. It has several advantages, including its simplicity of construction, ease of excitation, versatility, large gain, and good overall performance. There are different types of horn antennas defined by the direction of their taper, including E-plane, H-plane, pyramidal, and conical horns. The E-plane horn has a flare in the direction of the electric field. To analyze the radiation characteristics of horn antennas, equivalent current techniques are used which involve determining the aperture phase distribution and equivalent currents based on the feed waveguide mode and the quadratic phase variation across the aperture.
An antenna is a passive structure that serves as a transition between a transmission line and air used to transmit and/or receive electromagnetic waves. Antennas can be divided into two groups: wire antennas such as dipoles, loops, and Yagi-Uda antennas, and aperture antennas such as parabolic, horns, and microstrip antennas. Key antenna parameters include radiation pattern, directivity, gain, beamwidth, impedance, effective area, and polarization.
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The document is an internship report submitted by M. Umar Khalid to the University College of Engineering & Technology at the Islamia University of Bahawalpur, Pakistan. The report details the internship conducted at Pakistan Telecommunication Company Limited (PTCL). It provides an overview of PTCL's organizational structure, services offered such as landlines, broadband and wireless, and technical aspects of the network including the main distribution frame (MDF) and digital subscriber line (DSL) technology. It also describes the next generation network (NGN) architecture and equipment used by PTCL such as the Alcatel exchange switch.
Pakistan Civil Aviation Authority regulates civil aviation in Pakistan and has its headquarters in Karachi. The Electronic Engineering Department (EED) maintains and repairs aviation equipment across Pakistan, including navigational aids, communication systems, and radars. During the internship, the author visited EED's Navigational Aid section to learn about the equipment used for en route and terminal navigation, such as NDBs, VORs, DMEs, localizers, glide slopes, and marker beacons. They guide aircraft through different phases of flight and provide information like direction, distance, and vertical guidance for approaches and landings. The internship helped familiarize the author with the functions and operations of the key systems used in
The document discusses various types of drilling rigs and their components and functions. It describes the key parts of a land rig, including the derrick, rotary table, blowout preventers, mud pumps, and other equipment used for drilling oil and gas wells. It also outlines safety equipment and procedures for working on a drilling rig.
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This document provides a high-level overview of key concepts in GSM network structure and operation for drive testing. It describes the main components of a GSM network including the mobile station, base transceiver station, base station controller, mobile switching center, home location register, visitor location register, and gateway mobile switching center. It also covers control and traffic channels, cell types, antenna tilting, and an introduction to the TEMS drive testing software.
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A wound is a break in the integrity of the skin or tissues, which may be associated with disruption of the structure and function.
Healing is the body’s response to injury in an attempt to restore normal structure and functions.
Healing can occur in two ways: Regeneration and Repair
There are 4 phases of wound healing: hemostasis, inflammation, proliferation, and remodeling. This document also describes the mechanism of wound healing. Factors that affect healing include infection, uncontrolled diabetes, poor nutrition, age, anemia, the presence of foreign bodies, etc.
Complications of wound healing like infection, hyperpigmentation of scar, contractures, and keloid formation.
हिंदी वर्णमाला पीपीटी, hindi alphabet PPT presentation, hindi varnamala PPT, Hindi Varnamala pdf, हिंदी स्वर, हिंदी व्यंजन, sikhiye hindi varnmala, dr. mulla adam ali, hindi language and literature, hindi alphabet with drawing, hindi alphabet pdf, hindi varnamala for childrens, hindi language, hindi varnamala practice for kids, https://www.drmullaadamali.com
Strategies for Effective Upskilling is a presentation by Chinwendu Peace in a Your Skill Boost Masterclass organisation by the Excellence Foundation for South Sudan on 08th and 09th June 2024 from 1 PM to 3 PM on each day.
Gender and Mental Health - Counselling and Family Therapy Applications and In...PsychoTech Services
A proprietary approach developed by bringing together the best of learning theories from Psychology, design principles from the world of visualization, and pedagogical methods from over a decade of training experience, that enables you to: Learn better, faster!
ISO/IEC 27001, ISO/IEC 42001, and GDPR: Best Practices for Implementation and...PECB
Denis is a dynamic and results-driven Chief Information Officer (CIO) with a distinguished career spanning information systems analysis and technical project management. With a proven track record of spearheading the design and delivery of cutting-edge Information Management solutions, he has consistently elevated business operations, streamlined reporting functions, and maximized process efficiency.
Certified as an ISO/IEC 27001: Information Security Management Systems (ISMS) Lead Implementer, Data Protection Officer, and Cyber Risks Analyst, Denis brings a heightened focus on data security, privacy, and cyber resilience to every endeavor.
His expertise extends across a diverse spectrum of reporting, database, and web development applications, underpinned by an exceptional grasp of data storage and virtualization technologies. His proficiency in application testing, database administration, and data cleansing ensures seamless execution of complex projects.
What sets Denis apart is his comprehensive understanding of Business and Systems Analysis technologies, honed through involvement in all phases of the Software Development Lifecycle (SDLC). From meticulous requirements gathering to precise analysis, innovative design, rigorous development, thorough testing, and successful implementation, he has consistently delivered exceptional results.
Throughout his career, he has taken on multifaceted roles, from leading technical project management teams to owning solutions that drive operational excellence. His conscientious and proactive approach is unwavering, whether he is working independently or collaboratively within a team. His ability to connect with colleagues on a personal level underscores his commitment to fostering a harmonious and productive workplace environment.
Date: May 29, 2024
Tags: Information Security, ISO/IEC 27001, ISO/IEC 42001, Artificial Intelligence, GDPR
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Communicating effectively and consistently with students can help them feel at ease during their learning experience and provide the instructor with a communication trail to track the course's progress. This workshop will take you through constructing an engaging course container to facilitate effective communication.
1. Reflector Antennas
Equation Section 19
1. Introduction
High-gain antennas are required for long-distance radio communications
(radio-relay links and satellite links), high-resolution radars, radio-astronomy,
etc. Reflector systems are probably the most widely used high-gain antennas.
They can easily achieve gains of above 30 dB for microwave and higher
frequencies. Reflector antennas operate on principles known long ago from
geometrical optics (GO). The first RF reflector system was made by Hertz back
in 1888 (a cylindrical reflector fed by a dipole). However, the art of accurately
designing such antenna systems was developed mainly during the days of
WW2 when numerous radar applications evolved.
18.3 M INTELSAT EARTH STATION (ANT BOSCH TELECOM), DUAL
REFLECTOR
4. The simplest reflector antenna consists of two components: a reflecting
surface and a much smaller feed antenna, which often is located at the
reflector’s focal point. Constructions that are more complex involve a
secondary reflector (a subreflector) at the focal point, which is illuminated by a
primary feed. These are called dual-reflector antennas. The most popular
reflector is the parabolic one. Other reflectors often met in practice are: the
cylindrical reflector, the corner reflector, spherical reflector, and others.
2. Principles of parabolic reflectors
A paraboloidal surface is described by the equation (see plot b)
2 4F(F z f ), a . (19.1)
Here, is the distance from a point A to the focal point O, where A is the
projection of the point R on the reflector surface onto the axis-orthogonal plane
(the aperture plane) at the focal point. For a given displacement from the
axis of the reflector, the point R on the reflector surface is a distance rf away
from the focal point O. The position of R can be defined either by ( , z f ) ,
which is a rectangular pair of coordinates, or by (rf , f ) , which is a polar pair
5. of coordinates. A relation between (rf , f ) and F is readily found from (19.1):
r F
F
2
2
1 cos cos ( /2) f
f f
. (19.2)
Other relations to be used later are:
2 sin
sin f 2 tan
f
f f
1 cos f
2
F
r F
. (19.3)
The axisymmetric (rotationally symmetric) paraboloidal reflector is entirely
defined by the respective parabolic line, i.e., by two basic parameters: the
diameter D and the focal length F (see plot b). Often, the parabola is specified
in terms of D and the ratio F/D. When F/D approaches infinity, the reflector
becomes flat. Some parabolic curves are shown below. When F / D 0.25, the
focal point lies in the plane passing through the reflector’s rim.
0.5
0.4
0.3
0.2
0.1
0
-0.1
-0.2
-0.3
-0.4
-0.5
-0.5 -0.4 -0.3 -0.2 -0.1
zf
rho/D
F/D=1/2 F/D=1/3 F/D=1/4
Focal point
0
6. The angle from the feed (focal) point to the reflector’s rim is related to F / D as
0
2arctan 1
4(F / D)
. (19.4)
The focal distance F of a given reflector can be calculated after measuring
its diameter D and its height H0 :
2
F D
. (19.5)
H
16 0
Eq. (19.5) is found by solving (19.1) with D / 2 and z f F H0 . For
example, if F / D 1/ 4, then H0 D / 4 H0 F , i.e., the focal point is on
the reflector’s rim plane.
The reflector design problem involves mainly the matching of the feed
antenna pattern to the reflector.
The geometry of the paraboloidal reflector has two valuable features:
All rays leaving the focal point O are collimated along the reflector’s axis
after reflection.
All overall ray path lengths (from the focal point to the reflector and on to
the aperture plane) are the same and equal to 2F .
The above properties are proven by the GO methods, therefore, they are true
only if the following conditions hold:
The radius of the curvature of the reflector is large compared to the
wavelength and the local region around each reflection point can be
treated as planar.
The radius of the curvature of the incoming wave from the feed is large
and can be treated locally at the reflection point as a plane wave.
The reflector is a perfect conductor, i.e., 1.
7. 3. Dual-reflector antennas
The dual-reflector antenna consists of two reflectors and a feed antenna. The
feed is conveniently located at the apex of the main reflector. This makes the
system mechanically robust, the transmission lines are shorter and easier to
construct (especially in the case of waveguides).
The virtual focal point F is the point from which transmitted rays appear to
emanate with a spherical wave front after reflection from the subreflector.
The most popular dual reflector is the axisymmetric Cassegrain antenna.
The main reflector is parabolic and the subreflector is hyperbolic (convex).
A second form of the dual reflector is the Gregorian reflector. It has a
concave elliptic subreflector. The Gregorian subreflector is more distant from
the main reflector and, thus, it requires more support.
Dual-reflector antennas for earth terminals have another important
advantage beside the location of the main feed. They have almost no spillover
toward the noisy ground, as do the single-feed reflector antennas. Their
spillover (if any) is directed toward the much less noisy sky region. Both, the
Cassegrain and the Gregorian reflector systems have their origins in optical
telescopes and are named after their inventors.
8. The subreflectors are rotationally symmetric surfaces obtained from the
curves shown below (a hyperbola and an ellipse).
The subreflector is defined by its diameter Ds and its eccentricity e. The shape
(or curvature) is controlled by the eccentricity:
1, hyperbola
<1, ellipse
e c
a
(19.41)
Special cases are
e , straight line (plane)
e 0, circle (sphere)
e 1, parabola
Both, the ellipse and the hyperbola, are described by the equation
zs xs
a c a
2 2
2 2 2 1
. (19.42)
The function of a hyperbolic subreflector is to convert the incoming wave
from a feed antenna located at the focal point F to a spherical wave front w
that appears to originate from the virtual focal point F. This means that the
optical path from F to w must be constant with respect to the angle of
9. incidence:
FR RA FV VB c a VB. (19.43)
Since
RA FA FR FB FR, (19.44)
(FA FB because the reflected wave must be spherical)
FR FR c a (FB VB) c a (c a) 2a . (19.45)
Note: Another definition of a hyperbola is: a hyperbola is the locus of a point
that moves so that the difference of the distances from its two focal points,
FR FR, is equal to a constant, 2a.
The dual axisymmetric Cassegrain reflector can be modeled as a single
equivalent parabolic reflector as shown below.
The equivalent parabola has the same diameter, De D, but its focal length is
longer than that of the main reflector:
10. F e F M F
1
1 e
e
. (19.46)
Here, M (e 1) / (e 1) is called magnification.
The increased equivalent focal length has several advantages:
less cross-polarization;
less spherical-spread loss at the reflector’s rim, and therefore, improved
aperture efficiency.
The synthesis of dual-reflector systems is an advanced topic. Many factors
are taken into account when shaped reflectors are designed for improved
aperture efficiency. These are: minimized spillover, less phase error, improved
amplitude distribution in the reflector’s aperture.
4. Gain of reflector antennas
The maximum achievable gain for an aperture antenna is
4
G Du Ap
. (19.47)
max 2
This gain is possible only if the following is true: uniform amplitude and phase
distribution, no spillover, no ohmic losses. In practice, these conditions are not
achievable, and the effective antenna aperture is less than its physical aperture:
, (19.48)
2
4
G apDu apAp
where ap 1 is the aperture efficiency. The aperture efficiency is expressed as
a product of sub-efficiencies:
ap er t s a , (19.49)
where:
er is the radiation efficiency (loss),
is the aperture taper efficiency,
s is the spillover efficiency, and
a is the achievement efficiency.
t
The taper efficiency can be found using the directivity expression for
aperture antennas.
11. If the feed pattern extends beyond the reflector’s rim, certain amount of
power is not redirected by the reflector, i.e., it is lost. This power-loss is
referred to as spillover. The spillover efficiency measures that portion of the
feed pattern, which is intercepted by the reflector relative to the total feed
power:
The achievement efficiency a is an integral factor including losses due to:
random surface error, cross-polarization loss, aperture blockage, reflector phase
error (profile accuracy), feed phase error.
A well-designed and well-made aperture antenna should have an overall
aperture efficiency of ap 0.65 or more, where “more” is less likely.
The gain of a reflector antenna also depends on phase errors, which
theoretically should not exist but are often present in practice. Any departure of
the phase over the virtual aperture from the uniform distribution leads to a
significant decrease of the directivity. For paraboloidal antennas, phase errors
result from:
displacement of the feed phase centre from the focal point;
deviation of the reflector surface from the paraboloidal shape,
including surface roughness and other random deviations;
feed wave fronts are not exactly spherical.
Simple expression has been derived1 to predict with reasonable accuracy the
loss in directivity for rectangular and circular apertures when the peak value of
the aperture phase deviations is known. Assuming that the maximum radiation
is along the reflector’s axis, and assuming a maximum aperture phase
deviation m, the ratio of the directivity without phase errors D0 and the
directivity with phase errors D is given by
2 2
D m
D
0
1
2
. (19.59)
The maximum phase deviation m is defined as
| || | m, (19.60)
where is the aperture’s phase function, and is its average value. The
aperture phase deviation should be kept below / 8 if the gain is not to be
affected much.
12. The reflector design problem includes a trade-off between aperture taper and
spillover when the feed antenna is chosen. Taper and spillover efficiencies are
combined to form the so-called illumination efficiency i t s . Multiplying
(19.54) and (19.55), and using a 2F tan(0 / 2) yields
2 2
f f
2 0
o
F . (19.56)
i f f f
4 2
2 2
cot ( , ) tan
0 0
D
d d
Here,
2
F 2
0 0
4
| ( , )| sin
f
f f f f
D
d d
, (19.57)
is the directivity of the feed antenna. An ideal feed antenna pattern would
compensate for the spherical spreading loss by increasing the field strength as
f increases, and then would abruptly fall to zero in the direction of the
reflector’s rim in order to avoid spillover:
cos ( / 2) ,
2
2
( , ) cos ( / 2)
0,
o
f o
f f f
f o
F
(19.58)
This ideal feed is not realizable. For practical purposes, (19.56) has to be
optimized with respect to the edge-illumination level. The function specified by
(19.56) is well-behaved with a single maximum with respect to the edge-illumination.
The achievement efficiency a is an integral factor including losses due to:
random surface error, cross-polarization loss, aperture blockage, reflector phase
error (profile accuracy), feed phase error.
A well-designed and well-made aperture antenna should have an overall
13. aperture efficiency of ap 0.65 or more, where “more” is less likely.
The gain of a reflector antenna also depends on phase errors, which
theoretically should not exist but are often present in practice. Any departure of
the phase over the virtual aperture from the uniform distribution leads to a
significant decrease of the directivity. For paraboloidal antennas, phase errors
result from:
displacement of the feed phase centre from the focal point;
deviation of the reflector surface from the paraboloidal shape,
including surface roughness and other random deviations;
feed wave fronts are not exactly spherical.
Simple expression has been derived1 to predict with reasonable accuracy the
loss in directivity for rectangular and circular apertures when the peak value of
the aperture phase deviations is known. Assuming that the maximum radiation
is along the reflector’s axis, and assuming a maximum aperture phase
deviation m, the ratio of the directivity without phase errors D0 and the
directivity with phase errors D is given by
2 2
D m
D
0
1
2
. (19.59)
The maximum phase deviation m is defined as
| || | m, (19.60)
where is the aperture’s phase function, and is its average value. The
aperture phase deviation should be kept below / 8 if the gain is not to be
affected much. Roughly, this translates into surface profile deviation from the
ideal shape (e.g. paraboloid) of no more than /16.
1 D.K. Cheng, “Effects of arbitrary phase errors on the gain and beamwidth characteristics of radiation pattern,” IRE Trans. AP,
vol. AP-3, No. 3, pp. 145-147, July 1955.