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.
An antenna converts radio frequency electric current into electromagnetic waves that are radiated into space. The same antenna can transmit and receive signals. Key antenna concepts include reciprocity, radiation patterns, gain, and polarization. Antenna gain compares its power output to an isotropic antenna. Common antennas include dipole, parabolic reflective, and types are optimized for propagation modes like ground wave, sky wave, and line-of-sight. Signal strength is reduced by factors like free space loss, noise, multipath, and fading over the transmission path.
Space wave propagation involves radio waves that travel directly or after reflecting off the Earth's surface within the lower 20 km of the atmosphere. These waves can propagate line-of-sight between transmitter and receiver antennas in the VHF and UHF bands. Space waves follow two paths - direct or ground reflected - and may arrive in or out of phase, causing signal fluctuations. The maximum transmission distance is limited by the Earth's curvature and obstructions that can cause shadowing effects. Refractive phenomena like super-refraction can sometimes extend the radio horizon.
Pulse modulation is a technique used to transmit analog information by sampling continuous signals at regular intervals and transmitting the signal as a series of pulses. There are two main types of pulse modulation: analog and digital. Pulse amplitude modulation (PAM) is the simplest form of pulse modulation, where each sample is made proportional to the amplitude of the original signal at the time of sampling. PAM follows the amplitude of the original signal and can reconstruct the signal through a low pass filter. It is easy to generate and demodulate PAM but requires a large bandwidth and more noise compared to other techniques.
- Antennas convert electric currents into radio waves and vice versa. They are used in various technologies including radio, television, mobile phones, WiFi, and radar.
- The first antennas were built in 1888 by Heinrich Hertz to transmit and receive electromagnetic waves. Modern antennas come in different types for applications like broadcasting, communications, and space exploration.
- Antennas work by using an oscillating current to generate oscillating electric and magnetic fields that propagate as radio waves. During reception, the antenna intercepts some power from incoming radio waves to produce a voltage for the receiver.
Introduction To Wireless Fading ChannelsNitin Jain
The document summarizes key concepts related to wireless fading channels, including:
1. Multipath fading causes fluctuations in signal strength over small physical distances due to constructive and destructive interference from multiple signal paths.
2. Rayleigh fading occurs when there is no line-of-sight path between transmitter and receiver, resulting in fast, large fluctuations in signal strength over small physical distances.
3. Doppler spread and coherence time describe how quickly the wireless channel varies over time due to mobility, with fast fading occurring if the channel changes significantly within a symbol period.
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.
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.
An antenna converts radio frequency electric current into electromagnetic waves that are radiated into space. The same antenna can transmit and receive signals. Key antenna concepts include reciprocity, radiation patterns, gain, and polarization. Antenna gain compares its power output to an isotropic antenna. Common antennas include dipole, parabolic reflective, and types are optimized for propagation modes like ground wave, sky wave, and line-of-sight. Signal strength is reduced by factors like free space loss, noise, multipath, and fading over the transmission path.
Space wave propagation involves radio waves that travel directly or after reflecting off the Earth's surface within the lower 20 km of the atmosphere. These waves can propagate line-of-sight between transmitter and receiver antennas in the VHF and UHF bands. Space waves follow two paths - direct or ground reflected - and may arrive in or out of phase, causing signal fluctuations. The maximum transmission distance is limited by the Earth's curvature and obstructions that can cause shadowing effects. Refractive phenomena like super-refraction can sometimes extend the radio horizon.
Pulse modulation is a technique used to transmit analog information by sampling continuous signals at regular intervals and transmitting the signal as a series of pulses. There are two main types of pulse modulation: analog and digital. Pulse amplitude modulation (PAM) is the simplest form of pulse modulation, where each sample is made proportional to the amplitude of the original signal at the time of sampling. PAM follows the amplitude of the original signal and can reconstruct the signal through a low pass filter. It is easy to generate and demodulate PAM but requires a large bandwidth and more noise compared to other techniques.
- Antennas convert electric currents into radio waves and vice versa. They are used in various technologies including radio, television, mobile phones, WiFi, and radar.
- The first antennas were built in 1888 by Heinrich Hertz to transmit and receive electromagnetic waves. Modern antennas come in different types for applications like broadcasting, communications, and space exploration.
- Antennas work by using an oscillating current to generate oscillating electric and magnetic fields that propagate as radio waves. During reception, the antenna intercepts some power from incoming radio waves to produce a voltage for the receiver.
Introduction To Wireless Fading ChannelsNitin Jain
The document summarizes key concepts related to wireless fading channels, including:
1. Multipath fading causes fluctuations in signal strength over small physical distances due to constructive and destructive interference from multiple signal paths.
2. Rayleigh fading occurs when there is no line-of-sight path between transmitter and receiver, resulting in fast, large fluctuations in signal strength over small physical distances.
3. Doppler spread and coherence time describe how quickly the wireless channel varies over time due to mobility, with fast fading occurring if the channel changes significantly within a symbol period.
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.
hello readers i give my PPT presentation for about antenna and ther properties and working explain in this ppt
i hope you like it THANK YOU.......!!!!!!!
The document is a seminar report on smart antenna systems submitted by Ashok Behuria in partial fulfillment of the requirements for a Bachelor of Engineering degree. It discusses different types of smart antenna systems including switched beam and adaptive array systems. The report provides an overview of smart antennas, explaining that they combine antenna arrays with signal processing to optimize radiation and reception patterns automatically based on the signal environment.
This presentation is about Propagation of Electromagnetic Waves and covers the following topics:
-Introduction to EM Waves
-Electromagnetic Wave Spectrum
-Wave Propagation in Lossy Dielectrics
-Plane Waves in Free Space
-Properties of EM Waves
This presentation is as per the course of DAE Electronics ELECT-212.
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 the Yagi-Uda antenna, which consists of multiple parallel dipole elements including a reflector, driven element, and multiple directors. It operates in the HF to UHF bands and provides a directional radiation pattern with moderate gain. Key advantages are its directionality and ability to operate at high frequencies. Common applications include television reception and radar systems where its directional properties and moderate gain are beneficial.
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 wireless communication and radio wave propagation. It covers various types of fading that can occur for wireless signals, including small-scale and large-scale fading. Small-scale fading is caused by multipath propagation and can be frequency selective, flat, fast or slow depending on factors like bandwidth and receiver/transmitter motion. Doppler shift from movement introduces a change in frequency. Mitigation techniques for multipath fading include diversity methods using space, frequency or time as well as adaptive equalization and forward error correction.
High impedance surface_his_ris_amc_nurmerical_analytical_analysis利 金
Features of an AMC such as dispersion diagram and reflection phase are discussed numerically and analytically, along with their experimental set up. Parametric study on polarization (TE and TM,substrate thickness and dielectric constant and unit cell size and spacing is carried out. Their design equations are included from different references.
Data Communications,Data Networks,computer communications,multiplexing,spread spectrum,protocol architecture,data link protocols,signal encoding techniques,transmission media
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 key concepts related to antennas and electromagnetic waves. It defines that radio waves have electric and magnetic fields that are perpendicular to each other and the direction of wave propagation. It also describes how antennas can transmit electromagnetic waves by converting electrical energy to radio waves and receive waves by converting radio waves back to electrical energy. Antenna size is inversely proportional to frequency, with higher frequencies requiring smaller antennas. Antenna radiation patterns and near/far field regions are also discussed.
Rahul Kumar completed a PowerPoint presentation on wave propagation under the guidance of Miss Arzoo. The presentation covered three main types of wave propagation: ground wave propagation, which uses the area between the earth's surface and ionosphere; sky wave propagation, which involves reflections from the ionosphere; and space wave propagation, where waves travel directly or after reflecting from the earth's surface through the troposphere.
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.
Microwave technology can be used for LANs, extended LANs, and mobile computing. It uses either terrestrial (ground-based) links or satellite links. There are three forms of mobile computing: packet-radio networking, cellular networking, and satellite station networking. Terrestrial microwave links employ line-of-sight transmitters and receivers in the low gigahertz range, requiring stations every 30 miles, while satellite links use geosynchronous satellites to relay signals over long distances. Microwave systems offer advantages like no cables and wide bandwidth but have disadvantages like disruption from obstacles and signal absorption.
Sky wave propagation involves radio waves reflecting off ionized layers in the upper atmosphere, called the ionosphere, between 50-400km above the Earth's surface. This allows radio signals to travel beyond the horizon over very long distances of thousands of kilometers. The ionosphere is divided into D, E, and F layers based on ionization density, with the F layers primarily responsible for radio wave refraction. Sky wave propagation has enabled long-distance shortwave radio communication between 3-30MHz and amateur radio communication over long distances.
Ground waves propagate along the Earth's surface and are used for medium wave (MW) transmissions. Space waves travel in straight lines but are limited by the curvature of the Earth. Sky waves are used for short wave (SW) transmissions and reflect off the ionosphere which consists of layers (D, E, F1, F2) that vary in density and thickness depending on the time of day and sun exposure. Different propagation modes are used depending on the frequency band and conditions to maximize transmission range.
This document provides an overview of antenna properties and types. It discusses key antenna properties like gain, aperture, directivity, bandwidth, polarization, and effective length. It then describes several common antenna types including dipole antennas, monopole antennas, loop antennas, log-periodic antennas, travelling wave antennas like helical and Yagi-Uda, and reflector antennas like corner reflectors and parabolic reflectors. Radiation patterns are also characterized in terms of main beam, sidelobes, half power beamwidth, and sidelobe level.
This document provides an overview of microwave fundamentals including:
- Radio wave propagation characteristics such as reflection, refraction, scattering, and attenuation. Factors affecting propagation like moisture and rain are also discussed.
- Microwave frequency bands designated by the ITU from L band to W band along with common frequency ranges used in practical systems from 2-7 GHz for backhaul and 15-23 GHz for access networks.
- Key terminology used in microwave systems like azimuth, AMSL, dB, dBm, antenna gain, beamwidth, AGC, and spot frequency.
- Modulation techniques for digital microwave including FSK, QPSK, QAM, and their advantages over analog modulation in
Microwaves are a type of electromagnetic radiation, similar to radio waves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays. They are named "microwaves" because they are smaller than the waves used in traditional radio broadcasting, typically ranging in length from about one millimeter to one meter.
hello readers i give my PPT presentation for about antenna and ther properties and working explain in this ppt
i hope you like it THANK YOU.......!!!!!!!
The document is a seminar report on smart antenna systems submitted by Ashok Behuria in partial fulfillment of the requirements for a Bachelor of Engineering degree. It discusses different types of smart antenna systems including switched beam and adaptive array systems. The report provides an overview of smart antennas, explaining that they combine antenna arrays with signal processing to optimize radiation and reception patterns automatically based on the signal environment.
This presentation is about Propagation of Electromagnetic Waves and covers the following topics:
-Introduction to EM Waves
-Electromagnetic Wave Spectrum
-Wave Propagation in Lossy Dielectrics
-Plane Waves in Free Space
-Properties of EM Waves
This presentation is as per the course of DAE Electronics ELECT-212.
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 the Yagi-Uda antenna, which consists of multiple parallel dipole elements including a reflector, driven element, and multiple directors. It operates in the HF to UHF bands and provides a directional radiation pattern with moderate gain. Key advantages are its directionality and ability to operate at high frequencies. Common applications include television reception and radar systems where its directional properties and moderate gain are beneficial.
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 wireless communication and radio wave propagation. It covers various types of fading that can occur for wireless signals, including small-scale and large-scale fading. Small-scale fading is caused by multipath propagation and can be frequency selective, flat, fast or slow depending on factors like bandwidth and receiver/transmitter motion. Doppler shift from movement introduces a change in frequency. Mitigation techniques for multipath fading include diversity methods using space, frequency or time as well as adaptive equalization and forward error correction.
High impedance surface_his_ris_amc_nurmerical_analytical_analysis利 金
Features of an AMC such as dispersion diagram and reflection phase are discussed numerically and analytically, along with their experimental set up. Parametric study on polarization (TE and TM,substrate thickness and dielectric constant and unit cell size and spacing is carried out. Their design equations are included from different references.
Data Communications,Data Networks,computer communications,multiplexing,spread spectrum,protocol architecture,data link protocols,signal encoding techniques,transmission media
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 key concepts related to antennas and electromagnetic waves. It defines that radio waves have electric and magnetic fields that are perpendicular to each other and the direction of wave propagation. It also describes how antennas can transmit electromagnetic waves by converting electrical energy to radio waves and receive waves by converting radio waves back to electrical energy. Antenna size is inversely proportional to frequency, with higher frequencies requiring smaller antennas. Antenna radiation patterns and near/far field regions are also discussed.
Rahul Kumar completed a PowerPoint presentation on wave propagation under the guidance of Miss Arzoo. The presentation covered three main types of wave propagation: ground wave propagation, which uses the area between the earth's surface and ionosphere; sky wave propagation, which involves reflections from the ionosphere; and space wave propagation, where waves travel directly or after reflecting from the earth's surface through the troposphere.
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.
Microwave technology can be used for LANs, extended LANs, and mobile computing. It uses either terrestrial (ground-based) links or satellite links. There are three forms of mobile computing: packet-radio networking, cellular networking, and satellite station networking. Terrestrial microwave links employ line-of-sight transmitters and receivers in the low gigahertz range, requiring stations every 30 miles, while satellite links use geosynchronous satellites to relay signals over long distances. Microwave systems offer advantages like no cables and wide bandwidth but have disadvantages like disruption from obstacles and signal absorption.
Sky wave propagation involves radio waves reflecting off ionized layers in the upper atmosphere, called the ionosphere, between 50-400km above the Earth's surface. This allows radio signals to travel beyond the horizon over very long distances of thousands of kilometers. The ionosphere is divided into D, E, and F layers based on ionization density, with the F layers primarily responsible for radio wave refraction. Sky wave propagation has enabled long-distance shortwave radio communication between 3-30MHz and amateur radio communication over long distances.
Ground waves propagate along the Earth's surface and are used for medium wave (MW) transmissions. Space waves travel in straight lines but are limited by the curvature of the Earth. Sky waves are used for short wave (SW) transmissions and reflect off the ionosphere which consists of layers (D, E, F1, F2) that vary in density and thickness depending on the time of day and sun exposure. Different propagation modes are used depending on the frequency band and conditions to maximize transmission range.
This document provides an overview of antenna properties and types. It discusses key antenna properties like gain, aperture, directivity, bandwidth, polarization, and effective length. It then describes several common antenna types including dipole antennas, monopole antennas, loop antennas, log-periodic antennas, travelling wave antennas like helical and Yagi-Uda, and reflector antennas like corner reflectors and parabolic reflectors. Radiation patterns are also characterized in terms of main beam, sidelobes, half power beamwidth, and sidelobe level.
This document provides an overview of microwave fundamentals including:
- Radio wave propagation characteristics such as reflection, refraction, scattering, and attenuation. Factors affecting propagation like moisture and rain are also discussed.
- Microwave frequency bands designated by the ITU from L band to W band along with common frequency ranges used in practical systems from 2-7 GHz for backhaul and 15-23 GHz for access networks.
- Key terminology used in microwave systems like azimuth, AMSL, dB, dBm, antenna gain, beamwidth, AGC, and spot frequency.
- Modulation techniques for digital microwave including FSK, QPSK, QAM, and their advantages over analog modulation in
Microwaves are a type of electromagnetic radiation, similar to radio waves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays. They are named "microwaves" because they are smaller than the waves used in traditional radio broadcasting, typically ranging in length from about one millimeter to one meter.
Radio propagation is affected by various factors in the atmosphere including water vapor, ionization, and solar activity. Understanding how radio waves propagate under different conditions has practical applications for broadcasting, mobile phones, radar, and radio navigation. Propagation can occur through line-of-sight transmission, reflection from the ionosphere, or scattering from the troposphere, and the dominant mode depends on the frequency used and conditions in the atmosphere and ionosphere. Predicting radio propagation is complex due to changing environmental conditions.
This document provides an overview of microwave fundamentals including radio wave propagation characteristics, polarization, frequency bands, and key terminology. Radio waves propagate through mechanisms including reflection, refraction, scattering, and absorption. Polarization can be horizontal, vertical, or circular. Microwave frequencies are divided into bands such as L, S, C, X, Ku, K, and Ka. Important concepts covered include azimuth, AMSL, dB, dBm, antenna gain, beamwidth, and AGC.
The document discusses radio wave propagation and the factors that affect it. It covers topics like the ionosphere and how it influences radio waves, propagation modes like ground waves and sky waves, absorption and fading effects, and how solar activity impacts radio communications through changes in the ionosphere. Key points are that the ionosphere is made up of layers that refract radio waves to allow long distance communications, but that solar activity and sunspots impact the ionosphere's composition and ability to support different frequencies.
This document discusses factors that can impair satellite communications, including the atmosphere. It covers several key points:
1) The ionosphere and troposphere can both introduce impairments on signals depending on frequency. The ionosphere affects signals below 3 GHz while the troposphere affects those above 3 GHz.
2) Effects in the ionosphere include scintillation, which causes rapid fluctuations, as well as absorption and dispersion. Scintillation is most severe near the equator, poles and during sunrises/sunsets.
3) The troposphere's refractive index fluctuations can also cause scintillation on signals from C-band through V-band frequencies used in satellite communications. Its effects vary seasonally and daily
This document discusses radio frequency (RF) signal loss and techniques to minimize it for non-line-of-sight wireless connections. It highlights that RF signals lose strength when encountering natural and manmade obstacles. Some key causes of signal loss include free space loss, fading, and equipment loss. Non-line-of-sight solutions should provide high system gain, mitigate fading and dispersion, and compensate for multipath signals. Technologies like space time coding, adaptive modulation, OFDM can help achieve reliable non-line-of-sight connections by combating various types of signal loss and fading. The document focuses on using OFDM modulation to mitigate effects of frequency-flat and frequency-selective fading.
Propagation Effects and Their Impact on Satellite-Earth Links: Introduction,
Quantifying attenuation and depolarization,
Propagation effects that are not associated with hydrometeors, Prediction of rain attenuation,
Prediction of XPD,
Propagation impairments countermeasures.
This document discusses radio wave propagation. It begins by revisiting transverse electromagnetic waves and their properties. It then discusses different parameters of radio waves like frequency, wavelength, polarization, and intrinsic impedance. It describes various modes of propagation including ground waves, sky waves, and space waves. Ground waves travel along the Earth's surface up to 2 MHz. Sky waves are reflected by the ionosphere to propagate over longer distances on HF bands. Space waves use line-of-sight propagation on VHF and UHF bands. The document also reviews optical properties like reflection, diffraction and interference experienced by radio waves.
Chap 02 antenna & wave propagation EngkaderAMuse
This document summarizes key concepts about antennas and wireless signal propagation. It discusses different types of antennas like dipole antennas and parabolic reflective antennas. It also describes the main modes of wireless signal propagation including ground-wave propagation, sky-wave propagation, and line-of-sight propagation. Additionally, it outlines several factors that can impair wireless signals during propagation, such as attenuation, noise, multipath, and atmospheric absorption.
Radio waves can propagate from the transmitter to the receiver via three main ways: ground waves, sky waves, and space waves. Ground waves travel along the earth's surface for short-range communication. Sky waves travel upward and reflect off ionized layers in the ionosphere to allow long-range communication. Space waves travel directly through the air but are affected by factors like atmospheric conditions, earth curvature, and heights of transmitting and receiving antennas. The distance radio waves can propagate depends on the transmission method used and various environmental factors.
The document discusses HF aviation communication systems and complex radio wave propagation phenomena like refraction, absorption, and non-line-of-sight propagation that can occur. It covers topics like layer refraction, obstacle refraction, atmosphere absorption, ground wave propagation, reflection and multipath effects, sky wave propagation through the ionosphere, HF band allocation and characteristics, transmitter and receiver design considerations, selective calling systems, and factors that influence HF channel availability.
Loss of strength, A periodic reduction in the received strength of a radio transmission.
This is about the phenomenon of loss of signal in telecommunications.Fading refers to the
time variation of the received signal power caused by changes in the transmission medium or path.
This document discusses various aspects of signal propagation including:
1. It defines transmission, detection, and interference ranges for signal propagation. Receiving power decreases with distance and is influenced by factors like fading, shadowing, and reflection.
2. It describes three main propagation modes - ground-wave propagation below 2MHz, sky-wave propagation between 2-30MHz using ionosphere reflection, and line-of-sight propagation above 30MHz requiring direct path.
3. Key challenges for wireless signals include multipath propagation causing interference, and fading effects from mobility and environment that impact power levels over time. Error correction and adaptive equalization techniques aim to overcome these issues.
This document discusses various aspects of signal propagation including:
1. It defines transmission, detection, and interference ranges for wireless signals. The receiving power decreases with distance and is influenced by factors like fading, shadowing, reflection, refraction, scattering, and diffraction.
2. It describes three main propagation modes - ground-wave propagation below 2MHz, sky-wave propagation between 2-30MHz using ionospheric reflection, and line-of-sight propagation above 30MHz requiring a direct path.
3. Factors that impair line-of-sight wireless transmission include attenuation, free space loss, atmospheric absorption, multipath effects, noise, and mobility-induced fading. Techniques like error correction and
The document summarizes key aspects of amplitude modulation (AM) including:
1. AM varies the amplitude of a carrier wave based on the instantaneous amplitude of a modulating signal. This imparts the modulating signal's information onto the carrier wave.
2. The derivation of an AM wave shows it can be expressed as the carrier wave amplitude multiplied by the sum of 1 and the modulating signal, which varies the carrier amplitude.
3. The modulation index is defined as the ratio of the modulating signal amplitude to the carrier amplitude, and describes how much the carrier amplitude varies with respect to its unmodulated level.
This document discusses radio frequency spectrum and radio wave propagation. It defines different radio frequency ranges from very low frequency to extremely high frequency. It describes the different modes of radio wave propagation including ground wave propagation, space wave propagation, sky wave propagation and multipath scattering. It also discusses fading, satellite communication basics including different orbit types, and designing satellite communication links including link budget calculations and multiple access techniques.
This document discusses various topics related to radio wave propagation including:
1. Modes of propagation such as ground wave, sky wave, and space wave propagation. Sky wave propagation involves signal reflection from ionized layers in the atmosphere.
2. Characteristics of the ionospheric layers including the D, E, F1, and F2 layers which vary in ionization levels and affect the maximum usable frequency.
3. Key concepts in sky wave propagation such as virtual height, skip distance, maximum usable frequency, and how daylight impacts absorption and refraction of signals.
This document provides an overview of radio wave propagation and the ionosphere. It defines key concepts like ground wave propagation, sky wave propagation, space wave propagation, critical frequency, maximum usable frequency, and ray path. It describes how the ionosphere is structured in layers and how radio waves interact with and are refracted or reflected by the ionized layers, affecting long-distance radio communication. Factors that influence radio wave propagation like frequency, angle of incidence, and solar activity are also discussed.
The document provides an overview of microwave and satellite technologies. Some key points:
- Microwaves were originally used for long-haul telecommunications but have been displaced by fiber optics except in some cases.
- Microwave signals can experience impairments like equipment failures, fading, and absorption from the atmosphere.
- Satellite communications involve earth stations transmitting to satellites (uplink) and satellites transmitting back to earth stations (downlink). Satellites can be in low earth orbit, medium earth orbit, or geostationary orbit.
Similar to ANTENNA AND WAVE PROPAGATION: IONOSPHERIC FADING EFFECT (20)
DIGITAL COMMUNICATION: ENCODING AND DECODING OF CYCLIC CODE ShivangiSingh241
Cyclic codes are a type of linear code where any cyclic shift of a codeword is also a codeword. This allows for efficient encoding and decoding using shift registers.
Encoding of cyclic codes can be done by dividing the message polynomial by the generator polynomial, with the remainder becoming the parity bits. Encoding circuits use shift registers with feedback to efficiently perform this division. Decoding uses the syndrome, which is computed by shifting the received word into a syndrome register. A decoder then attempts to match the syndrome to an error pattern, correcting errors one symbol at a time by shifting the syndrome and received word simultaneously.
Digital television receivers allow viewers to receive digital television signals. They contain components like a tuner to select channels, a demodulator to convert signals to a binary format, decoders to transform the digital bits into a viewable format, and a central control unit as the brain. Digital TV receivers provide advantages over analog TV like superior image quality, smaller bandwidth, and compatibility with computers and the internet. They can receive signals from different sources like terrestrial antennas, cable, satellite, or over the internet.
Voice over IP allows communication between two parties over the Internet using packet switching rather than traditional circuit switching over telephone networks. There are two main protocols for Voice over IP calls: SIP and H.323. SIP establishes, manages, and terminates multimedia sessions using text-based messages with a header and body. A simple SIP call involves three steps - establishing the call with an INVITE message, communicating using temporary ports, and terminating with a BYE message. H.323 also allows internet phones to connect to traditional phones through a gateway and uses several sub-protocols like H.245 and Q.931 to negotiate connections and media encoding.
RADIOMETER AND BASICS OF SATELLITE COMMUNICATION SYSTEMSShivangiSingh241
Radiometers are instruments that measure power, which can be expressed as brightness temperature. A basic radiometer consists of an antenna and receiver with a power detector. There are different types of radiometers including total power radiometers. Radiometers must be calibrated to maintain accuracy over time. Satellite communication systems have space, control and ground segments. The space segment includes satellites and subsystems like transponders. Ground stations in the earth segment transmit and receive signals to and from satellites. Common satellite orbits and frequency bands are also discussed.
This document discusses minimum phase systems in digital signal processing. It defines minimum phase systems as those with all poles and zeros inside the unit circle, making both the system function and inverse causal and stable. Minimum phase systems are important because they have a stable inverse. The document outlines key properties of minimum phase systems including having the least phase delay, minimum group delay, and concentrating energy in the early part of the impulse response compared to other systems with the same magnitude response. An example demonstrates converting a mixed-phase system to minimum phase by adding an all-pass filter.
Radar technology is evolving towards high resolution 4D imaging radars capable of dense point clouds that enable object detection, classification, and tracking. This will blur the lines between radar and lidar. Innovative startups are developing novel radar technologies using CMOS, metamaterials, and UWB to enable truly 4D imaging from a single chip. Until 2030, the automotive radar market will be driven by sales of semi-autonomous vehicles, which will require short, medium, and long range radars for functions like adaptive cruise control and collision avoidance. Global forecasts predict continued growth in radar markets and applications through 2030 as capabilities advance.
Literature Review Basics and Understanding Reference Management.pptxDr Ramhari Poudyal
Three-day training on academic research focuses on analytical tools at United Technical College, supported by the University Grant Commission, Nepal. 24-26 May 2024
Using recycled concrete aggregates (RCA) for pavements is crucial to achieving sustainability. Implementing RCA for new pavement can minimize carbon footprint, conserve natural resources, reduce harmful emissions, and lower life cycle costs. Compared to natural aggregate (NA), RCA pavement has fewer comprehensive studies and sustainability assessments.
A review on techniques and modelling methodologies used for checking electrom...nooriasukmaningtyas
The proper function of the integrated circuit (IC) in an inhibiting electromagnetic environment has always been a serious concern throughout the decades of revolution in the world of electronics, from disjunct devices to today’s integrated circuit technology, where billions of transistors are combined on a single chip. The automotive industry and smart vehicles in particular, are confronting design issues such as being prone to electromagnetic interference (EMI). Electronic control devices calculate incorrect outputs because of EMI and sensors give misleading values which can prove fatal in case of automotives. In this paper, the authors have non exhaustively tried to review research work concerned with the investigation of EMI in ICs and prediction of this EMI using various modelling methodologies and measurement setups.
Low power architecture of logic gates using adiabatic techniquesnooriasukmaningtyas
The growing significance of portable systems to limit power consumption in ultra-large-scale-integration chips of very high density, has recently led to rapid and inventive progresses in low-power design. The most effective technique is adiabatic logic circuit design in energy-efficient hardware. This paper presents two adiabatic approaches for the design of low power circuits, modified positive feedback adiabatic logic (modified PFAL) and the other is direct current diode based positive feedback adiabatic logic (DC-DB PFAL). Logic gates are the preliminary components in any digital circuit design. By improving the performance of basic gates, one can improvise the whole system performance. In this paper proposed circuit design of the low power architecture of OR/NOR, AND/NAND, and XOR/XNOR gates are presented using the said approaches and their results are analyzed for powerdissipation, delay, power-delay-product and rise time and compared with the other adiabatic techniques along with the conventional complementary metal oxide semiconductor (CMOS) designs reported in the literature. It has been found that the designs with DC-DB PFAL technique outperform with the percentage improvement of 65% for NOR gate and 7% for NAND gate and 34% for XNOR gate over the modified PFAL techniques at 10 MHz respectively.
DEEP LEARNING FOR SMART GRID INTRUSION DETECTION: A HYBRID CNN-LSTM-BASED MODELgerogepatton
As digital technology becomes more deeply embedded in power systems, protecting the communication
networks of Smart Grids (SG) has emerged as a critical concern. Distributed Network Protocol 3 (DNP3)
represents a multi-tiered application layer protocol extensively utilized in Supervisory Control and Data
Acquisition (SCADA)-based smart grids to facilitate real-time data gathering and control functionalities.
Robust Intrusion Detection Systems (IDS) are necessary for early threat detection and mitigation because
of the interconnection of these networks, which makes them vulnerable to a variety of cyberattacks. To
solve this issue, this paper develops a hybrid Deep Learning (DL) model specifically designed for intrusion
detection in smart grids. The proposed approach is a combination of the Convolutional Neural Network
(CNN) and the Long-Short-Term Memory algorithms (LSTM). We employed a recent intrusion detection
dataset (DNP3), which focuses on unauthorized commands and Denial of Service (DoS) cyberattacks, to
train and test our model. The results of our experiments show that our CNN-LSTM method is much better
at finding smart grid intrusions than other deep learning algorithms used for classification. In addition,
our proposed approach improves accuracy, precision, recall, and F1 score, achieving a high detection
accuracy rate of 99.50%.
6th International Conference on Machine Learning & Applications (CMLA 2024)ClaraZara1
6th International Conference on Machine Learning & Applications (CMLA 2024) will provide an excellent international forum for sharing knowledge and results in theory, methodology and applications of on Machine Learning & Applications.
We have compiled the most important slides from each speaker's presentation. This year’s compilation, available for free, captures the key insights and contributions shared during the DfMAy 2024 conference.
2. IONOSPHERIC FADING EFFECT
Experience has shown that information concerning the mean value of the received
signal is not sufficient for planning radiocommunication systems.
The variations in time, space and frequency, collectively described as fading, also
have to be taken into consideration.
Fading has a decisive influence on the performance of radiocommunication systems
and on the type of modulation that may be used effectively.
It is essential to know the severity and rapidity of fading to be able to specify the
power required for transmitters, the necessary protection ratio to guard against
interference and, with additional knowledge of the correlation of signals at separate
antennas or frequencies, to be able to determine the most efficient and economical
diversity or coding systems.
Similar considerations may also apply to the noise and interference at the receiving
site.
3. CAUSES OF FADING
Fading may be caused by several different effects, such as:
– movement of the ionosphere, and multipath changes causing interference fading;
– rotation of the axes of the polarization ellipses;
– variations of the ionospheric absorption with time;
– focusing and temporary disappearance of the signal due to MUF failure.
Fading may appear either as amplitude fading or as a Doppler-frequency shift.
Amplitude fading may cause dispersion in both time and frequency. Motion of the
transmitter, receiver or ionospheric reflector causes Doppler shifts. In general
multipath signals have differing amplitudes and frequency shifts.
4. INTERFERENCE FADING
Interference fading results from interference between two or more waves which travel
by different paths to arrive at the receiving point.
This type of fading may be caused by interference between: sky-wave and ground-
wave, multiple reflected sky-waves, the ordinary (O) and extraordinary (X) waves,
and various scattered signals from irregularities.
Interference fading may last for a period of a fraction of a second to a few seconds,
during which time the resultant field intensity may vary over wide limits.
5. POLARIZATION FADING AND
ABSORPTION FADING
Polarization fading occurs as a result of changes in the direction of polarization of the
downcoming wave, relative to the orientation of the receiving antenna, due to random
fluctuations in the electron density along the path of propagation. Polarization fading
also lasts for a period of a fraction of a second to a few seconds.
Absorption fading is caused by variation in the absorption due to changes in the
densities of ionization and it may sometimes last longer than one hour.
6. SKIP FADING
Skip fading may be observed at receiving locations near the skip distance (the
minimum range from the transmitter before the ray passes through the ionospheric
layer rather than being refracted down from it) at about sunrise and sunset, when the
basic MUF for the path may oscillate around the operating frequency.
The signal may decrease abruptly when the skip distance increases past the receiving
point or increase with a decrease in the skip distance.
7. SELECTIVE FADING
Fading tends to be faster at high frequencies than at low frequencies, because for a
given movement in the ionosphere, there is a greater phase-shift on the shorter
wavelengths.
Motion of the ionized regions causes selective fading (frequency-dependent fading)
when, on a modulated carrier, the frequency components in the sidebands fade
independently, giving rise to distortion of the modulation envelope.
The motion produces changes in path length, and Doppler shifts of frequency on each
of the individual contributing signal components. Selective fading may also be caused
by multipath propagation at HF.
8. CHARACTERISTICS OF AMPLITUDE
FADING
I. Depth of fading
Depth of fading is measured by the amplitude distribution, or probability density
function of the amplitude of the down coming wave.
The amplitude distributions normally conform to one of three standard statistical
curves or distributions: Rayleigh, normal or Gaussian distribution, and log-normal.
II. Rapidity of fading
The rapidity or speed of fading can be characterized in different ways. One statistical
property of the instant-to-instant variation of amplitude is given by the
autocorrelation function.
The rapidity or the speed of fading can be described in terms of the time auto-
correlation function of the amplitude or in terms of the power spectrum of fading,
which is the Fourier transform of the auto-correlation function.
9. The frequency spectrum of the fading signal may be obtained with the aid of the auto-
correlation function. The width of the fading power spectrum is related to the speed of
fading.
Another definition of fading rate is the number of positive crossings per unit time
through any specified level, or the number of maxima N of the amplitude of the signal
envelope per unit time. It has been shown that if σ is the standard deviation of the
power spectrum of the received signal, N = 2.52 σ.
10. REGIONALANOMALIES
Features of fading encountered in the Tropical Zone
Fading of signals in the tropics at low geomagnetic latitudes has special characteristics
due to the regular daytime occurrence of sporadic E, and to irregularities in the night-
time F layer (spread F).
I. Fading due to sporadic E :Fading observed during daytime in the equatorial zone is
often attributed to sporadic E. In a narrow zone near the magnetic equator (±6°
magnetic dip), a special type of highly transparent sporadic E called equatorial
sporadic E or Es-q appears regularly during daytime.
II. Surge fading :Another type of fading in the Tropical Zone is surge fading, which is
slower than flutter fading, but is deeper and accompanied by severe distortion. It is
worst after sunset and more pronounced during autumn and winter. The recurrence
rate is a few surges per minute.
11. III. Flutter fading :
• Very rapid fading has been observed in the equatorial region after sunset, where it
represents one of the most important factors in the degradation of communications,
particularly for broadcast services.
• This flutter fading is caused by F-region irregularities, known as spread F.
• In the equatorial zone after local sunset, such irregularities develop in the F-region
ionization between 30°N and 30°S geomagnetic latitude, their occurrence being
particularly frequent within ±20° geomagnetic latitude.
• Under these conditions, the F region increases markedly in height and breaks up into
patchy irregular plumes associated with plasma instabilities.
12. • The spread-F irregularities are seen normally after sunset and before midnight. The
seasonal variations show maxima at the equinoxes near sunspot maximum.
• Both north-south circuits and east-west circuits are affected. The time of start is well
defined and sudden, but the time of disappearance is gradual.
• The fades are deep and the signal is almost completely drowned in noise, even though
the mean signal strength remains high.
• The flutter fading rate is proportional to the wave frequency, ten fades per second
being typical at 15 MHz.
13. IV. Fading allowances :
A discussion of the fading allowances required for planning broadcasting services in the
Tropical Zone is given in ITU-R Report BS.304. Recommendation BS.411 proposes
values of fadingallowance to ensure that the steady-state ratio is attained for 90% of the
time, under three conditionsof reception, i.e., where the RF signal-to-noise ratio is as
follows:
– ratio of wanted signal to interference: 16 dB;
– ratio of wanted signal to atmospheric noise: 17 dB;
– ratio of wanted signal to man-made noise: 12 dB.