A report on Microwave transmission

The atmospheric attenuation of microwaves in dry air with a precipitable water vapor level of 0.001 mm. The downward spikes in the graph corresponds to frequencies at which microwaves are absorbed more strongly, such as by oxygen molecules.
A parabolic satellite antenna for Erdfunkstelle Raisting, based in Raisting, Bavaria, Germany
C-band horn-reflector antennas on the roof of a telephone switching center in Seattle, Washington, part of the U.S. AT&T Long Lines microwave relay network
Dozens of microwave dishes on the Heinrich-Hertz-Turm in Hamburg, Germany
Communications tower on Frazier Mountain, Southern California with microwave relay dishes
Danish military radio relay node
Production truck used for remote broadcasts by television news has a microwave dish on a retractible telescoping mast to transmit live video back to the studio.
Antennas of 1931 experimental 1.7 GHz microwave relay link across the English Channel. The receiving antenna (background, right) was located behind the transmitting antenna to avoid interference.
US Army Signal Corps portable microwave relay station, 1945. Microwave relay systems were first developed in World War II for secure military communication.
Richtfunkstelle Berlin-Frohnau
Microwave spying

Transmission of information by electromagnetic waves with wavelengths in the microwave range of the electromagnetic spectrum.

- Microwave transmission
The atmospheric attenuation of microwaves in dry air with a precipitable water vapor level of 0.001 mm. The downward spikes in the graph corresponds to frequencies at which microwaves are absorbed more strongly, such as by oxygen molecules.

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A telecommunications tower with a variety of dish antennas for microwave relay links on Frazier Peak, Ventura County, California. The apertures of the dishes are covered by plastic sheets (radomes) to keep out moisture.

Microwave

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Form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively.

Form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively.

A telecommunications tower with a variety of dish antennas for microwave relay links on Frazier Peak, Ventura County, California. The apertures of the dishes are covered by plastic sheets (radomes) to keep out moisture.
The atmospheric attenuation of microwaves and far infrared radiation in dry air with a precipitable water vapor level of 0.001 mm. The downward spikes in the graph correspond to frequencies at which microwaves are absorbed more strongly. This graph includes a range of frequencies from 0 to 1 THz; the microwaves are the subset in the range between 0.3 and 300 gigahertz.
Waveguide is used to carry microwaves. Example of waveguides and a diplexer in an air traffic control radar
Disassembled radar speed gun. The grey assembly attached to the end of the copper-colored horn antenna is the Gunn diode which generates the microwaves.
A satellite dish on a residence, which receives satellite television over a Ku band 12–14 GHz microwave beam from a direct broadcast communications satellite in a geostationary orbit 35,700 kilometres (22,000 miles) above the Earth
The parabolic antenna (lower curved surface) of an ASR-9 airport surveillance radar which radiates a narrow vertical fan-shaped beam of 2.7–2.9 GHz (S band) microwaves to locate aircraft in the airspace surrounding an airport.
Small microwave oven on a kitchen counter
Microwaves are widely used for heating in industrial processes. A microwave tunnel oven for softening plastic rods prior to extrusion.
Absorption wavemeter for measuring in the Ku band.
1.2 GHz microwave spark transmitter (left) and coherer receiver (right) used by Guglielmo Marconi during his 1895 experiments had a range of 6.5 km
ku band microstrip circuit used in satellite television dish.
Heinrich Hertz's 450 MHz spark transmitter, 1888, consisting of 23 cm dipole and spark gap at focus of parabolic reflector
Jagadish Chandra Bose in 1894 was the first person to produce millimeter waves; his spark oscillator (in box, right) generated 60 GHz (5 mm) waves using 3 mm metal ball resonators.
Microwave spectroscopy experiment by John Ambrose Fleming in 1897 showing refraction of 1.4 GHz microwaves by paraffin prism, duplicating earlier experiments by Bose and Righi.
Augusto Righi's 12 GHz spark oscillator and receiver, 1895
Antennas of 1931 experimental 1.7 GHz microwave relay link across the English Channel.
Experimental 700 MHz transmitter 1932 at Westinghouse labs transmits voice over a mile.
Southworth (at left) demonstrating waveguide at IRE meeting in 1938, showing 1.5 GHz microwaves passing through the 7.5 m flexible metal hose registering on a diode detector.
The first modern horn antenna in 1938 with inventor Wilmer L. Barrow
thumb|Randall and Boot's prototype cavity magnetron tube at the University of Birmingham, 1940. In use the tube was installed between the poles of an electromagnet
First commercial klystron tube, by General Electric, 1940, sectioned to show internal construction
British Mk. VIII, the first microwave air intercept radar, in nose of British fighter. Microwave radar, powered by the new magnetron tube, significantly shortened World War II.
Mobile US Army microwave relay station 1945 demonstrating relay systems using frequencies from 100 MHz to 4.9 GHz which could transmit up to 8 phone calls on a beam.

Microwaves are widely used in modern technology, for example in point-to-point communication links, wireless networks, microwave radio relay networks, radar, satellite and spacecraft communication, medical diathermy and cancer treatment, remote sensing, radio astronomy, particle accelerators, spectroscopy, industrial heating, collision avoidance systems, garage door openers and keyless entry systems, and for cooking food in microwave ovens.

Earth station at the satellite communication facility in Raisting, Bavaria, Germany

Telecommunications

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Transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems.

Transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems.

Earth station at the satellite communication facility in Raisting, Bavaria, Germany
Visualization from the Opte Project of the various routes through a portion of the Internet
A replica of one of Chappe's semaphore towers
Optical fiber provides cheaper bandwidth for long-distance communication.
Digital television standards and their adoption worldwide
here
The OSI reference model

20th- and 21st-century technologies for long-distance communication usually involve electrical and electromagnetic technologies, such as telegraph, telephone, television and teleprinter, networks, radio, microwave transmission, optical fiber, and communications satellites.

A 1 Gbit/s point-to-point millimeter-wave link installed in the UAE

Point-to-point (telecommunications)

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In telecommunications, a point-to-point connection refers to a communications connection between two communication endpoints or nodes.

In telecommunications, a point-to-point connection refers to a communications connection between two communication endpoints or nodes.

A 1 Gbit/s point-to-point millimeter-wave link installed in the UAE
A point-to-point wireless unit with a built-in antenna at Huntington Beach, California

Other examples of point-to-point communications links are leased lines and microwave radio relay.

Erdfunkstelle, a large parabolic satellite communications antenna in Raisting, Bavaria, Germany, the biggest facility for satellite communication in the world. It has a Cassegrain type feed.

Parabolic antenna

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Antenna that uses a parabolic reflector, a curved surface with the cross-sectional shape of a parabola, to direct the radio waves to the receiver in its focal point.

Antenna that uses a parabolic reflector, a curved surface with the cross-sectional shape of a parabola, to direct the radio waves to the receiver in its focal point.

Erdfunkstelle, a large parabolic satellite communications antenna in Raisting, Bavaria, Germany, the biggest facility for satellite communication in the world. It has a Cassegrain type feed.
Parabolic antennas are based on the geometrical property of the paraboloid that the paths FP1Q1, FP2Q2, FP3Q3 are all the same length. So a spherical wavefront emitted by a feed antenna at the dish's focus F will be reflected into an outgoing plane wave L travelling parallel to the dish's axis VF.
Wire grid-type parabolic antenna used for MMDS data link at a frequency of 2.5-2.7 GHz. It is fed by a vertical dipole under the small aluminum reflector on the boom. It radiates vertically polarized microwaves.
Main types of parabolic antenna feeds.
Array of multiple feed horns on a German airport surveillance radar antenna to control the elevation angle of the beam
Effect of the feed antenna radiation pattern (small pumpkin-shaped surface) on spillover. Left: With a low gain feed antenna, significant parts of its radiation fall outside the dish. Right: With a higher gain feed, almost all its radiation is emitted within the angle of the dish.
Radiation pattern of a German parabolic antenna. The main lobe (top) is only a few degrees wide. The sidelobes are all at least 20 dB below (1/100 the power density of) the main lobe, and most are 30 dB below. (If this pattern was drawn with linear power levels instead of logarithmic dB levels, all lobes other than the main lobe would be much too small to see.)
The angle theta is normal to the aperture.

Parabolic antennas are used as high-gain antennas for point-to-point communications, in applications such as microwave relay links that carry telephone and television signals between nearby cities, wireless WAN/LAN links for data communications, satellite communications and spacecraft communication antennas.

Wireless icon

Wireless network

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Computer network that uses wireless data connections between network nodes.

Computer network that uses wireless data connections between network nodes.

Wireless icon
Computers are very often connected to networks using wireless links, e.g. WLANs
Wireless LANs are often used for connecting to local resources and to the Internet
Example of frequency reuse factor or pattern 1/4
In a hidden node problem Station A can communicate with Station B. Station C can also communicate with Station B. However, Stations A and C cannot communicate with each other, but their signals can interfere at B.
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Understanding of SISO, SIMO, MISO and MIMO. Using multiple antennas and transmitting in different frequency channels can reduce fading, and can greatly increase the system capacity.

The wireless connections between access points are usually point to point microwave links using parabolic dishes on the 2.4 GHz and 5.8 GHz band, rather than omnidirectional antennas used with smaller networks.

A variety of radio antennas on Sandia Peak near Albuquerque, New Mexico, US

Radio

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Technology of signaling and communicating using radio waves.

Technology of signaling and communicating using radio waves.

A variety of radio antennas on Sandia Peak near Albuquerque, New Mexico, US
Radio communication. Information such as sound is converted by a transducer such as a microphone to an electrical signal, which modulates a radio wave produced by the transmitter. A receiver intercepts the radio wave and extracts the information-bearing modulation signal, which is converted back to a human usable form with another transducer such as a loudspeaker.
Comparison of AM and FM modulated radio waves
Frequency spectrum of a typical modulated AM or FM radio signal. It consists of a component C at the carrier wave frequency f_c with the information (modulation) contained in two narrow bands of frequencies called sidebands (SB) just above and below the carrier frequency.
Satellite television dish on a residence
Satellite phones, showing the large antennas needed to communicate with the satellite
Firefighter using walkie-talkie
VHF marine radio on a ship
Parabolic antennas of microwave relay links on tower in Australia
RFID tag from a DVD
Satellite Communications Center Dubna in Russia
Communications satellite belonging to Azerbaijan
Military air traffic controller on US Navy aircraft carrier monitors aircraft on radar screen
ASR-8 airport surveillance radar antenna. It rotates once every 4.8 seconds. The rectangular antenna on top is the secondary radar.
Rotating marine radar antenna on a ship
A personal navigation assistant GPS receiver in a car, which can give driving directions to a destination.
EPIRB emergency locator beacon on a ship
Wildlife officer tracking radio-tagged mountain lion
US Air Force MQ-1 Predator drone flown remotely by a pilot on the ground
Remote keyless entry fob for a car
Quadcopter, a popular remote-controlled toy
Television receiver

Microwave relay – a long-distance high bandwidth point-to-point digital data transmission link consisting of a microwave transmitter connected to a dish antenna that transmits a beam of microwaves to another dish antenna and receiver. Since the antennas must be in line-of-sight, distances are limited by the visual horizon to 30-40 miles. Microwave links are used for private business data, wide area computer networks (WANs), and by telephone companies to transmit long- distance phone calls and television signals between cities.

One of the former TD-2 relays in the Mojave National Preserve, California. The tower appears to be in use for other purposes; the vertical antennas at the top and the round dark grey dish are not part of the original system.

TD-2

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One of the former TD-2 relays in the Mojave National Preserve, California. The tower appears to be in use for other purposes; the vertical antennas at the top and the round dark grey dish are not part of the original system.
The British Army's WS No. 10 sparked off post-war interest in microwave communications.
In 1946, Bell linked Catalina Island with Los Angeles using a small microwave relay system.
Early stations, like this one near Valparaiso, Indiana, were built of concrete. They housed the electronics mid-way up the tower, behind the window-like openings, to avoid line losses. These were replaced by the steel framework towers as the cost of steel dropped through the 1950s.

TD-2 was a microwave relay system developed by Bell Labs and used by AT&T to build a cross-country network of repeaters for telephone and television transmission.

A tropospheric scatter system can bridge large distances while a microwave relay system (below) requires multiple relay stations due to its line of sight limitation.

Tropospheric scatter

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A tropospheric scatter system can bridge large distances while a microwave relay system (below) requires multiple relay stations due to its line of sight limitation.
Boswell Bay, Alaska White Alice Site, Tropospheric scatter antenna and feeder.
Pacific Scatter System
Pole Vault used circular parabolic antennas, later systems generally used squared-off versions sometimes known as "billboards".
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Belarusian "Horizon" mobile tropospheric scatter communication system
US Army TRC-170 Tropo Scatter Microwave System

Tropospheric scatter, also known as troposcatter, is a method of communicating with microwave radio signals over considerable distances – often up to 500 km and further depending on frequency of operation, equipment type, terrain, and climate factors.

Line through western Montana, 1934

AT&T Communications Inc.

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Division of the AT&T Corporation that, through 23 subsidiaries, provided interexchange carrier and long-distance telephone services.

Division of the AT&T Corporation that, through 23 subsidiaries, provided interexchange carrier and long-distance telephone services.

Line through western Montana, 1934
Horn reflector antennas on AT&T Long Lines microwave relay station, Seattle, Washington
32 Avenue of the Americas, New York headquarters and principal switching center of AT&T Long Lines in mid 20th century; still used in 2008
Long Lines relay tower in Indiana. Earlier stations in the microwave network used concrete towers due to the post-war price of steel as well as the desire to place the electronics closer to the antennas - they are in rooms behind the windows half way up the tower.

The American Telephone & Telegraph Long Lines wire, cable, and microwave radio relay network provided long-distance services to AT&T and its customers.

A live television show set and cameras

Television show

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Any content produced for viewing on a television set which can be broadcast via over-the-air, satellite, or cable, excluding breaking news, advertisements, or trailers that are typically placed between shows.

Any content produced for viewing on a television set which can be broadcast via over-the-air, satellite, or cable, excluding breaking news, advertisements, or trailers that are typically placed between shows.

A live television show set and cameras
Tamvisio's camera operators film a television program at Frenckell's studio on January 2, 1965, in Tampere, Finland.
Arthur Schlesinger Jr.

The first national live television broadcast in the US took place on September 4, 1951, when President Harry Truman's speech at the Japanese Peace Treaty Conference in San Francisco was transmitted over AT&T's transcontinental cable and microwave radio relay system to broadcast stations in local markets.