8/3/2019 Microwave Transmission Refers to the Technology of Transmitting Information or Power by the Use of Radio Waves

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Microwave transmission refers to the technology oftransmittinginformation or power by the use ofradio waveswhose wavelengths are conveniently measured in small numbers of centimeters; these are called microwaves. This

part of theradio spectrumranges across frequencies of roughly 1.0 gigahertz(GHz) to 30GHz. These correspond towavelengths from 30 centimeters down to 1.0 cm.

Microwaves are widely used forpoint-to-point communications because their smallwavelengthallowsconveniently-sized antennas to direct them in narrow beams, which can be pointed directly at the receiving antenna.

This allows nearby microwave equipment to use the same frequencies without interfering with each other, as lowerfrequency radio waves do. Another advantage is that the high frequency of microwaves gives the microwave band avery large information-carrying capacity; the microwave band has abandwidth30 times that of all the rest of theradio spectrum below it. A disadvantage is that microwaves are limited toline of sight propagation; they cannot passaround hills or mountains as lower frequency radio waves can.

Properties

Suitable overline-of-sight transmission links without obstacles

Provides large usefulbandwidthwhen compared to lower frequencies (HF, VHF, UHF)

Affected by the refractive index (temperature, pressure and humidity) of the atmosphere, rain (seerainfade), snow and hail, sand storms, clouds, mist and fog, strongly depending on the frequency.

Uses

Wireless transmission of information

One-way (e.g.television broadcasting) and two-way telecommunication usingcommunications satellite

Terrestrial microwave radio broadcastingrelay links in telecommunications networks including e.g.backbone orbackhaul carriers in cellular networks linkingBTS-BSC and BSC-MSC

Wireless transmission of power

Proposed systems e.g. for connecting solar power collecting satellites to terrestrial power grids

History

FollowingWorld War II, which saw the development of high-power microwave emitters known ascavitymagnetrons, the idea of using microwaves to transmit power was researched. In 1964, William C. Browndemonstrated a miniaturehelicopterequipped with a combinationantennaand rectifierdevice called a rectenna. The

rectenna converted microwave power into electricity, allowing the helicopter to fly.[1]

In principle, the rectenna iscapable of very high conversion efficiencies - over 90% in optimal circumstances.

Most proposed MPT systems now usually include aphased arraymicrowave transmitter. While these have lower efficiencylevels they have the advantage of being electrically steered using nomoving parts, and are easier to scale to the necessary levelsthat a practical MPT system requires.

Using microwave power transmission to deliver electricity to communities without having

to build cable-based infrastructure is being studied at Grand Bassin onReunion Island in

the Indian Ocean.Common safety concerns

The common reaction to microwave transmission is one of concern, as microwaves are generally perceived by the public asdangerous forms of radiation - stemming from the fact that they are used in microwave ovens. While high power microwaves can

be painful and dangerous as in the United States Military'sActive Denial System, MPT systems are generally proposed to haveonly low intensity at therectenna.

Microwave radio relay

Microwave radio relay is a technology for transmitting digitaland analogsignals, such as long-distance telephonecalls,television programs, and computer data, between two locations on a line of sightradio path. In microwaveradio relay, radio waves are transmitted between the two locations with directional antennas, forming a fixed radioconnection between the two points. Longdaisy-chained series of such links form transcontinental telephone and/ortelevision communication systems

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inghttp://en.wikipedia.org/wiki/Communications_satellitehttp://en.wikipedia.org/wiki/Radio_broadcastinghttp://en.wikipedia.org/wiki/Backhaul_(telecommunications)http://en.wikipedia.org/wiki/Cellular_networkhttp://en.wikipedia.org/wiki/Base_Transceiver_Stationhttp://en.wikipedia.org/wiki/World_War_IIhttp://en.wikipedia.org/wiki/Magnetronhttp://en.wikipedia.org/wiki/Magnetronhttp://en.wikipedia.org/wiki/William_C._Brownhttp://en.wikipedia.org/wiki/Helicopterhttp://en.wikipedia.org/wiki/Antenna_(electronics)http://en.wikipedia.org/wiki/Rectifierhttp://en.wikipedia.org/wiki/Rectennahttp://en.wikipedia.org/wiki/Phased_arrayhttp://en.wikipedia.org/wiki/Moving_partshttp://en.wikipedia.org/wiki/Reunion_Islandhttp://en.wikipedia.org/wiki/Indian_Oceanhttp://en.wikipedia.org/wiki/Microwave_ovenshttp://en.wikipedia.org/wiki/Active_Denial_Systemhttp://en.wikipedia.org/wiki/Rectennahttp://en.wikipedia.org/wiki/Digital_signalhttp://en.wikipedia.org/wiki/Analog_signalhttp://en.wikipedia.org/wiki/Signalling_(telecommunication)http://en.wikipedia.org/wiki/Telephone_callhttp://en.wikipedia.org/wiki/Telephone_callhttp://en.wikipedia.org/wiki/Television_programhttp://en.wikipedia.org/wiki/Line-of-sight_propagationhttp://en.wikipedia.org/wiki/Microwavehttp://en.wikipedia.org/wiki/Radio_waveshttp://en.wikipedia.org/wiki/Directional_antennahttp://en.wikipedia.org/wiki/Daisy_chain_(network_topology)http://en.wikipedia.org/wiki/Transmit

8/3/2019 Microwave Transmission Refers to the Technology of Transmitting Information or Power by the Use of Radio Waves

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