Phased array

phased array radarphased-arrayphased-array radarphased array antennaarrayelectronically scanned arrayantenna arraysantenna arrayarrayslarge phased array
In antenna theory, a phased array usually means an electronically scanned array, a computer-controlled array of antennas which creates a beam of radio waves that can be electronically steered to point in different directions without moving the antennas.wikipedia
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Active electronically scanned array

AESAAESA radaractive phased array
An active phased array or active electronically scanned array (AESA) is a phased array in which each antenna element has an analog transmitter/receiver (T/R) module which creates the phase shifting required to electronically steer the antenna beam.
An active electronically scanned array (AESA) is a type of phased array antenna, which is a computer-controlled array antenna in which the beam of radio waves can be electronically steered to point in different directions without moving the antenna.

Antenna (radio)

antennaantennasradio antenna
In antenna theory, a phased array usually means an electronically scanned array, a computer-controlled array of antennas which creates a beam of radio waves that can be electronically steered to point in different directions without moving the antennas.
A phased array consists of two or more simple antennas which are connected together through an electrical network.

Microwave

microwavesmicrowave radiationmicrowave tube
Since the array must consist of many small antennas (sometimes thousands) to achieve high gain, phased arrays are mainly practical at the high frequency end of the radio spectrum, in the UHF and microwave bands, in which the antenna elements are conveniently small.
Another directive antenna practical at microwave frequencies is the phased array, a computer-controlled array of antennas which produces a beam which can be electronically steered in different directions.

Antenna array

directional arrayplanar arrayarray antenna
In antenna theory, a phased array usually means an electronically scanned array, a computer-controlled array of antennas which creates a beam of radio waves that can be electronically steered to point in different directions without moving the antennas.
Some antenna arrays (such as military phased array radars) are composed of thousands of individual antennas.

Conformal antenna

Conformal arrayconformal to the device shape
One possible physical implementation of a phased array is called a conformal antenna.
Conformal antennas are a form of phased array antenna.

Phased array ultrasonics

phased array imagingphased arrayphased array transducers
The phased array principle is also used in acoustics, and phased arrays of acoustic transducers are used in medical ultrasound imaging scanners (phased array ultrasonics), oil and gas prospecting (reflection seismology), and military sonar systems.
Single-element (non-phased array) probes, known technically as monolithic probes, emit a beam in a fixed direction.

Medical ultrasound

ultrasoundultrasonographymedical ultrasonography
The phased array principle is also used in acoustics, and phased arrays of acoustic transducers are used in medical ultrasound imaging scanners (phased array ultrasonics), oil and gas prospecting (reflection seismology), and military sonar systems.
Newer technology transducers use phased array techniques to enable the ultrasound machine to change the direction and depth of focus.

Karl Ferdinand Braun

Ferdinand BraunKarl BraunBraun
Phased array transmission was originally shown in 1905 by Nobel laureate Karl Ferdinand Braun who demonstrated enhanced transmission of radio waves in one direction.
Braun invented the phased array antenna in 1905.

Luis Walter Alvarez

Luis AlvarezLuis W. AlvarezLuis
During World War II, Nobel laureate Luis Alvarez used phased array transmission in a rapidly steerable radar system for "ground-controlled approach", a system to aid in the landing of aircraft.
In working on the Microwave Early Warning system (MEW), Alvarez invented a linear dipole array antenna that not only suppressed the unwanted side lobes of the radiation field, but also could be electronically scanned without the need for mechanical scanning.

Radar

radar stationradarsradar system
During World War II, Nobel laureate Luis Alvarez used phased array transmission in a rapidly steerable radar system for "ground-controlled approach", a system to aid in the landing of aircraft. Phased arrays were invented for use in military radar systems, to steer a beam of radio waves quickly across the sky to detect planes and missiles.
Another method of steering is used in a phased array radar.

Radio

radio communicationradio communicationswireless
Phased array transmission was originally shown in 1905 by Nobel laureate Karl Ferdinand Braun who demonstrated enhanced transmission of radio waves in one direction.

Fire-control radar

fire control radargunnery radarradar
Before using these systems, each surface-to-air missile in flight required a dedicated fire-control radar, which meant that radar-guided weapons could only engage a small number of simultaneous targets.
This works either by having the radar switch between sweeping the search sector and sending directed pulses at the target to be tracked, or by using a phased-array antenna to generate multiple simultaneous radar beams that both search and track.

X band

X-bandXX-band radar
The antenna, which uses the X band, used 26 radiative elements and can gracefully degrade.
X band is used in radar applications including continuous-wave, pulsed, single-polarization, dual-polarization, synthetic aperture radar, and phased arrays.

Phased-array optics

phased arrayPhased array opticsholographic display technology
Within the visible or infrared spectrum of electromagnetic waves it is possible to construct optical phased arrays.
An optical phased array (OPA) is the optical analog of a radio wave phased array.

Butler matrix

A Butler matrix allows several beams to be formed simultaneously, or one beam to be scanned through an arc. The most common kind of time domain beam former is serpentine waveguide.
A Butler matrix is a beamforming network used to feed a phased array of antenna elements.

Multiplexing

multiplexedmultiplexmultiplexes
Synthetic array heterodyne detection is an efficient method for multiplexing an entire phased array onto a single element photodetector.
In wireless communications, multiplexing can also be accomplished through alternating polarization (horizontal/vertical or clockwise/counterclockwise) on each adjacent channel and satellite, or through phased multi-antenna array combined with a multiple-input multiple-output communications (MIMO) scheme.

Mammut radar

Mammut
At the same time, the GEMA in Germany built the Mammut 1.
It was the world's first phased array radar and was able to detect targets flying at an altitude of 8,000m at a range of 300km.

AN/SPS-48

SPS-48EAN/SPS-48ESPS-48
This can be an advantage for communication links, and is used with the SPS-48 radar.
The AN/SPS-48 is a US naval electronically scanned array air search three-dimensional radar system manufactured by ITT Exelis and deployed in the 1960s as the primary air search sensor for anti-aircraft warships.

Passive electronically scanned array

PESAelectronically scannedelectronically steered
A passive phased array or passive electronically scanned array (PESA) is a phased array in which the antenna elements are connected to a single transmitter and/or receiver, as shown in the animation at top.
A passive electronically scanned array (PESA), also known as passive phased array, is an antenna in which the beam of radio waves can be electronically steered to point in different directions (that is, a phased array antenna), in which all the antenna elements are connected to a single transmitter (such as a magnetron, a klystron or a travelling wave tube) and/or receiver.

3D NowCasting

instant weather forecasts
A team from Japan's RIKEN Advanced Institute for Computational Science (AICS) has begun experimental work on using phased-array radar with a new algorithm for instant weather forecasts.
3D NowCasting refers to an experimental technology of nowcasting in meteorology that uses a rapid phased-array radar to predict precipitation several minutes in advance.

Side lobe

sidelobelobesidelobes
Other phasing adjustments can increase the downward radiation in the far field without tilting the main lobe, creating null fill to compensate for extremely high mountaintop locations, or decrease it in the near field, to prevent excessive exposure to those workers or even nearby homeowners on the ground.
For discrete aperture antennas (such as phased arrays) in which the element spacing is greater than a half wavelength, the spatial aliasing effect causes some sidelobes to become substantially larger in amplitude, and approaching the level of the main lobe; these are called grating lobes, and they are identical, or nearly identical in the example shown, copies of the main beams.

History of smart antennas

Braun created a phased array by positioning three antennas to reinforce radiation in one direction and diminish radiation in other directions.

Null fill

Other phasing adjustments can increase the downward radiation in the far field without tilting the main lobe, creating null fill to compensate for extremely high mountaintop locations, or decrease it in the near field, to prevent excessive exposure to those workers or even nearby homeowners on the ground.
This requires a phased array.

Beamforming

beam formingbeamformerAntenna beamforming
With narrow-band systems the time delay is equivalent to a "phase shift", so in this case the array of antennas, each one shifted a slightly different amount, is called a phased array.

Thinned-array curse

Thinned array cursesparse array
It states that a transmitting antenna which is synthesized from a coherent phased array of smaller antenna apertures that are spaced apart will have a smaller minimum beam spot size.