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Active electronically scanned array

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. In the AESA, each antenna element is connected to a small solid-state transmit/receive module (TRM) under the control of a computer, which performs the functions of a transmitter and/or receiver for the antenna. This contrasts with a passive electronically scanned array (PESA), in which all the antenna elements are connected to a single transmitter and/or receiver through phase shifters under the control of the computer. AESA's main use is in radar, and these are known as active phased array radar (APAR).

The Eurofighter Typhoon combat aircraft with its nose fairing removed, revealing its Euroradar CAPTOR AESA radar antenna

The AESA is a more advanced, sophisticated, second-generation of the original PESA phased array technology. PESAs can only emit a single beam of radio waves at a single frequency at a time. The PESA must utilize a Butler matrix if multiple beams are required. The AESA can radiate multiple beams of radio waves at multiple frequencies simultaneously. AESA radars can spread their signal emissions across a wider range of frequencies, which makes them more difficult to detect over background noise, allowing ships and aircraft to radiate powerful radar signals while still remaining stealthy, as well as being more resistant to jamming. Hybrids of AESA and PESA can also be found, consisting of subarrays that individually resemble PESAs, where each subarray has its own RF front end. Using a hybrid approach, the benefits of AESA (e.g., multiple independent beams) can be realized at a lower cost compared to pure AESA.

History

 
ZMAR concept sketch, 1962
 
An aerial view of the three domes of the Multifunction Array Radar prototype, surrounded by a clutter fence, at White Sands Missile Range, N.M.
 
Sketch of the FLAT TWIN antiballistic missile radar

Bell Labs proposed replacing the Nike Zeus radars with a phased array system in 1960, and was given the go-ahead for development in June 1961. The result was the Zeus Multi-function Array Radar (ZMAR), an early example of an active electronically steered array radar system.[1] ZMAR became MAR when the Zeus program ended in favor of the Nike-X system in 1963. The MAR (Multi-function Array Radar) was made of a large number of small antennas, each one connected to a separate computer-controlled transmitter or receiver. Using a variety of beamforming and signal processing steps, a single MAR was able to perform long-distance detection, track generation, discrimination of warheads from decoys, and tracking of the outbound interceptor missiles.[2]

MAR allowed the entire battle over a wide space to be controlled from a single site. Each MAR, and its associated battle center, would process tracks for hundreds of targets. The system would then select the most appropriate battery for each one, and hand off particular targets for them to attack. One battery would normally be associated with the MAR, while others would be distributed around it. Remote batteries were equipped with a much simpler radar whose primary purpose was to track the outgoing Sprint missiles before they became visible to the potentially distant MAR. These smaller Missile Site Radars (MSR) were passively scanned, forming only a single beam instead of the MAR's multiple beams.[2]

While MAR was ultimately successful, the cost of the system was enormous. When the ABM problem became so complex that even a system like MAR could no longer deal with realistic attack scenarios, the Nike-X concept was abandoned in favor of much simpler concepts like the Sentinel program, which did not use MAR. A second example, MAR-II, was abandoned in-place on Kwajalein Atoll.[3]

The first Soviet APAR, the 5N65, was developed in 1963-1965 as a part of the S-225 ABM system. After some modifications in the system concept in 1967 it was built at Sary Shagan Test Range in 1970-1971 and nicknamed Flat Twin in the West. Four years later another radar of this design was built on Kura Test Range, while the S-225 system was never commissioned.[citation needed]

US based manufacturers of the AESA radars used in the F-22 and Super Hornet include Northrop Grumman[6] and Raytheon.[7] These companies also design, develop and manufacture the transmit/receive modules which comprise the 'building blocks' of an AESA radar. The requisite electronics technology was developed in-house via Department of Defense research programs such as MMIC Program.[8][9] In 2016 the Congress funded a military industry competition to produce new radars for two dozen National Guard fighter aircraft.[10]

Basic concept

 
AESA basic schematic

Radar systems generally work by connecting an antenna to a powerful radio transmitter to emit a short pulse of signal. The transmitter is then disconnected and the antenna is connected to a sensitive receiver which amplifies any echos from target objects. By measuring the time it takes for the signal to return, the radar receiver can determine the distance to the object. The receiver then sends the resulting output to a display of some sort. The transmitter elements were typically klystron tubes or magnetrons, which are suitable for amplifying or generating a narrow range of frequencies to high power levels. To scan a portion of the sky, the radar antenna must be physically moved to point in different directions.

Starting in the 1960s new solid-state devices capable of delaying the transmitter signal in a controlled way were introduced. That led to the first practical large-scale passive electronically scanned array (PESA), or simply phased array radar. PESAs took a signal from a single source, split it into hundreds of paths, selectively delayed some of them, and sent them to individual antennas. The radio signals from the separate antennas overlapped in space, and the interference patterns between the individual signals were controlled to reinforce the signal in certain directions, and mute it in all others. The delays could be easily controlled electronically, allowing the beam to be steered very quickly without moving the antenna. A PESA can scan a volume of space much quicker than a traditional mechanical system. Additionally, thanks to progress in electronics, PESAs added the ability to produce several active beams, allowing them to continue scanning the sky while at the same time focusing smaller beams on certain targets for tracking or guiding semi-active radar homing missiles. PESAs quickly became widespread on ships and large fixed emplacements in the 1960s, followed by airborne sensors as the electronics shrank.

AESAs are the result of further developments in solid-state electronics. In earlier systems the transmitted signal was originally created in a klystron or traveling wave tube or similar device, which are relatively large. Receiver electronics were also large due to the high frequencies that they worked with. The introduction of gallium arsenide microelectronics through the 1980s served to greatly reduce the size of the receiver elements until effective ones could be built at sizes similar to those of handheld radios, only a few cubic centimeters in volume. The introduction of JFETs and MESFETs did the same to the transmitter side of the systems as well. It gave rise to amplifier-transmitters with a low-power solid-state waveform generator feeding an amplifier, allowing any radar so equipped to transmit on a much wider range of frequencies, to the point of changing operating frequency with every pulse sent out. Shrinking the entire assembly (the transmitter, receiver and antenna) into a single "transmitter-receiver module" (TRM) about the size of a carton of milk and arraying these elements produces an AESA.

The primary advantage of an AESA over a PESA is the capability of the different modules to operate on different frequencies. Unlike the PESA, where the signal is generated at single frequencies by a small number of transmitters, in the AESA each module generates and radiates its own independent signal. This allows the AESA to produce numerous simultaneous "sub-beams" that it can recognize due to different frequencies, and actively track a much larger number of targets. AESAs can also produce beams that consist of many different frequencies at once, using post-processing of the combined signal from a number of TRMs to re-create a display as if there was a single powerful beam being sent. However, this means that the noise present in each frequency is also received and added.

Advantages

AESAs add many capabilities of their own to those of the PESAs. Among these are: the ability to form multiple beams simultaneously, to use groups of TRMs for different roles concurrently, like radar detection, and, more importantly, their multiple simultaneous beams and scanning frequencies create difficulties for traditional, correlation-type radar detectors.

Low probability of intercept

Radar systems work by sending out a signal and then listening for its echo off distant objects. Each of these paths, to and from the target, is subject to the inverse square law of propagation in both the transmitted signal and the signal reflected back. That means that a radar's received energy drops with the fourth power of the distance, which is why radar systems require high powers, often in the megawatt range, to be effective at long range.

The radar signal being sent out is a simple radio signal, and can be received with a simple radio receiver. Military aircraft and ships have defensive receivers, called "radar warning receivers" (RWR), which detect when an enemy radar beam is on them, thus revealing the position of the enemy. Unlike the radar unit, which must send the pulse out and then receive its reflection, the target's receiver does not need the reflection and thus the signal drops off only as the square of distance. This means that the receiver is always at an advantage [neglecting disparity in antenna size] over the radar in terms of range - it will always be able to detect the signal long before the radar can see the target's echo. Since the position of the radar is extremely useful information in an attack on that platform, this means that radars generally must be turned off for lengthy periods if they are subject to attack; this is common on ships, for instance.

Unlike the radar, which knows which direction it is sending its signal, the receiver simply gets a pulse of energy and has to interpret it. Since the radio spectrum is filled with noise, the receiver's signal is integrated over a short period of time, making periodic sources like a radar add up and stand out over the random background. The rough direction can be calculated using a rotating antenna, or similar passive array using phase or amplitude comparison. Typically RWRs store the detected pulses for a short period of time, and compare their broadcast frequency and pulse repetition frequency against a database of known radars. The direction to the source is normally combined with symbology indicating the likely purpose of the radar – airborne early warning and control, surface-to-air missile, etc.

This technique is much less useful against a radar with a frequency-agile (solid state) transmitter. Since the AESA (or PESA) can change its frequency with every pulse (except when using doppler filtering), and generally does so using a random sequence, integrating over time does not help pull the signal out of the background noise. Moreover, a radar may be designed to extend the duration of the pulse and lower its peak power. An AESA or modern PESA will often have the capability to alter these parameters during operation. This makes no difference to the total energy reflected by the target but makes the detection of the pulse by an RWR system less likely.[11] Nor does the AESA have any sort of fixed pulse repetition frequency, which can also be varied and thus hide any periodic brightening across the entire spectrum. Older generation RWRs are essentially useless against AESA radars, which is why AESAs are also known as low probability of intercept radars. Modern RWRs must be made highly sensitive (small angles and bandwidths for individual antennas, low transmission loss and noise)[11] and add successive pulses through time-frequency processing to achieve useful detection rates.[12]

High jamming resistance

Jamming is likewise much more difficult against an AESA. Traditionally, jammers have operated by determining the operating frequency of the radar and then broadcasting a signal on it to confuse the receiver as to which is the "real" pulse and which is the jammer's. This technique works as long as the radar system cannot easily change its operating frequency. When the transmitters were based on klystron tubes this was generally true, and radars, especially airborne ones, had only a few frequencies to choose among. A jammer could listen to those possible frequencies and select the one to be used to jam.

Most radars using modern electronics are capable of changing their operating frequency with every pulse. This can make jamming less effective; although it is possible to send out broadband white noise to conduct barrage jamming against all the possible frequencies, this reduces the amount of jammer energy in any one frequency. An AESA has the additional capability of spreading its frequencies across a wide band even in a single pulse, a technique known as a "chirp". In this case, the jamming will be the same frequency as the radar for only a short period, while the rest of the radar pulse is unjammed.

AESAs can also be switched to a receive-only mode, and use these powerful jamming signals to track its source, something that required a separate receiver in older platforms. By integrating received signals from the targets' own radar along with a lower rate of data from its own broadcasts, a detection system with a precise RWR like an AESA can generate more data with less energy. Some receive beamforming-capable systems, usually ground-based, may even discard a transmitter entirely.

However, using a single receiving antenna only gives a direction. Obtaining a range and a target vector requires at least two physically separate passive devices for triangulation to provide instantaneous determinations, unless phase interferometry is used. Target motion analysis can estimate these quantities by incorporating many directional measurements over time, along with knowledge of the position of the receiver and constraints on the possible motion of the target.

Other advantages

Since each element in an AESA is a powerful radio receiver, active arrays have many roles besides traditional radar. One use is to dedicate several of the elements to reception of common radar signals, eliminating the need for a separate radar warning receiver. The same basic concept can be used to provide traditional radio support, and with some elements also broadcasting, form a very high bandwidth data link. The F-35 uses this mechanism to send sensor data between aircraft in order to provide a synthetic picture of higher resolution and range than any one radar could generate. In 2007, tests by Northrop Grumman, Lockheed Martin, and L-3 Communications enabled the AESA system of a Raptor to act like a WiFi access point, able to transmit data at 548 megabits per second and receive at gigabit speed; this is far faster than the Link 16 system used by US and allied aircraft, which transfers data at just over 1 Mbit/s.[13] To achieve these high data rates requires a highly directional antenna which AESA provides but which precludes reception by other units not within the antennas beamwidth, whereas like most Wi-Fi designs, Link-16 transmits its signal omni-directionally to ensure all units within range can receive the data.

AESAs are also much more reliable than either a PESA or older designs. Since each module operates independently of the others, single failures have little effect on the operation of the system as a whole. Additionally, the modules individually operate at low powers, perhaps 40 to 60 watts, so the need for a large high-voltage power supply is eliminated.

Replacing a mechanically scanned array with a fixed AESA mount (such as on the Boeing F/A-18E/F Super Hornet) can help reduce an aircraft's overall radar cross-section (RCS), but some designs (such as the Eurofighter Typhoon) forgo this advantage in order to combine mechanical scanning with electronic scanning and provide a wider angle of total coverage.[14] This high off-nose pointing allows the AESA equipped fighter to employ a Crossing the T maneuver, often referred to as 'beaming' in the context of air-to-air combat, against a mechanically scanned radar that would filter out the low closing speed of the perpendicular flight as ground clutter while the AESA swivels 40 degrees towards the target in order to keep it within the AESA's 60 degree off-angle limit.[15]

Limitations

With a half wavelength distance between the elements, the maximum beam angle is approximately  °. With a shorter element distance, the highest field of view (FOV) for a flat phased array antenna is currently 120° ( °),[16] although this can be combined with mechanical steering as noted above.[17][18]

List of existing systems

Airborne systems

KAI FA-50 Block 20

 
Close up of the Thalès RBE2-AA mounted on Rafale since F3R standard. (The OSF behind it is not part of the radar.)
 
The HAL Tejas combat aircraft equipped with Uttam AESA radar

Surface systems (land, maritime)

The first AESA radar employed on an operational warship was the Japanese OPS-24 manufactured by Mitsubishi Electric introduced on the JDS Hamagiri (DD-155), the first ship of the latter batch of the Asagiri-class destroyer, launched in 1988.

  • Elta
    • EL/M-2080 Green Pine ground-based early warning AESA radar
    • EL/M-2106 ATAR air defense fire control radar
    • EL/M-2180 - WatchR Guard Multi-Mode Staring Ground Surveillance Radar
    • EL/M-2248 MF-STAR multifunction naval radar
    • EL/M-2258 Advanced Lightweight Phased Array ALPHA multifunction naval radar
    • EL/M-2084 multimission radar (artillery weapon location, air defence and fire control)
    • EL/M-2133 WindGuard - Trophy active protection system radar
 
3DELRR long-range radar system
 
SAMPSON AESA on board the Type 45 destroyer

See also

References

  1. ^ Bell Labs 1975, p. I-35.
  2. ^ a b Bell Labs 1975, p. 2-3.
  3. ^ Bell Labs 1975, p. 2-22.
  4. ^ Tomohiko Tada (March 2010). "4. Radar/ECM/ESM (Shipboard weapons of JMSDF 1952-2010)". Ships of the World (in Japanese). Kaijin-sha (721): 100–105.
  5. ^ a b "Japan Upgrading 60 F-2s With AAM-4, J/APG-2". Retrieved 17 June 2015.
  6. ^ "Northrop Grumman Successfully Completes F-22 Radar Flight-Test Certification (NYSE:NOC)". Retrieved 17 June 2015.
  7. ^ Raytheon Corporate Communications. . Archived from the original on 2008-07-07. Retrieved 17 June 2015.
  8. ^ (PDF). Archived from the original (PDF) on 26 September 2007.
  9. ^ (PDF). Archived from the original (PDF) on 2007-09-26. Retrieved 2007-08-18.{{cite web}}: CS1 maint: archived copy as title (link)
  10. ^ Albon, Courtney. “Concerned about Industrial Base: Senate Appropriators Call For Broader F-16 AESA Radar Upgrade.” Inside the Air Force, vol. 26, no. 23, Inside Washington Publishers, 2015, pp. 3–3, JSTOR website Retrieved 13 March 2022.
  11. ^ a b "IEEE TEMS Home - IEEE Technology and Engineering Management Society" (PDF). IEEE Technology and Engineering Management Society.
  12. ^ (PDF). Archived from the original (PDF) on June 30, 2015. Retrieved 17 June 2015.
  13. ^ Page, Lewis. "F-22 superjets could act as flying Wi-Fi hotspots." The Register, 19 June 2007. Retrieved: 7 November 2009.
  14. ^ "NAVAIR - U.S. Navy Naval Air Systems Command - Navy and Marine Corps Aviation Research, Development, Acquisition, Test and Evaluation".[permanent dead link]
  15. ^ Rogoway, Tyler (21 November 2015). "SAAB's Gripen NG Fighter Has An Awesome Way To Make Its Radar More Capable". jalopnik.com. Kinja. Retrieved 12 April 2016.
  16. ^ Introduction to Electronic Warfare Modeling. Artech House. 2001. ISBN 9781596933118 – via Google Books.
  17. ^ Adamy, David (26 March 2018). Introduction to Electronic Warfare Modeling. Artech House. ISBN 9781596933118 – via Google Books.
  18. ^ . Archived from the original on 6 May 2015. Retrieved 17 June 2015.
  19. ^ "PICOSAR - DETAIL - Leonardo". Retrieved 27 July 2016.
  20. ^ "RAVEN ES-05". Leonardocompany.com. Retrieved 27 July 2016.
  21. ^ . Archived from the original on 2013-12-19. Retrieved 2013-12-19.
  22. ^ "SeaSpray 5000E - DETAIL - Leonardo". Retrieved 27 July 2016.
  23. ^ "SeaSpray 7000E - DETAIL - Leonardo". Retrieved 27 July 2016.
  24. ^ "SeaSpray 7500E - DETAIL - Leonardo". Retrieved 27 July 2016.
  25. ^ "VIXEN 500E - DETAIL - Leonardo". Retrieved 27 July 2016.
  26. ^ "VIXEN 1000E - DETAIL - Leonardo". Retrieved 27 July 2016.
  27. ^ "Saab launches GlobalEye multi-role airborne surveillance system". Airforce Technology. 17 February 2016.
  28. ^ a b http://www.ausairpower.net/APA-PLA-AWACS-Programs.html PLA-AF Airborne Early Warning & Control Programs
  29. ^ . Archived from the original on 2011-12-05. Retrieved 2011-12-10. Chinese Military Aviation - Fighters (Cont.)
  30. ^ "China's New J-16D Aircraft Might Have a Terrifying New Military Capability | The National Interest". 30 November 2017.
  31. ^ Jane's Navy International, August 2010, "Expanding coverage from sea to sky"
  32. ^ MINNICK, WENDELL (22 November 2014). "China's Anti-Stealth Radar Comes to Fruition". www.defensenews.com. Gannett. Archived from the original on 24 November 2014. Retrieved 25 November 2014.
  33. ^ http://www.ausairpower.net/APA-HQ-9-12-Battery-Radars.html HQ-9 and HQ-12 SAM system battery radars
  34. ^ John C Wise (13 January 2009). "PLA Air Defence Radars". p. 1. Retrieved 17 June 2015.
  35. ^ "TRML-4D - Multi-Functional Air Surveillance and Target Acquisition Radar System | HENSOLDT".
  36. ^ "Hensoldt presenting TRML- 4D multi-function air surveillance and target acquisition radar | Defense News May 2021 Global Security army industry | Defense Security global news industry army year 2021 | Archive News year".
  37. ^ "HENSOLDT presents new ground-based Air Defence Radar". 19 June 2018.
  38. ^ "Lockheed Martin completes first AN/TPY-4 radar production". 5 May 2022.
  39. ^ http://www.rada.com/capabilities-3/land-radars-2.html 2020-05-13 at the Wayback Machine RADA Tactical Land Radars
  40. ^ "The Swiss Army knife of radars - For soldiers, the KuRFS radar does it all and all at once | Raytheon Missiles & Defense".
  41. ^ http://www.janes.com/article/38219/saab-expands-surface-radar-portfolio Saab expands surface radar portfolio
  42. ^ . Archived from the original on 18 March 2015. Retrieved 17 June 2015.
  43. ^ . Archived from the original on 17 March 2015. Retrieved 17 June 2015.
  44. ^ "SMART-L MM | Thales Group".
  45. ^ Low Level Transportable Radar (LLTR) - Ashwini https://www.drdo.gov.in/sites/default/files/inline-files/lltr.pdf
  46. ^ . drdo.gov.in. Archived from the original on 23 July 2014. Retrieved 25 July 2016.
  47. ^ "Air Defence Tactical Control Radar (ADTCR)". Defence Research and Development Organisation, Ministry of Defence, Government of India. from the original on 2020-07-08. Retrieved 2021-10-07.
  48. ^ "Air Defence Fire Control Radar". Defence Research and Development Organisation, Ministry of Defence, Government of India. from the original on 2020-08-15. Retrieved 2021-10-07.
  49. ^ a b . Archived from the original on 2016-11-03. Retrieved 2016-11-01.
  50. ^ "Defexpo 2016: Larsen & Toubro highlights new Air Defence Fire Control Radar system". Army Recognition. from the original on 2016-04-01. Retrieved 2021-10-07.

Bibliography

  • Bell Labs (October 1975). ABM Research and Development at Bell Laboratories, Project History (PDF) (Technical report). Retrieved 13 December 2014.

External links

  • Active Electronically Steered Arrays – A Maturing Technology (ausairpower.net)
  • (flug-revue.rotor.com)
  • (mwjournal.com)


active, electronically, scanned, array, this, article, needs, additional, citations, verification, please, help, improve, this, article, adding, citations, reliable, sources, unsourced, material, challenged, removed, find, sources, news, newspapers, books, sch. This article needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed Find sources Active electronically scanned array news newspapers books scholar JSTOR April 2015 Learn how and when to remove this template message 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 In the AESA each antenna element is connected to a small solid state transmit receive module TRM under the control of a computer which performs the functions of a transmitter and or receiver for the antenna This contrasts with a passive electronically scanned array PESA in which all the antenna elements are connected to a single transmitter and or receiver through phase shifters under the control of the computer AESA s main use is in radar and these are known as active phased array radar APAR The Eurofighter Typhoon combat aircraft with its nose fairing removed revealing its Euroradar CAPTOR AESA radar antenna The AESA is a more advanced sophisticated second generation of the original PESA phased array technology PESAs can only emit a single beam of radio waves at a single frequency at a time The PESA must utilize a Butler matrix if multiple beams are required The AESA can radiate multiple beams of radio waves at multiple frequencies simultaneously AESA radars can spread their signal emissions across a wider range of frequencies which makes them more difficult to detect over background noise allowing ships and aircraft to radiate powerful radar signals while still remaining stealthy as well as being more resistant to jamming Hybrids of AESA and PESA can also be found consisting of subarrays that individually resemble PESAs where each subarray has its own RF front end Using a hybrid approach the benefits of AESA e g multiple independent beams can be realized at a lower cost compared to pure AESA Contents 1 History 2 Basic concept 3 Advantages 3 1 Low probability of intercept 3 2 High jamming resistance 3 3 Other advantages 4 Limitations 5 List of existing systems 5 1 Airborne systems 5 2 Surface systems land maritime 6 See also 7 References 8 Bibliography 9 External linksHistory EditThe examples and perspective in this section may not represent a worldwide view of the subject You may improve this section discuss the issue on the talk page or create a new section as appropriate November 2015 Learn how and when to remove this template message ZMAR concept sketch 1962 An aerial view of the three domes of the Multifunction Array Radar prototype surrounded by a clutter fence at White Sands Missile Range N M Sketch of the FLAT TWIN antiballistic missile radar Bell Labs proposed replacing the Nike Zeus radars with a phased array system in 1960 and was given the go ahead for development in June 1961 The result was the Zeus Multi function Array Radar ZMAR an early example of an active electronically steered array radar system 1 ZMAR became MAR when the Zeus program ended in favor of the Nike X system in 1963 The MAR Multi function Array Radar was made of a large number of small antennas each one connected to a separate computer controlled transmitter or receiver Using a variety of beamforming and signal processing steps a single MAR was able to perform long distance detection track generation discrimination of warheads from decoys and tracking of the outbound interceptor missiles 2 MAR allowed the entire battle over a wide space to be controlled from a single site Each MAR and its associated battle center would process tracks for hundreds of targets The system would then select the most appropriate battery for each one and hand off particular targets for them to attack One battery would normally be associated with the MAR while others would be distributed around it Remote batteries were equipped with a much simpler radar whose primary purpose was to track the outgoing Sprint missiles before they became visible to the potentially distant MAR These smaller Missile Site Radars MSR were passively scanned forming only a single beam instead of the MAR s multiple beams 2 While MAR was ultimately successful the cost of the system was enormous When the ABM problem became so complex that even a system like MAR could no longer deal with realistic attack scenarios the Nike X concept was abandoned in favor of much simpler concepts like the Sentinel program which did not use MAR A second example MAR II was abandoned in place on Kwajalein Atoll 3 The first Soviet APAR the 5N65 was developed in 1963 1965 as a part of the S 225 ABM system After some modifications in the system concept in 1967 it was built at Sary Shagan Test Range in 1970 1971 and nicknamed Flat Twin in the West Four years later another radar of this design was built on Kura Test Range while the S 225 system was never commissioned citation needed The first military ground based AESA was the J FPS 3 which became fully operational with the 45th Aircraft Control and Warning Group of the Japan Self Defense Forces in 1995 The first series production ship based AESA was the OPS 24 a fire control radar introduced on the Japanese Asagiri class destroyer DD 155 Hamagiri launched in 1988 4 The first airborne series production AESA was the EL M 2075 Phalcon on a Boeing 707 of the Chilean Air Force that entered service in 1994 The first AESA on a combat aircraft was the J APG 1 introduced on the Mitsubishi F 2 in 1995 5 The first AESA on a missile is the seeker head for the AAM 4B an air to air missile carried by the Mitsubishi F 2 and Mitsubishi built McDonnell Douglas F 15J 5 US based manufacturers of the AESA radars used in the F 22 and Super Hornet include Northrop Grumman 6 and Raytheon 7 These companies also design develop and manufacture the transmit receive modules which comprise the building blocks of an AESA radar The requisite electronics technology was developed in house via Department of Defense research programs such as MMIC Program 8 9 In 2016 the Congress funded a military industry competition to produce new radars for two dozen National Guard fighter aircraft 10 Basic concept Edit AESA basic schematic Radar systems generally work by connecting an antenna to a powerful radio transmitter to emit a short pulse of signal The transmitter is then disconnected and the antenna is connected to a sensitive receiver which amplifies any echos from target objects By measuring the time it takes for the signal to return the radar receiver can determine the distance to the object The receiver then sends the resulting output to a display of some sort The transmitter elements were typically klystron tubes or magnetrons which are suitable for amplifying or generating a narrow range of frequencies to high power levels To scan a portion of the sky the radar antenna must be physically moved to point in different directions Starting in the 1960s new solid state devices capable of delaying the transmitter signal in a controlled way were introduced That led to the first practical large scale passive electronically scanned array PESA or simply phased array radar PESAs took a signal from a single source split it into hundreds of paths selectively delayed some of them and sent them to individual antennas The radio signals from the separate antennas overlapped in space and the interference patterns between the individual signals were controlled to reinforce the signal in certain directions and mute it in all others The delays could be easily controlled electronically allowing the beam to be steered very quickly without moving the antenna A PESA can scan a volume of space much quicker than a traditional mechanical system Additionally thanks to progress in electronics PESAs added the ability to produce several active beams allowing them to continue scanning the sky while at the same time focusing smaller beams on certain targets for tracking or guiding semi active radar homing missiles PESAs quickly became widespread on ships and large fixed emplacements in the 1960s followed by airborne sensors as the electronics shrank AESAs are the result of further developments in solid state electronics In earlier systems the transmitted signal was originally created in a klystron or traveling wave tube or similar device which are relatively large Receiver electronics were also large due to the high frequencies that they worked with The introduction of gallium arsenide microelectronics through the 1980s served to greatly reduce the size of the receiver elements until effective ones could be built at sizes similar to those of handheld radios only a few cubic centimeters in volume The introduction of JFETs and MESFETs did the same to the transmitter side of the systems as well It gave rise to amplifier transmitters with a low power solid state waveform generator feeding an amplifier allowing any radar so equipped to transmit on a much wider range of frequencies to the point of changing operating frequency with every pulse sent out Shrinking the entire assembly the transmitter receiver and antenna into a single transmitter receiver module TRM about the size of a carton of milk and arraying these elements produces an AESA The primary advantage of an AESA over a PESA is the capability of the different modules to operate on different frequencies Unlike the PESA where the signal is generated at single frequencies by a small number of transmitters in the AESA each module generates and radiates its own independent signal This allows the AESA to produce numerous simultaneous sub beams that it can recognize due to different frequencies and actively track a much larger number of targets AESAs can also produce beams that consist of many different frequencies at once using post processing of the combined signal from a number of TRMs to re create a display as if there was a single powerful beam being sent However this means that the noise present in each frequency is also received and added Advantages EditAESAs add many capabilities of their own to those of the PESAs Among these are the ability to form multiple beams simultaneously to use groups of TRMs for different roles concurrently like radar detection and more importantly their multiple simultaneous beams and scanning frequencies create difficulties for traditional correlation type radar detectors Low probability of intercept Edit See also Low probability of intercept radar Radar systems work by sending out a signal and then listening for its echo off distant objects Each of these paths to and from the target is subject to the inverse square law of propagation in both the transmitted signal and the signal reflected back That means that a radar s received energy drops with the fourth power of the distance which is why radar systems require high powers often in the megawatt range to be effective at long range The radar signal being sent out is a simple radio signal and can be received with a simple radio receiver Military aircraft and ships have defensive receivers called radar warning receivers RWR which detect when an enemy radar beam is on them thus revealing the position of the enemy Unlike the radar unit which must send the pulse out and then receive its reflection the target s receiver does not need the reflection and thus the signal drops off only as the square of distance This means that the receiver is always at an advantage neglecting disparity in antenna size over the radar in terms of range it will always be able to detect the signal long before the radar can see the target s echo Since the position of the radar is extremely useful information in an attack on that platform this means that radars generally must be turned off for lengthy periods if they are subject to attack this is common on ships for instance Unlike the radar which knows which direction it is sending its signal the receiver simply gets a pulse of energy and has to interpret it Since the radio spectrum is filled with noise the receiver s signal is integrated over a short period of time making periodic sources like a radar add up and stand out over the random background The rough direction can be calculated using a rotating antenna or similar passive array using phase or amplitude comparison Typically RWRs store the detected pulses for a short period of time and compare their broadcast frequency and pulse repetition frequency against a database of known radars The direction to the source is normally combined with symbology indicating the likely purpose of the radar airborne early warning and control surface to air missile etc This technique is much less useful against a radar with a frequency agile solid state transmitter Since the AESA or PESA can change its frequency with every pulse except when using doppler filtering and generally does so using a random sequence integrating over time does not help pull the signal out of the background noise Moreover a radar may be designed to extend the duration of the pulse and lower its peak power An AESA or modern PESA will often have the capability to alter these parameters during operation This makes no difference to the total energy reflected by the target but makes the detection of the pulse by an RWR system less likely 11 Nor does the AESA have any sort of fixed pulse repetition frequency which can also be varied and thus hide any periodic brightening across the entire spectrum Older generation RWRs are essentially useless against AESA radars which is why AESAs are also known as low probability of intercept radars Modern RWRs must be made highly sensitive small angles and bandwidths for individual antennas low transmission loss and noise 11 and add successive pulses through time frequency processing to achieve useful detection rates 12 High jamming resistance Edit Main article radar jamming and deception Jamming is likewise much more difficult against an AESA Traditionally jammers have operated by determining the operating frequency of the radar and then broadcasting a signal on it to confuse the receiver as to which is the real pulse and which is the jammer s This technique works as long as the radar system cannot easily change its operating frequency When the transmitters were based on klystron tubes this was generally true and radars especially airborne ones had only a few frequencies to choose among A jammer could listen to those possible frequencies and select the one to be used to jam Most radars using modern electronics are capable of changing their operating frequency with every pulse This can make jamming less effective although it is possible to send out broadband white noise to conduct barrage jamming against all the possible frequencies this reduces the amount of jammer energy in any one frequency An AESA has the additional capability of spreading its frequencies across a wide band even in a single pulse a technique known as a chirp In this case the jamming will be the same frequency as the radar for only a short period while the rest of the radar pulse is unjammed AESAs can also be switched to a receive only mode and use these powerful jamming signals to track its source something that required a separate receiver in older platforms By integrating received signals from the targets own radar along with a lower rate of data from its own broadcasts a detection system with a precise RWR like an AESA can generate more data with less energy Some receive beamforming capable systems usually ground based may even discard a transmitter entirely However using a single receiving antenna only gives a direction Obtaining a range and a target vector requires at least two physically separate passive devices for triangulation to provide instantaneous determinations unless phase interferometry is used Target motion analysis can estimate these quantities by incorporating many directional measurements over time along with knowledge of the position of the receiver and constraints on the possible motion of the target Other advantages Edit Since each element in an AESA is a powerful radio receiver active arrays have many roles besides traditional radar One use is to dedicate several of the elements to reception of common radar signals eliminating the need for a separate radar warning receiver The same basic concept can be used to provide traditional radio support and with some elements also broadcasting form a very high bandwidth data link The F 35 uses this mechanism to send sensor data between aircraft in order to provide a synthetic picture of higher resolution and range than any one radar could generate In 2007 tests by Northrop Grumman Lockheed Martin and L 3 Communications enabled the AESA system of a Raptor to act like a WiFi access point able to transmit data at 548 megabits per second and receive at gigabit speed this is far faster than the Link 16 system used by US and allied aircraft which transfers data at just over 1 Mbit s 13 To achieve these high data rates requires a highly directional antenna which AESA provides but which precludes reception by other units not within the antennas beamwidth whereas like most Wi Fi designs Link 16 transmits its signal omni directionally to ensure all units within range can receive the data AESAs are also much more reliable than either a PESA or older designs Since each module operates independently of the others single failures have little effect on the operation of the system as a whole Additionally the modules individually operate at low powers perhaps 40 to 60 watts so the need for a large high voltage power supply is eliminated Replacing a mechanically scanned array with a fixed AESA mount such as on the Boeing F A 18E F Super Hornet can help reduce an aircraft s overall radar cross section RCS but some designs such as the Eurofighter Typhoon forgo this advantage in order to combine mechanical scanning with electronic scanning and provide a wider angle of total coverage 14 This high off nose pointing allows the AESA equipped fighter to employ a Crossing the T maneuver often referred to as beaming in the context of air to air combat against a mechanically scanned radar that would filter out the low closing speed of the perpendicular flight as ground clutter while the AESA swivels 40 degrees towards the target in order to keep it within the AESA s 60 degree off angle limit 15 Limitations EditWith a half wavelength distance between the elements the maximum beam angle is approximately 45 displaystyle pm 45 With a shorter element distance the highest field of view FOV for a flat phased array antenna is currently 120 60 displaystyle pm 60 16 although this can be combined with mechanical steering as noted above 17 18 List of existing systems EditAirborne systems Edit Aselsan MURAD for the Baykar Bayraktar Akinci F 16 and TAI TF X Northrop Grumman AN APG 77 for the F 22 Raptor AN APG 80 for the General Dynamics F 16 Fighting Falcon AN APG 81 for the F 35 Lightning II AN APG 83 SABR for the F 16V Viper and B 1B Lancer upgrades Option forKAI FA 50 Block 20 AN APG 85 for the F 35 Lightning II Block 4 AN APY 9 for the E 2D Advanced Hawkeye Multi role Electronically Scanned Array MESA radar for the Boeing E 7 Wedgetail AEW amp C aircraft AN ASQ 236 Podded AESA Radar AN ZPY 1 STARLite Small Tactical Radar Lightweight for manned and unmanned aircraft AN ZPY 2 Multi Platform Radar Technology Insertion Program MP RTIP AN ZPY 3 Multi Function Active Sensor MFAS for MQ 4C Triton Vehicle Dismount and Exploitation Radar VADER Raytheon AN APG 63 V 2 and AN APG 63 V 3 for the F 15C Eagle Republic of Singapore s F 15SG AN APG 79 for the F A 18E F Super Hornet and EA 18G Growler AN APG 82 V 1 for the F 15E Strike Eagle AN APG 84 RACR Raytheon Advanced Combat Radar for F 16 and F A 18 upgrades Option for KAI FA 50 Block 20 AN APQ 181 upgrade from PESA to AESA for Northrop Grumman B 2 Spirit bomber AAS Advanced Airborne Sensor AESA follow on to the Littoral Surveillance Radar System LSRS APS 149 also built by Raytheon for the Boeing P 8 Poseidon Raytheon Sentinel ASTOR Airborne STand Off Radar Close up of the Thales RBE2 AA mounted on Rafale since F3R standard The OSF behind it is not part of the radar Captor E CAESAR CAPTOR Active Electronically Scanning Array Radar for the Eurofighter Typhoon Selex ES now Leonardo PicoSAR 19 Raven ES 05 AESA 20 for the JAS 39E Gripen NG 21 Seaspray 5000E 22 Seaspray 7000E 23 for helicopters Seaspray 7500E 24 for General Atomics MQ 9 Reaper Vixen 500E 25 Vixen 1000E 26 Mitsubishi Electric Corporation J APG 1 J APG 2 AESA for the Mitsubishi F 2 fighter HPS 104 for the Mitsubishi SH 60 Multifunction RF Sensor for Mitsubishi ATD X Thales RBE2 AESA for Rafale fighter Toshiba HPS 106 air amp surface search radar for the Kawasaki P 1 maritime patrol aircraft three antenna arrays Ericsson Erieye AEW amp C PS 05 A MK 5 for JAS 39 Gripen EMB 145 AEW amp C Saab GlobalEye AEW amp C advanced version of the Erieye with extended range 27 Phazotron NIIR Zhuk A AM optional for MiG 35 Tikhomirov NIIP N036 Byelka for Sukhoi Su 57 Elta EL M 2083 aerostat mounted air search radar EL M 2052 for fighters Interim candidate for HAL Tejas Suitable for F 15 MiG 29 Mirage 2000 FA 50 Block 20 EL M 2075 radar for the IAI Phalcon AEW amp C system EL W 2085 advanced version of the radar for the EL M 2075 used on the Gulfstream G550 EL W 2090 similar to the EL W 2085 only used on the Ilyushin Il 76 NRIET Nanjing Research Institute of Electronic Technology 14 institute 607 institute and 38 institute Radar for KJ 2000 AEW amp C system 28 Radar for KJ 500 amp Y 7 AWACS Radar for KJ 200 28 KLJ 7A for JF 17 Thunder Block 3 ZDK 03 Chengdu J 20 Type 1475 Radar Chengdu J 10B C 29 Shenyang J 16 30 Z 8AEW The HAL Tejas combat aircraft equipped with Uttam AESA radar Defence Research and Development Organisation DRDO LSTAR Radar for Airborne Early Warning platform Uttam AESA multifunction radar for HAL Tejas Vega Radio Engineering Corporation radar for Vega Premier Hanwha Systems AESA radar for KAI KF 21 BoramaeSurface systems land maritime Edit The first AESA radar employed on an operational warship was the Japanese OPS 24 manufactured by Mitsubishi Electric introduced on the JDS Hamagiri DD 155 the first ship of the latter batch of the Asagiri class destroyer launched in 1988 APAR active phased array radar Thales Netherlands multifunction radar is the primary sensor of the Royal Netherlands Navy s De Zeven Provincien class frigates the German Navy s Sachsen class frigates and the Royal Danish Navy s Ivar Huitfeldt class frigates APAR is the first active electronically scanned array multifunction radar employed on an operational warship 31 BUR Bodenuberwachungsradar by Cassidian for the Bundeswehr Cassidian TRS 4D COBRA Counter battery radar China Road mobile Anti Stealth JY 26 Skywatch U 3 D long range air surveillance radar 32 H LJG 346 8 on Chinese aircraft carrier Liaoning H LJG 346 on Type 052C destroyer H LJG 346A on Type 052D destroyer H LJG 346B on Type 055 destroyer Type 305A Radar Acquisition radar for the HQ 9 missile system 33 YLC 2 Radar 34 EL M 2248 MF STAR on board a Kolkata class destroyer Elta EL M 2080 Green Pine ground based early warning AESA radar EL M 2106 ATAR air defense fire control radar EL M 2180 WatchR Guard Multi Mode Staring Ground Surveillance Radar EL M 2248 MF STAR multifunction naval radar EL M 2258 Advanced Lightweight Phased Array ALPHA multifunction naval radar EL M 2084 multimission radar artillery weapon location air defence and fire control EL M 2133 WindGuard Trophy active protection system radarHensoldt TRML 4D de 35 36 37 AN TPQ 53 phased array radar Lockheed Martin AN TPQ 53 Counterfire Target Acquisition Radar AN SPY 7 Long Range Discrimination Radar AN MPQ 64A4 Sentinel AN TPY 4 3DELRR Three Dimensional Expeditionary Long Range Radar 38 Northrop Grumman AN TPS 80 Ground air task oriented radar G ATOR HAMMR Highly Adaptable Multi Mission Radar RADA Electronic Industries 39 RPS 10 RPS 15 RPS 40 RPS 42 RHS 44 3DELRR long range radar system Raytheon FlexDAR Flexible Distributed Array Radar U S National Missile defense Sea based X band Radar XBR AN TPY 2 Anti Ballistic Missile radar that can stand alone or be a part of the THAAD ABM system AN SPY 3 multifunction radar for U S DD X and CVN 21 next generation surface vessels AN SPY 6 Air and Missile Defense Radar AMDR multifunction radar for U S Arleigh Burke destroyers Gerald R Ford class aircraft carrier Cobra Judy Replacement CJR Cobra King on USNS Howard O Lorenzen T AGM 25 AN FPS 132 Upgraded Early Warning Radar UEWR PAVE PAWS upgrade from PESA to AESA KuRFS 40 Saab Group GIRAFFE Radar GIRAFFE 1X GIRAFFE 4A GIRAFFE 8A 41 Selex ES KRONOS Land 42 amp Naval 43 3D multi function radar RAN 40L 3D EWR RAT 31DL RAT 31DL M ThalesRaytheonSystems M3R Thales Ground Master 200 Ground Master 400 Ground Master 200 MM SMART L MM 44 Sea Fire 500 on FREMM ER frigates Sea Master 400 Sea Watcher 100 Mitsubishi Electric Corporation Type 3 Chu SAM Medium Range Surface to Air MissileSystem Chu SAM SAM 4 multifunction radar OPS 24 The world s first Naval Active Electronically Scanned Array radar on Asagiri class destroyers Murasame class destroyer 1994 and Takanami class destroyers OPS 50 FCS 3 on the Hyuga class helicopter destroyer Izumo class helicopter destroyer and Akizuki class destroyer 2010 J FPS 3 Japanese main ground based air defense J FPS 5 Japanese ground based next generation missile defense radar JTPS P14 Transportable air defence radar JTPS P16 Counter battery radar Toshiba J FPS 4 Cheaper than J FPS 3 produced by Toshiba JMPQ P13 Counter battery radar Toshiba MEADS s fire control radar SAMPSON AESA on board the Type 45 destroyer BAE Systems SAMPSON multifunction radar for the UK s Type 45 destroyers ARTISAN Type 997 multifunction radar for the UK s Type 23 and Type 26 Frigates and the Queen Elizabeth class aircraft carriers J TPS 102 Self propelled ground based radar cylindrical array antenna NEC CEA Technologies CEAFAR a 4th generation S Band multifunction digital active phased array radar installed on all RAN ANZAC class frigates NNIIRT 1L119 Nebo SVU mobile AESA 3 dimensional surveillance radar VNIIRT Gamma DE mobile 3 dimensional solid state AESA surveillance radar 50N6A multifunctional radar of the Vityaz missile system and 42S6 Morfey Morpheus National Chung Shan Institute of Science and Technology CS MPQ 90 Bee Eye multifunction radar CS SPG 6N naval radar with surface search and fire control variants Defence Research and Development Organisation Ashwini LLTR Radar 4D AESA radar used by Indian Air Force 45 Arudhra Radar Multi function AESA radar used by Indian Air Force 46 Swordfish Long Range Tracking Radar Target acquisition and fire control radar for Indian Ballistic Missile Defence system Air Defence Tactical Control Radar ADTCR Tactical control radar 47 Atulya Air Defence Fire Control Radar ADFCR X band 3D Fire control radar 48 Bharat Electronics RAWL 03 Multi Function Active phased array Air Surveillance Radar 49 Naval Missile Defense Radar NMDR S Band Multi Function Active phased array Radar 49 Larsen amp Toubro Air Defence Fire Control Radar System 3D surveillance radar 50 LIG Nex1 SPS 550K medium range air and surface surveillance radar for Incheon class frigates and Daegu class frigatesSee also EditRadar configurations and types Receiver Passive electronically scanned array Low Probability of Intercept Radar Terrain following radar Solid State Phased Array Radar SystemReferences Edit Bell Labs 1975 p I 35 a b Bell Labs 1975 p 2 3 Bell Labs 1975 p 2 22 Tomohiko Tada March 2010 4 Radar ECM ESM Shipboard weapons of JMSDF 1952 2010 Ships of the World in Japanese Kaijin sha 721 100 105 a b Japan Upgrading 60 F 2s With AAM 4 J APG 2 Retrieved 17 June 2015 Northrop Grumman Successfully Completes F 22 Radar Flight Test Certification NYSE NOC Retrieved 17 June 2015 Raytheon Corporate Communications Raytheon Archived from the original on 2008 07 07 Retrieved 17 June 2015 A DARPA Perspective on the Future of Electronics PDF Archived from the original PDF on 26 September 2007 Archived copy PDF Archived from the original PDF on 2007 09 26 Retrieved 2007 08 18 a href Template Cite web html title Template Cite web cite web a CS1 maint archived copy as title link Albon Courtney Concerned about Industrial Base Senate Appropriators Call For Broader F 16 AESA Radar Upgrade Inside the Air Force vol 26 no 23 Inside Washington Publishers 2015 pp 3 3 JSTOR website Retrieved 13 March 2022 a b IEEE TEMS Home IEEE Technology and Engineering Management Society PDF IEEE Technology and Engineering Management Society tech conf papers A14 PDF Archived from the original PDF on June 30 2015 Retrieved 17 June 2015 Page Lewis F 22 superjets could act as flying Wi 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July 2016 VIXEN 500E DETAIL Leonardo Retrieved 27 July 2016 VIXEN 1000E DETAIL Leonardo Retrieved 27 July 2016 Saab launches GlobalEye multi role airborne surveillance system Airforce Technology 17 February 2016 a b http www ausairpower net APA PLA AWACS Programs html PLA AF Airborne Early Warning amp Control Programs Chinese Military Aviation China Air Force Archived from the original on 2011 12 05 Retrieved 2011 12 10 Chinese Military Aviation Fighters Cont China s New J 16D Aircraft Might Have a Terrifying New Military Capability The National Interest 30 November 2017 Jane s Navy International August 2010 Expanding coverage from sea to sky MINNICK WENDELL 22 November 2014 China s Anti Stealth Radar Comes to Fruition www defensenews com Gannett Archived from the original on 24 November 2014 Retrieved 25 November 2014 http www ausairpower net APA HQ 9 12 Battery Radars html HQ 9 and HQ 12 SAM system battery radars John C Wise 13 January 2009 PLA Air Defence Radars p 1 Retrieved 17 June 2015 TRML 4D Multi Functional Air Surveillance and Target Acquisition Radar System HENSOLDT Hensoldt presenting TRML 4D multi function air surveillance and target acquisition radar Defense News May 2021 Global Security army industry Defense Security global news industry army year 2021 Archive News year HENSOLDT presents new ground based Air Defence Radar 19 June 2018 Lockheed Martin completes first AN TPY 4 radar production 5 May 2022 http www rada com capabilities 3 land radars 2 html Archived 2020 05 13 at the Wayback Machine RADA Tactical Land Radars The Swiss Army knife of radars For soldiers the KuRFS radar does it all and all at once Raytheon Missiles amp Defense http www janes com article 38219 saab expands surface radar portfolio Saab expands surface radar portfolio KRONOS LAND DETAIL Selex ES Archived from the original on 18 March 2015 Retrieved 17 June 2015 KRONOS NAVAL DETAIL Selex ES Archived from the original on 17 March 2015 Retrieved 17 June 2015 SMART L MM Thales Group Low Level Transportable Radar LLTR Ashwini https www drdo gov in sites default files inline files lltr pdf DRDO Radar List drdo gov in Archived from the original on 23 July 2014 Retrieved 25 July 2016 Air Defence Tactical Control Radar ADTCR Defence Research and Development Organisation Ministry of Defence Government of India Archived from the original on 2020 07 08 Retrieved 2021 10 07 Air Defence Fire Control Radar Defence Research and Development Organisation Ministry of Defence Government of India Archived from the original on 2020 08 15 Retrieved 2021 10 07 a b BEL Products Archived from the original on 2016 11 03 Retrieved 2016 11 01 Defexpo 2016 Larsen amp Toubro highlights new Air Defence Fire Control Radar system Army Recognition Archived from the original on 2016 04 01 Retrieved 2021 10 07 Bibliography EditBell Labs October 1975 ABM Research and Development at Bell Laboratories Project History PDF Technical report Retrieved 13 December 2014 External links EditActive Electronically Steered Arrays A Maturing Technology ausairpower net FLUG REVUE December 1998 Modern fighter radar technology flug revue rotor com Phased Arrays and Radars Past Present and Future mwjournal com Wikimedia Commons has media related to Active electronically scanned arrays Retrieved from https en wikipedia org w index php title Active electronically scanned array amp oldid 1135603239, wikipedia, wiki, book, books, library,

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