Active electronically scanned array: Difference between revisions

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An '''active electronically scanned array''' ('''AESA''') is a type of [[phased array]] antenna, which is a computer-controlled [[antenna array]] in which the beam of radio waves can be electronically steered to point in different directions without moving the antenna.<ref>{{Citation |title=The Insane Engineering of the F-35B |url=https://www.youtube.com/watch?v=1lCOgFPtaZ4 |access-date=2024-02-16 |language=en}}</ref> 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 (radio)|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 shifter]]s under the control of the computer. AESA's main use is in [[radar]], and these are known as active phased array radar (APAR).

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 [[Noise (radio)|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==

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===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 (signal processing)|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 [[Wi-Fi|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 &nbsp;Mbit/s.<ref>Page, Lewis. [https://www.theregister.co.uk/2007/06/19/super_stealth_jet_acts_as_flying_wifi_hotspots/ "F-22 superjets could act as flying Wi-Fi hotspots."] ''The Register'', 19 June 2007. Retrieved: 7 November 2009.</ref> 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 PESAs 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.