Active electronically scanned array

Hver enkelt radioantenne har et tilhørende sende/modtage-modul (kort TRM, TR fra engelsk *transmit/receive-module*). Modulet anvendes som signalforstærker og fase-controller for det luftbårne radarsystem på et Eurofighter "CAPTOR-E" fly.^[1]

En active electronically scanned array (akronym AESA, men også set kaldet Active Electronically Steered Arrays) er et antal radioantenner samlet i en gruppe og styret elektronisk.^[2] Hver enkelt radioantenne har et tilhørende sende/modtage-modul (kort TRM, TR fra engelsk transmit/receive-module), hvilket gør hver radioantenne i stand til at sende og modtage radiosignaler uafhængigt af de øvrige antenner i gruppen.

Kampflys AESA har typisk 1.000 til 2.000 små radioantenner monteret på en rund skive i spidsen af flyet.^[3] Sende/modtage-modulerne (og dermed radioantennernes radiosignaler) er forbundet til en computer. Derved kan software beregne hvilke signalfaser og amplituder hvert enkelt sende/modtage-modul skal have, for at rette en konstruktiv interferens radiostråle ud fra AESA-systemet, mod en bestemt retning.^[3] Effekten af denne konstruktive interferens er, at AESA-systemet opfører sig som én radioantenne med stor retningsforstærkning, under både udsendelse og modtagelse af radiosignaler.

Da gruppen af radioantenner bliver styret elektronisk, kan radiostrålens retning ændres meget hurtigt (indenfor en vis vandret og lodret vinkel i forhold til AESA-pladen), uden at flytte AESA-systemet .^[3]^[2]

Tidligere radarantenner blev mekanisk rettet mod målet. Derved blev flyet “blind” for alle andre end den fjende, man ville holde øje med. Man kunne også scanne himlen, med risiko for at miste et bestemt fly af syne. AESA-radarer kan allokere en vis procentdel af radarelementerne til at følge et bestemt mål, samtidigt med at de andre radarelementer scanner himlen for andre trusler.

(AESA-systemet er anderledes end en passive electronically scanned array (PESA), i hvilken alle antenner er forbundet til én enkelt radiosender og én enkelt radiomodtager via faseskiftere under computerstyring.^[3])

AESAs hovedanvendelse er med radar, og disse kendes som active phased array radar (akronym APAR).^[2]

AESAen er mere avanceret, sofistikeret og er anden generation af den originale PESA fasede radioantennegruppe teknologi. (PESAs kan kun udsende én radiostråle ad gangen.) AESAen kan udsende flere radiobølgestråler samtidigt.^[3] AESA-radarer kan sprede deres signaludsendelse over et bredere frekvensinterval, hvilket gør dem meget sværere af opdage, hvilket tillader skibe og luftfartøjer at udstråle radarsignaler, men alligevel være svære at opdage.^[3]^[4]

Udover AESAs anvendelse til radar, kan AESA også anvendes til højhastighedskommunikation.^[4]

Se også

Kilder/referencer

^ airpower.at: Ein neues Radar für den Eurofighter "CAPTOR-E" ready für Tranche 3, backup
^ ^a ^b ^c Sep 12, 2017, blog.bliley.com: Understanding AESA: A Game-Changer in RADAR Technology Citat: "...Active Electronically Scanned Arrays are considered a phased array system, which consists of an array of antennas which form a beam of radio waves that can be aimed in different directions without physically moving the antennae themselves. The primary use of AESA technology is in radar systems....", backup
^ ^a ^b ^c ^d ^e ^f 10/4/2010, GOKULA KRISHNANS: Active Electronically Scanned Array - (AESA) Radar Citat: "...AESAs aim their "beam" by broadcasting a number of different frequencies of coherent radio energy that interfere constructively at certain angles in front of the antenna. They improve on the older passive electronically scanned radars by spreading their broadcasts out across a band of frequencies, which makes it very difficult to detect over background noise...Unlike the PESA, where the signal was generated at single frequencies by a small number of transmitters, in the AESA each module broadcasts its own independent signal. This allows the AESA to produce numerous "sub-beams" and actively "paint" a much larger number of targets...A phased array antenna is composed of lots of radiating elements each with a phase shifter. Beams are formed by shifting the phase of the signal emitted from each radiating element, to provide constructive/destructive interference so as to steer the beams in the desired direction. The signal is amplified by constructive interference in the main direction. The beam sharpness is improved by the destructive interference...As can be expected, the technology comes at a cost. Each TR module is independent radar. Initial cost of a TR module was reportedly around $2000. Fighter radars are usually in the 1000 to 2000 modules size range...", backup
^ ^a ^b May 27, 2011, aviationintel.com: The great RADAR race: AESA development in high gear Citat: "...On the other hand, AESA radars can be very hard to detect by the enemy via multiple methods such as frequency hoping, modulating a continuous wave signal and using the very least amount of power to detect, track and engage a target...Finally, AESA radars and their incredibly capable software and computer backends can act as information transmitters as well. This sounds strange but it is true, because the radars can modulate and transmit radiation so quickly they can also eventually transmit large amounts of information such a high-resolution streaming video to receivers...", backup

Bibliografi

Bell Labs (oktober 1975). ABM Research and Development at Bell Laboratories, Project History (PDF) (Teknisk rapport). Hentet 13. december 2014.

Eksterne henvisninger

[1] rpower.at: Ein neues Radar für den Eurofighter "CAPTOR-E" ready für Tranche 3, backup

[bliley-2] Sep 12, 2017, blog.bliley.com: Understanding AESA: A Game-Changer in RADAR Technology Citat: "...Active Electronically Scanned Arrays are considered a phased array system, which consists of an array of antennas which form a beam of radio waves that can be aimed in different directions without physically moving the antennae themselves. The primary use of AESA technology is in radar systems....", backup

[KRISHNANS-3] ^ ^a ^b ^c ^d ^e ^f 10/4/2010, GOKULA KRISHNANS: Active Electronically Scanned Array - (AESA) Radar Citat: "...AESAs aim their "beam" by broadcasting a number of different frequencies of coherent radio energy that interfere constructively at certain angles in front of the antenna. They improve on the older passive electronically scanned radars by spreading their broadcasts out across a band of frequencies, which makes it very difficult to detect over background noise...Unlike the PESA, where the signal was generated at single frequencies by a small number of transmitters, in the AESA each module broadcasts its own independent signal. This allows the AESA to produce numerous "sub-beams" and actively "paint" a much larger number of targets...A phased array antenna is composed of lots of radiating elements each with a phase shifter. Beams are formed by shifting the phase of the signal emitted from each radiating element, to provide constructive/destructive interference so as to steer the beams in the desired direction. The signal is amplified by constructive interference in the main direction. The beam sharpness is improved by the destructive interference...As can be expected, the technology comes at a cost. Each TR module is independent radar. Initial cost of a TR module was reportedly around $2000. Fighter radars are usually in the 1000 to 2000 modules size range...", backup

[aviationintel-4] May 27, 2011, aviationintel.com: The great RADAR race: AESA development in high gear Citat: "...On the other hand, AESA radars can be very hard to detect by the enemy via multiple methods such as frequency hoping, modulating a continuous wave signal and using the very least amount of power to detect, track and engage a target...Finally, AESA radars and their incredibly capable software and computer backends can act as information transmitters as well. This sounds strange but it is true, because the radars can modulate and transmit radiation so quickly they can also eventually transmit large amounts of information such a high-resolution streaming video to receivers...", backup

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