Passive electronically scanned array

A passive electronically scanned array (PESA), also known as passive phased array, is a phased array antenna, that is an antenna in which the beam of radio waves can be electronically steered to point in different directions, 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. This contrasts with an active electronically scanned array (AESA) antenna, which has a separate transmitter and/or receiver unit for each antenna element, all controlled by a computer. AESA is a more advanced, sophisticated versatile second-generation version of the original PESA phased array technology.

The largest use of phased arrays is in radars. Most phased array radars in the world are PESA. The civilian microwave landing system uses PESA transmit-only arrays.

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.

In 1959, DARPA developed an experimental phased array radar called Electronically Steered Array Radar ESAR. The first module, a linear array, was completed in 1960. It formed the basis of the AN/FPS-85.[1]

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, 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 was 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. 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.

The Mikoyan MiG-31 combat aircraft with nose fairing removed, showing its Zaslon passive electronically scanned array radar antenna.
Phased array animation with arrow 10frames 371x400px 100ms
Animation showing how a passive electronically scanned array works. It consists of an array of antenna elements (A) powered by a single transmitter (TX). The feed current for each antenna passes through a phase shifter (φ) controlled by a computer (C). The moving red lines show the wavefronts of the radio waves emitted by each element. The individual wavefronts are spherical, but they combine (superpose) in front of the antenna to create a plane wave, a beam of radio waves travelling in a specific direction. The phase shifters delay the radio waves progressively going up the line so each antenna emits its wavefront later than the one below it. This causes the resulting plane wave to be directed at an angle to the antenna. The velocity of the radio waves is shown slowed down enormously.

List of PESA radars

See also


  1. ^
  2. ^ DRDO LRDE Radar Systems

The AN/APQ-181 is an all-weather, low probability of intercept (LPI) radar system designed by Hughes Aircraft (now Raytheon) for the U.S. Air Force B-2A Spirit bomber aircraft. The system was developed in the mid-1980s and entered service in 1993. The APQ-181 provides a number of precision targeting modes, and also supports terrain-following radar and terrain avoidance. The radar operates in the Ku band (a subset of the J band). The original design uses a TWT-based transmitter with a 2-dimensional passive electronically scanned array (PESA) antenna.

In 1991, the B-2 Industrial Team (including Hughes as a major subcontractor) was awarded the Collier Trophy in recognition of the "design, development, production, and flight testing of the B-2 aircraft, which has contributed significantly to America's enduring leadership in aerospace and the country's future national security."

In 2002, Raytheon was awarded a contract to develop a new, active electronically scanned array (AESA) version of the APQ-181. This upgrade will improve system reliability, and will also eliminate potential conflicts in frequency usage between the B-2 and commercial satellite systems that also use the J band.

In 2008 the Federal Communications Commission accidentally sold the APQ-181 frequency to a commercial user resulting in the need for installing new radar arrays at a cost of over $1 billion. All B-2 aircraft are expected to have the upgraded radar by 2010.


The AN/TPS-75 is a transportable passive electronically scanned array air search 3D radar produced in the United States. It was originally designated the TPS-43E2. Although the antenna is a radically new design from the TPS-43, the radar van itself, which houses the transmitter, receiver processors, and displays is very similar to the older TPS-43E2. It is produced in the United States originally by Westinghouse Defense and Electronic Division, which was later purchased by Northrop-Grumman.

Asr (radar)

Asr (Persian: رادار عصر‎ Radar) is an Iranian passive electronically scanned array long-range radar unveiled in 2013.

The Air Surveillance Radar or ASR is a 3-D solid state phased array radar, capable of detecting boats, clow flying aircraft with a radar cross section (RCS) of 4 m2 (43 sq ft) at a range of 5–110 nmi (6–127 mi; 9–204 km). The radar is jointly designed and built by the Islamic Republic of Iran Navy and the Ministry of Defence and Armed Forces Logistics (Iran).

Don-2N radar

The Don-2N radar (Russian: Дон-2Н, NATO: Pill Box) is a large missile defense and early warning passive electronically scanned array radar outside Moscow, and a key part of the Russian A-135 anti-ballistic missile system designed for the defense of the capital against ballistic missiles. Located in the Pushkino district of Moscow it is a quadrangular frustum 33 metres (108 ft) tall with sides 130 metres (427 ft) long at the bottom, and 90 metres (295 ft) long at the top. Each of its four faces has an 18 metres (59 ft) diameter Ultra high frequency band radar giving 360 degree coverage. The system is run by an Elbrus-2 (Russian: Эльбрус-2) supercomputer.It has a range of 3,700 km for targets the size of a typical ICBM warhead.Under the 1972 Anti-Ballistic Missile Treaty both the United States and the Soviet Union had to designate one area to protect from missile attack. The USA chose North Dakota and the Soviet Union chose Moscow. The Don-2N radar is designed to be the control centre of the system and can operate autonomously if connection is lost to its command and control centre.

The 1998 SIOP targeted this radar facility with 69 consecutive nuclear weapons.


EMPAR (European Multifunction Phased Array Radar) is a PESA rotating C band multifunction passive electronically scanned array radar built by Selex ES (previously SELEX Sistemi Integrati, since 2016 merged in Finmeccanica, than Leonardo S.p.A.). It is designed to be the principal radar system aboard naval vessels of medium and large sizes. The radar offers full volumetric search coverage, low altitude and surface search, the tracking of multiple targets, and the capability to uplink information for missile guidance.

Giraffe radar

The Saab (formerly Ericsson Microwave Systems AB) GIRAFFE Radar is a family of land and naval two- or three-dimensional G/H-band (4 to 8 GHz) Passive electronically scanned array radar-based surveillance and air defense command and control systems tailored for operations with medium- and Short Range Air Defense (SHORAD) missile or gun systems or for use as gap-fillers in a larger air defense system. The radar gets its name from the distinctive folding mast which when deployed allows the radar to see over nearby terrain features such as trees, extending its effective range against low-level air targets. The first systems were produced in 1977. By 2007, some 450 units of all types are reported as having been delivered.

Military Technical Institute Belgrade purchased a licence for Giraffe 75 and producing a new model with several modifications. Domestic Serbia designation is M85 "Žirafa" on chassis of FAP 2026

Saab Electronic Defence Systems (EDS) on May 2014 unveiled two new classes of active electronically scanned array (AESA) radar—three land-based systems (Giraffe 1X, Giraffe 4A and Giraffe 8A) and two naval variants (Sea Giraffe 1X and Sea Giraffe 4A) in X- and S-band frequencies—to complement its existing surface radar portfolio.

Herakles (radar)

Herakles is a passive electronically scanned array multi-function radar manufactured by Thales Group. It is installed on board the FREMM multipurpose frigates and the Formidable-class frigates of the Republic of Singapore Navy.

It has a track capacity of 400 air and surface targets and is able to achieve automatic target detection, confirmation and track initiation in a single scan, while simultaneously providing mid-course guidance updates to the MBDA Aster missiles launched from the ship.


Irbis-E (Snow Leopard) is a Russian multi-mode, hybrid passive electronically scanned array radar system developed by Tikhomirov NIIP for the Su-35 multi-purpose fighter aircraft. NIIP developed the Irbis-E radar from the Bars radar system used on Sukoi SU-30MK aircraft.


OPS-12 is a shipborne long range air search 3D radar adopting passive electronically scanned array (PESA) technology. It was one of the first PESA radars employed on an operational warship, introduced in 1980 by the Japan Maritime Self-Defense Force.

Organ-pipe scanner

An organ-pipe scanner is a system used in some radar systems to provide scanning in azimuth or elevation without moving the antenna. It consists of a series of waveguides and feed horns arranged in front of a shaped reflector, each one positioned to reflect the beam in a different direction. The wave guides meet at a central point where a small rotating waveguide feeds the microwave signal into each of the horns in turn as it rotates past them.

The system was found in a number of 1950s and 60's era radars, notably the US's AN/FPS-50 radar used in the BMEWS network, and the High Speed Aerial of the UK's RX12874 Passive Detection System. The concept fell from use with the increasing use of passive electronically scanned array, which provided a similar steering mechanism in purely electronic form with no moving parts.

A similar concept is the Foster scanner, which is typically found on lower-power systems like counter-battery radars.


The Pesa is a river in Italy

PESA or Pesa may refer to:

Pesa (currency), a subdivision of the German East African rupie

Percutaneous epididymal sperm aspiration

Passive electronically scanned array

Public Expenditure Statistical Analyses

Pesa SA, Polish train and tram manufacturer

Panchayats (Extension to Scheduled Areas) Act 1996, Indian legislation

Phase shift module

A phase shift module is a microwave network module which provides a controllable phase shift of the RF signal. Phase shifters are used in phased arrays.

Rajendra Radar

Rajendra is a passive electronically scanned array radar developed by the Defence Research and Development Organisation (DRDO), an agency of the Republic of India. It is a multifunction radar, capable of surveillance, tracking and engaging low radar cross section targets. It is the heart of the Akash surface-to-air missile system and is the primary fire control sensor for an Akash battery.


The S1850M is a long range passive electronically scanned array radar for wide area search. The S1850M is produced by BAE Systems Integrated System Technologies (formerly AMS UK) and Thales. It is a modified version of the Thales Nederland SMART-L radar. The S1850M is advertised as being capable of fully automatic detection, track initiation and tracking of up to 1,000 targets at a range of 400 kilometres (250 mi). It is also claimed to be highly capable of detecting stealth targets, and is able to detect and track outer atmosphere objects at short range, making it capable of forming part of a Theatre Ballistic Missile Defence system.

The contract for initial production of the S1850M was signed in 2001; 2 for the UK, 1 for France and 1 for Italy, with a common prototype based in Toulon. In 2005 a follow-on contract was signed for 5 more for the UK, 1 more for France and 1 more for Italy.

An even stronger version of the S1850M is under testing, which is actually an updated version of the current SMART-L radar that the Dutch Navy will call the SMART-L-EWC (Early Warning Capability) Radar. This will have a greater search radius, be capable of detecting ballistic missiles and have a tracking range of 2000 km for ballistic missile defence and 480 km for air defence. SMART-L EWC is an programmable AESA radar which is characterized by full flexibility. Additional capabilities can be introduced during lifetime according to customer needs. This makes the radar future proof in case of evolving requirements.


The Hughes SCANFAR was the first phased array radar system to be deployed by the US Navy, installed on the USS Long Beach (CGN-9) and USS Enterprise (CVN-65). It consisted of two search radars, the AN/SPS-32 and the AN/SPS-33. In 1982, the system was removed from Long Beach, and was replaced by the AN/SPS-48 during a comprehensive overhaul. Aboard the Long Beach, the system used AN/SPG-55 radars for missile guidance.

Despite its failure to enter widespread service, the lessons learned were applied to the follow-on Aegis Combat System and the associated AN/SPY-1 passive electronically scanned array (PESA) radar.


SMART-L (Signaal Multibeam Acquisition Radar for Tracking, L band) is a naval long-range search radar from Thales Nederland, formerly Hollandse Signaalapparaten (Signaal).

The passive electronically scanned array antenna has 24 elements; all are used for reception, while 16 are used for creating virtual receiver beams through digital beamforming. The beams' vertical elevation, and compensation for ship movement, is done electronically. Horizontal training is done by mechanically rotating the entire array.

As designed, SMART-L has a maximum range of 400 km (220 nmi) against patrol aircraft, and 65 km (35 nmi) against stealthy missiles. A software upgrade, Extended Long Range (ELR) Mode, extends the maximum range to 480 km (260 nmi). In 2006 HNLMS Tromp used the ELR Mode to track an ARAV-B missile from 150 km (81 nmi) during a US Navy ballistic missile defence exercise.


SMART-S Signaal Multibeam Acquisition Radar for Tracking, S band is a naval medium to long-range air and surface surveillance multibeam passive electronically scanned array 3D radar designed by Thales Nederland, formerly Hollandse Signaalapparaten (Signaal). SMART-S Mk2 is very successful. Only six years after its introduction, 30 systems were sold to navies all over the world. The radar transmitter/receiver (T/R) modules for the MK-2 are purchased by Thales from ASELSAN of Turkey.The system has two operating modes: medium range up to 150 km (81 nmi) at 27 RPM

and long range up to 250 km (130 nmi) at 13.5 RPM.


Zoopark-1 1L219 is a Counter-battery radar system developed jointly by Almaz-Antey for the Russian Armed Forces. It is a mobile Passive electronically scanned array radar based on a tracked MT-LBu chassis for the purpose of enemy field artillery acquisition. The system can detect moving ground targets at a distance of up to 40 kilometers.

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