Radar is a system that uses radio waves to determine the distance (ranging), direction, and radial velocity of objects relative to the site. It is a radiodetermination method used to detect and track aircraft, ships, spacecraft, guided missiles, motor vehicles, map weather formations, and terrain.
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. The general theory of an electromagnetic phased array also finds applications in ultrasonic and medical imaging application and in optics optical phased array.
A radio telescope is a specialized antenna and radio receiver used to detect radio waves from astronomical radio sources in the sky. Radio telescopes are the main observing instrument used in radio astronomy, which studies the radio frequency portion of the electromagnetic spectrum emitted by astronomical objects, just as optical telescopes are the main observing instrument used in traditional optical astronomy which studies the light wave portion of the spectrum coming from astronomical objects. Unlike optical telescopes, radio telescopes can be used in the daytime as well as at night.
PAVE PAWS is a complex Cold War early warning radar and computer system developed in 1980 to "detect and characterize a sea-launched ballistic missile attack against the United States". The first solid-state phased array deployed used a pair of Raytheon AN/FPS-115 phased array radar sets at each site to cover an azimuth angle of 240 degrees. Two sites were deployed in 1980 at the periphery of the contiguous United States, then two more in 1987–95 as part of the United States Space Surveillance Network. One system was sold to Taiwan and is still in service.
A Yagi–Uda antenna, or simply Yagi antenna, is a directional antenna consisting of two or more parallel resonant antenna elements in an end-fire array; these elements are most often metal rods acting as half-wave dipoles. Yagi–Uda antennas consist of a single driven element connected to a radio transmitter or receiver through a transmission line, and additional passive radiators with no electrical connection, usually including one so-called reflector and any number of directors. It was invented in 1926 by Shintaro Uda of Tohoku Imperial University, Japan, with a lesser role played by his boss Hidetsugu Yagi.
Chain Home, or CH for short, was the codename for the ring of coastal early warning radar stations built by the Royal Air Force (RAF) before and during the Second World War to detect and track aircraft. Initially known as RDF, and given the official name Air Ministry Experimental Station Type 1 in 1940, the radar units were also known as Chain Home for most of their life. Chain Home was the first early warning radar network in the world and the first military radar system to reach operational status. Its effect on the war made it one of the most powerful systems of what became known as the "Wizard War".
Operation Biting, also known as the Bruneval Raid, was a British Combined Operations raid on a German coastal radar installation at Bruneval in northern France, during the Second World War, on the night of 27–28 February 1942.
Direction finding (DF), or radio direction finding (RDF), is the use of radio waves to determine the direction to a radio source. The source may be a cooperating radio transmitter or may be an inadvertant source, a naturally-occurring radio source, or an illicit or enemy system. Radio direction finding differs from radar in that only the direction is determined by any one receiver; a radar system usually also gives a distance to the object of interest, as well as direction. By triangulation, the location of a radio source can be determined by measuring its direction from two or more locations. Radio direction finding is used in radio navigation for ships and aircraft, to locate emergency transmitters for search and rescue, for tracking wildlife, and to locate illegal or interfering transmitters. During the Second World War, radio direction finding was used by both sides to locate and direct aircraft, surface ships, and submarines.
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. 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).
Freya was an early warning radar deployed by Germany during World War II; it was named after the Norse goddess Freyja. During the war, over a thousand stations were built. A naval version operating on a slightly different wavelength was also developed as the Seetakt.
Beamforming or spatial filtering is a signal processing technique used in sensor arrays for directional signal transmission or reception. This is achieved by combining elements in an antenna array in such a way that signals at particular angles experience constructive interference while others experience destructive interference. Beamforming can be used at both the transmitting and receiving ends in order to achieve spatial selectivity. The improvement compared with omnidirectional reception/transmission is known as the directivity of the array.
A fire-control radar (FCR) is a radar that is designed specifically to provide information to a fire-control system in order to direct weapons such that they hit a target. They are sometimes known as narrow beam radars, targeting radars, tracking radars, or in the UK, gun-laying radars. If the radar is used to guide a missile, it is often known as a target illuminator or illuminator radar.
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, in which all the antenna elements are connected to a single transmitter and/or receiver. 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 in World War II greatly influenced many important aspects of the conflict. This revolutionary new technology of radio-based detection and tracking was used by both the Allies and Axis powers in World War II, which had evolved independently in a number of nations during the mid 1930s. At the outbreak of war in September 1939, both the United Kingdom and Germany had functioning radar systems. In the UK, it was called RDF, Range and Direction Finding, while in Germany the name Funkmeß (radio-measuring) was used, with apparatuses called Funkmessgerät . By the time of the Battle of Britain in mid-1940, the Royal Air Force (RAF) had fully integrated RDF as part of the national air defence.
The Wasserman radar was an early-warning radar built by Germany during World War II. The radar was a development of FuMG 80 Freya and was operated during World War II for long range detection. It was developed under the direction of Theodor Schultes, beginning in 1942. Wasserman was based on largely unchanged Freya electronics, but used an entirely new antenna array in order to improve range, height-finding and bearing precision.
The FuG 200 Hohentwiel was a low-UHF band frequency maritime patrol radar system of the Luftwaffe in World War II. It was developed by C. Lorenz AG of Berlin starting in 1938 under the code name "Hohentwiel", an extinct volcano in the region of Baden-Württemberg in southern Germany.
Eglin AFB Site C-6 is a United States Space Force radar station which houses the AN/FPS-85 phased array radar, associated computer processing system(s), and radar control equipment designed and constructed for the U. S. Air Force by the Bendix Communications Division, Bendix Corporation. Commencing operations in 1969, the AN/FPS-85 was the first large phased array radar. The entire radar/computer system is located at a receiver/transmitter building and is supported by the site's power plant, fire station, 2 water wells, and other infrastructure for the system. As part of the US Space Force's Space Surveillance Network its mission is to detect and track spacecraft and other manmade objects in Earth orbit for the Combined Space Operations Center satellite catalogue. With a peak radiated power of 32 megawatts the Space Force claims it is the most powerful radar in the world, and can track a basketball-sized object up to 22,000 nautical miles (41,000 km) from Earth.
Selex RAN-40L is a naval 3D L band search radar developed by Leonardo. The radar is used for long range maritime air surveillance and early warning. The radar uses a fully solid state active phased array antenna and capable of tracking and detecting air targets like aircraft or drones up to 400 km away. RAN-40L is based on existing land based 3D RAT-31DL radar which is a system widely used by NATO Countries for long air surveillance.
German Luftwaffe and Kriegsmarine Radar Equipment during World War II, relied on an increasingly diverse array of communications, IFF and RDF equipment for its function. Most of this equipment received the generic prefix FuG, meaning "radio equipment". During the war, Germany renumbered their radars. From using the year of introduction as their number they moved to a different numbering scheme.
The Multi-role Electronically Scanned Array (MESA) is an active electronically scanned array surveillance radar system for the Boeing E-7 Wedgetail airborne early warning and control aircraft. The radar is produced by Northrop Grumman.
