For fighters, radar is the eye. Today, the performance of airborne radar will directly affect the outcome of air combat. Therefore, what kind of radar a fighter is equipped with has become one of the important standards to measure its combat capability. For example, Russia's su-57 fighters are said to be equipped with multiple radars, have a circular field view and have the ability to track and strike multiple targets. The forward-looking X-band radar installed at the nose has a maximum detection range of 350-400 km. The "combination" of the "beetle" - AME active phased array radar developed by fazotrong Radar Research Institute and the MiG-35 fighter makes the latter "reach the full state". Not long ago, an American company developed a compact airborne active phased array radar with a weight of about 50kg, light weight and low cost. It is expected to be installed on a variety of aircraft, including UAVs and helicopters. This indicates that the current and future R & D and competition among countries in this regard will continue. Airborne radar: sharp aerial "eagle eye" ■ Liu Chuanwu, Luo nailing, Zhang Hao "Beetle" - AME radar of MiG-35 fighter The continuous evolution of airborne radar makes fighters "hear and see" Airborne radar is vividly called "eagle eye" in the air. The world's first airborne radar appeared in Britain. In response to enemy submarines, Britain conducted the first radar air test in 1937. The radar can also be used to assist carrier aircraft to take off and land on warships. After more than 80 years of development, countries around the world have developed a variety of radars with different systems and uses. Their functions have already broken through the scope of initial ranging, velocity and direction finding, and expanded to high-resolution map mapping, meteorological detection, target recognition and electronic countermeasure. According to different functions and carrier platforms, airborne radars are generally divided into the following types: Weather navigation radar: usually equipped with transport aircraft and helicopters, it is mainly used for dangerous weather detection such as thunderstorm, turbulence and wind shear to guide the carrier to avoid flight. Early warning radar: generally equipped with large early warning command aircraft, it is used for battlefield long-range early warning and air command and guidance. Search and monitoring radar: usually equipped with large and medium-sized transport aircraft and UAVs, it is mostly used to search and monitor sea targets, and some have submarine search function. Imaging reconnaissance radar: it is mainly equipped with large and medium-sized transport aircraft and UAVs. Through synthetic aperture radar (SAR) imaging, it can carry out imaging reconnaissance on land and sea battlefield and monitor ground and sea targets. Some radars have the function of monitoring air dynamic targets. Multifunctional fire control radar: it is usually equipped with fighter, bomber, etc. it generally has the functions of multi-target search and tracking, map mapping, meteorological navigation, etc. it is mainly used for the search, tracking and weapon guidance of air, ground and sea targets. Among them, the performance of airborne fire control radar is closely related to the "door-to-door" effect of fighter attack. The original airborne fire control radar adopts the pulse system, which depends on transmitting microwave pulse signal and detecting echo pulse to determine whether the target exists and distance. Because the ground echo intensity is much greater than the air target echo intensity when looking down, the airborne fire control radar with simple pulse system does not have the ability to look down and guide weapons to shoot down. In addition, this method is easy to be disturbed by the enemy, and the accuracy is not high. In the 1950s, pulse Doppler fire control radar appeared. This radar uses the pulse Doppler effect and the difference between the perceived moving target echo and the ground echo frequency under the flight state to suppress the ground echo and detect the concealed moving target echo, so as to have the ability to detect the low altitude flying target under the down view. After that, pulse Doppler fire control radar has experienced the development process from reflector antenna to low sidelobe plate slot array antenna, from analog signal processing to digital signal processing and digital control display. With the emergence of fighter fire control radar with high, medium and low pulse repetition frequency full waveform and digital signal processing capability, the fighter has the ability of omni-directional detection and simultaneous multi-target search and tracking. Typical pulse doppler radars include an / APG-68 radar equipped with F-16 series aircraft, an / apg-73 radar equipped with F-18 series aircraft, an / apg-78 "Longbow" radar equipped with Apache armed helicopter, Grifo series radar of Italy, captor radar of European radar group, and "beetle" series radar of Russia. Pulse Doppler radar can guide medium range air-to-air missiles to attack, and also has the ability to search, track and guide attacks on ground and sea targets, as well as high-resolution imaging of ground targets. However, due to the limitations of antenna mechanical scanning, transmitter power and working bandwidth, the development of pulse Doppler radar also has a bottleneck, which is difficult in detection range, multi-target tracking Reliability and anti-interference further. Therefore, active phased array radar came into being. The antenna of active phased array radar is different from that of pulse Doppler radar. The core of its antenna is hundreds of transceiver components (T / R components), each of which contains a group of small transmitters, receivers and phase shifters. Radar beam scanning can be realized by adjusting the phase of the transmitted and received signals of the phase shifter in each T / R module. This scanning has no inertia limitation of mechanical scanning, so it can realize the agility (jump) of beam scanning and improve the multi-target tracking performance and anti-interference ability. Limited by the traveling wave tube transmitter, the working bandwidth of pulse Doppler radar is difficult to exceed 1 GHz. Now the working bandwidth of active phased array radar can reach the level of 4 GHz, which greatly improves the anti-jamming ability. As a result, the radars of some fourth generation aircraft have acquired the capabilities of EW reconnaissance, jamming and data link guidance weapons. For example, when implementing high gain electronic support (reconnaissance) and high-power electronic countermeasure (jamming) in electronic warfare, the traditional airborne EW system can only intercept and reconnaissance the opponent's radar main lobe signal, while some fourth generation aircraft radars can intercept and reconnaissance the long-range radar side lobe signal. In the long-range high-power suppression and jamming of enemy radar, the jamming effective power of traditional airborne EW system can only reach the order of 100 watts, and the jamming effective power of some fourth generation aircraft radars can reach more than 1 MW. MiG-35 fighter New combat methods are pushing radar performance to the extreme Modern air combat is developing along the direction of over the horizon combat, emphasizing first discovery and first attack. New combat methods are pushing radar performance to the extreme. At present, in the theory of over the horizon air combat, the air-to-air combat area has been subdivided into different areas such as situation awareness, engagement / avoidance decision, over the horizon attack, threat avoidance and threat confrontation. Each area has a clear boundary and requirements for sensors. Therefore, the engineer specially designed a variety of targeted radar working modes to give full play to the technical advantages of active phased array fire control radar, such as air advantage mode, advanced air-to-air mode, advanced strike mode, electronic countermeasure mode, etc. These working modes include some sub modes. For example, the air superiority mode includes search plus tracking and short-range combat sub modes. The advanced air-to-air mode includes search while ranging, scanning while tracking, single target tracking, intrusion group target resolution sub modes, etc. Air superiority mode is a highly automated air combat mode, which is usually used in the fierce air combat confrontation stage. In this mode, the radar searches for the target in the designated airspace, automatically intercepts, finds the target and turns to the tracking state, which can effectively reduce the working pressure of pilots operating the radar in air combat. In the advanced air-to-air mode, pilots have many operation options, which are mainly used for long-range situational awareness to prepare for fierce air combat confrontation. The advanced strike mode is set for map navigation, reconnaissance and mapping and ground / sea target strike. The pilot operates the radar to search the designated area, finds the target, enters the interception and tracking, and guides missiles, bombs and other missiles to attack fixed or moving targets. With the current fighters paying more attention to multi services and multi aircraft cooperative operation, airborne radar has also been given more and stronger capabilities in this regard to support fighters to achieve a high degree of cooperation by sharing battlefield information. The combination of early warning radar carried by early warning command aircraft and multi-functional fire control radar equipped by fighters, attack aircraft and bombers is common. The early warning radar of some early warning aircraft can detect medium-sized fighters at a distance of more than 400 kilometers and process more than 2000 batches of targets, which can detect enemy incoming aircraft in advance. In order to realize the cooperation among multiple aircraft and types of aircraft in combat aircraft formation, the new generation of airborne radar is developing the capabilities of "cooperative detection", "cooperative jamming" and "cooperative attack". Su-57 fighter The future air battlefield calls for better coordination of airborne radar A major feature of the future battlefield is accompanied by high-intensity and complex electromagnetic countermeasures. This game based on the systematic architecture requires an airborne detection and sensing system with stronger function, performance and anti electromagnetic attack ability. In the future, the development of airborne radar will not only pursue the performance of a single airborne radar, but pay more attention to the cooperation between radar and external platforms. Fusion with other electromagnetic sensors. In addition to radar, airborne electromagnetic sensors also include electronic warfare system, data link and photoelectric detection and tracking system. In the future, the direction of airborne radar and its fusion includes cooperative detection, fusion of detection information and integration of physical entities. Through the cooperative detection of heterogeneous multi-sensor and the fusion of detection information, the acquisition source of information can be increased, the dimension and reliability of information can be increased, the possibility of radiation signal interception can be reduced, and the anti-interference ability can be improved. The fusion of physical entities can greatly reduce the volume, weight and power consumption of the sensor system, which is very important for the carrier platform. Some advanced fourth generation machines have realized a certain degree of electromagnetic sensor fusion. It is mainly reflected in the following aspects: using advanced radio frequency electronic technology and bus technology, the traditional independent sensors such as radar, electronic warfare and communication navigation identification are integrated to form a multi spectrum, multi means and adaptive integrated avionics system; Realize antenna sharing by region and frequency division, reduce the number of antennas, not only meet the stealth requirements of carrier aircraft, but also reduce weight, volume and cost; Reduce the types of modules, realize module sharing and reduce the cost of maintenance; The use of centralized and unified core processor is conducive to information fusion and sharing of backup processing capacity. Integrated with distributed target aware network. One of the main characteristics of systematic operation is multi platform distributed target detection, intelligence acquisition and electromagnetic countermeasure, as well as networked cooperative operation and information sharing. In the future, only by further integrating the airborne radar into the distributed target sensing network, can it take advantage of the advantages of multi platform distributed detection to better combat stealth aircraft and electromagnetic interference, reduce the requirements for the comprehensive performance of a single radar, and adapt to new combat styles such as manned unmanned cooperation and unmanned drone swarm combat in the future. Integrated with the carrier platform body. The airborne integrated electromagnetic sensor with radar function as the core is realizing conformal with aircraft skin through ultra-thin and lightweight. This design can expand the antenna area and reduce the radar scattering area. In the future, this integration will gradually move towards "intelligent skin"; The detection is realized through the layout of multiple antennas distributed on the body