radar
radar
This data is reviewed by the project of data compilation and application of Science Encyclopedia of science popularization in China.
Radar, a transliteration of radar, is derived from the abbreviation of radio detection and ranging, which means "radio detection and ranging", that is to use radio method to find targets and determine their spatial position. Therefore, radar is also called "radio location". Radar is an electronic equipment that uses electromagnetic wave to detect targets. Radar transmits electromagnetic wave to irradiate the target and receive its echo, so as to obtain the distance, range change rate (radial velocity), azimuth, altitude and other information from the target to the electromagnetic wave transmitting point.
origin
The emergence of radar was due to the fact that during the war between Britain and Germany, Britain urgently needed a kind of radar (Technology) which could detect metal objects in the air and help to search for German aircraft in the anti air war. During World War II, radar technology with the functions of ground to air, air to ground (search) bombing, air to air (intercept) fire control and IFF has appeared. after World War II, radar developed new radar systems, such as monopulse angle tracking, pulse Doppler signal processing, high resolution of synthetic aperture and pulse compression, combined system of IFF, automatic fire control system combined with computer, terrain avoidance and terrain following, passive or active phase array, frequency agility, multi-target detection and tracking, etc. later, with the progress of microelectronics and other fields of science and the continuous development of radar technology, its connotation and research content are constantly expanding. The detection method of radar has developed from only radar detector to the integration of infrared, ultraviolet, laser and other optical detection methods. the multi-function capability of contemporary radar makes battlefield commanders scan targets in various search / track modes and automatically correct jamming errors. Moreover, most of the control functions are completed within the system. Automatic target identification (ATR) can make the weapon system play its role to the maximum extent. The integrated radar system with battlefield IFF capability such as AWACS and jstars has actually become the information command center in the future battlefield.
Development history
In 1842, Austrian physicist Christian Andreas Doppler first proposed a Doppler radar using Doppler effect. In 1864, the British physicist James Clerk Maxwell deduced a formula for calculating the characteristics of electromagnetic waves. In 1886, German physicist Heinrich Hertz launched a series of experiments to study radio waves. In 1888, Hertz successfully used instruments to generate radio waves. In 1897, J. J. Thomson began to study cathode rays in vacuum tubes. in 1904, Christian h ü lsmeyer invented the teleobilloscope, which is a device using radio wave echo detection to prevent collision between ships at sea. In 1906, deforest Lee invented vacuum triode, which is the first active electronic component in the world to amplify signals. In 1916, Marconi and Franklin began to study the reflection of short wave signal. In 1917, Robert Watson watt successfully designed a thunderstorm location device. In 1922, Marconi delivered a speech at the American Institute of electrical and radio engineers on the topic of plane angle radar to prevent collision between ships. In 1922, Taylor and Yang proposed to equip two warships with high frequency transmitters and receivers to search for enemy ships. In 1924, Appleton and Barnett measured the height of ionosphere by reflecting radio waves from the ionosphere. In the United States, Blair and Duff used pulse waves to measure the Haversian layer. 1925 Baird（ JohnL.Baird ）Invention of mobile TV (the predecessor of modern TV). In 1925, Gregory Breit, in cooperation with Merle Antony tuve, successfully used radar for the first time to display short radio pulses reflected from the ionosphere on cathode ray tubes. In 1931, the U.S. Naval Research Laboratory used beat frequency principle to develop radar, and began to let the transmitter transmit continuous wave. Three years later, it switched to pulse wave. in 1935, guton, France, developed a magnetron to generate a signal with a wavelength of 16 cm, which can detect other ships in foggy days or at night. This is the beginning of the peaceful use of radar. In 1935, Robert Watson Watt invented the first practical radar. In January 1936, Robert Watson watt set up Britain's first radar station on the coast of sofuk. The British air force added five more, which played an important role in the Second World War. In 1937, Marconi Company built 20 additional chain direction radar stations for Britain. In 1937, the first US warship radar XAF test was successful. In 1937, Russell and Sigurd Varian developed a high-power microwave oscillator, also known as klystron. Henry boot and Randall in 1939（ JohnT.Randall ）Invented electron tube, also known as resonant cavity magnetron. in 1941, the Soviet Union first equipped early warning radar on aircraft. In 1943, MIT developed the airborne radar plane position indicator and early warning radar. In 1944, Marconi Company successfully designed, developed and produced bagful system and carpet radar jamming system. The former was used to intercept German radio communications, while the latter was used to equip the RAF's bombing fleet. after the end of World War II in 1945, the Allied forces were able to defeat Germany only by the radar equipped with specially designed vacuum tube magnetron. In 1947, the bell telephone laboratory developed the linear frequency modulation pulse radar. In the mid-1950s, the United States was equipped with the over range early warning radar system, which can explore supersonic aircraft. The pulse Doppler radar was developed soon. In 1959, the US General Electric Company developed a ballistic missile early warning radar system, which can track missiles 3000 miles away and 600 miles high. The early warning time is 20 minutes. in 1964, the United States installed the first space orbit surveillance radar to monitor man-made earth satellites or space vehicles. in 1971, three people invented holographic matrix radar. At the same time, digital radar technology appeared in the United States. In 1993, Dreher McGill in Manchester, the United States, invented the multi tower chuck super intelligent radar.
working principle
The specific uses and structures of various radars are different, but the basic forms are the same, including transmitter, transmitting antenna, receiver, receiving antenna, processing part and display. There are power supply equipment, data acquisition equipment, anti-interference equipment and other auxiliary equipment. the function of radar is similar to that of eyes and ears. Of course, it is no longer a masterpiece of nature. At the same time, its information carrier is radio waves. In fact, both visible light and radio waves are essentially the same thing. They are all electromagnetic waves. The speed of propagation in vacuum is the speed of light C. The difference lies in their respective frequencies and wavelengths. The principle is that the transmitter of radar equipment shoots the electromagnetic wave energy to a certain direction in space through the antenna, and the object in this direction reflects the electromagnetic wave; the radar antenna receives the reflected wave, sends it to the receiving equipment for processing, and extracts some information about the object (distance between the target object and the radar, range change rate or radial velocity, azimuth, height, etc.). the principle of velocity measurement is the frequency Doppler effect produced by the relative motion between radar and target. The target echo frequency received by radar is different from the radar transmitting frequency, and the difference between them is called Doppler frequency. One of the main information that can be extracted from Doppler frequency is the range change rate between radar and target. When target and jamming clutter exist in the same spatial resolution unit of radar, radar can detect and track target from jamming clutter by using the difference of Doppler frequency between them. The principle of measuring the target azimuth is to use the sharp azimuth beam of the antenna to calculate the target altitude according to the elevation and distance by measuring the narrow elevation beam. the principle of distance measurement is to measure the time difference between the transmitted pulse and the echo pulse. Because the electromagnetic wave propagates at the speed of light, it can be converted into the precise distance between the radar and the target.
classification
There are many kinds of radar, and the classification method is also very complex. Generally, it is military radar. Generally, it can be classified according to the use of radar, such as early warning radar, search warning radar, guidance and command radar, gun aiming radar, altimeter radar, battlefield surveillance radar, airborne radar, radio altimeter radar, radar fuze, weather radar, navigation control radar, navigation radar, anti-collision and IFF radar, etc. 1. According to the radar
Chinese PinYin : Lei Da
radar
