Radar was invented through bats. It is a transliteration of radar in English, which comes from the abbreviation of radio detection and ranging, which means "radio detection and ranging", that is, using radio methods to find targets and determine their spatial position. Therefore, radar is also known as "radio positioning". Radar is an electronic device that uses electromagnetic waves to detect targets. The radar emits electromagnetic wave to irradiate the target and receives its echo, so as to obtain the distance, distance change rate (radial velocity), azimuth, altitude and other information from the target to the electromagnetic wave transmitting point.