The role 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 electromagnetic waves. The speed of propagation in vacuum is the speed of light C. The difference lies in their respective frequencies and wavelengths. Its principle is that the transmitter of radar equipment sends electromagnetic wave energy to a certain direction of space through the antenna, and the object in this direction reflects the electromagnetic wave encountered; The radar antenna receives the reflected wave and sends it to the receiving equipment for processing to extract some information about the object (distance from the target object to the radar, distance change rate or radial velocity, azimuth, altitude, etc.).
The principle of measuring distance 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 accurate distance between the radar and the target.
The principle of measuring the target azimuth is to use the sharp azimuth beam of the antenna to measure the elevation beam with narrow elevation angle, so as to calculate the target height according to the elevation angle and distance.
The principle of measuring velocity is the frequency Doppler effect produced by the relative motion between the radar and the target. The target echo frequency received by the radar is different from the radar transmission 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 the target and jamming clutter exist in the same spatial resolution unit of the radar at the same time, the radar can detect and track the target from the jamming clutter by using the difference of Doppler frequency between them.