There are many types of radar, and the classification method is also very complicated. Generally military radar. It can usually be classified according to the purpose of the radar, such as early warning radar, search warning radar, guidance command radar, gunsight radar, altimetry radar, battlefield surveillance radar, airborne radar, radio altimetry radar, radar fuze, meteorological radar, navigation control radar , Navigation radar, collision avoidance and enemy identification radar, etc.

The advantage of radar is that it can detect long-distance targets both day and night, and is not blocked by fog, clouds and rain. It has the characteristics of all-weather and all-weather, and has a certain penetration ability.

The ultrashort wave communication system is composed of terminal stations and relay stations. The terminal station is equipped with a transmitter, receiver, carrier terminal and antenna. Relay stations only have transmitters and receivers in two directions, and corresponding antennas.

The basic factors of the human body's various physiological reactions caused by ultrashort wave are thermal effect and non-thermal effect.

Compared with other communication methods, ultrashort wave communication has its remarkable characteristics. Ultrashort wave communication uses line-of-sight propagation mode, which is more stable than shortwave sky wave propagation mode. It is affected by seasonal and day-night changes. Small antennas have small size, simple structure and high gain Directional antenna.

Communication using radio waves in the 30-300 MHz band to transmit information. Because the ultrashort wave has a wavelength between 1 and 10 meters, it is also called meter wave communication. The bandwidth of the entire ultrashort wave is 270 MHz, which is 10 times the width of the shortwave band.