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. Therefore, it has not only become an indispensable military equipment, but also widely used in social and economic development (such as weather forecast, resource detection, environmental monitoring, etc.) and scientific research (astronomical research, atmospheric physics, ionospheric structure research, etc.). Spaceborne and airborne synthetic aperture radars have become very important sensors in remote sensing today. Ground-targeted radar can detect the precise shape of the ground. Its spatial resolution can reach several meters to several tens of meters, and it has nothing to do with the distance. Radar also shows good application potential in flood monitoring, sea ice monitoring, soil moisture survey, forest resource inventory, and geological survey.