HY-70D radio altimeter works in C band, which is the frequency modulation continuous wave working system. It adopts closed-loop tracking measurement technology, and has the ability to resist asynchronous interference of the same frequency. When multiple aircraft are lifted up and flying at the same time, the altimeter will not interfere with each other; anti blocking, anti burn, power control and beam control, frequency agility or FM technology are adopted to achieve anti-active interference; increase The microwave components are controlled by power supply silently. The antenna is equipped with band-pass filter and the customized radome with frequency selection function is selected to achieve the internal wave transmission rate of working frequency ≥ 85%, and the out band wave transmission rate is less than 10%, and the stealth function is realized.