Modeling And Simulation For LFMCW Radar Altimeter System

Radar altimeter's measurement of the altitude of an aircraft is based upon the measurement of the time elapsing between the transmitted signal and its return after reflection by the target. It has a widely application in civil and military field. Radar altimeter's high measurement precision is paid attention to all the time.Firstly, this chapter modeling the fluctuant terrain and its echo, simulating and analyzing the method of signal processing of radar altimeter. We use fluctuant terrain model to model the actual ground in the situation of unable to do outfield experiment, from the result we know that the bit spectrum corresponding to fluctuant terrain is broaden and shifted while the forward edge of spectrum is fixed, because of above this chapter adopt the technology of forward edge of spectrum detected to get the lowest height. Because of the fixed precision error aroused by fence effect of FFT, this chapter adopts the method of Chirp-z spectrum subdivision to get high precision. The measured height has a large fluctuation when the aircraft has both horizontal and vertical velocity, so this chapter carrying outα-βfilter to smooth and track the height.Finally, we use the method of Chirp-z spectrum subdivision andα-βfilter in a LFMCW radar altimeter, and we realize high measurement precision whose relative error is less than 1% and get a real-time tracking of height in the situation of fixed bandwidth.