Mechanism and experiment of code intensity-modulation on synthetic aperture ladar

Synthetic aperture ladar is a generalization of the synthetic aperture technique in the field of laser coherent detection with a higher resolution compared with the conventional synthetic aperture radar. Due to the frequency modulation rate and frequency nonlinear, the traditional frequency modulated mode can't be applied on the high-speed platform. In this article, combined with optical communication modulation method, the functions of synthetic aperture ladar imaging based on the pseudo code intensity modulation were deduced in detail and the compression performances of M codes were simulated simultaneously. By analyzing the ambiguity function, it proves that the pseudo code intensity modulation signal is not affected by the multi value ambiguity or the intercoupling error. An experiment system of the pseudo code intensity modulation was set up by fiber of 2 000 m to test the range resolution with M codes in length of 1 023 and code width of 5 ns. Under consideration of intensity jitter of the signal carrier, a range resolution of 0.787 5 m with 5% accuracy error was obtained. Through the above analysis, it has been proved that synthetic aperture ladar based on the pseudo code intensity modulation is feasible in theory and experiments and it provides practical support for the project implementation.