Synthetic aperture lidar(SAL) is a new active imaging system,which can offer a finer azimuth resolution than conventional SAR systems.The concept of equivalent phase center was described.After analysis of the conflict between the modulation of laser signal and pulse repetition frequency(PRF) of the lidar system,which leads to the ambiguity of the Doppler domain in the azimuth direction,a proper system was given,which uses a series of telescopes placed in the azimuth direction.This system makes u...