为使星载激光高度计实现高空间分辨率，提出了一种联合采用伪随机码(PRC)相位调制光纤激光器和外差探测的测距方法。推导了用于测高时的信噪比公式。对激光发射功率、参考光功率、望远镜口径、调制速率以及PRC序列长度对信噪比和距离分辨率的影响进行了数值模拟。对系统参数进行分析，得到了相关参数的关系和优化的参数。结果表明,当激光出射功率约为10 W，参考光功率约为10 mW，望远镜口径为0.4 m，调制速率为1 GHz，单周期内PRC序列长度约为300 μs时，基于PRC相位调制和外差探测的星载激光测高计能够实现系统信噪比为10和距离分辨率为15 cm的设计目标。

A method base on the techniques of pseudorandom code (PRC) phase modulation of the fiber laser and heterodyne detection to realize a high spatial resolution for the space-borne laser altimeter is proposed. The altimeter′s equation of the signal to noise ratio is deduced. The relations between the signal to noise ratio and range resolution with the laser transmit power, local oscillator power, telescope aperture, modulation rate and pseudorandom code length are numerically simulated. The relations between the parameters and the optimized parameters are obtained after the system analysis. Results show that the space-borne altimeter can achieve the design objective of the signal to noise ratio of 10, and the distance resolution of 15 cm when the transmit laser power is about 10 W, local oscillator power is about 10 mW, telescope aperture is 0.4 m, modulation rate is 1 GHz, and PRC length is about 300 μs in a single periodic time.