针对雷达高度表二相编码回波信号受多普勒和回波相位差双重调制问题，在深入分析雷达高度表回波信号模型及回波功率分布特征的基础上，提出了基于天底点的二相编码解调算法。该算法通过检测天底点回波中的多普勒和相位差信息，进行相应补偿从而实现码解调。仿真和实验表明：该算法多普勒频率检测误差小于20 Hz，相位检测误差小于2°，可有效实现码解调。

The binary-phase-coded echo signal is modulated by both Doppler and the echo phase displacement.Aiming at this problem,we analyzed the echo model and the power distribution characteristic of the echo signal of radar altimeter,and proposed a demodulation algorithm for the binary-phase-coded echo signal based on nadir point.In the algorithm,the Doppler and the phase displacement information of the nadir point echo was detected,and corresponding compensation was made to realize demodulation.Simulation and experiment results show that the maximum error of the Doppler frequency is less than 20 Hz and the maximum error of the phase is less than 2°.It proves that the algorithm is effective to demodulate the echo signal.