星载雷达高度计系统设计及测高精度分析

Design of a Spaceborne Radar Altimeter System with it's Height Precision Analysis

在总结机载海洋雷达高度计研制及其飞行实验的基础上，根据海面回波的性质，设计了一个星载雷达高度计系统。系统工作在脉冲有限足迹方式，发射脉冲为线性调频（Ｃｈｉｒｐ）脉冲，接收系统采用“全去斜坡”技术及频谱分析方法将海面回波信号从时域转换至频域处理，自适应跟踪器可抑制大于７５％的噪声，高脉冲重复频率使有效独立脉冲数达到最大，保证最大限度地抑制海面斑点噪声；设计了系统的主要工作模式：双分辨率捕获跟踪模式使海面回波信号的捕获时间小于５ｓ，定标模式可保证系统达到设计的测高精度；分析了主要噪声，即海面斑点噪声和接收机热噪声对高度估值的影响，通过对几种典型海况海面回波的模拟分析表明，系统则高精度可达±２ｃｍ。

Based upon the development and flight experiments of the airborne radar altimeter, and according to the characteristics of the signal returned from ocean surface, a spaceborne radar altimeter system is designed. The system operates on pulse limited mode, transmitting pulses are FM Chirp pulses, the returned signal is processed in receiver in frequency domain instead of time domain by adopting “Full De ramp” technique and frequency spectrum analysis method. Adaptive tracker can remove about 75% of the noise power. High pulse repetition rate results in maximum effective number of independent pulses and are best effective in eliminating ocean surface backscatter speckle noise. The main operating modes are desiged: dual resolusion acquisition and tracking mode makes acquisition time of the returned signal within 5 s, calibration mode can assure the designed height precision. The effects to height evaluation of the main noises, i.e. ocean surface backscatter speckle noise and receiver thermal noise, are analyzed. By analyzing the returned signals of several typical sea states, the results have shown that the system height measurement precision can be ±2cm.