Considering the fact that the analog system is not so good as the digital system on the respect of variation of bandwidths and on the respect of switch between different bandwidths . this paper proposes to adopt the dds ( direct digital synthesis ) technique that produces chirp signals of different bandwidths to improve the situation of losing tracks for the ocean satellite altitude indicator in measuring coarse surfaces 现在的雷达基本上采用模拟系统产生线性调频信号，由于模拟系统在带宽变化方面和不同带宽间切换方面不如数字系统，本文采用dds （ directdigitalsynthesis ）技术产生不同带宽的线性调频信号以改善海洋卫星高度计在测量粗糙表面时存在的失锁现象。
