一种扩展水下扩频信号多普勒容限方法

扩频信号的模糊函数图呈图钉型,对多普勒频移比较敏感,影响了扩频信号的使用性能.本文分析了扩频信号的多普勒敏感性问题,提出了一种基于回波预处理的方法.首先将回波信号经过正交混频得到零中频I,Q通道信号,然后将零中频I,Q通道信号送入多普勒预处理系统进行处理,通过时间延迟处理方法得到的2个输出信号,分别经过匹配滤波器后再进行合并处理,脉压输出相关函数中不含多普勒频移和时间乘积,消除了多普勒频移对匹配滤波器输出的影响.数值仿真证明了该方法的有效性,且具有实现简单,运算量小的优点.

A Method for Extending Doppler Tolerance of Underwater Spread Spectrum Signal

Spread spectrum signal is sensitive to Doppler frequency shift, which limits the service property of the spread spectrum signal. This paper proposes a method for echo pre-processing by analyzing the sensitivity of spread spectrum signal to Doppler frequency shift. Zero intermediate frequencyI, Q channel signals are obtained through the orthogonal frequency mixing of echo. Then the signals are processed in the echo pre-processing system to obtain two output signals by time-delay processing method. The two output signals are further processed by a matching filter to achieve a combined signal which doesn＇t contain Doppler frequency shift and time product. Numerical simulation demonstrates the validity of the proposed method with simplicity and smaller amount of computation.