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 frequency I, 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.