DIGITAL CORRELATION RECEIVER FOR ACTIVE SONAR SIGNAL

Abstract

A new algorithm for a Digital Correlation Receiver for active sonar signal has been developed. By applying Doppler-shift compensation to the outputs of the filter banks employed in the receiver, a "Composite Display" of the correlation result which enables the exact number of targets detected to be determined has been developed. On the basis of the Composite Display, a "Linear Estimation" technique has been developed to calculate accurately the velocity and position of the targets. Simulation results show that our proposed algorithm can achieve a much higher resolution both in position and in velocity while the computation load increases by only a small percentage comparing with the traditional techniques An system based on the ADSP-21062 has been built to demonstrate the real-time processing capability of our proposed receiver. Most of the time critical programs are written in assembly language to fully exploit the capability of the DSP hardware. Tests show that this experimental system can perform real-time processing without any stall. A user-friendly Windows 95 based control interface has also been developed. The performance of the LFM, HFM and PN-coded BPSK waveforms and their respective ambiguity functions have been investigated. It is found that the HFM waveform is suitable for search mode while the PN-coded BPSK waveform has the highest range resolution. The traditional LFM waveform is still the best choice according to simulation results due to our proposed new algorithm, which greatly improves its resolution in velocity and range.