Research On Time-frequency Processing Of Underwater Acoustic Beacon Signals

The detection of underwater acoustic beacon signals is in strong demand in marine search and rescue work,and is one of the important subjects of underwater acoustic signal processing.Due to the short pulse of the underwater acoustic beacon signal,it is difficult to detect under long-distance or high background noise conditions,coupled with the actual ocean channel multipath effect,Doppler frequency shift and other effects,it is even more difficult.In this paper,combining the characteristics of underwater acoustic beacon signals,research on high-gain,high-robustness time-frequency processing methods and experimental verification of actual data are carried out.The specific work is as follows:(1)The characteristics of underwater acoustic beacon signals and various factors that affect signal detection are analyzed in detail.Based on this,an improved method of multi-copy correlation integral matching detection and peak line spectrum amplitude correction periodogram detection is proposed to reduce the sensitivity of the algorithm to Doppler shift and improve the performance of beacon signal detection.(2)In order to improve the detection gain of the underwater acoustic beacon signal,using the multi-pulse characteristics of the underwater acoustic beacon signal,a high-gain detection algorithm based on multi-pulse coherent accumulation is proposed.The two-dimensional search overcomes the problem of the degradation of multi-pulse integration performance caused by the deviation of the period and pulse width of the received signal,and improves the integration gain and the detection performance of the detector in the case of low signal-to-noise ratio and channel distortion.(3)A high-gain detection algorithm based on the characteristics of the multi-pulse envelope spectrum is proposed,using the periodic characteristics of the multi-pulse signal of underwater acoustic beacon.It uses frequency domain filtering to improve the Hilbert transform method of extracting the signal envelope and uses the grid search window to extract the multi-pulse envelope spectrum feature,which improve the multi-pulse frequency domain detection performance of the underwater acoustic beacon signal.The method of the thesis has been applied in the actual system and has been verified by the actual lake trial data.