Research On Baseband Code Estimation Of Non-cooperative Underwater Acoustic Communication Signals

Non-cooperative underwater acoustic communication signal interception and analysis is an important subject of underwater acoustic signal processing,and baseband code estimation is one of the problems.The marine environment is complex and changeable,there are many uncontrollable factors of interference,and the influence of complex underwater acoustic channels such as multi-path propagation and dispersion effects increases the difficulty of baseband code estimation.Based on the characteristics of underwater acoustic communication,this paper studies the baseband code estimation algorithm of non-cooperative common underwater acoustic communication signals(PSK,FSK).The specific work is as follows:(1)A baseband code estimation method for PSK underwater acoustic communication signals based on multi-scale analysis code rate estimation is proposed.The effects of unknown signal parameters and the marine environment on the baseband code estimation of PSK underwater acoustic communication signals under noncooperative conditions are analyzed in detail.A PSK code rate estimation method using multi-scale analysis,and multiwavelet-based demodulation and demodulation quality evaluation are proposed.The combined baseband signal optimization method improves the adaptability to the signal distortion caused by the unknown wide parameter range PSK signal and underwater acoustic channel propagation under noncooperative conditions.Finally,based on high-quality baseband signals and code rate information,synchronous search is used to realize the estimation of underwater PSK baseband codes.(2)A method of baseband code estimation for FSK underwater acoustic communication signals by secondary spectrum analysis is proposed.For the unknown underwater acoustic FSK signal,the short window DSTFT is used to realize the rough estimation of the baseband code signal of the signal,and the code rate of the FSK signal is further estimated by the secondary spectral analysis of the coarse estimated baseband code signal,and then the matching is designed based on the estimated code rate Function,and proposed a fast search method of timing synchronization using the dichotomy method to achieve fast estimation of the underwater FSK baseband code.(3)In order to verify the feasibility of the research work in this paper,a large number of laboratory simulation signals and underwater experimental measured underwater acoustic communication signals were calculated and analyzed with baseband codes.The experimental results show that the proposed method has better baseband codes for signals with higher SNR Estimate correctness.