Research And Implementation Of Digital Processing Method Of Marine Underwater Acoustic Detection And Acquisition System Under Lévy Noise

With the rapid development of modern science and technology and the continuous improvement of various stealth technologies of underwater targets,coupled with the increasingly complex and changeable marine environment,the signal-to-noise ratio of signals received by various underwater acoustic detection and acquisition systems is lower and lower,and contains strong marine background noise.When the underwater signal is seriously affected by marine noise,the underwater acoustic detection and acquisition system will have high signal-to-noise ratio threshold,limited detection bandwidth The problem that unknown frequency signals cannot be detected effectively.In view of the above problems,this thesis focuses on the marine environmental noise model and the digital processing method of underwater weak signal.Firstly,this thesis studies the sources and characteristics of marine environmental noise and non-Gaussian white noise,and selects Lévy noise model to describe the marine noise environment;Then,the definition and related properties of Lévy process are analyzed and studied,and the generation of Lévy noise is simulated;A parameter estimation method for Lévy noise model is proposed.The experimental results show that this method is effective and applicable.Secondly,aiming at the problem of weak signal detection with known frequency under Lévy noise,an improved FFT-CDDVD detection method is proposed,and a numerical solution is given.Under the Lévy noise with characteristic index ? =1.5,deflection parameter ? =0 and noise intensity D =0.1,the lowest detection signalto-noise ratio of the improved FFT-CDDVD chaotic detection system is reduced by15.8345 d B,10.7022 d B and 8.9726 d B respectively compared with the detection systems of single Duffing oscillator,coupled Duffing oscillator,coupled Duffing and Vander pol Duffing oscillator,which proves that this method is feasible.Then,an improved ST-VSI-CDDVD detection algorithm is proposed to detect the weak signal with unknown frequency under Lévy noise,and the detection performance under different types of Lévy noise models is analyzed.Under the background of Lévy noise with characteristic index ? =1.5,deflection parameter ? =0 and noise intensity D =0.1,the detection error rate of the improved ST-VSI-CDDVD detection system for weak signals with unknown frequency is 0.05%,the lowest detected signal amplitude is A =0.010 V,the lowest detected signal-to-noise ratio is-23.925449 d B,and the frequency of multi-frequency weak signals to be measured can be obtained,and the estimation error of frequency detection is 0.33%.Finally,the digital processing method of marine underwater acoustic detection and acquisition system is realized by FPGA.The experimental verification is carried out with real underwater acoustic data.When the actual underwater acoustic signal frequency is 10 Hz,the detection and estimation frequency of the system is9.9946 Hz and the estimation error rate is 0.054%.Experiments show that the digital processing method proposed in this thesis and the use of the Lévy noise model to describe the marine noise environment are feasible and effective in practical application.