Anti-reverberation Camouflage Covert Detection Method By Mimicking Whale Sound

The bionic camouflage covert detection method disguises the detection signal as the call of marine mammals,and realizes the covert detection through camouflage and deception,which has the advantage of being difficult to be identified by the enemy,and has attracted great attention.The core of the bionic camouflage covert detection method is concealment and effectiveness,but due to the characteristics of the bionic objects,its effectiveness needs to be continuously improved.Antireverberation ability is one of the important indicators of detection effectiveness.Research on anti-reverberation methods for camouflage covert detection is very important to improve its detection effectiveness.In this regard,this paper focuses on the bionic covert sonar waveform design and echo signal processing,and research on anti-reverberation methods for camouflage covert detection.The main work is as follows:1.The key indicators of the active sonar waveform and the matched filtering mechanism are given.The double-peak characteristics of clicks’ spectrum of bottlenose dolphins and false killer whales and the characteristics of the timefrequency structure of whale whistles containing chirp-like segments are analyzed.These analyses support for the design of anti-reverberation camouflage covert detection methods.2.Taking bottlenose dolphins and false killer whales as the research object,the anti-reverberation camouflage covert detection method based on the double pulse combination of speed-range measurement is proposed.Analyzed the characteristics of clicks speed and distance resolution,anti-reverberation ability and other characteristics;Aiming at the problem of poor speed resolution of clicks,double high range resolution and fixed time difference clicks are used to design a double pulse combination of speed-range measurement,and based on its Doppler expansion factor,the accurate estimation of target speed and distance is achieved.A camouflage sonar waveform design method based on the double LFM signal model is designed,and the combination of two Gaussian enveloped LFM signals is used to imitate the click sound.And by adjusting LFM pulse width and frequency,it can suppress the sonar waveform distance ambiguity sidelobe,and improve the antireverberation performance of the sonar waveform.3.Taking the whistle with chirp-like segments as the research object,a camouflage sonar waveform design method based on the chirp signal replacement and a matching high-efficiency anti-reverberation echo signal processing method are proposed.Based on the strong reverberation suppression performance of the fractional Fourier transform on the LFM signal,the whale envelope modulated LFM signal is used to replace the LFM-like segment in the whistle,and the LFM replacement camouflage sonar signal that matches the fractional Fourier transform is obtained.The LFM signal rapid positioning method based on the synchronization signal is designed.The front whistle segment connected with the LFM signal is intercepted as the synchronization signal,so that it carries the search step and interval prior information,and the LFM signal is quickly located through the synchronization signal matching filter.And the prior information reduces the search step size and interval,which improves the calculation accuracy of the echo signal processing method while reducing the amount of calculation.4.Aiming at the problem of the fixed width sonar signal that it is difficult to take into account the detection distance and detection blind area,a long-distance and small blind area anti-reverberation camouflage covert detection method imitating "whistle-click superposition" is proposed.Using the LFM replaced camouflage sonar signal and the superimposition of the double pulse combination of speed-range measurement to construct the camouflage sonar signal.The low-frequency,largepulse-width imitation whistle sonar signal is used to detect long-distance targets,and the small-pulse-width double pulse combination of speed-range measurement is used to detect short-distance targets,achieving long-distance and small blind area detection.