Research On Design Of Active Sonar Anti-reverberation Waveform

Reverberation is one of the main interferences of active sonar systems,which seriously restricts the detection performance of the system.And the generation mechanism of reverberation causes the reverberation signal to have a strong correlation with the transmitted signal,which makes it impossible to easily separate the echo signal from the reverberation signal when the target echo is processed at the receiving end,which increases the complexity of echo signal processing.Therefore,how to suppress the reverberation signal has always been a hot and difficult point in the research of active sonar signal processing.Aiming at the above problems,in order to improve the detection performance of the active sonar system in the reverberation background,this paper starts from the perspective of waveform design,and realizes the effective suppression of reverberation interference by designing the optimal anti-reverberation waveform.This paper mainly studies the design of anti-reverberation waveforms for the detection of low-speed moving targets and randomly extended stationary targets.First,the theoretical basis of anti-reverberation waveform design is introduced.The basic concept,category and difference between reverberation signal and common ocean noise are expounded,and a reverberation model that uses scattering function to generate submarine reverberation is given.At the same time,two waveform analysis tools,ambiguity function and Q function,are introduced to compare the performance of different transmitted signals,and the resolution and anti-reverberation performance of commonly used sonar signals are analyzed.In addition,the principle of matched filter technology and the process of target echo detection are described in detail,thus providing a theoretical basis for the design of anti-reverberation waveforms.Then,the CutFM waveform is designed for the problem of low speed moving target detection.Because the existing wideband doppler sensitive signal cannot have good antireverberation ability and excellent distance resolution at the same time,a new doppler sensitive signal CutFM signal based on LFM signal is designed in this paper.In this paper,the cutting signal is used to cut the LFM signal,so that certain gaps appear periodically in the frequency spectrum,so that the signal has Doppler sensitivity while ensuring a certain distance resolution.The analysis of ambiguity function and Q function shows that CutFM signal has similar antireverberation ability and better distance resolution to SFM signal.And the CutFM signal has multiple design parameters,and the ability of the system to meet various design indicators can be significantly improved through the selection of parameters.In addition,the optimal receiver of CutFM signal is designed by using Q function theory.The simulation test shows that under the optimal receiver processing,the CutFM signal can still have good detection performance under the condition of strong reverberation.Finally,an adaptive anti-reverberation waveform design is carried out for the problem of random extended stationary target detection under the combined effects of reverberation and noise.On the basis of reverberation modeling and target modeling,the optimal transmitting waveform is designed by using the SCNR criterion and NP criterion,and the energy spectral density of the optimal waveform is obtained.On this basis,in order to make full use of the power of the transmitter,the transmitted signal in time domain with constant mode characteristic is synthesized by the least square error iterative algorithm.Compared with the traditional LFM signal,the optimal transmit waveform allocates more energy in the frequency band with weaker reverberation response and stronger target response,and under the optimal receiving process,the optimized waveform has a larger SCNR and more excellent detection performance.