The Research On Signal Direction Finding Technology In Underwater Acoustic Communication Countermeasure

The key to high-efficient and accurate acoustic warfare system is to detect and interfere the target signal,while detection extremely relies upon the estimation of direction finding of the target signal.With the rapid development of communication technology,DSSS(Direct Sequence Spread Spectrum)signal is widely used in the field of military acoustic communication thanks to its the character of cyclostationity.Meanwhile,direction finding becomes an important method to get communication information.Restricted by the long period,high cost and condition,the computer simulation is used to evaluate the communication countermeasure and underwater acoustic direction finding rather than making hardware experiments.According to communication countermeasure of DSSS underwater acoustic signals,on the basis of putting forward a kind of underwater DSSS communication countermeasure system,this paper mainly makes innovative and exploratory study on improving the precision and speed of direction finding detection and parameters estimation algorithm in lower signal-to-noise ratio of the complex marine environment.Aiming at these problems,the first one is with the time-delay difference of signal propagation,which occurs when the target signal reaches the sensor arrays and in which such information of target signal as direction and distance ensconces.It's the very reason why we should determine the correct time-delay difference upon estimating the direction finding of signal.In view of the traditional single frequency based on cyclic cross-correlation of time-delay estimation precision is low,this article proposes,based on the cyclic spectrum of DSSS signal,to construct a multi-cycle frequency time-delay estimator,which will estimate more accurately the time-delay difference in the circumstance of low SNR so as to improve the precision of direction finding.Meanwhile,the article the phase-delay difference of signal propagation,which occurs when the target signal reaches the sensor arrays and in which such information of target signal as direction and distance ensconces,through the determination of signal phase difference to determine the direction of the underwater acoustic target signal.The Cyclic MUSIC algorithm,derived from the cyclic and reposeful characteristics of DSSS signal,possesses some advantages such as selecting direction finding of signal,high resolving ability and outstanding multi-signal processing.However,it also has limits,that is,heavycomputation and low precision.To resolve this problem,the article puts forward a method of direction finding of DSSS signal based on sparse recovery,by combining the sparse characteristics of compressed sensing and Cyclic MUSIC algorithm,and the method was validated by computer simulation not only had the great advantage in time but also had high accuracy.