The Jamming Technology Of Dsss Communication System Based On Sequence Jitter

Direct Sequence Spread Spectrum(DSSS)communication system has a series of advantages of low interception,strong anti-interference and strong confidentiality.It has been widely used in military and civil fields.At the same time,communication confrontation,as an indispensable part of the modern war,has even become one of the key factors that determine the success or failure of the war.Therefore,people pay more and more attention to it and the DSSS communication system an indispensable part of modern military.And precisely because of the good characteristics of DSSS signal,it brings great difficulties to communication reconnaissance and communication jamming.Currently,there is no particularly efficient way to detect and interfere with DSSS signals.Therefore,in this paper,the DSSS signal is taken as the research object.Based on the effective reconnaissance of the DSSS signal,the high efficiency jamming of the DSSS system is the final research goal.Two aspects are studied in depth.One is the detection and parameter estimation method of DSSS signal at low signal-to-noise ratio;the other is the traditional jamming,the optimal jamming and analysis the jamming effectiveness.First of all,the basic principle,signal analysis and spectrum analysis of DSSS communication system are studied in detail,laying the foundation for the next step research.Secondly,for the blind detection of DSSS signals,the squared frequency doubling,delay multiplication,cyclic spectrum,time-domain autocorrelation and quadratic power spectrum are studied,and the simulation results and performance analysis of these methods are given.The simulation results show that the above five methods can not only detect the existence of signal under low signal-to-noise ratio,but also can make more accurate parameter estimation.The estimated parameters include carrier frequency,pseudo-code rate and pseudo-code period.Thirdly,for the traditional jamming of DSSS signals,the effectiveness of jamming of narrow band jamming,noise FM jamming and chirp are studied emphatically.On the basis of theoretical analysis,the effectiveness of jamming of each jamming under different jamming bandwidths and jamming frequencies is studied.The simulation shows that both of them can affect the final jamming effectiveness.When the best jamming bandwidth and frequency are selected,each methods can achieve the more efficient jamming.Finally,for the optimal jamming of the DSSS signal,the effectiveness of jamming of the related jamming is studied.The simulation shows that it has extremely strict requirements on synchronization,and effective jamming can only be implemented under precise synchronization.Aiming at the shortcomings of related jamming,a method based on time-varying jitter PN sequence(jitter-related jamming)is proposed.The algorithm injects jitter into the PN sequence to obtain a jittered PN sequence,and uses this sequence to modulate the jamming signal.Due to the existence of jitter,the slope of the correlation curve of the jitter PN sequence and the original sequence becomes smaller,that is,the correlation value is insensitive to the time offset.As the offset increases,the correlation value decreases less.Two methods are compared under the condition of synchronization and non-synchronization.The simulation results show that the jitter-related jamming can improve the jamming effectiveness of the related jamming under the non-synchronization condition and achieve effective jamming.