Algorithms Design And Implementation For Digital Signal Detection And Estimation

With the rapid development of information technology,modern war has entered the information stage.Information warfare,as a new mode of warfare in modern military war,plays an important role in the whole game.As the carrier of information,the detection and estimation of digital signals is the most critical step in information warfare.Whether it can effectively detect,receive or even crack and interfere with enemy communications has a great impact on the development of the game.Nowadays,the communication mode is complicated,which poses a greater challenge to the detection and estimation of digital signals.Based on this background,this thesis makes an in-depth study on the detection and estimation algorithm of digital signals.For the non-spread spectrum signal,direct sequence spread spectrum(DSSS)signal and combination of frequency hopping and direct sequence spread spectrum(FHDS)variable rate signal,the thesis makes an in-depth study on the correlation algorithm from three levels of signal existence detection,signal parameter estimation and signal modulation classification,and corresponding detection and estimation systems are designed for the above three communication signals.The specific contents are as follows: firstly,for the non-spread spectrum digital modulation signals,the thesis presents the theory and implementation of the existence detection algorithm,frequency offset estimation algorithm,symbol rate estimation algorithm and automatic modulation classification algorithm based on symbol sequence,and designs the detection and estimation system for the non-spread spectrum communication signals.Then,for DSSS signal,this thesis gives the existence detection algorithm,spread spectrum period estimation,spread spectrum code length estimation algorithm,spread spectrum synchronization estimation algorithm and spread spectrum code sequence estimation algorithm in detail,and designs the detection and estimation system for DSSS signal.Then,aiming at the communication signal of FHDS variable rate,this thesis proposes the existence detection algorithm based on the signal and the estimation algorithm of second frequency hopping time based on time-frequency analysis,and presents the design of detection and estimation system of FHDS variable rate signal.Finally,this thesis verifies the effectiveness and realizability of the above detection and estimation system by collecting the actual communication signals.The specific contributions of this thesis are as follows:Algorithm part:(1)on the basis of the existing symbol rate estimation algorithm based on delay multiplication correlation,this thesis proposes a precision estimation method of frequency slice symbol rate based on Discrete Fourier Transform(DFT).The simulation shows that the estimation accuracy is improved by an order of magnitude compared with the original estimation algorithm based on delay multiplication correlation.(2)this thesis proposes a simple neural network modulation classification algorithm based on constellation.Simulation shows that this algorithm has better anti-interference and anti-noise performance,and has lower complexity than GoogleNet and AlexNet neural networks used in [63,64],and the classification performance is basically the same.Implementation part:(1)the thesis designs a detection and estimation system for non-spread spectrum communication signals and DSSS signals,simulates and analyzes the system performance,and completes the effectiveness verification.(2)the thesis designs the detection and estimation system for FHDS variable rate signal,simulates and analyzes the system performance,and completes the validity verification.