【作者】 胡艳华；

【导师】 黄显高；

【作者基本信息】 汕头大学 ， 信号与信息处理， 2008， 硕士

【摘要】 直接序列扩频(DSSS)通信具有频谱宽、工作信噪比低、抗干扰抗多径效应能力强、可实现码分多址、低截获和低检测概率等特点。正日益取代常规通信而广泛应用于现代军事和商用通信系统中,如码分多址(CDMA)通信、定位系统(GPS)、测控和敌我识别等。因此,与之对应的直扩通信对抗技术也就成了通信对抗领域亟待解决的问题。针对受强高斯噪声污染的DSSS/BPSK信号对抗技术中的盲参数估计问题,着重研究了以下检测估计方法:首先,研究了传统延时相乘法伪码码速率估计的改进方法。传统的延时相乘法研究对象是基带信号的延时相乘输出,或中频信号延时相乘输出的基带部分。分析发现,中频信号延时相乘输出包括基带部分和中频部分,基带部分的功率谱包含码速率信息,中频部分的功率谱包含2倍载频信息。通过选取不同的时延,可以分别估计出伪码码速率和载波频率。将传统的延时相乘法发展成为多参数估计法,并利用进一步的自相关处理降低了估计的信噪比容限。其次,研究了Duffing混沌振子检测微弱直扩信号的原理。利用Duffing振子对微弱小周期信号的敏感性和对噪声的免疫力,运用到DSSS信号的检测中,对DSSS/BPSK信号进行非线性平方变换后通过Duffing振子能够检测出淹没在强噪声背景中的直扩信号。最后,研究了在没有直扩信号任何先验知识的情形下,利用随机微分方程和能量检测法,从负信噪比直扩信号中盲检测出载波信号。再利用非线性信号噪声减缩的理论和小波多尺度算法,从载波信号中盲检测出扩频码序列。而且文章对以上DSSS/BPSK信号检测的各方法,进行了计算机模拟,给出了仿真结果,并对各检测方法的性能进行了分析。更多还原

【Abstract】 Direct sequence spread spectrum(DSSS)communication systems have the characteristics ofwide spectrum, working at low Signal-to-Noise ratio(SNR), anti-interference, anti-multipatheffect, easily realizing code division multiple access(CDMA), low probability of intercept(LPI)and low probability of detection(LPD). DSSS signal has more virtues than conventionalcommunication systems and it is widely adopted in modern military and commercialcommunication systems, for example, CDMA communication system, Global PositioningSystem (GPS), measuring and control system, friend or foe identification, etc. Therefore, thecorresponding DSSS electronic counter technique becomes a key problem to be solved inelectronic warfare domain.For the issue of blind parameter estimation of DSSS signal contaminated by strong additivewhite Gaussian noise (AWGN), this dissertation mainly researches on the following methods:First, the algorithm of chip rate estimation using delay and multiply (DM) method is studied.The research object of traditional DM method is the base-band output by the delay andmultiplication processing or the base-band output component of medium frequency (IF)DSSS/BPSK signal by the delay and multiplication processing. Theoretical analysis indicatesthat the output of IF DSSS/BPSK signal by the delay and multiplication processing is composedof base-band and IF components. The base-band component contains information of chip rate,and IF component contains information of double carrier frequency. Through selecting differentdelay, chip rate and carrier frequency can be detected respectively. Thus, traditional DM methodis improved into multi-parameters estimation method. Combined with the autocorrelationprocessing technique, DM method can obtain lower SNR limitation of chip rate and carrierestimation.And next, detected technique of Duffing oscillator weak signal is introduced. Then bymaking use of Duffing oscillator’s sensibility to small periodic signals and immunity againstnoise, the sine signal is detected which derives from square transform of DSSS/BPSK signal andis submerged in strong noise.The last part, a new theory and algorithm can be used in blind detection of the carrier wavesignal and the pseudo-random (PN) sequence of DSSS signal with negative SNR. First, without any priori knowledge of the DSSS signal, the carrier wave signal can be detected from DSSSsignal with negative SNR by using stochastic differential equations and energy detection method.Based on this, the pseudo-random sequence can also be blindly detected in DSSS signal withnegative SNR by reducing noise of the nonlinear signal and the algorithm of wavelet multi-scaledecomposition.Moreover, this research has conducted computer simulations of the above-mentioneddetection methods of the DSSS signal, provided simulation results, and analyzed theperformance of these detection methods discussed in this thesis.更多还原