DS/QPSK信号盲检测和估计算法的研究

【作者】 肖治宇；

【导师】 吕明；

【作者基本信息】 电子科技大学 ， 信号与信息处理， 2007， 硕士

【摘要】 直接序列扩频(DSSS)信号由于其工作信噪比低、强抗干扰性、低截获率、能够抑制多径效应等优点,已经得到广泛应用,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、全球定位系统(GPS)、测控、卫星链路和敌我识别等。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。直扩通信对抗包括直扩信号的盲检测、盲参数估计和扩频码序列恢复等内容。针对受强高斯噪声污染的DSSS/QPSK信号对抗技术的盲检测,盲参数估计及码序列恢复问题,本文主要内容如下:1、分同步和非同步两种情况生成了DSSS基带信号,并对DSSS基带信号进行了QPSK调制,生成DSSS/QPSK调制信号。同时介绍了DSSS/QPSK信号的解调方案。2、运用几种常用的检测方法对低信噪比下的DSSS/QPSK信号进行检测。检测方法包括功率谱检测法、时域相关检测方法、高阶统计量检测法等,文中对各种检测方法进行了计算机仿真,分析和比较。3、在充分分析了DSSS/QPSK信号特点的基础上,分别采用平方倍频法,时域自相关法和延时相乘法对DSSS/QPSK信号的载波频率,码周期和码速率等参数进行估计。同时文中采用高阶累积量多参数估计方法对信号的参数进行估计。4、总结和介绍了几种常用的码同步和恢复方法,包括特征值分解法,子空间跟踪法等,并进行了计算机仿真。基于子空间跟踪理论,本文将基于新息准则的快速子空间跟踪算法运用于直接序列扩频(DS/SS)信号的扩频码盲估计问题。计算机仿真表明这种算法降低了运算的复杂度和存储量,易于硬件实现,具有良好的收敛特性,能在较低的信噪比下快速准确的恢复出扩频序列。5、建立了对DSSS/QPSK信号进行检测,参数估计和码序列恢复的联合处理系统,并对系统进行仿真和性能分析。更多还原

【Abstract】 Direct sequence spread spectrum (DSSS) communication systems has been widely used in these years for its advantage of wide spectrum, low working Signal-to-Noise ratio (SNR), anti-interference, anti-multipath effect and capability of LPI and LPD. They are increasingly replacing conventional communication forms and obtaining extensively applications in modern military and commercial communication systems, for example, CDMA communication system, GPS , measuring and control system, satellite chain, identification of friend or foe and etc. Therefore, corresponding DSSS electronic counter technique becomes a big problem to solve in electronic warfare domain. DSSS electronic counter technique including blind detection, blind parameter estimation and spreading sequences estimation. For the issue of DSSS electronic counter technique of DSSS/QPSK signal damaged by strong additive white Gaussian noise (AWGN), the main research content in this dissertation as follow.1、Both synchronous and asynchronous DSSS baseband signal are created and modulated to create DSSS/QPSK signal. At the same time, we introduce the demodulated method of DSSS/QPSK signal.2、The characteristics of power spectrum, time-domain correlation and high-order statistics of the DSSS/QPSK signal are used to detect the signal. And the computer simulation is launched to analyze and compare the capability of different detection method.3、Base on the adequate analysis of the characteristic of DSSS/QPSK signal, this dissertation mainly used carrier doubler method (CDM), auto-correlation method (ACM) and delay-and-multiply (DM) method to estimate the carrier frequency, the symbol period and the chip rate of DSSS/QPSK signal. At the same time, we introduced fourth-order cumulant 2-D slice method to realize multi-parameter estimate.4、Several usual blind code synchronization and spreading sequences estimation methods, including matrix eigenvalue decomposition (EVD) and subspace tracking algorithms, are summed up and analyzed by computer simulations. Base upon the theoretics of subspace tracking, this dissertation introduce the algorithm based on fast subspace tracking by a Novel Information Criterion to solve the problem of blind estimation of DS/SS spreading sequence. Computer simulations show that this algorithm descends the storage consuming memory, is prone to hardware realization and has fast convergence properties, and this algorithm can estimate PN spreading sequence quickly and accurately at low SNR.5、Finally, we established an associated system to process DSSS/QPSK signal including detection, parameter estimate and spreading sequences estimation. And the computer simulation was launched to analyze and compare the capability of different method combination.更多还原