【作者】 杜利刚；

【导师】 田日才；

【作者基本信息】 哈尔滨工业大学 ， 信息与通信工程， 2010， 硕士

【摘要】 直接序列扩频信号具有频带宽、信噪比低、低截获率和高抗干扰等特点,已经广泛用于军事通信、卫星通信、移动通信等领域。随着电子战与信息战的发展,对于直扩信号的侦查成为了通信领域的一个研究热点。本文以BPSK调制的直扩信号为例,对低信噪比情况下的信号进行检测与PN码速率码周期估计。简要介绍了直接序列扩频通信系统的基本原理以及伪随机序列的基本知识。在载频检测方面运用了平方倍频检测法,给出了平方倍频法的算法推导与理论仿真,对于直扩信号的PN码速率采用了延时相乘法与循环谱法来检测,给出了算法推导与仿真结果,并分析了两种方法各自的优缺点。采用二次功率谱法和倒谱法对PN码周期进行估计,针对上述两种方法的缺点进行了改进,采用基于延时相关的二次功率谱法,很好地解决了关于长PN码周期的估计问题。在无码解扩方面做了部分工作,分析了本地截取信号的获取方法,并对原理做出了数学推导。仿真结果表明,运用平方倍频法检测载频的信噪比检测门限是-22dB;对于延时相乘法和循环谱法检测PN码速率的信噪比检测门限分别是-20dB和-16dB;在对PN码周期进行估计时,二次功率谱法和倒谱法的信噪比检测门限分别为-14dB和-15dB,延时相关二次功率谱法虽然解决了长码周期估计的问题,但是相应的信噪比检测门限却上升为-12dB。更多还原

【Abstract】 Direct sequence spread spectrum signal has wide bandwidth, low SNR, low interception rate and high anti-interference and so on .It has been widely used for military communications, satellite communications, mobile communications and other fields. With the electronic warfare and information warfare development, the DS signal detection has become a hot topic in the field of communications.This paper takes DS BPSK modulated signals for example to research on detection of DS-SS signals and parameter estimation of PN sequence. It introduces a direct sequence spread spectrum communication system and the pseudo-random sequence of the basic principles of the basic knowledge. It uses the square harmonic detection method in the detection area of Carrier frequency. We derive an algorithm square multiplier method and the theoretical simulation. We use multiply delay and cyclic spectrum to detect the signal for the DS PN code rate, and show derivation and simulation results of the algorithm and analyzes their advantages and disadvantages of two methods. The paper adopts quadratic power spectrum and cepstrum method to estimate the PN code period, for the shortcomings of both methods has been improved, based on delay-related second power spectrum method provides a good solution on the long PN code period the estimation. Despreading without the code has done some work on the analysis of the local method of interception of the signal, and the mathematical theory is derived.Simulation results show that the use of the square of carrier frequency harmonic noise ratio assay detection threshold is -22dB. For the delay with multiplication and cyclic spectrum, PN code detection rate of detection threshold SNR is -20dB and -16dB. In estimate of the PN code period, the second power spectrum and cepstrum SNR detection threshold is -14dB and -15dB. Delay related to the second power spectrum method has solved the estimate of the long code period, but the corresponding SNR detection threshold increases to -12dB.更多还原