【作者】 孙铭芳；

【导师】 吴芝路；

【作者基本信息】 哈尔滨工业大学 ， 信息与通信工程， 2006， 硕士

【摘要】 扩频通信具有低截获率、抗衰落能力强、抗多径干扰等优点,广泛应用于军事通信和民用通信。随着电子战和信息战技术的发展,非合作通信条件下扩频信号盲解扩成为扩频通信领域的研究热点,扩频信号PN码速率和码周期的盲检测和盲估计是实现盲解扩的前提。本文以工程应用为目的,对低信噪比情况下直扩信号的检测和PN码速率和码周期估计进行了理论研究。首先简要概述了扩频通信的基本知识,指出基带DS信号可分为短PN码调制和长PN码调制。然后采用延时相乘法对直扩信号进行了检测和PN码速率估计研究,提出了改进算法,给出了算法推导和理论仿真。采用二次功率谱法和倒谱法对PN码周期进行估计研究,针对长PN码调制提出了一种基于延时相乘的二次功率谱法的新方法,给出了算法推导和理论仿真。由于目前尚未有对长PN码调制信号进行检测和参数估计的研究,而长码调制较好的保密性能以及抑制部分符号间干扰的优点,使其在军事通信中有着较好的应用前景,因而此部分工作具有重要的意义。最后给出了基于FPGA的直扩信号数据采集系统设计方案。理论仿真表明,以上检测和估计方法对码长为63~1023的短PN码调制直扩信号均适用。延时相乘法对长PN码调制信号PN码速率估计也适用,其改进法的信噪比容限比改进前降低;二次功率谱法和倒谱法对短PN码调制有很好的检测和估计性能,但对长PN码调制不适用,而基于延时相乘的二次功率谱法可以很好的估计出长PN码调制信号的PN码周期。更多还原

【Abstract】 The advantages of spread spectrum communication are as follows: low probability of intercept, good anti-fading and anti-multipath interference capability. It is widely used in military and civil communication. With the development of the electron and information technology, the blind de-spread of spread spectrum signals in non-cooperation communication has been a research hot spot. The blind detection and estimation of the chip rate and period of pseudo noise (PN) sequence are the precondition for the realization of blind de-spread.The theory research on the detection and estimation chip rate and period of PN sequence in low signal to noise ratios (SNR) are accomplished in order to put it into realization. Firstly, the paper summarize the basic knowledge of spread spectrum communication, point out that the baseband of DS signals are divided into short PN sequence modulation and long PN sequence modulation. Secondly, the delay and multiply approach is used to detect the DS signals and estimate the chip rate of PN sequence, and then an improved algorithm is proposed. The algorithm is deduced and the theory simulation results are given. Thirdly, the power spectrum reprocessing approach and cepstrum approach are used to estimate the period of PN sequence. A new method that a power spectrum reprocessing based on delay and multiply is introduced to estimate the period of long PN sequence modulation signals. The algorithm is deduced and the theory simulation results are given. Although the long PN sequence modulation has been used widely in the military communication with the good secrecy performance and restraint of jam between symbols, there is scarcely any research of long PN sequence modulation signals. So it is significant to research the estimation of long PN sequence modulation signals. Finally, the DS signals data acquisition project based on FPGA is given.Theory simulation results show that the methods mentioned are feasible to detect and estimate the short PN sequence modulation DS signals whose PN sequence length is 63 to 1023. The delay and multiply approach can be used to estimate the chip rate of long PN sequence modulation DS signals, and the improved algorithm of it is available in lower input SNR. The performance of the更多还原