非周期性扩频信号的检测与估计

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1、杭州电子科技大学硕士学位论文非周期性扩频信号的检测与估计姓名：濮俊杰申请学位级别：硕士专业：信号与信息处理指导教师：赵知劲20091201杭州电子科技大学硕士学位论文 I 摘 要 由于对通信安全、抗干扰能力、频带利用率和信号隐秘性等要求的提高，一种有效的信号形式非周期性直扩信号在民用和军用通信中逐渐得到广泛应用。由于它的一个扩频码序列周期包括多个信息码元周期，即不同信息码元对应的扩频伪码序列是变化的，它有别于以往一般的直扩信号；且不同信息码互相独立，破坏了伪码的相关性；使非周期性直扩信号的检测与参数估计成为非协作通信领域研究的热点和难点。 本文主要研究基于高阶统计量和循环相关谱理论的非周期性直

2、扩信号检测与参数估计。 首先简要介绍了非周期性直扩通信系统组成与信号模型、 高阶统计量和循环相关谱理论。 然后，推导了非周期性直扩信号的二阶矩( )2sm及四阶矩切片()40,0,0sm、()40,0,sm、()40, ,sm 、()4, ,sm 和混噪非周期性直扩信号的二阶矩( )2xm及四阶矩切片()40,0,0xm、 (), 0 , 04xm、()40, ,xm 、()4, ,xm ；根据二阶矩和四阶矩切片特性，提出了基于二阶矩检测法（EJJ）和基于二次四阶矩时域检测法（ECSJS）；根据混噪非周期直扩信号四阶矩切片含有载频信息，提出了基于二次四阶矩频域检测法（ECSJP）；接着推导了四

3、阶矩切片 (), 0 , 04xm的循环相关谱( )ySf，根据循环频域上含有载频信息，提出了基于四阶矩切片的循环相关谱检测法（SJXH）。仿真结果表明：本文提出的 SJXH 法检测性能最好，在检测概率为 90%时， 比时延数取最佳的 ECSJS 法改善信噪比约 0.5dB， 比 ECSJP 法改善信噪比约 1.5dB，比 EJJ 法改善信噪比约 3dB， 检测性能比已有方法好得多， 如： 比二次谱法改善信噪比约 10dB，比平方倍频法改善信噪比约 15dB。 最后，根据混噪非周期直扩信号四阶矩切片及其循环相关谱含有载频信息，提出了基于二次四阶矩切片的载频估计方法（ECSJSP）和基于四阶矩切

4、片的循环相关谱的载频估计方法（SJXHP）；并推导给出了基带非周期性直扩信号的四阶矩切片的二次谱，基于此二次谱分别提出了伪码周期估计方法和伪码速率估计方法。仿真结果表明：载频估计方法中，当估计归一化标准差低于210时，本文提出的ECSJSP法和SJXHP法比倍频法改善信噪比分别为12dB和13dB，倒谱法无法估计非周期性直扩信号载频；在估计归一化标准差为310时，本文所提出的伪码周期估计方法比时域相关法改善信噪比约4dB，比二次谱法改善约5dB；在估计归一化标准差为210时，本文提出的伪码速率估计方法比时域相关法和二次谱法改善信噪比约2dB，比倒谱法改善信噪比6dB以上。 关键词：非周期性直扩

5、信号，二阶矩，四阶矩切片，循环相关谱，二次谱，信号检测，参数估计 杭州电子科技大学硕士学位论文 II ABSTRACT With the increase of the demand of communications security, anti-jamming capabilities, bandwidth utilization and signal secrecy, an effective signal formnon-periodic Direct Sequence Spread Spectrum (DSSS) signal has been widely used in the

6、civilian and military communications. One cycle of the spread-spectrum sequence includes some cycles of the information symbol. That is, different information symbol codes correspond to different spread-spectrum PN codes. So the non-periodic DSSS signal is different from the general DS signal. Since

7、 different information codes are independent of each other and the correlation of the PN code is undermined, the detection and the parameter estimation of non-periodic DSSS signal become a hotspot in the non-cooperative communication. The dissertation focuses on the research of the detection and the

8、 parameter estimation for the non-periodic DSSS signal based on the theory of high-order statistics and cycle-related spectral. First of all, the non-periodic DSSS communication system, signal model, high-order statistics and cycle-related spectral theory are introduced. Then, through analyzing the

9、non-periodic DSSS signals second-order moment ( )2sm), fourth-order moment chips()40,0,0sm, ()40,0,sm, ()40, ,sm , ()4, ,sm ) and the received signals second-order moment ( )2xm), fourth-order moment chips()40,0,0xm、(), 0 , 04xm、()40, ,xm 、()4, ,xm ), two new detection methods(EJJ, ECSJS) based on t

10、he second-order moment and the quadratic fourth-order moment chip are proposed, respectively. According to the fact that the received signals fourth-order moment chips have the information of carrier frequency, the detection method(ECSJP) in frequency based on quadratic fourth-order moment chip is p

11、roposed. Because the cycle-related spectrum ( )ySf) of the fourth-order moment chip (), 0 , 04xm) has the information of carrier frequency, the new detection method(SJXH) based on the cycle-related spectrum is proposed. Experimental results show that the SJXH method has the best performance on non-p

12、eriodic DSSS signal detection. When the detection probability is 90%, the SJXH method has better performance than the ECSJS method to improve SNR about 0.5dB, compared with ECSJP method to improve the SNR about 1.5dB, compared with EJJ method to improve the SNR about 3dB, compared with spectrum-repr

13、ocessing method to improve the SNR about 10dB and compared with double frequency method to improve the SNR about 15dB. After all, according to the fact that the fourth-order moment chip and the cycle-related spectral have the information of carrier frequency, two kinds of carrier frequency estimatio

14、n methods(ECSJSP,SJXHP) of non-periodic DSSS signal based on quadratic fourth-order moment chip and the fourth-order moment chips cycle-related spectral are proposed. Through analyzing the 杭州电子科技大学硕士学位论文 III received signals fourth-order moment reprocessing-spectrum, an estimation method for PN sequ

15、ence period and for PN chip rate are proposed, respectively. Experimental results show that when the normalized estimation relative error(NERE) of carrier frequency estimation is smaller than 210, the ECSJSP method and SJXHP method have better performance than the double frequency method to improve

16、SNR about 12dB and 13dB, respectively. But cepstrum method can not estimate the non-periodic DSSS signals carrier frequency. When the normalized estimation relative error(NERE) of PN sequence period estimation is smaller than 310, the proposed estimation method for PN sequence period has better performance than the time-domain correlation method to improve SNR about 4dB, compared with spectrum-reprocessing method to improve the SNR abo