带残余频偏的QPSK-DSSS信号参数盲估计

Blind Parameter Estimation of QPSK-DSSS Signal with Residual Carrier

本文对带残余频偏的正交相移键控(QPSK)调制的直接序列扩频(DSSS)信号参数估计问题展开研究。将二次谱法拓展到带残余频偏的QPSK-DSSS信号伪码周期估计中,即对信号的功率谱再进行傅氏变换并取模平方。其原理在于信号的二次谱将在伪码周期的整数倍处出现代表信号存在的尖锐三角形脉冲。对于残余频偏大小以及伪码码片速率的估计,采用基于循环谱的方法,即利用循环谱的频率截面和循环频率截面提取频偏和码片速率等信息。研究表明,在低信噪比下,本文采用的方法能够有效估计出带残余频偏的QPSK-DSSS信号的各个参数。

This paper investigated the problem of direct sequence spread spectrum(DSSS)signal parameter estimation with quadrature phase shift keying(QPSK)modulation with residual carrier.Aiming at the problem of pseudo noise(PN)period estimation of QPSK-DSSS signal with residual carrier,a method of the reprocessing of the power spectrum was proposed,that is,the power spectrum of the signal was subjected to Fourier transform and the modulus square was taken.The principle is that the quadratic spectrum of the signal will appear at integer multiples of the PN period to represent the existence of sharp triangular pulses.For the estimation of the residual carrier and the PN chip rate,the method based on the cyclic spectrum was adopted,that is,the frequency section and the cyclic frequency section of the cyclic spectrum were used to extract information such as frequency offset and chip rate.Research shows that under low signal-to-noise ratio,the method used in this paper can effectively estimate the various parameters of the QPSK-DSSS signal with residual carrier.