Blind Parameter Estimation of QPSK-DSSS Signal with Residual Carrier

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.