In this paper

a new method based on the reprocessing of power spectrum density is proposed to detect and estimate the PN sequence period of the M-ary spread spectrum signals in low SNR.In this method

the power spectrum of the received signals is first acquired and taken as input signals

their power spectrum is acquired again.Pointed impulses will emerge at the position of integer times of PN sequence period and the PN sequence period of the M-ary spread spectrum system can be estimated by detecting the intervals of these impulses.Theoretical analysis and computer simulation results show that this method can effectively estimate the PN sequence period and the less the information bits transmitted by each PN sequence

the better the estimation performance.