The spectrum of the baseband spread spectrum signal has a wide frequency range, when the signal is transmitted in the band limited channel, the bandwidth of the signal needs to be limited, thereby causing intersymbol interference. Therefore, in order to reduce the inter-symbol crosstalk between baseband spread spectrum signals and their occupied bandwidth, this paper studied the main parameters of its low interception performance of the baseband spread spectrum signal after it passed through the pulse shaper, and it estimated pseudocode period by using twice power spectrum. The theoretical analysis proved that the signal after twice power spectrum extends spectral line on the period of impulse sequence, and the main energy of the signal would gather in some sharpness similar to that of the quadratic spectrum of the baseband shaping pulse. The pseudo-code period of the baseband spread spectrum signal could be estimated by measuring the spacing between these sharp pulses. Simulation results show that the method of twice power spectrum can be used to estimate the pseudo-code period of pulse shaped spread baseband signal under low signal-to-noise ratio condition. And accuracy of the algorithm to estimate the proposed pseudo-code period improves approximately 7 dB compared to the method without pulse shaping.

[2019-08-05] Printed Article /doc/2018.02.0106/v2