Anti-interference receiver structures for direct sequence spread spectrum signals

Conventional narrowband interference (NBI) rejection algorithms often assumed perfect pseudo-noise (PN) code synchronization. The functions of NBI rejection and code tracking are performed separately and independently by an adaptive filter and a code tracking loop, respectively. This paper presents two new receiver structures for direct sequence spread spectrum (DS/SS) systems, one operates in coherent mode and the other operates in noncoherent mode. Both receivers are designed to suppress NBI and minimize tracking jitter. Numerical results show that the proposed coherent receiver performs as good as the conventional receiver that uses an LMS NBI rejection filter with zero tracking jitter. The noncoherent receiver, when compared with the coherent one, suffers less than 3 dB degradation for bit error probability smaller than 10(-3)