Performance analysis of the DS/SS communications receiver implementing a short time Fourier transform interference excision system

The short-time Fourier transform (STFT) is employed for nonstationary jammer excision in direct sequence spread spectrum (DS/SS) communication systems. The received signal is first analyzed by the STFT. The localized interferers in the time-frequency (t-f) domain are then removed by binary excisions. Finally, the synthesized signal is correlated with the PN sequence and passed to the detector. The selection of both the data window and the distribution of the binary excision values in the t-f domain are key to effective removal of the jammer with a minimum distortion of the DS/SS communication signal. Proper data windows localize the interference in as few t-f bins as possible, whereas good binary excision assigns zero values to only those t-f bins contaminated by the jammer t-f signature. The closed form expression of the receiver SNR is derived as a function of the binary excision values in the t-f domain. The specific cases of impulsive and sinusoidal jammers are analyzed.