AM-FM Interference Excision in Spread Spectrum Communications via Projection Filtering

Recently, Amin et al. introduced a projection filtering method for excising constant amplitude FM jammers from DSSS communications, with minimal distortion to the PN sequence. In this paper, we show that this approach can be applied to AM-FM jammers as well, with a simple modification. Theoretical performance measures (correlator SNR) of the AM-FM projection method are derived, and demonstrate that near ideal performance is achieved for unbiased estimates of the jammer parameters. Results showing the effects of estimation errors in the AM and FM of the jammer on SNR are also provided. In general, FM errors cause greater performance degradation than the same level of error in estimating the AM.