Mitigation of periodic interferers in GPS receivers using subspace projection techniques

Frequency modulated signals in the frequency band 1.217-1.238 GHz and 1.565-1.586 GHz present a source of interference to the GPS, which should be properly mitigated. We derive the signal-to-interference-and-noise ratio (SINR) of the GPS receiver implementing subspace projection techniques for suppression of FM jammers. We consider the general case in which the jammer may have equal or different cycles than the coarse acquisition (C/A) code of the GPS signals. It is shown that the weak correlations between the FM interference and the Gold codes allow effective interference cancellation without significant loss of the desired signal.