Subspace projection techniques for anti-FM jamming GPS receivers

This paper applies subspace projection techniques as a pre-correlation signal processing method for the FM interference suppressions in GPS receivers. The FM jammers are instantaneous narrowband and have clear time-frequency (t-f) signatures that are distinct from the GPS C/A spread spectrum code. In the proposed technique, the instantaneous frequency (IF) of the jammer is estimated and used to construct a rotated signal space in which the jammer occupies one dimension. The anti-jamming system is implemented by projecting the received sequence onto the jammer-free subspace. This paper focuses on the characteristics of the GPS C/A code and derives the signal to interference plus noise ratio (SINR) of the GPS receivers implementing the subspace projection techniques.