A multi-state notch filter for GNSS jamming mitigation

Adaptive notch filters have been proven to be effective solutions for mitigating the impact of jamming and extending the operational capabilities of GNSS receivers. In this paper, a multi-state model is at first proposed for the characterization of jamming signals. In particular, jamming signals can move outside the input band of the victim receiver and their instantaneous frequency can be affected by abrupt jumps. These features are accounted for in the multi-state model which is used to design a new class of adaptive notch filters able to cope with the state transitions of the jamming signal. The adaptive notch filter proposed has been designed to be computationally efficient and to track the fast frequency variations of a jamming signal. The performance of the technique proposed is experimentally studied using a real cigarette lighter jammer and a custom software receiver. The tests show the benefits of the notch filter proposed.