Design and analysis of activation strategies for adaptive notch filters to suppress GNSS jamming

Adaptive notch filters (ANFs) have been widely investigated in literature for their low complexity and good performance, and used in many signal processing applications. More recently, they have been proven to be an effective solution against jamming interferences, considered more than ever a real threat to Global Navigation Satellite System signals. This article focuses on a specific family of ANF, where the adaptation algorithm is implemented as a frequency-lock-loop (FLL), namely FLL-equivalent ANFs. It presents the theoretical derivation of two detection approaches, namely power ratio-based and gradient-based, in charge of activating/deactivating such kind of filters. Both the theoretical and statistical analysis in case of swept-frequency jamming signals are provided. The performance evaluation for several interference-to-noise ratio conditions shows a tradeoff between the two solutions, with a slight advantage of the power ratio-based strategy. The results achieved in simulation clearly demonstrate that the proposed activation strategies can be combined with ANFs and that they can be effectively adopted for the mitigation of jamming signals.