GNSS Jammers: Effects and countermeasures

GNSS jammers are small portable devices able to broadcast disruptive interference and overpower the much weaker GNSS signals. In this paper, the effects of GNSS jammers on GPS and Galileo receivers are thoroughly analyzed and the use of an adaptive notch filter is suggested as an effective countermeasure to jamming. Signals generated by a commercial jammer are broadcast in a large anechoic chamber along with the GPS and Galileo signals generated by a hardware simulator. The analysis is conducted in terms of C/N₀ degradation and different jammer power levels are considered. The use of mitigation techniques, such as notch filtering, significantly improves the performance of GNSS receivers even in the presence of strong and fast-varying jamming signals. The presence of a pilot tone in the Galileo E1 signal enables pure PLL tracking and makes the processing of Galileo signals more robust to jamming.