Adaptive notch filtering against complex interference scenarios

Interference events in the global navigation satellite system (GNSS) spectrum are becoming commonplace. Therefore, the likelihood of receiving multiple simultaneous interference signals is increasing. A common approach to such complex scenarios is to cascade multiple mitigation processors. This paper analyses the response of cascaded adaptive notch filtering (ANF) against two simultaneous frequency-modulated continuous-wave (FMCW) interferences. Results show that if the amplitude differences between the FMCW interferences are sufficient, then a cascaded approach can be successful. However, if the amplitudes are similar, then an ANF would lock onto the wrong frequency-typically a frequency between the two interferences-causing significant performance losses. This effect emphasizes the need for more advanced interference mitigation methods to overcome these limitations, such as the use of multi-spectral methods.