Switchable Beam Steering/Null Steering Algorithm for CW Interference Mitigation in GPS C/A Code Receivers

CW interference can be a severe threat to Global Positioning System coarse acquisition (GPS C/A) code receivers because it can mix with one of the spectrum lines of the GPS C/A code and affect the signal quality even with a very low power. Spatial domain processing techniques in CW interference mitigation as alternatives to frequency and time domain processing are investigated. Using a multi-antenna system some common adaptive filtering criteria are examined in the presence of CW interference. No single criterion performs best when the relative frequency of the CW interference and the satellite signal changes. An algorithm is proposed---the switchable steering algorithm---which combines both beam steering and null steering criteria and is influenced by the frequency difference between the CW interference and the satellite Doppler. Mathematical analyses and simulation results demonstrate that this algorithm can outperform either single criterion.