AM-FM interference suppression for GPS receivers based on time-frequency analysis and synthesis

Global positioning system (GPS) has created a new civilian industry that crucially depends on GPS signal reception. However, interference, intentional or unintentional, is a major threat to the GPS community. Many GPS mitigation methods have been developed and their effectiveness has been tested and quantified. As anti-jamming techniques become increasingly effective, jammers themselves have become smarter and more sophisticated, and generate signals that are difficult to combat. AM-FM interference is a typical interference signal. In this paper, interference signal is suppressed by applying time-frequency analysis and synthesis techniques. GPS signal contaminated by interference is firstly transformed into time frequency domain with Wigner-Ville distributions, and then interference is reconstructed using time-frequency synthesis techniques. Interference subspace and its orthogonal subspace are created on basis of the principle of subspace projection techniques. Interference is suppressed by projecting the receiver signal into orthogonal subspace of interference. Simulations results verify the effectiveness of the method proposed.