LFM interference suppression for GPS receiver based on oblique projection

A LFM interference suppression method based on oblique projection is proposed for GPS receiver. It is applicable to the GPS propagation environment with LFM interferences, multipath and noise. By using the concentration property of LFM interferences in fractional Fourier domain, the initial frequency, frequency modulation rate and direction-of-arrival (DOA) of LFM interferences are first estimated. Afterwards, the space-time interferences subspace is constructed. According to the properties of oblique projection, LFM interferences are suppressed by projecting the received signal onto the joint signal-noise subspace. Then, the multiple constrained minimum variance algorithm is used to extract the desired GPS signal. Different from the existing algorithms, the proposed method not only can directly solve the DOA of LFM interferences, but also can construct the interferences subspace with the time-variant steering vector of interferences. Moreover, our method can completely suppress LFM interferences without the desired signal distortion, and significantly improve the performance. Simulation results demonstrate the effectiveness of the proposed method.