Adaptive filter based low complexity digital intensive harmonic rejection for SDR receiver

Harmonic rejection mixing is indispensable in software defined radio receivers employing switched mixers. Current analog multi-path mixing solution suffers from phase and gain mismatches along the paths and as a consequence cannot provide sufficient harmonic rejection. In this paper, we present a low complexity flexible digital intensive harmonic rejection architecture and show how it can be used to enhance the rejection of any single harmonic interference by adaptively combining the different mixing paths. Simulation results show that the proposed method can reject any single interferer adaptively by over 80 dB, which is sufficient for practical applications.