A novel narrow-band interference suppression algorithm based on digital zero-intermediate frequency

The existing Narrow-Band Interference (NBI) suppression methods in spread spectrum system will destroy the original signal to some extent. What's more, the later compensate algorithm is complex and needs great hardware expense, so it is difficult for engineering realization. To cope with such inefficiency, we proposed a new NBI suppression model by separating the interference detection and interference suppression. Firstly, the interference detection based on threshold analysis is designed in frequency domain. Secondly, we proposed a frequency spectrum shifting algorithm which is inspired by the quadratic demodulation idea in communication system. Then the intermediate frequency signal is shifted to base band, and the interference suppression is finished at zero-frequency. Finally, we implement this adaptive notch filter based on FPGA. What's more, the proposed algorithm is different from the common technology in structure and algorithm. Simulation and real test verify the performance of the proposed method. Experiment results showed that the direct sequence spectrum system with this trapped method had excellent suppression ability in terms of strong narrow-band interference.