Tone interference suppression in DS-SS systems with modified DFT

The performance of traditional interference excision methods based on the discrete Fourier transform (DFT) in direct sequence spread spectrum (DS-SS) systems varies significantly with the frequency of the interference because the DFT of the interference becomes more dispersive with the increase of grid biases in the DFT operation. This paper presents a new excision method using modified DFT (MDFT) with an estimated grid bias. Minimum dispersion of the interference is achieved in the MDFT domain. Both theoretical analysis and experimental simulation are presented to show that the interference can be excised with a minimum distortion of the desired signal in a large range of interference-to-signal ratio.