Hybrid successive continuous wave interference cancellation scheme for global positioning system receivers

The authors propose a hybrid successive continuous wave interference (CWI) cancellation scheme for GPS receivers. The proposed hybrid scheme successively detects and estimates CWIs in the time domain and nulls the estimated contaminated frequencies in the frequency domain. An adaptive second-order infinite impulse response (IIR) filter to perform the CWI detection and estimation is devised. One IIR filter is able to estimate one CWI in each iteration. Then, the detected CWI is fed back to the excision module in the frequency domain. Therefore, the hybrid scheme can successively null multiple CWIs. Moreover, the proposed architecture allows additional cascading of IIR filters to handle multiple CWIs simultaneously. Unlike the existing frequency-domain approach, CWI estimation does not rely on the statistical values in the frequency domain. Therefore the proposed hybrid scheme can be implemented using a fast Fourier transform (FFT) with fewer points. Simulation results show that the proposed hybrid scheme can operate normally with only a 256-point FFT and can perform better than the conventional N-sigma and consecutive mean excision algorithms in terms of the effective signal to interference plus noise ratio of the acquisition results