Design of GPS Anti-Jamming Systems Using Adaptive Notch Filters

Continuous wave interferences (CWIs) can reduce the positioning accuracy of a Global Positioning System (GPS) receiver and even paralyze its normal operation. Therefore, we have designed a low-cost anti-jamming system to combat CWIs for GPS receivers. The anti-jamming system comprises cascaded CWI-detectable adaptive notch filter (ANF) modules, and each module is able to mitigate one CWI. The ANF module is composed of a second-order infinite-impulse response (IIR) filter with a lattice structure. The proposed ANF detects the existence of the CWI and estimates its power by exploiting the statistic value and internal state associated with the IIR filter, respectively. The impact of the ANF module on the acquisition and tracking loops is analyzed. Properly controlling the -3-dB bandwidth of the ANF module allows its impact to be neglected. Moreover, more modules can be cascaded to deal with multiple CWIs. We have also designed an adaptation algorithm for the ANF modules and proven that the module can adaptively notch the strongest CWI at its input. This merit enables us to notch the primary CWIs with a limited number of ANF modules. Simulation results show that our approach considerably outperforms related works in both CWI detection and rejection capabilities.