Adaptive notch filter and time-varying ar modeling for anti-jamming PN code radar

The Direct Sequence Spread Spectrum (DSSS) technique is used in several types of radar systems, such as automotive radar, and docking and rendezvous radar. DSSS has a certain inherent immunity to jammers. However, in the case of non- stationary jammer in a DSSS signal, the spreading gain may be insufficient to provide enough jamming resistance. The non-stationary jammer can be effectively suppressed by time- varying direct notch filter with its zeros placed at an instantaneous frequency(IF) estimation of the jammer, and TVAR is used to IF estimation. In this paper, the optimal basis function of time-varying AR(TVAR) model for the instantaneous frequency(IF) estimation of the LFM signal was obtained by comparing IF estimation precise and anti- noise performance of several types of basis functions, including time basis function, Fourier basis function, and Lagrange basis function. The closed solution of correlation output SINR improvement, when a single frequency jammer passes through direct IIR notch filter, was derived, and its performance was compared with those of five coefficient FIR filters. Based on this, a novel method for LFM jammer suppression based on Fourier basis TVAR model and direct IIR notch filter was proposed. The simulation results confirmed the effectiveness of the method proposed.