NLFM Interference Suppressing Based on Time-Varying AR Modeling and Adaptive IIR Notch Filter

Uing TVAR (Time varying AR) model and adaptive notch filter is a new method for the nonstationary jammer suppression in DSSS (Direct sequence spread spectrum). The performance of TVAR model for IF (Instantaneous frequency) estimation will be affected by some factors such as basis functions. Focusing on this problem, the optimal basis function of TVAR model for the IF estimation of the NLFM signal is obtained in this paper. Besides the depth and width of notching, the phase properties of notch filter affect the SINR of correlation output to the narrow band jammer suppression in DSSS, in response to the problem the closed solution of correlation output SINR improvement has been derived when a single frequency jammer passes through direct IIR notch filter, and its performance has been compared with those of five coefficient FIR filters. Later, a novel method for NLFM jammer suppression based on Fourier basis TVAR model and direct IIR notch filter is proposed. The simulation results show the effectiveness of the proposed method.