Research on the method of countering off-board active decoy

From the perspective of estimating the target angle of arrival (AOA), in this paper, the problem of how to counter the interference of off-board active decoys based on the monopulse radar system is studied. The signal model under the condition of centroid jamming formed by the off-board active decoy is established, and the statistical characteristics of target and off-board active decoy jamming echoes are analyzed. Based on this, two methods of AOA estimation, the improved maximum likelihood estimation method and moment estimation method, are proposed. The Monte Carlo simulation experiment are conducted to study the performance of the angle estimators for various values of subpulses N, signal-to-interference ratio (SIR), signal-to-noise ratio (SNR), etc. The asymptotic statistical properties of the probability distribution function (PDF) of the target AOA are also studied. The accuracy of the proposed methods and algorithm complexity are compared with the existing methods and the Cramér-Rao lower bound (CRLB) as well. The results show that the PDF of target AOA obeys the Gaussian distribution asymptotically, and the estimation performance of the proposed method is closer to the square root of CRLB as the increase of the number of subpulses N, SIR and SNR. Theoretical analysis and simulation experiments verify the feasibility of the proposed methods.