Research On Anti-interference Methods Of Array Radar Antenna

With the rapid development and the wild application of radar to various areas in modern society, the anti-jamming capability of radar has become increasingly important to modern radar. The two main interference signals that impact radar performance are active jamming and passive jamming,and the active jamming radiating from the electronic jammers can most influence the normal operation of radar receivers. In accordance with the position of interference signal in the beam, active jamming can be classified into main lobe jamming and side lobe jamming. The adaptive side-lobe cancellation algorithm, as an effective method for suppressing the side lobe jamming, has been widely used due to its low cost, easy to be applied and other good features. After considerable and in-depth researches conducted by several generations, the principle of this algorithm has become perfect. However, the adaptive side-lobe cancellation algorithm is subject to the external factors during the actual engineering application, and therefore has the problem of cancellation performance degradation. For the main lobe jamming signal, the conventional adaptive beam-forming technology can raise the side-lobe level, distort the main beam and deviate the peak value. Therefore, the study of a new kind of algorithm will be essential to the elimination of the jamming signal from the main lobe and the side lobe directions.In this paper,the main work is as follows. First and foremost, the author introduces the signal model of the far-field, narrow-band and the uniform linear array antenna, studies the three optimal criteria of adaptive beamforming algorithm. Then, several factors affecting the performance of the cancellation system are interpreted by the mechanism of adaptive side-lobe cancellation algorithm and the performance index. When the stronger desired signals leak into the auxiliary antenna, the desired signal cancellation occurred. In order to deal with that problem, two kinds of adaptive beam-forming algorithms based on side-lobe cancellation which adopt blocking matrix and eigen-subspace projection, respectively, are put forward. The simulation results indicate that these two kinds of algorithms can effectively solve the problem of desired signal cancellation and both can well suppress the side-lobe jamming signal in the radar antenna. Thirdly,as to the jamming signal entering from the main-lobe direction of the radar antenna,the simulation analyses three kinds of adaptive beam-forming algorithms suppressing this kind of jamming signal, i.e. the adaptive main-lobe interference suppression algorithm of pretreatment of blocking matrix, pretreatment of eigen-projection and the eigen-projection and covariance matrix reconstruction. In this paper,the author also summarizes and analyses the adaptive beam-forming method which can handle the offset of the peak values in the main lobe interference suppression algorithm. Then,with the co-existence of the main lobe jamming signal and the side lobe jamming signal, and the higher power of the main lobe jamming signal, the eigen-projection preprocessing algorithm may have the problem of narrowing or disappearing of the null in the side lobe jamming direction. To cope with that problem, the improved main lobe interference suppression algorithm based on the eigen-sub space and the main lobe interference suppression algorithm based on linear constraints and covariance matrix reconstruction are put forward. The simulation results have shown that the algorithms put forward in this paper can ensure the deeper null in the side lobe jamming signal direction while effectively suppressing the main lobe jamming signals, and thus raised the output SINR of the system.