The Low Sidelobe Beamforming Algorithm On Nonuniform Linear Array

In the era of the information warfare, the modern signal processing techniques and algorithms have become a very important topic on research. With the change of the signal environment, the adaptive beam-forming can automatically adjust the weight vector, in order to enhance the useful signals,and to effectively improve the performance of the system.Therefore, the adaptive beamforming becomes an extremely important field of the array signal processing. It has been widely used in communication, sonar and radar and many other fields. In the research of the adaptive beamforming, an important direction is the formation of low sidelobe, which can suppress the interference and noise from the area of the side-lobe effectively in order to reduce the false alarm probability of the system, and to improve the performance of the antenna array. The existing research is mostly for uniform linear arrays, so there are certain limitations. Therefore,we need to design a new algorithm,aiming at the non-uniform linear array, the planar array and many other antenna arrays which are more complex and flexible, to reduce the sidelobe level. That has more practical research value.The main work of this paper is as follows: in the first part I use the notch noise-field method to reduce the sidelobe. Based on the maximum signal to interference and noise ratio(SINR) criterion, a large amount of interference is applied to the field of the sidelobe, and the power of the interference is corrected to obtain the pattern with the uniform low sidelobe. On the basis of the notch noise-field method, the desired voltage is changed into a variable reference voltage, and the lowest sidelobe level can be obtained under a certain mainlobe width. Then both the mainlobe and the sidelobe are controlled. The interference is also applied to some area of the mainlobe to solve the problem of distortion when the main value is further broadened. In the second part I use the optimization theory to reduce the sidelobe.The method of sparse constraint is introduced to reduce the sidelobe. And some sidelobe constraints are added to obtain the uniform low sidelobe level. Then by changing the objective function, the minimum sidelobe beamforming is achieved by using the minimax criterion under a certain width of the mainlobe. By comparing the notch noise-field method with the convex optimization algorithm,the conclusion is drawn that the second is better. At last,a new hybrid algorithm is proposed,which can further reduce the sidelobe by combining the notch noise-field method with the convex optimization, and with the increase of the array element number, the effect is better. The robustness of the convex optimization algorithm is studied also, and the robust lowest sidelobe level beamforming is achieved.