Complicated Antenna Array Beamforming And Its Application On Airborne Radar

Conformal antenna array has shown broad application prospects in the field of airborne radars.Compared to the 1-D linear array or the 2-D planar array,the configuration of conformal array's elements is nearly the same as the structure of the platform,which is not only able to increase the area of the antenna array and extend the antenna array's horizon,but won't affect the design of aerodynamic-stealthy shape,so the aircraft's capacity of fighting and living is developed.On the one hand,conformal array beamforming can provide the ability of suppress the clutter and space interference on the foundation of playing conformal antenna's advantages;on the other hand,it is facing a series of problems which severely impact the performance of the beamformer in the practical application scenarios as well,for example the lack of the training sample,the polluted training samples and the difficulty of mutual coupling calibration.This thesis mainly study the beamforming technology of the complicated antenna array like conformal array in non-ideal conditions such as low sample support,polluted sample and mutual coupling.By analyzing the reason why the performance of the conventional adaptive beanforming algorithms decrease,this thesis made breakthrough in developing the robustness of beamforming algorithms,three improved complicated antenna array beamforming methods were proposed.The main contents of this thesis are given as follows:1.We study the basic principle of beamforming and discuss its performance when applied to complicated antenna arrays.First,the general model the antenna array receiving signals is built;then,the basic principle of adaptive beamforming is introduced;on this basis,the performance between the simple-structure array and the complicated-structure array is compared combing theoretical analysis and simulation tests,and the development potential and study value of complicated antenna array beamforming technology is demonstrated.2.We study the robust adaptive beamforming when amount of training sample is small or the training sample is polluted by the signal of interest(SOI).First,starting from the practical application scenarios,the problems conventional adaptive beamforming may face on the aspect of computation complexity,the need of sample amount and sample characteristic is analyzed;then,aiming at these problems,several existing robust adaptive beamforming algorithms is deeply analyzed;on this basis,we propose an improved interference-plus-noise matrix reconstruction adaptive beamforming method,this method relatively accurately estimates the noise power,has good performance in the condition where the training samples are scarce or polluted by the SOI and the computation complexity is relatively low.3.We study the robust adaptive beamforming of circular array under mutual coupling.First,we make analysis and modeling to the mutual coupling between the elements of the antenna array and the array error it brings,and quantify the mutual coupling's influence to beamforming algorithms;then,for this sort of influence,the mutual coupling characteristics of uniform circular array is analyzed;on this basis,two kinds of robust adaptive beamforming methods are proposed,one is based on the solution of spherical constraint optimization problem,another depends on the iterative estimation of direction of arrival and mutual coupling parameters.Simulation data validates that both of the two methods possess outstanding robustness under mutual coupling conditions.