Research On Decoupling Method Of Array Antenna In Digital Domain

Conformal arrays are increasingly used in radar,communications and electronic warfare systems,where array performance is severely affected by mutual coupling between elements,thus deteriorating performance in terms of DOA estimation,beam-forming and isolation.How to cope with the strong mutual coupling between array elements,eliminate the severe consequences of the mutual coupling effect and restore the good performance of the array has become an important issue for engineers.In view of this,this paper will investigate the mutual coupling calibration technique for arrays,and the research contents are as follows:Firstly,based on the array signal model and the mechanism of the mutual coupling effect,the mutual coupling calibration technique in planar arrays is investigated,and the principles of the joint DOA and mutual coupling matrix estimation algorithm and the auxiliary array element self-calibration method are analyzed correspondingly.The algorithms are based on the properties of the mutual coupling matrix and decouple the mutual coupling matrix from the array manifold by means of transformation relations.The performance of the algorithm is simulated with the aid of uniform linear array and uniform rectangular array,and it is found that the joint estimation algorithm has better performance in compensating for the mutual coupling and has a wide range of applications.Secondly,a modified joint estimation algorithm is proposed to solve the problem of pseudo-peaks arising when the joint estimation algorithm is used for uniform circular arrays.The algorithm compensates for the rank loss defect of the mutual coupling matrix of the uniform circular array by weighting the numerator,and effectively eliminates the phase ambiguity caused by the mutual coupling.It is verified through simulation that the algorithm can accurately estimate the mutual coupling factor and DOA parameters,which can effectively calibrate the mutual coupling error and reduce the phase ambiguity.Then,based on the signal characteristics of the conformal array and the array structure,the mutual coupling matrix characteristics of the conformal array are analyzed and a modified joint estimation algorithm for the conformal adaptive array is proposed.A three-layer cylindrical conformal array composed of patch antenna units is used to simulate the performance of the algorithm,and the simulation data verifies that the algorithm has good performance in parameter estimation and mutual coupling compensation.Finally,in the area of spatial filtering,the principle of adaptive beamformers is presented and a beamforming scheme based on reciprocal calibration is proposed.The scheme uses the element pattern reconstruction method to calculate the mutual coupling compensation matrix and uses the array signal data compensated by this matrix for beamforming.The performance of the beamformer is verified using a physical eight element line polarised conformal antenna array.The test results confirm that the scheme is effective in creating zero traps in the interference direction and thus suppressing interference,and also has excellent filtering performance under the mutual coupling effect.