Electromechanical Coupling Analysis Of Array Antenna Based On Infinitesimal Dipole Model

Array antenna can form different array forms according to the number and arrangement of array elements.By applying different excitation amplitude and phase,flexible radiation pattern can be obtained,which makes it widely used in communication,radar and many other fields.In practical engineering,the array antenna structure is affected by self-weight,wind,heat and other loads,which makes the array surface deform.At the same time,processing and assembly errors will also lead to the array element position offset.In order to evaluate these effects quickly and effectively,it is necessary to analyze the electromechanical coupling of deformable array antenna.However,the strategies to analyze the electrical performance of deformable array antenna are relatively limited at present: the pattern product theorem cannot consider the mutual coupling between array elements;subarray extrapolation can only be applied to planar array without considering the influence of deformation factors;full wave analysis software is accurate,but the cost is high,so it is difficult to apply to large array.Therefore,in this paper,the infinitesimal dipole model(IDM)is proposed to replace the array elements,and the mutual coupling effect of the array elements is characterized as the mutual admittance between IDM,and construct the influence relationship between the position and orientation offset of the array elements on the radiation field of the array,so as to realize the electromechanical coupling analysis of the deformed array.This paper mainly includes the following three aspects.(1)According to the radiation field of the antenna,the field intensity expression of IDM is deduced and programmed.Then,based on the near-field data and physical boundary of the target array element,the objective function is constructed,and the number of infinitesimal dipoles and the range of optimization variables are determined at the same time.Establish the optimization model,and the parameters such as the dipole moment amplitude and phase,the angle with the coordinate axis and the position vector of the infinitesimal dipoles are optimized by using the quantum particle swarm optimization algorithm,so that the field strength of the model at the same observation point is consistent with that of the target antenna.The IDM equivalent of the actual array element is realized.(2)IDM is used to replace each element of the target array antenna.Based on the reciprocity theorem,the analytical expression of mutual admittance between IDM is derived.At the same time,considering the deformation factor,analyze the influence mechanism of position and attitude offset on mutual admittance,and the expression of mutual admittance between IDM in different positions and attitudes is derived and programmed.(3)On the basis of obtaining the admittance parameters of IDM,considering the port input admittance,the mutual admittance matrix of the array is calculated,and then the actual excitation current of each array element and the pattern in the array are obtained.According to the spatial phase factor of the array element,the pattern in the array is spatially superimposed to obtain the far-field pattern of the array antenna.Finally,using half wave dipole antenna and butterfly antenna as array elements,the electrical performance of different forms and sizes of deformable array antenna is analyzed by IDM method,and the calculation results are compared with the simulation results of mom,which verifies the accuracy and superiority of IDM method.