Research On Electrical Properties Analysis And Surface Reconstruction Of Reflector Antennas Based On Zernike Polynomials

With the continuous development of large aperture,high gain,high reliability,high frequency and high pointing accuracy of reflector antennas,the effect of surface error on far-field radiation performance cannot be ignored anymore.And how to adjust the error surface to gain the desired or ideal far-field electrical performance is also the focus of current research.Therefore,based on the previous work,this paper takes a positive feed single-reflector antenna as an example,to study the influence rule of surface error distribution on the far-field electrical performance and the reconstruction of error surface based on the far-field electrical performance.Now what has been down is summarized as follows.(1)The influence of surface error distribution on the electromagnetic performance of antenna is studied.Zernike polynomials are introduced to represent the surface error,and a relation model between Zernike polynomial and far-field electrical performance based on the piecewise linear fitting method is established,which uses a series of straight lines to approximate the exponential error term.The relations model of the effect of each term and all the terms of Zernike polynomials describing surface error on electromagnetic performances is established.A database for the integrals is built to realize rapid calculation of the far-field electrical performance.The numerical results proved the correctness of the theory discussed above,and the influence rule of the first 37 Zernike polynomial terms on electrical performance is summarized.(2)The reconstruction and adjustment of deformation surface based on radio holography are studied.In this part,the deformation surface is directly deduced from the measured far-field pattern from theoretical level.Firstly the polar form of the radio holographic method based on geometrical optics method is deduced,and the field distribution on the aperture surface is obtained according to the electrical properties of the deformed electric performance,from which the error distribution is obtained.The linear equations are established to obtain the Zernike polynomials and the corresponding coefficients that described the error distribution.Numerical results show that the proposed method is feasible,effective and correct.(3)A kind of analysis software for calculation of far-field electrical properties and reconstruction and adjustment of deformation surface is developed.The analysis software is described in terms of functional requirements,workflow,the realization of the functions.During using the software,the corresponding far-field pattern can be quickly obtained based on the user-entered surface error,and the deformable surface error distribution that generates the far-field electrical performance can be quickly obtained based on the arbitrary far-field electrical properties which user inputs,and some adjustment to the pattern can be made.This analysis software provides convenience for antenna structural designers and electromagnetic designers.