Antenna radiation and scattering analysis based on infinitesimal dipole modeling

Abstract

For accurate operation of the antenna, the radiation pattern of the antenna must be accurately analyzed. If multipleantennas are arranged, mutual coupling between the antennas should be considered. For large objects around theantenna, the radiation pattern distortion due to scattered waves should be calculated. Electromagnetic numericalanalysis techniques have been used to obtain accurate radiation patterns that take into account such distortioneffects. However, MoM technique requires much time and memory cost. Additionally, the MoM should be calculatedrepeatedly when the antenna operation environment changes. Antenna current Green's function (ACGF)can be used to efficiently handle these effects. Once the data is obtained, it is not necessary to calculate the MoMrepeatedly according to the environment. If the receiving environment is changed and the incident waves arecalculated, the antenna pattern considering mutual coupling effects can be obtained. Two methods for obtaining ACGF are well known. The first is a method of calculating ACGF through a mathematical solution. It is accuratebut most of realistic antennas are not theoretically perfect. It is also difficult to derive ACGF analytically, exceptfor a few simple antennas. Next, ACGF can be obtained by numerical method using MoM. If the model is accuratelymodeled by CAD, the induction current distribution can be obtained with a relatively high accuracy, and ACGF can be obtained by using it. However, when the antenna is large and complex, huge memory and timecost are required to calculate the solution of MoM. Also, the difference between the actual antenna structure andthe CAD model can cause the simulation result to differ from the actual value. Method to replace ACGF withoutthe above disadvantages using infinitesimal dipole modeling (IDM) is proposed. IDM is a rigidly arbitrary antennamodeling technique with multiple infinitesimal dipole arrays. The ID model can be obtained using theradiation pattern of the antenna. Radiation patterns can also be obtained through measurements in addition tosimulations using electromagnetic analysis techniques. Each ID obtained in the radiation pattern is regarded asa point current source, which has the same shape as the antenna organic current element obtained by MoMcalculation. A method to replace the induced current distribution obtained by MoM by using ID model as ACGFis proposed. The advantage is that the substitute can be obtained without MoM because the ID model can beoptimized using the measured radiation pattern. The proposed method requires less time compared to MoMtechnique. In addition, since the CAD model is not used, an error caused by the difference between the actualantenna and the CAD model does not occur. In this paper, method to efficiently obtain IDM using convex optimization,which is a kind of optimization algorithm is proposed. Existing IDMs required unnecessary modelingdata because IDs were all placed at uniformly distributed grid points in a specific bounding box. An algorithmwhich increases the sparsity of the ID model is used by applying recursive optimization to minimize $reweightedl_1-norm$. Using the proposed algorithm, IDM with almost similar accuracy is obtained with fewer data. Next, wewill introduce new ways to use IDM. The ID model is used as an organic current distribution to replace ACGF.Therefore, we can obtain data to replace ACGF by using measured radiation pattern without MoM simulation.This is verified using the measured antenna radiation pattern and simulation data.