Integral equation solution for near-field to far-field transformation

A simple and accurate integral equation solution is presented for computing far-field antenna patterns from near-field measurements. The equivalence principle is used to replace the aperture of the antenna by equivalent electric or magnetic currents. An E-field integral equation (EFIE) is developed to relate these equivalent currents to the near-field data. The method of moments (MoM) is utilized to transform the integral equation into a matrix one and a conjugate gradient (CG) procedure is applied to solve it numerically. Accurate far-fields over large elevation and azimuthal ranges are calculated from simple measurements based on planar and spherical scanning