Efficient and accurate method for calculating and representing power density in the near zone of microwave antennas

A method for computing and exhibiting Fresnel-region fields radiated by microwave antennas that uses plane-wave scattering matrix analysis is presented. Near-fields are calculated by numerically integrating the complex far-field antenna pattern. The predicted near fields are exhibited as relative power density contours lying in a longitudinal plane bisecting the antenna´s aperture. With spatial-coordinate scaling, each set of contours becomes a function of the relative aperture distribution and the electrical size of the antenna. If the electrical diameter is much larger than any normalized transverse coordinate of interest, the contour set becomes invariant with respect to antenna size. The coordinate normalization can produce contours applicable to any antenna with the same relative aperture distribution, regardless of antenna size