Incremental Diffraction Coefficients for Planar Surfaces. Part 2. Calculation of the Nonuniform Current Correction to PO (Physical Optics) Reflector Antenna Patterns

摘要

A general and convenient method was provided for determining incremental length diffraction coefficients directly from the conventional two-dimensional diffraction coefficients. This sequel provides a detailed analysis of how the nonuniform incremental diffraction coefficients for the half-plane are integrated around the rim of a reflector. These computed far fields of the nonuniform current, when added to the far fields computed from the physical optics current, produce a more accurate total far field of the reflector. Excellent agreement with the far fields obtained from a method moments solution to the electric field integral equation applied to a 20-wavelength-diameter reflector shows that the cross polarization, further-out sidelobes, and fields near nulls of reflector antennas can be appreciably changed by the fields of the nonuniform currents. Finally, we evaluate the fields of the nonuniform current of the reflector through conventional asymptotic evaluation of the diffraction integrals and compare these approximate results with the far fields obtained by numerically integrating the nonuniform incremental diffraction coefficients. Keywords: Diffraction coefficients; Incremental length; Reflector antenna. (JHD)