Calculation of radiation patterns of reflector antennas by high/frequency asymptotic techniques

TLDR: In this paper, a focus-fed paraboloid is calculated by asymptotic physical optics (APO) and geometrical theory of diffraction (GTD) for dipole and Huygens source feeds.

Abstract: Radiation pattern of a focus-fed paraboloid is calculated by asymptotic physical optics (APO) and geometrical theory of diffraction (GTD) for dipole and Huygens source feeds. It is shown that the GTD diffraction coefficients are approximations to the PO diffraction coefficients and are valid only in the proximity of the shadow and reflection boundaries. Some errors in the calculation of GTD diffraction coefficients are corrected. Rear radiation is calculated by another asymptotic expansion of the physical optics integral and is compared with the results obtained by other asymptotic techniques. This new expansion is finite in the back direction of the antenna where other methods diverge. Also front to back ratio of a paraboloid, ratio of front radiation to back radiation, is derived by using this new expansion and the results are compared with those predicted by equivalent edge currents method.