A comparative study among GTD and PTD techniques for circular discs

Abstract

Two groups of techniques based on the geometric theory of diffraction (GTD) and the physical theory of diffraction (PTD) are studied by using a canonical problem consisting of a conducting circular disc and an infinitesimal dipole feed. The GTD group includes the GTD, the uniform geometrical theory of diffraction, and the uniform asymptotic theory. The PTD group includes Mitzner's incremental length diffraction coefficients, Michaeli's equivalent edge currents, and Ando's modified physical theory of diffraction, which are modifications of Ufimstev's PTD. These solutions are compared with those obtained by the physical optics and the method of moments. Features of the far-field radiation patterns that are of particular interest include the performances at reflection boundaries, boresight caustics, and near theta =90 degrees as well as the prediction of cross-polarized fields, sidelobe levels, and nulls. Although only far-field radiation is considered, these methods can also be used for near-field calculations. The bistatic radar cross section calculated by these techniques is also examined. >