A new integration algorithm and its application to the analysis of symmetrical Cassegrain microwave antennas

An efficient numerical algorithm for physical optics (PO) analysis of reflectors is presented. Cylindrical symmetry of the reflector is not essential but is assumed for purposes of illustration, and this leads to the use of Fourier representation in the azimuthal variable. The algorithm is based on quadratic approximation of the phase and polynomial approximation of the remaining portion of the integrand. The necessary integrals are generated recursively and they involve the Fresnel integral. Additional efficiency is achieved by means of an interpolation scheme. Therein one interpolates all but the rapidly varying edge diffraction contribution to the integral and then adds the explicitly calculated edge contribution at each far-field point. A few illustrative examples are included.