The authors present efficient algorithms that can be incorporated in a physical-optics integration to account for migrating feed- and observation-point-dependent geometrical shadows caused by obstacles in the aperture of a reflector antenna with the feed under focused or scanned conditions. The expressions involve only addition and multiplication of simple low-order polynomials and hence do not introduce expensive overhead into the numerical integration. Obstacle shapes considered are disks, polygons, cylinders, and polyhedrons. Some appropriate diffraction corrections are presented which are compatible with the blocking algorithms. >

Observation-point-dependent blocking shadows on a reflector antenna

Publisher Summary This chapter presents an overview of paraboloidal-reflector systems. The rf performance of paraboloidal reflectors may be analyzed using various techniques of diffraction theory. Such techniques generally involve the integration of the dyadic Green's function over the currents induced on the reflector. These induced currents are estimated using geometrical optics. In principle, however, they may also be calculated using moment-method techniques or by applying classical results to appropriate boundary-value problems. Once the currents are determined, evaluation of the fields becomes straightforward although the computations may be lengthy and laborious. Computers are generally needed for all but a few special cases that may be integrated in closed form. The analysis of the transmitting properties of the antenna is presented in the chapter. An analysis and the geometry of the paraboloid with a prime-focus feed are also elaborated and illustrated. The aperture projection of blocked portions of a paraboloidal reflector is displayed and the classical dual-reflector antenna systems are analyzed. The calculation of radiation from dual-reflector systems by applying physical optics (PO) is also discussed.

W.V.T. Rusch

Papers

1.3. Analysis of Paraboloidal-Reflector Systems