Theory of imaging in Cassegrainian and Gregorian antennas
Abstract
The transformation relating the field distributions over two conjugate surfaces, Sigma(0) and Sigma, is determined in the present discussion of the formation of an image by an ellipsoidal reflector under illumination from one of its foci. It is shown that the image generated by the reflected field E over Epsilon is not an exact replica of the illumination of Sigma(0), but rather E=E(i) + deltaE, where E(i) is the image according to geometric optics. This theory is applicable to any multireflector arrangement derived from quadric surfacesofrevolution, and especially to Cassegrainian and Gregorian antennas. A simple solution to the classical problem of illuminating the aperture of a reflector antenna efficiently is given as an illustrative example.
 Publication:

IEEE Transactions on Antennas and Propagation
 Pub Date:
 May 1986
 DOI:
 10.1109/TAP.1986.1143870
 Bibcode:
 1986ITAP...34..689D
 Keywords:

 Cassegrain Antennas;
 Fresnel Reflectors;
 Gregorian Antennas;
 Image Processing;
 Reflector Antennas;
 Spherical Waves;
 Apertures;
 Maxwell Equation;
 Polar Coordinates;
 Spherical Coordinates;
 Communications and Radar