Crosspolarisation in beamwaveguide feeds
Abstract
Earlier studies have shown that the theory of the propagation of Gaussian beams takes into account the higherorder crosspolarized modes generated by offset reflectors used in beam waveguides. The paper demonstrates that by assuming an idealized Gaussian radiation pattern for the feedhorn and ignoring the finite sizes of the reflectors, the Gaussian mode analysis enables the residual crosspolarization transmitted by a beam waveguide to be predicted by relatively simple formulas. The discussion is limited to beam waveguide designs of paraboloid and ellipsoid configuration. The computed patterns radiated from the beam waveguide on a spherical surface corresponding to the Cassegrain subreflector position are plotted for the paraboloid and ellipsoid designs. Good agreement is found between Gaussian mode theory and numerical approach. It is concluded that the crosspolarization intrinsic to the reflection of radiation by offset curved surfaces is the dominant factor in the overall performance of a beam waveguide.
 Publication:

Electronics Letters
 Pub Date:
 September 1976
 DOI:
 10.1049/el:19760403
 Bibcode:
 1976ElL....12..529H
 Keywords:

 Antenna Radiation Patterns;
 Beam Waveguides;
 Horn Antennas;
 Polarization Characteristics;
 Wave Excitation;
 Antenna Feeds;
 Ellipsoids;
 Microwave Transmission;
 Parabolic Reflectors;
 Subreflectors;
 Wave Reflection;
 Communications and Radar