The multiband beam waveguide antenna

Satellite communications currently occupy microwave frequency bands at 4/6 GHz, 11/14 GHz and 12/17 GHz. Future needs may also see the use of frequencies above 20 GHz. The high cost of installing a large earth station antenna makes it appropriate to consider designing antennas to operate over several of these bands, either separately or simultaneously. The paper reviews the possibilities of a multiband antenna with conventional beam waveguide feed. The bandwidth limitations of beam waveguides are discussed, and a number of multiband feed systems employing offset reflectors are described. One possible feed complex, which enables a 19 meter Cassegrain to operate from 3.7 GHz to 21 GHz, is analyzed in depth, using physical optics/spherical wave techniques.