COMSTAR Experiment: The Crawford Bill 7-Meter Millimeter Wave Antenna

The Crawford Hill 7-meter antenna (Fig. 1) was built for propagation measurements with the COMSTAR beacons at 19 and 28.5 GHz, and for radio astronomy at frequencies from 70 to 300 GHz. It demonstrates that low sidelobes and high cross-polarization rejection can be obtained in an earth station antenna serving several satellites simultaneously. The antenna will also serve as a test bed for future propagation and antenna measurements. The main part of this paper is contained in the following three sections. Section II describes the 7-meter antenna starting with the initial requirements. Section III gives a detailed description of the 19/28.5-GHz 1257 Fig. 1--The 7-meter offset Cassegrainian millimeter wave antenna. The subreflector is mounted below antenna aperture, and key structural parts are covered with insulation.