Preliminary announcement of an 85 percent efficient reflector antenna

The aperture efficiency is defined in the usual way to include the spillovers, illumination, phase, and cross polarization efficiencies of the projected circular aperture. The antenna comprises a 157.1-lambda main reflector, a 47.1-lambda subreflector, and a 5.1-lambda aperture feedhorn. Both reflectors are shaped in such a way as to provide quasi-uniform aperture illumination with a degree of spillover control. By using an offset feed geometry, the configuration provides an unblocked main reflector. An analysis of expected performance yields a theoretical 86.5% aperture efficiency, whereas the measurement technique yields 84.9%. The estimated measurement tolerance is now + or - 3% (approximately + or - 0.15 dB) on a high confidence (approximately + or - 3sigma) basis.