TEXAS 5-M ANTENNA APERTURE EFFICIENCY DOUBLED FROM 230-300 GHZ WITH ERROR COMPENSATING SECONDARY

A study to upgrade the high frequency performance of the University of Texas 5-m millimeter wave reflector antenna established surface tolerance of the reflector as the limiting factor. The prime focus antenna was converted to a folded Gregorian geometry. The resulting trireflector system was measured holographically at 113 GHz. A machined secondary reflector was fabricated on a highly accurate computer-controlled milling machine. The inverse of the measured surface perturbations of the primary was machined into the secondary reflector. The modifying of ray path lengths effectively reduced the surface tolerance of the antenna. Radiometric measurements on a remote transmitter and on planets demonstrated an increase in antenna aperture efficiency by more than a factor of two over the frequency range of 230-300 GHz.