Electronically controllable primary feed for profile-error compensation of large parabolic reflectors

The paper shows that it is possible to compensate for the effects of mechanical profile errors in large parabolic reflectors, by means of a specially designed multielement feed array situated in the focal plane of the reflector. The factors relating the magnitude and period of these profile errors to the size and complexity of the compensating feed are discussed, and a novel method is described for achieving this compensation by controlling the phasing of the array. The system employs a spatial Fourier-transforming device, and its use is mainly restricted to long-period profile errors. Experimental results of this process, derived from a small-scale laboratory system employing a 1-dimensional 5ft parabolic reflector incorporating an 8-element feed, are presented. These results demonstrate compensation for profile errors up to ¿/2 radians. The possible application of this technique to existing and new reflectors is discussed.