Determination of the aperture field of an antenna by a beam-displacement measurement

A method is given for obtaining the scalar amplitude distribution in the aperture of an antenna through the single precise measurement of the aberration of the direction of the peak of the radiated beam caused by partially obscuring the aperture by a refiectionless dielectric sheet of known small phase-insertion delay. Analysis is presented whereby the distribution obtained can be presented as the sum of presumed modes in the aperture, although the scalar treatment does not allow the phases of such modes to be assumed. Agreement with experiment is shown to be quite good for a linear aperture in the form of an Eplane sectoral horn, and extremely good for a circular antenna with a monopulse feed giving precise measurements of the angular beam displacement.