Simple analysis method of beam scanning characteristic of a subreflector-displaced reflector antenna

A simple method is proposed to calculate the beam scanned angle of a dual reflector antenna due to subreflector statement displacement. After noting that beam scan by subreflector displacement is equivalent to beam scans by displacements of the feed horn and main reflector, the subreflector movement is translated into feed and main reflector displacement and the beam scanned angle is then the sum of an equivalent feed displacement component and an equivalent main reflector focal-point displacement component. The proposed formula is similar to that used in the case of a single parabolic reflector.<>