An organ-pipe scanner

In designing many scanning antennas, it is desirable to move a feed horn for an objective, a lens, or a reflector, along a curve on the focal surface of the objective. The most direct way to solve this problem is to move a horn on the desired curve mechanically; however, there are mechanical and electrical problems inherent in this type scanner which one would like to avoid. Another approach is the use of a simple mechanical motion, such as a rotation, which could be transformed into an apparent motion along the desired curve. Organ pipes use this approach, they usually consist of a structure for propagating energy from a feed horn through a transition region of waveguide channels to a radiating aperture. By rotating some part of this structure, different portions of the aperture are used, and hence the apparent motion along the line occupied by the aperture, or scanning, is accomplished.