Generation of elliptical beams of an arbitrary beam ellipticity and low cross-polarization using offset dual parabolic cylindrical reflectors

It is shown that dual parabolic cylindrical reflectors can be designed to yield elliptical beam shapes with an arbitrary beam ellipticity, defined as the ratio of the beamwidths in the principal planes. The only limitation affecting the beam ellipticity is the practical geometry of the antenna in a particular use, where certain feed or sub-reflector dimensions may not be desirable. To confirm computations, an experimental unit was designed to yield a beam ellipticity of about 12, and was fed by a dielectric rod feed to reduce the aperture blockage. The measured patterns closely match the computations. An offset configuration which may be used to eliminate feed blockage is also investigated. Its performance is also verified by an offset experimental unit.