A novel twin conjugate matched feed for dual-beam offset reflector antennas

In this article, the design and development of a novel twin conjugate matched feed horn at Ku-band is presented. This type of multimode feed cancels the undesired high cross-polar components generated because of offset reflector geometry having lower f/D and higher offset angle. Three symmetrically located axial arrays of radial posts are used in the circular waveguide for the generation of TE 21 mode along with the dominant TE 11 mode. The design and development of a Ku-band twin conjugate feed horns were carried out. The measured return loss of both the feed horns are better than 22 dB, and there is an excellent agreement of measured and simulated radiation pattern of the feed. The simulated cross-polar bandwidth is 5% for better than 10 dB improvement in cross-polarization for an offset parabolic reflector antenna having f/D = 0.5 and offset angle = 90°. In this work, it has been established that the conjugation operation as reported in single feed is maintained in spite of aperture sharing of the twin feed horns.