Theoretical study of the corrugated hard horn used as feed in multi-beam antennas for dual band operation at 20/30 GHz

We have demonstrated that in a cluster-fed reflector, a normal single-tuned hard horn can satisfy the usual -25 dB system requirements for the cross polarization over a large frequency band, but it cannot completely satisfy the requirements for the copolar level in the neighboring beam We have also tried larger reflector diameters than those presented here. In those cases, the beam isolation becomes better, but the 30 GHz footprint gets a dip in the center The reason for the dip is that the sidelobe of the feed is illuminating the reflector at 30 GHz. This may be improved for finite lengths of the horn, for which phase of the aperture field at the horn causes a beam broadening mainly at 30 GHz.