Ultrawideband square and circular quad-ridge horns with near-constant beamwidth

Two quadruple-ridged, flared horns, one with circular aperture and the other with square aperture, are presented achieving nearly constant beamwidth and excellent return loss over 6:1 and 4:1 frequency bandwidths, respectively, are presented. The circular and square quad-ridge horns are designed with nominal 10 dB beamwidths of 85 and 140 degrees, respectively. Radiation pattern measurements show excellent beamwidth stability in Φ = 0, 45 degree planes for both horns. Measured return loss is >; 10 dB over the entire band for the circular quad-ridge horn and much better for 85% of the frequency band. The square quad-ridge horn also has return loss ≥ 15 dB over much of the target frequency range. To the best knowledge of the authors, these horns are the first demonstrations of ultrawideband reflector antenna feeds with near-constant beamwidth which can accommodate widely different optical configurations.