E- and H-Plane Constant Beamwidth Horn Antenna Over 4:1 Frequency Band

A wideband corrugation slot, called stepped-shape slot, is proposed in the design of E-plane corrugated double-ridged horn antenna (DRHA) with H-plane pin sidewalls to extend the constant beamwidth bandwidth (BW) of horn antennas. Closed-form expressions for the input admittance of the new slot are derived, and the BW is compared with the BWs of other conventional corrugations. The proposed slot presents wideband characteristics with a BW ratio of more than 4:1. The use of stepped-shape slot in a corrugated wall keeps the surface reactance capacitive over a relatively large frequency band. The H-plane sidewalls of the designed antenna are formed by curved pinwalls. The flare includes ridges to extend the frequency range, and the E-plane walls are corrugated with a wideband slot to improve the beamwidth constancy in elevation. Thus, constant beamwidth horn antenna (CBWHA) is obtained at both azimuth and elevation planes over the desired frequency band from 4.5 to 18 GHz. The measured performance of the proposed CBWHA reveals wideband characteristics with 31.0° ± 2.5° H-plane and 37.4° ± 5.2° E-plane half power beamwidths over 4:1 frequency range.