Compact Over-Octave Horn Antenna with Stable Radiation Pattern

In this work a new compact wideband design of horn with stable radiation pattern over the frequency band 8-18 GHz is proposed and successfully tested. The suggested antenna is the modified design of conical horn with the sharp bend of generating line. The horn is excited with the original ultra-compact coaxial-to-waveguide transition from 50-Ohm coaxial line to standard double-ridged waveguide. For impedance matching the stepped transformer consisting of the double-ridged waveguide sections with various characteristic impedances is used. The designed compact horn maintains the operation in over-octave frequency band (2.25:1 bandwidth, fractional bandwidth 77%). Designed antenna has compact dimensions 60×60×68 mm. The proposed horn shows high electrical performances within operational frequency band 8-18 GHz: measured VSWR < 1.44, stable gain 11.6…11.9 dB, stable beamwidth of radiation pattern for the level -10 dB in H-plane $\Delta \theta_{0.1, H}=83^{\circ} \ldots 85^{\circ}$ and in E-plane $\Delta \theta_{0.1, E}=71^{\circ} \ldots 100^{\circ}$ This basic design may be utilized for development of the compact wideband antennas as well as the feeds of reflector antennas and lens antennas for microwave and millimeter wave applications.