Ultra‐wideband directional electrically small antenna for UHF through C‐band 5G and beyond 5G applications

Abstract A semi‐spherical combined transverse electromagnetic (TEM) horn and loop antenna is designed for directional ultra‐wideband operation from 0.42 to 6 GHz for 5G and beyond 5G applications across military and commercial sectors. The antenna structure fits within a sphere with 3‐cm radius, thus operating as electrically small over the lower part of the band ( ka = 0.5 at 0.795 GHz and ka = 1 at 1.59 GHz). To spread the currents across the volume while maintaining the required relationship between the lowest order TE and TM modes, the loop section is modified to conform with the enclosing minimum sphere. The TEM horn, bowtie, and resistive loading are then tuned to achieve improvement over the conventional topology in the radiation efficiency by >7% when ka = 0.5 and >22% when ka = 1.