Increasing the Focused Response of Impulse Radiating Antennas Through Polarization Control of Aperture Fields

Wide-band, focused aperture antennas like impulse radiating antennas (IRAs) can see improved aperture efficiency through control of the aperture shape and aperture field distribution. The shape of the aperture fields is largely dictated by the transverse electromagnetic mode distribution on the nondispersive feed of the IRA. In this paper we consider reshaping the aperture field by controlling the polarization of the fields reflected or transmitted by the focusing optic. In reflector IRAs, this polarization control is obtained by making the reflector out of uniaxially conducting filaments or wires. In lens IRAs, the polarization control is obtained by using a spatially varying wire grid polarizer. Optimum configurations are derived, and the expression for the far-zone radiated fields are given and compared with experimental measurements. For common antenna configurations and impedances, the aperture height can be increased by amounts ranging from 7 % to 67 %. An experimental prototype of a 200 Ω reflector IRA demonstrated a 23% improvement in aperture height, and agreed almost exactly with the numerical predictions.