Application of double-negative materials to improve an ultra-wideband TEM horn

Ultra-wideband TEM horns are used to transmit short, high-power electromagnetic pulses. Return loss is a problem for high-power applications, as reflected power can damage the source. For a typical short pulse, the return loss needs to be small over several frequency decades. Techniques exist to achieve a small return loss at the low and high-frequency ends, but the intermediate frequency range remains a challenge. This paper describes how double-negative (DNG) materials, having negative permittivity and permeability, can be used to reduce return loss at selected frequencies without sacrificing performance at other frequencies.