Anisotropic artificial material with ENZ and high refractive index property for high gain Vivaldi antenna design

In this paper, an anisotropic artificial material (AAM) is proposed which shows epsilon near zero (ENZ) or zero index metamaterial (ZIM) property and effective refractive index greater than 1, simultaneously in a direction. Further, the proposed material is investigated to improve the gain of an ultrawideband (UWB) Vivaldi antenna (VA). The unit cell of AAM consists of compact meandered line metallic strip on a dielectric substrate. The AM shows the ENZ property in the frequency band of 8 GHz-12 GHz due to the electrical resonance along the meandered axis of the AAM. While, due to the non-resonant electrical property in the direction orthogonal to the meandered axis high refractive index property is observed in UWB. Significant gain enhancement of up to 2 dBi is observed due to the AAM. The VA with AAM shows good unidirectional radiation characteristics with improved front to back ratio in the UWB.