A compact and broadband NRI-TL metamaterial monopole antenna

Abstract

A compact and broadband negative-refractive-index transmission-line (NRI-TL) metamaterial antenna is proposed, which consists of a conventional printed monopole loaded in a left-handed fashion. The metamaterial loading allows the antenna to be modeled as a short folded monopole around 5.5 GHz, and simultaneously acts as a a balun for the ground plane around 3.55 GHz, therefore enabling the ground plane to radiate at this frequency. Consequently, the metamaterial-loaded monopole antenna exhibits a very wide impedance bandwidth by virtue of the orthogonality between these two radiating modes. The NRITL metamaterial monopole antenna has a simulated -10 dB return-loss bandwidth of 3.84 GHz while maintaining a very high efficiency in the order of 90%, and achieves orthogonal pattern diversity in both the 3.3 - 3.8 GHz WiMax and 5.15 - 5.85 GHz WiFi bands.