A Metamaterial Inspired ZOR Antenna Using IDC and Spiral Inductor with Partial Ground Plane for WLAN Application

Abstract

In this article, an open-ended metamaterial antenna structure is designed for WLAN application. The antenna comprises of an interdigital capacitor (IDC) and spiral inductor with a partial ground plane. The IDC (shunt element) act as a varying parameter to control the zeroth-order resonance (ZOR) frequency, whereas spiral inductor (series element) is used to form a first negative order resonance frequency at 2.29 GHz. The ZOR mode has been excited at 4.53 GHz by employing complimentary right/left handed transmission line model in the structure and the first positive order resonance (FPOR) frequency is obtained at 4.9 GHz. A rectangular shaped stub has been used to act as a virtual ground for IDC. The proposed antenna design has total foot-print size of 0.29λ0 × 0.27λ0 × 0.024λ0. The fractional bandwidth of 20.41% (4.36–5.35 GHz) is achieved due to the merging of ZOR and FPOR mode respectively. In addition, it also exhibits a measured peak gain of 2.12 dB and 2 dB with a radiation efficiency of 77.76% and 87.62% at ZOR and FPOR frequencies respectively. A prototype of the proposed antenna structure has been fabricated and simulation results are experimentally rectified. A good agreement between simulation and measured results are obtained.