Bandwidth Enhancement of CPW-Fed Antenna Based on Epsilon Negative Zeroth- and First-Order Resonators

A coplanar waveguide (CPW)-fed metamaterial (MTM) antenna using an epsilon negative transmission line (ENG-TL) is presented. The bandwidth characteristics of zeroth-order resonance (ZOR) and first-order resonance (FOR) are analyzed and described using circuit elements based on the ENG-TL theory. The bandwidth enhancement of the MTM antenna can be achieved by merging the two extended-bandwidth resonances. The CPW geometry adopted as the host TL offers design freedom to modulate the circuit elements. Based on the analysis, the wideband antenna is fabricated and tested. The measured results show that the fractional bandwidth is extended up to 70.5%, and radiation efficiencies of the ZOR and FOR are 84.75% and 86.7%, respectively. With wide bandwidth, high efficiency, and omnidirectional radiation, the proposed antenna is very suitable for wireless communication systems (GSM, UMTS, LTE, WLAN, WiMAX).