Novel Compact Asymmetric Coplanar Strip (ACPS)-Fed Zeroth-Order Resonant Antennas with Bandwidth Enhancement

Two compact zeroth-order resonant antennas employing short-ended mu-negative transmission line (MNG-TL) are presented. Both antennas are fed by asymmetric coplanar strip (ACPS), so strong miniaturization and simple structure can be achieved. Proposed antenna 1 operates at 2.38-2.47 GHz (fractional bandwidth is 3.7%), with a size of 0.093 lambda(0) x 0.145 lambda(0) x 0.008 lambda(0) at center frequency. In order to extend the bandwidth further, a tapered structure (using parabola curves) is designed in proposed antenna 2. Then an operating band of 2.41-2.97 GHz (fractional bandwidth is 20.8%) is obtained with a size of 0.095 lambda(0) x 0.225 lambda(0) x 0.009 lambda(0) at center frequency. Finally both antennas are fabricated and measured; measurements and EM (electromagnetic) simulations are in good agreement. And the results demonstrate that the proposed antennas have satisfactory omnidirectional radiation patterns with reasonable gains and extended efficiencies within the operating bands.