Comparative study of a CRLH TL based Zeroth Order Resonant antenna

In this paper, a comparative study between a compact microstrip Zeroth Order Resonant antenna with another coplanar waveguide (CPW) based vialess ZOR antenna is presented. But the drawback of this microstrip based CRLH TL is that a narrow bandwidth of about 0.75% with an improved gain of about 3.6256dB is achieved. In order to circumvent this drawback we demonstrate a vialess CPW fed structure using the same substrate, RT Duroid (5880) (ε_R = 2.2, h = 1.57mm) and compare the performance of both these antennas. In the CPW fed case we obtain a bandwidth enhancement of about 7.84% with a dumb-bell shaped radiation pattern at phi=90deg (E-radiation pattern). The zeroth order mode obtained in this case is at 2.14GHz while with the microstrip based ZOR antenna, the zeroth order freq is at 3.995GHz with a monopolar radiation pattern at phi=90deg. The CPW fed antenna is easy to fabricate as it is based on a single layer. The drawback of this CPW fed antenna is that the gain reduces to 1.6949dB as the structure is electrically much smaller than the microstrip based ZOR antenna. Simulated results for both the cases are shown. The operational bandwidth of the CPW based ZOR antenna at 2.14 (2.06 to 2.2195) GHz covers the required bandwidths of the IEEE 802.11 for wireless local-area networks (WLAN) applications while in case of the microstrip ZOR antenna, the operational bandwidth at 3.995Ghz and at 3.095 GHz encompasses worldwide interoperability for microwave access (WiMax) standards suitable for point to point multiband applications.