Compact and Bandwidth-Enhanced Zeroth-Order Resonant Antenna

In this letter, a simple bandwidth-enhanced zeroth- order resonant (ZOR) antenna is proposed. The presented antenna is composed of two unit cells of the composite right/left-handed (CRLH) artificial structure and operates in the series resonant mode. In order to enhance the operational bandwidth, in particular, the interdigital capacitor in a unit cell was properly designed so as to reduce the quality factor of the resonator while occupying a relatively small area. Additionally, to facilitate implementation of the short-circuited boundary condition, the coplanar waveguide (CPW) was applied to develop a via-less uniplanar antenna prototype. Experimental results show that the presented ZOR antenna achieves a 10-dB bandwidth of 15.1% and a peak radiation gain of 1.62 dBi with a compact size of 0.14λ₀ ×0.22λ₀ at the operating frequency. Measured and simulated results are in good agreement.