Bandwidth and gain-enhanced composite right/left-handed antenna for ultra-wideband applications

A coplanar waveguide-fed metamaterial antenna is presented for ultra-wideband (UWB) applications. The proposed antenna is designed with single unit-cell composite right/left-handed transmission line (CRLH-TL) loaded with a split-ring resonator (SRR). The UWB characteristic is obtained by merging the zeroth-order resonance of CRLH-TL with two additional resonances due to the ground plane and SRR respectively. Subsequently, a partial reactive impedance surface is embedded on the rear side of the proposed antenna to enhance the realized gain without affecting the UWB response. The overall size of the antenna is 0.241 lambda(o) x 0.267 lambda(o) x 0.013 lambda(o) (28.8 x 32 x 1.6 mm(3)), where lambda(o) is the free space wavelength at 2.51 GHz. The measured results indicate -10 dB fractional bandwidth of 139.19% (2.51-14 GHz) with realized gains of 2.3, 4.6, and 6 dBi at the resonant frequencies 4, 7.84, and 10.29 GHz respectively. The measured peak realized gain is 6.6 dBi at 10.6 GHz. The radiation efficiency is above 63.85% for the entire UWB range with a peak value of 86.84%. A fairly stable group delay with variation within 1 ns is obtained throughout the operating frequency band. A good agreement has been observed between the measured and simulated results.