Composite right/left-handed ultra-wideband metamaterial antenna with improved gain

A coplanar waveguide-fed ultra-wideband (UWB) composite right/left-handed (CRLH) antenna is presented. It is designed by embedding CRLH unit-cell on the top side and split-ring resonator (SRR) on the bottom side of FR4 epoxy substrate. The UWB response is obtained by merging the resonances of CRLH unit-cell and SRR with two additional resonances due to patch feed-line and ground plane, respectively. Subsequently, the gain of UWB CRLH antenna is enhanced by loading two partial reactive impedance surfaces (PRISs) on the double layer FR4 substrate. First PRIS is embedded directly on the rear side of CRLH antenna (upper layer substrate) whereas the second PRIS is designed on the backside of the lower layer substrate. A considerable improvement in gain is observed over the frequency range from 6.2 to 10.6 GHz with peak enhancement of 1.75 dB. The proposed antenna is fabricated and measured. The measured results indicate -10 dB fractional bandwidth of 126.15% (3-13.25 GHz) with realized gains of 2.2, 5.25, 5.5, and 7.3 dBi at 3.57, 7.46, 8.92, and 10.59 GHz, respectively. The simulated radiation efficiency is above 61% with a peak value of 86.21%. All measured and simulated results match reasonably well.