A Circularly-Polarized Zero Beam-Squinting Leaky-Wave Antenna Using NRI-TL Metamaterials with Increased Gain

A circularly-polarized metamaterial leaky-wave antenna (LWA) at 5.5 GHz is presented, which exhibits zero beam-squinting (ZBS) at broadside with an increased gain. It consists of two oppositely-directed negative-refractive-index transmission-line (NRI-TL) LWAs. The two LWAs radiate their main beams in opposite directions, and the combination of the two beams results in a broadside beam. The two LWAs are fed through a NRI-TL balun that adds a 180° phase difference between the two output signals. The addition of the balun doubles the gain of the metamaterial LWA, and makes it circularly polarized. The gain of the antenna is 11.75 dBi at 5.5 GHz, 3.35 dBi higher compared to the antenna without the balun. The ZBS bandwidth of the antenna is 0.9 GHz, the axial ratio ranges from 1.1 to 1.4, and the average radiation efficiency is 80%.