A Miniaturized Metamaterial-Loaded Switched-Beam Antenna Array System With Enhanced Bandwidth for 5G Applications

Abstract

In this research study, a metamaterial (MTM) based $1\times4$ linear antenna array is designed with an integrated butler matrix (BM) beamforming network (BFN) to execute the switched-beam antenna array (SAA) operation, which can be employed for sub-6 GHz 5G applications. The proposed SAA is designed and simulated using CST microwave studio and then fabricated using FR4 epoxy glass substrate with the thickness ( $h$ ) = 1.6mm and dielectric constant ( $\varepsilon{r}$ ) = 4.3. The MTM-BM BFN has shown excellent performance in both simulated and measured results, having return-loss of below 14 dB and insertion-loss at ports 5-8 to be 7 ± 2dB between the frequency range of 3.2-3.75GHz, respectively. Moreover, the phase difference between the output ports of the BM is simulated and measured. The $0.5\lambda $ spaced complementary split-ring resonator (CSRR) based antenna array integrated with MTM-BM BFN achieved a measured gain of 4.8-6.1 dB when each input port of BM was excited. The SAA analysis has been performed to identify the variation of gain and grating lobes; the distance between MTM antennas was altered by $0.3\lambda $ , $0.5\lambda $ , and $0.7\lambda $ , respectively. Depending on the BM input ports excitation, the main beam of the SAA is steered in four different directions -40°, -15°, +15°, and +45°, respectively. These radiation pattern studies have shown that the MTM-BM connected with four linear MTM antennas has successfully generated four beams in four different directions, which can be utilized for 5G applications to improve the channel capacity and enhance the transmission quality.