Microstrip patch beamforming linear antenna array with complementary split ring resonator for fifth generation applications

Abstract

The next generation cellular standard which is called fifth generation (5G) requires high gain beamforming antenna array to provide high speed and secured communication. Therefore, the proposed research work investigates the design and development of a four-element linear microstrip patch array operating at 25 GHz for 5G beamforming application. To investigate the radiation characteristics of the proposed array, five beamforming radiation patterns (main beam at 0', +15' and +20') have been considered. The mutual coupling between array elements raise the challenge of designing the antenna array system. The coupling alters the array element input impedance and distorts the overall radiation performance. Hence, a simple complementary split ring resonator (CSRR) structure has been developed to alleviate the coupling problem. The modeled configuration is numerically analyzed, verified and implemented between the array elements. The existence of the CSRR configuration in antenna array, controls the unnecessary surface current flow between the array elements, thus the mutual coupling between array elements has been significantly reduced from -23 dB to -55 dB. The effect of coupling on the array radiation patterns has been studied in the presence and absence of CSRRs. Most importantly, the effectiveness of CSRR has been studied by steering the main beam as well as the nulls in different angles. By implementing the CSRR elements in array antenna, the distorted array patterns have been recovered and are presented. The proposed CSRR implemented in antenna array have the advantage of easy and low cost fabrication and it offers excellent coupling suppression without changing the antenna profile. Moreover, to the best of the authors knowledge, it was observed for the first time that the CSRR worked effciently in reducing the effect of mutual coupling when the beam was steered off from broadside direction from -20' to +20'. The simulation tools such as MATLAB and Ansys HFSS have been used for array weights calculation and antenna design respectively. Finally, the fabricated prototype has been experimentally verified, and it shows that the analytical and computed results agree well with the measured results.