Design of a wideband antenna with beam steering for sub-6 band of 5G

Abstract

5G is the 5th generation of wireless communication technology. The frequency range of 5G is higher than the 4G LTE. High-frequency wave has high attenuation due to short wavelength, so high gain antennas and small cell base stations are being used in 5G network technologies. This project designed a wideband antenna with beam steering for the sub-6 band of 5G. The design is a Multiple-Input-Multiple-Output (MIMO) antenna operating at 2.6GHz which can be used in base stations. The antenna consists of 8 ports, each pair of ports connected to one antenna array. The beam steering can be achieved by adjusting the phase of the current in different input ports to control the direction of the mainbeam. The antenna array consists of 4 dual-polarized Magneto-Electric (ME) dipole antennas which is an existing design. The existing design was modified to connect with the microstrip line power divider. These ME dipole antennas are fed by two 1-to-4 transmission line power dividers. Two power dividers feed the antenna array to give linear polarization in positive 45 degrees and negative 45 degrees, respectively, so two polarizations are orthogonal and isolated. The current is feed from the output ports of power dividers to the ME dipole antennas through a coaxial structure waveguide with 50 Ohm impedance. The bandwidth with the reflection coefficient lower than -10dB is 17.1% (2.40GHz – 2.85GHz), which covered the 5G NR standard frequency band N41 (2.496GHz – 2.690GHz). The maximum gain of the antenna array is 21dBi, and the front-to-back ratio is above 24dB. The mutual coupling effect between either two input ports is below -27dB. The design in this project can further develop to be used in the massive MIMO base stations.