A Circularly Polarized Differentially Fed Transmission-Line-Excited Magnetoelectric Dipole Antenna Array for 5G Applications

A circularly polarized (CP) differentially fed magnetoelectric dipole (ME-dipole) array is proposed for fifth-generation applications. The proposed transmission-line-excited antenna, fabricated on a printed circuit board, can achieve wide impedance and axial ratio (AR) bandwidths and high gain. The antenna consists of a $2 \times 2$ ME-dipole array enclosed by a circular cavity. It is modified from our previous work on linearly polarized (LP) array with its element orientation selectively rotated by ±45° with respect to the differentially fed transmission line and the use of sequential rotation technique to generate CP radiation. A differential feed network is utilized to feed the prototype for experiments. Experiments show that the antenna can present an overlapping impedance and AR bandwidth of 32.2% from 52.2 to 72.2 GHz with a broadside left-handed CP gain from 10.2 to 11.8 dBic. The proposed CP antenna retains all the salient features of our previously proposed LP antenna in symmetric and stable radiation patterns and relatively low back radiation levels.