Circularly Polarized 28 GHz Compact Patch Antenna for 5G Mobile Communications

This paper presents a complete design of modified circular patch antenna to produce circular polarization at 28 GHz for the fifth generation (5G) of mobile communications with experimental verification. One of the novelty aspects of the proposed patch design is the use of tapered microstrip line feeder for impedance matching instead of the conventional inset feed to maintain the diagonal geometric symmetry required for good circular polarization with good impedance matching. Another novelty aspect of the proposed patch design is the use of defects of the ground plane (by making diagonally aligned circular cuts) to realize odd and even symmetries of the entire antenna structure instead of modifying the patch itself. The results obtained by experimental measurements show good agreement with those obtained by the CST® simulator. It is shown that the experimentally achieved bandwidth of impedance matching is about 1.6 GHz. The axial ratio obtained at 28 GHz is about 2dB and the 3dB-axial ratio bandwidth is about 0.4 GHz. Also, it is shown that 3dB-axial ratio beam width is 90° at 28 GHz where the antenna efficiency is 91% and the maximum gain is 7.3 dBi.