On the Design of Circularly Polarized MIMO Antenna with Polarization Diversity

A simple-topology circularly polarized (CP) multiple-input-multiple-output (MIMO) antenna with polarization diversity is presented. The proposed design comprises two parallel placed coplanar waveguide (CPW)-fed antennas with the opposite senses of polarization. Circular polarization is induced in the antenna by simple geometrical modification of the conducting coplanar ground planes on the right/left side of the microstrip transmission line. To achieve polarization diversity, the left-hand and right-hand CP is realized by simply switching the positions of the ground plane with respect to the microstrip line monopole. Owing to this configuration, the proposed antenna features a wide impedance bandwidth $(\vert \mathbf{S11}\vert\leqslant-\mathbf{10\ dB})$ and axial ratio (AR) bandwidth from 5.2 GHz to 6.3 GHz along with high isolation of $\vert \mathbf{S21}\vert\leqslant-\mathbf{20\ dB}$ in the entire operating frequency range. The peak realized gain of the antenna is 5.8 dBic, the envelope correlation coefficient (ECC) is less than 0.004 with the maximum diversity gain (DG) of approximately 9.99 dB.