Eight-Port Wideband MIMO Antenna for Sub-6 GHz 5G Base Stations

An eight-port wide-band multiple-input multiple-output (MIMO) antenna is presented for base stations applications. The antenna is composed by four unit cells
$\boldsymbol{(2\times 2)}$
separated by a cross-shaped isolating block with a total size of
$\boldsymbol{220\times 220\times 28}$
mm ‘
$(\mathbf{2.42}\lambda\times \mathbf{2.42}\lambda\times \mathbf{0.3}\lambda$
, at central frequency
$\boldsymbol{\mathrm{f}=\mathrm{f}_{c}=3.3}$
GHz). The unit cell is defined by a square cavity-backed antenna fed with two I-shaped crossed dipoles. The antenna provides 8 independent ports with 21.5 dB of minimum isolation and an impedance bandwidth
$(\mathbf{S}_{11} < -10\mathbf{dB})$
of 97% ranging at 1.8-5 GHz. Results show an efficiency higher than 87%, unidirectional radiation patterns and low envelope correlation coefficient. The geometry of the antenna is suitable for scaling this design to a massive MIMO system with the replication of the proposed antenna.