A compact quad element MIMO antenna for LTE/5G (sub-6 GHz) applications

In this paper, a compact I shaped monopole radiator with a dimension of 24 x 22 x 1.6 mm(3) is proposed. The monopole radiator achieved an impedance bandwidth of 1.46 GHz (4.06-5.52 GHz) using partial ground plane. Further to cover the sub-6 GHz spectrum (3.4-3.6 GHz) for future 5G communications, a four-element multi-input multi-output (MIMO) antenna configuration is designed by utilizing the single element antenna. The operation bandwidth of 2.27 GHz (3.37-5.64 GHz) is enhanced by using a tapered microstrip feed line. Isolation is increased upto 40 dB over the operating band (3.37-5.64 GHz) by using a modified rectangular stub in the partial ground plane. This stub also provides a decoupling path and consequently limited amount of current couples to the neighbouring element due to surface waves. The modified stub suppress the surface waves and the near fields reducing the coupling between the antennas keeping it below -10 dB for the whole desired frequency range. Therefore, the proposed MIMO antenna achieved wide bandwidth of (3.37-5.64 GHz) and minimum isolation between antenna elements 1 & 4 is -10 dB in 3.4-3.6 GHz frequency band, whereas -15 dB between 3.8 and 5.64 GHz frequency band. The suggested MIMO antenna is designed on a FR4 substrate with a dielectric constant of 4.4 and a loss tangent of 0.02 and a 0.45 lambda (0) x 0.45 lambda (0) dimension. In terms of the envelope correlation coefficient (ECC), diversity gain (DG), mean effective gain (MEG), total active reflection coefficient (TARC), isolation between the ports, and channel capacity loss (CCL), the proposed antenna's diversity performance characteristics are investigated and the obtained values are 0.04, 9.98, +/- 3, -11, -15 dB, 0.10 bits/s/Hz respectively. The antenna prototypes have been fabricated, and the measurements and simulations have been found to be in close agreement. Therefore, the proposed MIMO antenna covers n77/n78/n79 for 5G (sub-6 GHz) and LTE bands of 42/43/46.