In this article, a compact dual-port single element MIMO antenna is presented for millimeter wave (mmWave) 5G wireless applications. The presented antenna design consists of an annular ring slot that is fed by a Substrate Integrated Waveguide (SIW) at the two opposite sides of the substrate. The antenna resonates at 28GHz and its 10dB impedance bandwidth is 400MHz. The isolation between the ports is reduced by introducing additional annular slot that acts as a cavity which results in an isolation better than 20dB at 28GHz. The measured gain of both ports are 6.9 dBi which is the highest gain per unit element at 28GHz in the literature. The measured diversity gain and envelope correlation coefficient are 9.98dB and 0.065, respectively, at the band of interest. The measured and simulated results are in good agreement.
