Mutual Coupling Reduction and Isolation Enhancement Using Periodic EBG Structure in a Compact MIMO Antenna

This paper presents the design and analysis of a compact two-port MIMO antenna system integrated with a periodic Electromagnetic Band Gap (EBG) structure for enhanced isolation at 28 GHz, intended for 5 G millimeterwave applications. The antenna elements are inset-fed microstrip patches, designed on a low-loss Rogers 5880 substrate, and spaced to accommodate a column of circularslotted EBG unit cells. The unit cell geometry is optimized through parametric variation of the slot radius to suppress surface wave propagation and reduce mutual coupling. The structure achieves a reflection coefficient (S11) better than 40 dB and improves isolation (S21) by approximately 20 dB with the inclusion of the EBG. Surface current distributions confirm effective decoupling behavior, while the calculated Envelope Correlation Coefficient (ECC) and Channel Capacity Loss (CCL) remain below 0.005 and $0.1 \text{bps} / \text{Hz}$ respectively, demonstrating excellent MIMO diversity performance. The proposed antenna's compact form factor and high isolation performance make it ideal for integration in space-constrained 5 G wireless device. The results shows the EBG structure's ability to significantly improve MIMO antenna performance without increasing the form factor.