High Isolation 4-Port MIMO Antenna using FSS Decoupling Structure for Wireless Applications

Mutual coupling poses a significant challenge in compact MIMO antenna systems because it lowers isolation, radiation efficiency, and diversity performance. This paper presents a compact frequency selective surface (FSS) technique to effectively reduce mutual coupling between closely spaced antenna elements that are 0.117λ0 apart. The designed FSS changes the polarization of incoming waves, which minimizes surface current interactions and enhances port isolation. We analyze the antenna performance using full-wave simulations and experimental measurements in the 2-5 GHz band. The results show a coupling reduction of 16-38 dB and excellent diversity characteristics, including ,ECC < 0.0017, TARC < -12.1413 dB, CCL < 0.0074 bit/s/Hz, MEG < -5.0567 dB, and DG> 9.99973 dB, and a radiation efficiency of 96.71%. The proposed structure demonstrates stable radiation behavior with improved isolation, confirming its potential for practical use. Due to its compact design and high isolation, this FSS-integrated MIMO antenna is a promising solution for modern high speed wireless communication systems.