Abstract: This work presents an innovative approach to enhancing GHz-range MIMO antenna systems through the implementation of an advanced Frequency Selective Surface (FSS) framework. Leveraging modern computational methodologies and the principles of metamaterials, the design targets substantial improvements in both gain and isolation performance metrics. The antenna prototype is realized on a silicon dioxide substrate, measuring 70 × 76 mm2 with a thickness of 1.52 mm. Central to the design is a novel FSS unit cell architecture, inspired by metamaterial behaviour, which enables precise frequency filtration and refined electromagnetic wave manipulation. To elevate the antenna's overall efficiency, a dual-layer FSS strategy is adopted. One FSS layer is placed at the rear of the antenna to reflect reverse-propagating waves, thereby amplifying directional gain. A second FSS layer is strategically embedded between the MIMO elements, effectively mitigating mutual coupling and enhancing radiation quality. Simulation data confirms the efficacy of this configuration, showcasing an increase in antenna gain from 7.6 dBi to 10.6 dBi and an isolation performance exceeding 85 dB. These improvements underscore the potential of the proposed structure as a forward-looking solution for next-generation wireless systems that operate in the high-frequency GHz domain.

Keywords: Frequency Selective Surface (FSS), Gain Enhancement, Isolation Improvement, FSS reflector.

| DOI: 10.17148/IARJSET.2025.124116