STATE-OF-THE-ART TRI-BAND MIMO ANTENNA SYSTEMS FOR MULTI-STANDARD SUB-6 GHZ WIRELESS COMMUNICATIONS: DESIGN, PERFORMANCE, AND RESEARCH CHALLENGES

Abstract

The rapid deployment of fifth-generation (5G) wireless networks has intensified the demand for compact, high-performance antenna systems capable of delivering high data rates, low latency, and reliable connectivity, particularly within the Sub-6 GHz spectrum due to its balanced coverage and penetration characteristics. In this context, Multiple-Input Multiple-Output (MIMO) antennas have emerged as a key enabling technology; however, achieving multi-band operation within compact MIMO architectures remains challenging because of mutual coupling, limited impedance bandwidth, and strict size constraints. This work presents the design, simulation, and experimental validation of a compact tri-band MIMO antenna operating at 2.4–2.5 GHz, 3.4–3.6 GHz, and 4.6–4.8 GHz, specifically targeting Sub-6 GHz applications such as 5G New Radio, Internet of Things (IoT), smart city infrastructure, cloud-based communication, and fixed wireless access systems. The antenna is designed on a low-cost FR4 substrate and optimized using ANSYS HFSS to enhance impedance matching, isolation, and diversity performance. Simulated results demonstrate return loss values below −10 dB, voltage standing wave ratio (VSWR) less than 2, and inter-element isolation exceeding 20 dB across all operating bands. Key MIMO performance metrics, including channel capacity loss, are carefully evaluated, with values maintained below 0.1, indicating excellent diversity efficiency and minimal correlation between antenna elements. A fabricated prototype is experimentally characterized using a vector network analyzer, showing close agreement between simulated and measured results. The proposed tri-band MIMO antenna is expected to offer improved radiation efficiency, robust isolation, and reliable multi-band performance while maintaining compact size and cost-effectiveness, making it a strong candidate for next-generation Sub-6 GHz wireless communication systems and providing a scalable design framework for future enhancements such as reconfigurable structures and intelligent optimization techniques.