Compact octagonal MIMO antenna system for broadband applications with enhanced isolation and wideband performance

This work introduces a compact and novel MIMO antenna system with close spacing and exceptional isolation, tailored for broadband usage across frequencies from 3.7 to 11 GHz. The antenna configuration consists of two octagonal radiators, each individually powered by a 50 Ω microstrip line. The use of a modified ground structure ensures a wideband frequency range. A key novelty of this design is the incorporation of a strategically placed stub (25.6875 × 0.5 mm²) between the radiating sections, which significantly enhances inter-port isolation, achieving over 15 dB despite the minimal 3 mm port separation—an improvement over conventional MIMO antennas. This design enables high isolation without increasing antenna size, making it highly efficient for compact wireless systems. Performance evaluation, including fabrication and testing, demonstrates a strong alignment between simulation and experimental data. Metrics such as envelope correlation coefficient (ECC), diversity gain (DG), and channel capacity loss (CCL) were analyzed to assess MIMO efficiency. The proposed antenna is ideal for broadband wireless systems with a peak gain of 6.5 dBi and excellent resonance, offering superior isolation and compactness compared to existing designs.