Experimental Real-Time Electromagnetic Knee Imaging Using Pattern and Polarization Diversity

An electromagnetic imaging system for real-time knee injury detection and monitoring is presented. The system features an 8-element MIMO antenna array with pattern and polarization diversity designed to operate over a wide bandwidth (0.8–2.7 GHz). Each MIMO element employs four orthogonal feed lines and a substrate-integrated waveguide cavity for enhanced directivity and unidirectional radiation. A flexible matched layer is used to ensure efficient energy transfer and compatibility with the dynamic knee motion. The MIMO module is fabricated and tested on a realistic knee phantom. A modified delay-and-sum imaging algorithm is used to generate knee images for cases emulating various scenarios, considering early-stage cases and the challenges of dynamic movement. The results demonstrate the capability of the system to accurately detect and localize ligament tears, outperforming conventional linear and dual-polarized systems.