A Distributed 4-Port Hilbert Slot MIMO Antenna with Full-Body Phantom Validation for mmWave Wearable Telemetry

This paper proposes a compact four-port Hilbert-slot MIMO antenna (HSMA)for 5G FR2 mmWave wearable medical telemetry and body-centric communication. The antenna is realized on a semi-flexible Rogers RT/Duroid 5880 substrate with an overall footprint of 12.32 × 12.32 × 0.508 mm3. The proposed work develops a compact Hilbert-slot radiator into a four-port 2 × 2 MIMO configuration to enhance port diversity, inter-port isolation, and body-centric link robustness. The simulated four-port HSMA provides super-wideband impedance matching from 24.05 to 62.64 GHz, while the fabricated prototype achieves measured matching from 24.71 to 63.81 GHz, corresponding to a 39.1 GHz measured bandwidth. The measured inter-port transmission coefficients remain mostly below −20 dB across the main operating band, confirming suitable MIMO isolation within the compact layout. The proposed HSMA also demonstrates practical radiation and diversity performance over the highlighted 24–64 GHz band. The measured realized gain reaches 7.52 dBi, and the measured radiation efficiency remains between 51.43% and 76.23%. The calculated measured MIMO diversity parameters show ECC values below 0.0175 and DG values above 9.998 dB, confirming weak correlation between ports and near-ideal diversity behavior. To assess wearable suitability, the antenna is further investigated under bending and realistic body-loading conditions using the CST Gustav voxel human model. In addition, orientation-based body placements are considered to evaluate telemetry paths between distributed body-worn nodes. CST-simulated S21 parameters are then used to calculate received power and link margin, providing a link-level assessment of the proposed wearable telemetry system. The results show that the proposed compact four-port HSMA combines continuous super-wideband operation, good MIMO isolation, low ECC, high DG, SAR compliance, bending robustness, and body-centric link feasibility, making it a promising candidate for 5G FR2 wearable biomedical telemetry, WBAN, and future mmWave body-centric communication systems.