Design and Simulation of a Flexible UWB MIMO Antenna for mm‐Wave IoT Applications: Performance and SAR Evaluation

Abstract This study introduces a compact quad‐element Multiple‐Input Multiple‐Output (MIMO) all‐textile antenna designed for Ultra‐Wideband (UWB) Internet of Things (IoT) applications. The antenna employs felt as the substrate and conductive fabric as the radiating element, optimizing it for wearable devices. Its pentagon‐shaped radiator with L‐shaped slots, partial rectangular ground, and circular parasitic patch ensures a compact UWB response. The orthogonal arrangement of elements enhances MIMO performance, while a circular slotted structure with vertical interconnects provides high isolation (>20 dB) and a unified ground plane. Simulations demonstrate an operational bandwidth of 21–50 GHz with 81.69% impedance bandwidth (–10 dB return loss), peak gain of 8.92 dBi at 27.5 GHz, and radiation efficiency exceeding 89%. Specific Absorption Rate (SAR) values at 29, 38, and 44 GHz are within safe limits (0.315, 0.248, and 0.446 W/kg −1 , respectively). Additionally, diversity metrics such as Envelope Correlation Coefficient (ECC < 0.003) and Diversity Gain (DG ≈ 10) indicate excellent performance. This flexible, high‐speed, and reliable antenna is a promising solution for future IoT systems, meeting the requirements of wearable UWB communication with safe operation and outstanding diversity characteristics.