A tri-band flexible wearable antenna loaded with an electromagnetic bandgap structure

Abstract This paper presents a tri-band flexible wearable monopole antenna integrated with an electromagnetic bandgap (EBG) structure. The antenna uses a flexible PDMS (polydimethylsiloxane) substrate, with resonant frequencies at 2.45, 3.5, and 5.8 GHz, and operates within the frequency bands of 2.42–2.60 GHz, 3.11–3.70 GHz, and 5.32–6.81 GHz. To further optimize the antenna’s impedance matching and radiation characteristics, a defected ground structure is introduced in the design. Additionally, an EBG reflective surface is used to enhance reflection properties, reduce back radiation, improve antenna gain, and decrease the specific absorption rate (SAR). A 4 × 4 tri-band EBG array structure is integrated on the back of the monopole antenna, with each EBG unit consisting of two circular rings and a polygon, achieving zero reflection phase at 2.45, 3.5, and 5.8 GHz. The antenna demonstrates good impedance matching across the designed frequency bands, with a significant gain enhancement of 8.1, 6.64, and 8.21 dBi at the respective frequencies. Simulations with a human model show that the SAR values are below international standards within the operating frequency bands. The antenna also exhibits excellent robustness in its bent state, showing promising potential for applications in medical health monitoring.