A Novel Finger-Worn Dual-Band Ring Antenna for BDS B1 and 2.4 GHz Wireless Communication

This paper presents a compact dual-band ring antenna designed for finger-worn wearable devices requiring both satellite navigation and short-range wireless communication. The antenna is fabricated on a hybrid polyimide (PI) and PTFE substrate with an outer diameter of 23.07 mm and a length of 15 mm, while the inner cavity is filled with resin of adjustable thickness to fit different finger sizes. Dual-band operation at 1.575 GHz (BDS B1) and 2.45 GHz (ISM) is achieved by introducing a coupled microstrip branch that modifies the current paths and excites two resonant modes. The antenna exhibits quasi-omnidirectional and conical radiation patterns at the respective bands. Its electromagnetic performance is evaluated in free space and on a multilayer finger phantom. Measured results show stable impedance and radiation characteristics, with radiation efficiencies of 45%/69% (free space) and 31%/46% (on finger) at the two bands, and SAR values of 1.024 W/kg and 1.578 W/kg, demonstrating safe and reliable operation for compact wearable GNSS and 2.45 GHz wireless applications.