Efficiency‐Enhanced Open Earbud Earphone Antenna Using Dual‐Feed Technique

ABSTRACT The stringent spatial constraints and high antenna‐efficiency requirements in wireless earphones present critical engineering challenges. This letter proposes and investigates an earphone antenna design for open earbud wireless earphones. Unlike the conventional single‐feed designs of earphone antennas, this work employs a dual‐feed technique with a phase difference. The proposed dual‐feed technique enhances the effective radiating area, resulting in an efficiency improvement of over 1 dB compared to single‐feed designs. The −6 dB impedance bandwidth of the fabricated prototype covers the 2.4 GHz ISM band. The measured efficiencies are −8.5 dB in free space and −9.5 dB in the on‐head condition. The achieved high efficiency within a compact space highlights the antenna's potential for practical applications.