Analysis and Design of Compact and High-Performance Ear-Bar TWS Earphone Antenna With Characteristic Mode Analysis

Analysis and design of compact ear-bar true wireless stereo (TWS) earphone antenna based on characteristic mode analysis (CMA) is presented. The proposed earphone antenna consists of an L-shaped branch and an inverted- L-shaped ground with an integrated inductor which can simulate the ear-bar TWS earphone. The CMA reveals that there are mainly two modes, namely, the half-wavelength mode of the ground and the quarter-wavelength mode of the branch, for the TWS earphone antenna. The two modes are mainly controlled by the ground and the branch, respectively. And for the compact earphone with a short ear bar, only the half-wavelength mode contributes to the radiation at the 2.45-GHz band which is mainly controlled by the integrated inductor on the ground. The measured results of the compact TWS earphone antenna prototypes illustrate that, the integrated inductor improves the −6-dB impedance bandwidth from 136 MHz (2364–2500 MHz) to 160 MHz (2360–2520 MHz) on the head. The measured average efficiencies within the 2400–2484-MHz band are improved from −11.2 to −6 dB on the head. The proposed ear-bar TWS earphone antenna with a compact size and improved performance is promising for modern TWS earphone applications.