A Dipole-Mode Smart Glasses Antenna with Suppressed Ground Current and Enhanced On-Head Efficiency

In multifunctional smart glasses, the mainboard is typically implemented as a flexible printed circuit (FPC) passing through both the frame and the temples. However, conventional antenna designs may excite strong ground currents on the FPC, resulting in severe efficiency degradation when worn on the head. This paper presents a smart-glasses antenna that excites a dipole mode to suppress ground current and enhance on-head efficiency. The proposed antenna is located in the hinge region of the glasses, where a probe-fed dipole is excited above the through-frame FPC ground. Compared with conventional inverted-F and monopole antennas, the proposed design effectively suppresses ground current and, being positioned at the farthest point from the head, significantly reduces power absorption by the head, thereby improving efficiency. The proposed antenna is fully compatible with through-frame FPC routing and its operating bandwidth fully covers 2.4 GHz ISM band (2.4 ~ 2.48 GHz). In the operating band, the proposed work exhibits an on-head efficiency of 71.8 ~ 76.9% and a 1g SAR below 0.45 W/kg across the 2.4 GHz ISM band.