Textile Via-Loaded Bandwidth-Enhanced Half-Mode Substrate-Integrated Cavity Antenna for WLAN Communications

A textile via-loaded bandwidth-enhanced half-mode substrate-integrated cavity (HMSIC) antenna is presented in this article for wireless local area network (WLAN) communications. A strategy for adding shorting vias within the cavity is proposed based on the simulated E-field distributions of different modes of the HMSIC antenna. More specifically, the number and positions of vias are studied for maximum shift of lower resonance (TM1,1,0HM mode) so that it merges with higher resonance (rotated TM2,2,0HM mode) to achieve a wide 10 dB return loss impedance band. Two prototypes of the designed structure are realized using textile manufacture techniques. A first realization uses embroidered sidewalls to create the cavity and metallic rivets for the shorting vias, and a second prototype uses embroidered vias and a stripline feed. The proposed antenna can operate from 5.09 to 5.9 GHz with a fractional bandwidth of 14.7% according to measurements. The simulated radiation efficiency is above 95% in free space and 82% when worn on the human body in the 5 CHz WLAN band (5.15-5.825 GHz).