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 ( \rm TM_{1,1,0}^{HM} mode) so that it merges with higher resonance (rotated \rm TM_{2,2,0}^{HM} 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 GHz WLAN band (5.15-5.825 GHz).