Wearable Pattern-Diversity Dual-Polarized Button Antenna for Versatile On-/Off-Body Communications

A wearable dual-port button antenna that excites pattern-diversity dual-polarized waves is proposed for on-/off-body applications. Its simple structure comprises of two radiators and a common ground plane designed into two substrates. The crossed-dipole radiator is made by two symmetric bowtie dipoles printed on a circular-shaped semi-rigid substrate, which covers an ultra-wideband (UWB) application with circular polarization and directional radiation patterns, high gain, and high efficiency suitable for off-body communication. The annular-ring radiator and common ground plane are made by a conductive textile on the square-shaped flexible-felt substrate. The annular-ring radiator is shorted to the ground plane using four vias, which generates triple TM modes covering the 2.45/5.85 GHz wireless body area networks (WBAN) with omni-directional radiation patterns and a 3.8 GHz C-band with a directional radiation pattern suitable for on-/off-body communications. The fabricated antenna is verified by measurement in both free space and phantom body environment. Measurements agreed well with simulations. Simulated specific absorption rates (SARs) under US and EU standards are below the safe level, making the proposed antenna suitable for on-/off-body communications.