Low-Profile Head-Worn Antenna With a Monopole-Like Radiation Pattern

Abstract

We present a low-profile antenna derived from a center-fed circular patch to provide uniform spatial coverage around a human head in 5.8-GHz ISM band. With the thickness of only 7 mm, it provides a compelling solution for a beacon-like radiator or harvester embedded in a smart headgear or in an in/off-body communication relay-station. We will first outline the development of an ellipsoid head model for numerically efficient optimization of the antenna and then detail the antenna development based on full-wave simulations. The results are validated using an anatomical head model and measurements both in air and in head-worn configuration. The measured results show that the antenna achieves a 0-dBi gain in the spatial angles around the head. The simulated radiation efficiency is 76%, and specific absorption rate (SAR) is well below ICNIRP and FCC limits even with 100 mW antenna power.