Robust low-profile metasurface-enabled wearable antennas for off-body communications

This paper presents a low-profile metasurface-enabled wearable antenna operating in the newly released medical wireless body-are network (MBAN) band from 2.36 to 2.40 GHz for off-body communications. The performance of the antenna was made possible by the introduction of a properly designed anisotropic metasurface which consists of only a 2 by 2 array of I-shaped resonating elements. Together with the finite-sized metallic ground plane on the back of the metasurface, it provides a +90° reflection phase band to achieve the desired impedance matching for the planar monopole feed above the metasurface. The integrated antenna was fabricated and characterized, showing a strong correspondence between simulated and measured results. The resulting antenna has a remarkably low profile of only one-fiftieth of the operating wavelength, all while achieving a 5.5%-10 dB impedance bandwidth from 2.30 to 2.43 GHz, a gain of around 6.2 dBi, and a font-to-back ratio higher than 23 dB, thus making it a promising candidate for incorporation into various wearable systems.