Designing a Metasurface-based Tag Antenna for Wearable Vital Sign Sensors

This paper aims to design a tag antenna with metasurfaces for use in a wearable vital-sign sensing system. The system is based on a bistatic self-injection-locked (SIL) radar that consists of a chest-worn SIL oscillator (SILO) tag and a wireless handheld receiver. A frequency selective surface (FSS) and an electromagnetic bandgap (EBG) surface are placed on the front and back side of the tag antenna to reduce the influence of moving clutter and body proximity, respectively, on the system. In the experiment, a 5.8 GHz prototype system was implemented with the proposed tag antenna to monitor vital signs of a wearer who was walking in place.