Adjustable Passive RFID Skin Mounted Sticker

Abstract

Passive Radio Frequency Identification (RFID) can be limited by such aspects as size that make overcoming the capacitive loading introduced by human tissue difficult when intending to produce an efficient antenna with a high read range. It is still possible to design a small and thin RFID tag with a read range above half a meter. Here we present such a design with a diameter of less than 3 cm, By utilizing a breathable polyurethane polymer with two thicknesses, it is possible to use a single tag design for human tissue (dielectric constants ranging from a 22 to 40) with only a slight loss in antenna read range. It is more cost effective to just adjust the polyurethane thickness for a single design than to tune the antenna design itself. Volunteers one and two had read ranges above one meter while volunteer three (with permittivity of 40) caused the largest shift in antenna resonance from 865 MHz (EU band) and required an increase in polyurethane thickness from 1.1 mm to 1.5 mm. However, both designs still produced read ranges above 0.5 meters which could be further tuned with future adjustments to increase read range. This led to a passive RFID design that can be worn by most people with a simple thickness adjustment if needed.