Electro-Textile UHF-RFID Compression Sensor for Health-Caring Applications

Electro-textile Ultra High Frequency (UHF, 865–868 MHz) Radio Frequency Identification (RFID) devices have great potential to be explored as sensors due to the features of fabric materials. In this work, an electro-textile UHF-RFID compression sensor base on T-match structure with a corresponding interface are developed and evaluated for two application scenarios. For accurate textile UHF-RFID antenna design and maximize the read range, the impedance of the electro-textile based on snap buttons is modelled and characterized an a measured read range of 5.22m is experimentally obtained. If the distance of the RFID reader and RFID sensor remain constant at 1 m. The experimental results show that RSSI range change from −42 dBm to −58 dBm as a quadratic function in terms of the knee angle bending and from −45 dBm to −40 dBm during expiration and inspiration phase when the sensor is located on the chest, which validated the usefulness of the proposed sensor.

I. Introduction

With Radio Frequency Identification (RFID) technology development, many commercial devices are applied in diverse scenarios [1]–[3] such as health-caring monitoring [4], goods tracking [5], [6], classification, localization and stuff management [7]. Especially in health-caring monitoring scenarios, the wireless RFID devices are expected to play a role as respiration sensors [8], [9], skin temperature sensors [5], [14], [15] and strain sensors [16], [17]. Generally, the operation frequency selection and structure designs of RFID sensors depend on the required sensing functions. With regard to the working frequency selection, Ultra High Frequency (UHF) RFID devices are getting more attention due to their lower cost, long-distance transmission and fast-easy identification. There are two ways to achieve sensing functions for wireless UHF-RFID devices. One way is that tags can be designed to connect sensors with different functions [18]. For these types of UHF-RFID sensors, chips need to have extendable ports for sensors connection (such as the ROCKY100) [18]. Another way is to use the antenna as a sensor.