Development and Testing of Split-ring Antennas for Wearable Electro-textile UHF RFID Tags

Wireless body area network(WBAN) is developed from personal area network that helps different sensors to communicate while being worn on human body. The passive UHF (Ultra-high frequency) RFID (Radio frequency identification technology) is one of the fundamental technology used for tracking animals, people and objects. Currently, an emerging area of development is the use of wearable RFID tags in health care systems. The personal healthcare systems demand information about sensed or measured biological parameters to be reliable and rapidly sent over a wireless communication link for investigation purposes. Furthermore, the communication system must be absolutely flexible, low-power, maintenance-free and low-cost in order to be utilized on different parts of the patient’s body for continuous monitoring of physiological parameters such as blood pressure, body temperature, glucose level, and respiration system. Therefore, due to the extensive need for the implementation on flexible and conformal material, researchers have been working on textile based RFID tags. One of the hottest topics is the development of electro-textile based RFID tags for body area networks. In this thesis, to measure the performance of wearable split ring antennas on electro-textile material, different split ring antennas have been developed that are materialized with two different kinds of materials such as copper and electro-textile. The development of wearable antenna is quite challenging task due to antenna material properties, environmental issues and radiation absorbing nature of human body at higher frequencies. By considering these factors, 85% antenna-IC power transfer efficiency at 915MHz has been achieved in body-worn configuration. Furthermore, to analyze the near body performance of developed antenna, distance between antenna and the human body has been varied, for example 2 mm, 3mm, 5mm and air. Moreover, to measure the performance of antenna on clothes, EPDM (Ethylene-Propylene-Diene-Monomer) substrate of different thicknesses i.e 2mm and 5mm have been used. From the simulated and measured results, it has been noticed that copper based split ring UHF RFID tag shows excellent match between measured and simulated results in body-worn configuration. Furthermore, provides excellent tag performance at variable antenna-body separations down to two millimeters and also in the air. Interestingly, this is novel feature of wearable antennas based on a single conductor layer. On the other hand, it has been analyzed that electro-textile based split ring RFID tag shows some variation between simulated and measured on-body/off-body results