A Small All-Corners-Truncated Circularly Polarized Microstrip Patch Antenna on Textile Substrate for Wearable Passive UHF RFID Tags

We present a wearable passive UHF RFID tag based on a circularly polarized (CP) patch antenna on a textile substrate. The antenna miniaturization is based on applying a combination of the cross- and L-shaped slots in the radiator. In conjunction, the right-hand circular polarization is achieved by asymmetrically truncating all four corners of the square-shaped radiator. Despite using a regular low-permittivity textile as the antenna substrate, we downsized the antenna to a 5 cm times ,5 cm footprint with the thickness of 4 mm, which is equal to 0.1525 {lambda }, times ,0.1525 {lambda }, times ,0.0091 {lambda } , where {lambda } is the free space wavelength at 915 MHz. In the numerical modeling and optimization of the antenna, we used a simplified cuboid-shaped and anatomical human body models. In addition to simulated conventional antenna performance indicators, we introduce spatial coverage as a new parameter for assessing the detection reliability of UHF RFID tags. Finally, we measured a manufactured tag worn in four different configurations on the body. The measured axial ratio value was approximately 2 dB in all cases and the tag provided a high attainable read range of around 5.8 meters for a right-hand CP reader emitting 3.28 W EIRP.acceptedVersionPeer reviewe

Advances in Antennas and High-Frequency Material Characterization for Wireless Body-Area Networks

The development of the personal body-centric communication system is an essential part of the novel generation of wireless communication systems and one of the communication technology challenges. The versatility of body-centric communication revolutionizes healthcare by allowing continuous and in-all- conditions human health monitoring and human-centered authentication. Recently, with the extra-low power consumption and low-complexity backscatter communications, the passive ultra-high-frequency (UHF) radio-frequency identification (RFID) technology has been considered a promising approach for the wireless body area network. An inevitable part of this system is the wearable antenna, which plays a critical role in ensuring the efficient wireless link of the signal in the presence of the wearer. The wearable antenna should be fabricated with textile materials and equipped with various radiation configurations to enhance robustness and the operation’s versatility for long-term use. The difficulty of the wearable antenna development is to obtain the property information of the unknown textile substrate and conductor. To address the above-mentioned challenges, this thesis starts with the novel textile material characterization method to single out the relative permittivity and loss tangent of the substrate and bulk conductivity of the conductor. Unlike conventional approaches, our method simply applied the testing structure of the microstrip line composed of the textile material and simple data processing with the least square estimation. Then, a variation of the textile wearable antenna development with a low-profile planar in geometry is proposed in the next part of the thesis. The headgear RFID tag and forearm RFID reader antennas were developed based on quasi-Yagi configurations and periodic surface to obtain a directive pattern along the body surface. Another type of antenna configuration developed in this thesis is the circular polarization patch antenna for the wearable RFID tag. This type of antenna significantly reduced the polarization mismatch between the reader and the tag; hence, the detection capability and radiation efficiency are remarkably upgraded. The promising performance of the antennas was rigorously analyzed in simulation and verified with on-body measurement

Wireless and Battery-Free Biosignal Monitoring using Passive RFID Tags

Wearable health monitoring devices are becoming increasingly ubiquitous in clinical settings and even in monitoring daily activities. This recent spurt in wearable devices has been made possible through the development of low power electronics, small footprint components and efficient data transmission methods. The next big step in making monitoring devices more 'wearable' is the elimination of batteries. Without the need to replace and recharge batteries, monitoring can be uninterrupted and the monitoring device itself can be seamlessly integrated into garments. However, to achieve this goal, merely reducing sensor power consumption is not enough. There is a need for unconventional methods of health monitoring. par In this work, a novel passive Radio Frequency Identification (RFID) based method for transmitting health parameters wirelessly and without batteries is described. The dissertation proposes an innovative method of transmitting health parameter data by simply turning RFID tags on and off. Technology for RFID based continuous monitoring that include a wireless power harvester and low-power circuits for amplification and health parameter detection are developed in this research. The dissertation includes practical applications of the technology that are demonstrated using heart rate and uterine contraction monitoring as examples. Empirical tests for characterizing the heart rate monitoring system are also conducted. The heart rate monitoring technology is validated with human testing which showed a correlation of over 99% between actual and detected heart rate data.Ph.D., Electrical Engineering -- Drexel University, 201

The Design, Fabrication and Practical Evaluation of Body-centric Passive RFID Platforms

Passive ultra-high-frequency (UHF) radio-frequency identification (RFID) technology is increasingly being recognized as a compelling approach to utilizing energy- and costefficient wireless platforms for a wireless body area network (WBAN). The development of WBANs has stimulated a lot of research over recent years, as they can offer remarkable benefits for the healthcare and welfare sectors, as well as having innovative sportsrelated applications.This thesis is to evaluate and develop the RFID tags used in an integrated wearable RFID platform working in a realistic environment. Each of the wearable antennas were specifically designed for a target part of the body, such as the back or the hand. The antennas were manufactured in different ways, using copper tape, electro-textiles (Etextile) and embroidered conductive threads. After they had been produced, the tags were subjected to on-body measurement and reliability tests. The reliability tests were performed under tough conditions in which the tags were stretched, for instance, or exposed to high humidity and washing. Our results show that the tags can perform well when worn on-body in a harsh environment.This thesis provides several integrated solutions for wireless wearable devices. By different RFID antenna design and fabrication methods, the RFID tag can be used as the moisture and strain sensor with lightweight, small size, flexible pattern and great dailyuse reliability