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

Abstract

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.