Wearable Antenna and Rectenna Designs for WBAN and H-IoT Applications

The evolution of Wireless Body Area Networks (WBAN) and Healthcare Internet of Things (H-IoT) technologies has foregrounded the pivotal role of wearable antennas and rectennas (WANRs) in the upcoming technological paradigm, promising unprecedented innovations. Despite their potential, the seamless integration of these devices encounters challenges, spanning from material and body-induced factors to system-level requirements. This research has sought to bridge these gaps in the domain of wearables, exploring some innovative WANRs with high performance from a system perspective.

In this work, a novel method based on Characteristic Mode Analysis (CMA) has been proposed to enhance the performance of low-profile wearable circularly polarized (CP) antennas in the 2.4 GHz band. By introducing a unique parasitic slit-loading technique, which enables to address the troublesome strong capacitive effects in traditional low-profile designs, the CP bandwidth of wearable antennas has been significantly expanded to a new benchmark.

A novel strategy was also proposed for the effective integration of antennas and rectifiers in wearable rectennas. This integration sidesteps numerous conventional losses and culminates in a state-of-the-art system power conversion efficiency (PCE) at ultralow -20dBm input power and obtains the highest sensitivity among wearable rectennas. Demonstrated practical applications suggest a novel paradigm for powering wearables using everyday devices like PCs and mobile phones.

As the last part, this research presents an innovative +/- 45o-polarized dual planar inverted-F antenna (PIFA) system tailored for wearable Backscatter Communication (BSC) applications. A symmetric via wall shorting strategy is proposed to generate the 45o slant polarization. Further, a defected ground structure (DGS) is incorporated to enable mutual coupling suppression while the antenna system features +/- 45o-polarization. By adopting hybrid PCB/flexible substrates to design, a balance between flexibility, fabrication simplicity, and cost has been struck, underlining the necessity of adopting a system-level outlook.

In essence, this thesis underscores that while wearable technologies hold vast potential, their mass implementation demands a holistic strategy, striking a balance between leading-edge performance and real-world practicality.