Design of Wearable Antennas for Micro-and Millimeter Wave WBAN Applications

Abstract

In this dissertation, I propose design of wearable antennas for micro-and millimeter wave WBAN applications. Firstly, a wearable all-textile substrate integrated waveguide (SIW) cavity-backed circular ring slot antenna for off-body WBAN communications is proposed in chapter 3. All components of the proposed antenna consist of textile materials, and the antenna has a SIW cavity-backed feed structure. The radiating element was made of conductive textile with a circular ring slot and shorting vias for the SIW structure made of conductive threads. Since the textile antenna integrated on a cloth product can be bent, the effect of antenna deformation on the antenna performance must be considered. The proposed antenna fully covers the 5.8 GHz industrial, scientific, and medical (ISM) band with broadside radiation even when the antenna was bent. The performance of the proposed antenna was verified both numerically and experimentally by utilizing a two-thirds muscle equivalent phantom. The characteristics of the proposed antenna were not critically affected by the external effect due to the shielding effect of the SIW cavity structure. In chapter 4, dual-mode antenna for on-on-off repeater systems is proposed. For proper communication link between the two on-body transceivers, an antenna should generate the field propagating along the body surface like vertical monopole antenna. On the other hand, for proper communication link between the on-body and off-body devices, an on-body antenna should have unidirectional radiation pattern toward off-body direction. Thus, one of the key requirements in on-body antenna for on-on-off repeater system is dual mode characteristics. The antenna has a vertical monopole-like radiation pattern in the 2.45 GHz ISM band and a horizontal monopole-like radiation pattern in the 5.8 GHz ISM band. The performance of the proposed antenna is verified both numerically and experimentally when it is attached to muscle equivalent phantoms. To verify the biomedical exposure, the specific absorption rate (SAR) of the proposed antenna on the realistic human body model was analyzed. The limited input power of the antenna by the SAR regulation level is presented. Finally, a 60-GHz patch antenna array with parasitic elements for millimeter-wave WBAN applications is proposed in chapter 5. The fabricated antenna is fed by a 1.85-mm end-launch V-band connector (Southwest Microwave). To account for the effect of using an actual connector on the antenna performance, the simulation was conducted with a modeled V-band end-launch connector. To demonstrate the antenna performance in a practical wearable environment, the radiation characteristics were analyzed on a 60-GHz head phantom and Google Glass frame. When a 60-GHz array antenna is used in wearable environment, the highly directional beam can have detrimental health effects on the human body. In the International Commission on Non-Ionizing Radiation Protection (ICNIRP) regulations, the peak PD value is limited to 10 W/m2 (averaged over 20 cm2) for millimeter-wave electromagnetic field exposure. The SAR and power density (PD) were calculated to evaluate the electromagnetic exposure on the head phantom. The proposed design techniques of the various wearable antennas can be applied to the antennas for the wearable on-body WBAN devices such as smart clothing and glasses.