Wireless propagation channel modeling and antenna design for on-body applications.

The Wireless Body Area Networks (WBAN) is promising in a variety of applications such as remote health monitoring and assisted living. A typical WBAN consists of wearable body sensor units (BSU) and a body control unit (BCU). The BCU can receive physiological signal data from the BSUs and relay them to a remote access point regarding impending emergencies. One important issue in implementing a WBAN is to ensure reliable and efficient wireless communication links on a human body. This is particularly challenging since the human body represents a difficult propagation environment where body tissues introduce high loss to electromagnetic waves propagating along, around and through the body. The antenna radiation performance may also be affected due to the presence of the human body. Extensive research involving on-body propagations have been conducted over the past decade through experiments, simulations and theories. However, most studies focus only on signal strength attenuation loss of on-body waves at a single frequency on a non-moving human body. Wearable antennas have been designed for on-body applications, but most designs concentrate on optimizing conventional antenna performance on human body. It remains to be studied how to design compact antennas which can couple on-body wave mechanisms efficiently over a broad range of frequencies. In this dissertation electromagnetic wave propagations over a broad frequency band (300 MHz- 3GHz) and within short ranges (<50 cm) are investigated for on-body wireless channel communications. Experimental, simulation and theoretical methods are used to examine two scenarios: along and around the body surface. The study is conducted on both non-moving and moving human bodies. Both signal strength and phase delay are studied. Dominant propagation mechanisms are extracted and analyzed. An electrically-small wearable antenna as well as directive array are designed for on-body applications, and human body effects on antenna performance are discussed.