The effect of tissues in galvanic coupling Intrabody Communication

Intrabody Communication (IBC) is a technique that uses the human body as a transmission medium for electrical signals to connect wearable electronic sensors and devices. Understanding the contributions of tissues for signal transmission in IBC, which requires a good understanding of dielectric properties of biological tissues, paves a way for practical implementation of IBC in Body Sensor Networks. Presently, there is a lack of accurate and clear analysis on how the different tissues affect signal propagation through human body. In this work, we introduce a simple and efficient approach to understand the influence of different tissues on signal propagation through human body. In this approach, we propose a single Cole-Cole dispersion for the dielectric spectrum of four tissues (skin, fat, muscle, and cortical bone) for the frequency range of 100 KHz to 10 MHz. We measured gain and phase shift of galvanic coupling type IBC on the upper arm of three subjects. It was found that for the given frequency range, the impedance magnitude of skin decreases quickly whereas impedances of the other tissues were less affected. In a similar manner, the impedance phase angle of skin is up to 60 degrees larger than that of the other tissues. From the measurement, we observed that these characteristics of skin highly affect the measured gain and phase shift. As a result, we infer skin mainly affects signal propagation through the human body in galvanic coupling.