Noise analysis for intra-body communication based on parasitic capacitance measurement

Abstract This paper describes noise transmission analysis for near-field intra-body communication systems based on parasitic capacitance measurement around the human body. Intra-body communication systems use the human body as the signal transmission medium. In communication systems of this type, the transmission line’s impedance balance between the signal line and the ground line is extremely degraded by human body contact. Such systems are affected by large common-mode noise from various kinds of electronic equipment in living spaces, such as lighting devices, air conditioners, liquid crystal televisions, and refrigerators. Impedance balance deteriorates as a result of adding parasitic impedance to the transmission lines. Changes in the impedance balance are estimated by measuring parasitic capacitance in the human body, transmission lines, electrodes, and floor ground. It was verified that impedance balance between the signal line and the ground line is related to the noise power of a near-field intra-body communication system. It was found that connecting a compensative electrode or a compact capacitor to a ground node is an effective way to improve impedance balance and reduce common-mode noise.