Transmission Model and Circuit Design for Communication Method that uses Human Body as part of the Transmission Medium

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Transmission method that uses human body as part of its transmission medium, which we will refer to as "intra-body communication" hereafter, is one of the promising technologies for communication between electronic devices. The objective of this research was to clarify the transmission model, and to establish circuit design method so that electronic engineers can readily utilize this technology in practical applications. Impedance matching was first investigated in order to obtain optimum input impedance for receivers. When the receiver in embedded in a stationary equipments or apparatus, the optimum input impedance was 2000 ohm to 2800 ohm at carrier frequency of MHz, and 180 ohm to 330 ohm at 20 MHz. The optimum input impedance decrease as the carrier frequency increases. Maximum gain was obtained at 10MHz. When the receiver was attached to the wearer of the transmitter, which means that the receiver is not connected to stationary devices, the optimum input impedance of the receiver was 80 to 200 ohm. The impedance of the medium, which is the human body in this case, is necessary for design of output stage of the transmitter. This impedance was measured by using output transformers of different transforming ratios. At carrier frequency of 10MHz, the output impedance was approximately 190 ohm Maximum transmission efficiency will be achieved by designing the final stage of the transmitter to match this impedance.Furthermore, impedance characteristics of electrode structures of wearable transmitter for body-centric networks were analyzed by TLM (Transmission Line modeling) method. Relationships of electrode dimensions and arrangements were organized in a set of equations for electrode design. These equations can be utilized to determine the size and arrangement of electrodes for a given impedance value of the transmission channel in intra-body communication.