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

使用人体作为其传输介质的一部分的传输方法（下文中我们将其称为“体内通信”）是用于电子设备之间的通信的有前景的技术之一。本研究的目的在于厘清传输模型，并建立电路设计方法，以方便电子工程师将此技术应用于实际应用中。首先研究阻抗匹配以获得接收器的最佳输入阻抗。当接收机安装在固定设备或仪器中时，最佳输入阻抗在载频MHz时为2000 ~ 2800欧姆，在20 MHz时为180 ~ 330欧姆。最佳输入阻抗随着载波频率的增加而减小。在10 MHz处获得最大增益。当接收器附在发射器的佩戴者身上时，这意味着接收器没有连接到固定设备，接收器的最佳输入阻抗为80至200欧姆。介质的阻抗，在这种情况下是人体，是设计发射机输出级所必需的。通过使用不同变压比的输出变压器测量该阻抗。在10 MHz的载波频率下，输出阻抗约为190 ohm，通过设计发射器的末级以匹配该阻抗，可以获得最大的传输效率。此外，采用TLM（Transmission Line modeling）方法分析了可穿戴式发射器电极结构在体心网络中的阻抗特性。电极尺寸和排列的关系被组织在一组用于电极设计的方程中。这些方程可以用于确定体内通信中传输通道的给定阻抗值的电极的尺寸和布置。

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.