Data Communication Research In Implantable Devices Based On Volume Conduction

Implantable electronic devices are made up of the vitro and the vivo, the transportation of information is said to the volume conduction communications. Necessary of this communications:①the vivo is in the tissue, its volume must be strictly controlled to a certain scope, limiting the size of some in vivo;②For some Implantable medical electronic the vitro source is required;③The parameters picked up by implantable electronic devices must be transported to the vitro, providing diagnostic evidence of medical workers, which send signals to adjust the vivo;④The energy of the vivo limit the size of the vivo part circuit. Therefore, Implantable electronic devices communication between the vitro and the vivo is essential.The communication,which use conduction current of biological organization to communicate to the vivo part ,is a novel communication model (it's said to the volume conduction communications). The author has completed the following research:①Based on the research results of volume conduction communication,the author design a digital model of the volume conduction data communication model, using Manchester encoding to transmit information,using FPGA to achieve the Manchester encoding and decoding functions. A volume conduction communication experiment system is completed.②Fresh pork simulated biological tissue is ussed to the out body experiment including the feasibility of conducting experiments, the frequency characteristic experiment, the electrode distance experiment.By the out body experiment and theoretical analysis, experimental results obtained are as following:①The amplitude of the vitro square wave is 5V, pork organizations are established in the electric field distribution under electrodes, the body electrode open circuit voltage of square wave maximum 48.5mV, over time, and finally stabilized at 42.7mV. Electrodes can pick up electrical signals in vivo, indicating that volume conduction communication is feasible.②Frequency in the system were 1kHz, 2kHz, 3kHz ... 10kHz, the measurement system error rate result: when the system frequency is 6kHz the bit error rate is best.③When the system frequency is 6kHz and square wave amplitude is 5V ,at the same time changing the distance between the probes, varying from 2mm-20mm from the measurement system error rate, while the measured distance is 12mm, the error rate is smallest. Therefore, the best distance between electrodes is 12mm.Conclusion:The author design and complete a digital volume conduction communication system. The possibility of volume conduction data communication in the kHz is proved; The bit error rate of the volume conduction communication system is effected by the system frequency and electrode distance. When the frequency is 6kHz and electrode distance is 12mm, the bit error rate is best.The data communication of volume conduction test system wok in a low frequency and has no radio frequency interference, anti-jamming capability, transmission accuracy. Therefore, the data communication of volume conduction has certain academic and practical value.