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Ch83-I044963.fm Page 414 Monday, August 7, 2006 11:30 AM
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for the blood. High relative permittivity results in the electromagnetic waves to decay in a short
distance. The results of this experiment indicate that the transmission path is most likely the surface
and proximity of the body rather than the interior.

FDTD
FDTD
I FDTD IZZ1 Meas s s. . .
FDTD
FDTD
Meas.
a
a
Meas.
Me
Me
120
120
V m 120
s ] ] ]
s
rms
[mV r m 100
Receiver
Transmitter
Transmitter Receiver V rm 100
100
[m
al l [ nal gna ign sig 80
80
80
60
60
60
40
40
Phantom si d s ed ved ive eiv cei ece 40
20
20
20
Conductor plate Rec Re R 0 0 0
Conductor plate
10
-1 -1 -1 -1 0 0 0 0 1 1 1 1 5 5 5 5 1 10 0 0 No plate e e
No plate
No plat
1
No plat
m an
d c
ductor
nto
pha
een
Gap between phantom and conductor plate [mm]
Gap betw
at
e [mm]
Gap between phantom and conductor plate [mm]
Gap betw een pha nto m an d c o o n n ductor p p l l at e [mm]
a) Experimental system
a) Experimental system b) Comparison of signal power with gap
b) Comparison of signal power with gap
Figure 7: Investigation of signal transmission path
CONCLUSION
The four-terminal circuit model is effective in calculating the transmission gain in kHz range. The new
two-electrode model shows a higher gain compared to the previous four-electrode model. The
experimental results match well to confirm the calculation. From the measurement of the phase shifts
using the improved transmitter, it was suggested that intra-body communication is a combination of
not only the capacitive coupling but also of a radio wave transmission and of imbalances in the
electrical impedances among the electrodes of the transmitter and receiver. Additional experiments in
the electrical anechoic chamber suggest that the signal is propagated on the surface and proximity of
the body. In practical use, intra-body communication devices are to be wearable devices. Further
downsizing will be done in following research.
REFERENCES
Fujii K., Ito K., Hachisuka K., Terauchi Y., Sasaki K. and Itao K. (2004). Study on the optimal direction of
electrodes of a wearable device using the human body as a transmission channel. Proceedings of the 2004
International Symposium on Antennas and Propagation vol2, 1005-1008
Hachisuka K., Nakata A., Takeda T., Shiba K., Sasaki K., Hosaka H. and Itao K. (2003). Development of
wearable intra-body communication devices. Sensors and Actuators A: Physical 105:1, 109-115
Handa T., Shoji S., Ike S., Takeda S. and Sekiguchi T. (1997). A Very Low-Power Consumption Wireless
ECG Monitoring System Using Body as a Signal Transmission Medium. Proceedings of the 1997
International Conference on Solid-State Sensors and Actuators, 1003-1006
Matsushita N., Tajima S., Ayatsuka Y. and Rekimoto J (2000). Wearable Key: Device for Personalizing
nearby environment. Proceedings of the 4th International Symposium on Wearable Computers, 119-126
Terauchi Y., Hachisuka K., Sasaki K., Hosaka H. and Itao K. (2003). Study on electromagnetic propagation
within the human body. Proceedings of 2003 JSPE Autumn Meeting, 509, (in Japanese)
Zimmerman T. G. (1995). Personal Area Networks (PAN): Near-Field Intra-Body Communication MIT
Media Laboratory M.S. thesis