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An investigation on power loss of an out-to-in body wireless radio frequency link.

BACKGROUND
Implantable medical sensors for monitoring and transmitting physiological signals like blood glucose, blood oxygen, electrocardiogram, and endoscopic video present a new way for health care and disease prevention. Nevertheless, the signals transmitted by implantable sensors undergo significant attenuation as they propagate through various biological tissue layers.


OBJECTIVE
This paper mainly aims to investigate the power loss of an out-to-in body wireless radio frequency link at 2.45 GHz.


METHODS
Two simulation models including the single-layer human tissue model and three-layer human tissue model were established, applying the finite element method (FEM). Two experiments using physiological saline and excised porcine tissue were conducted to measure the power loss of a wireless radio frequency link at 2.45 GHz. Various communication distances and implantation depths were investigated in our study.


RESULTS
The results from our measurements show that each 2 cm increase in implantation depth will result in an additional power loss of about 10 dB. The largest difference in values obtained from the measurements and the simulations is within 4 dB, which indicates that the experiments are in good agreement with the simulations.


CONCLUSIONS
These results are significant for the estimate of how electromagnetic energy changes after propagating through human tissues, which can be used as a reference for the link budget of transceivers or other implantable medical devices.