RF Signal Loss in Through-body Wireless Transmission and Implications for Implantable Devices

Physicians and researchers require systems that provide real-time collection of physiological data sets to explore new diagnostics and therapies. Implantable devices used to monitor a variety of physiological parameters and administer therapies lend themselves to the development of customizable platforms that can be applied to individualized disease treatment. Radio frequency (RF) communication can provide a reliable data path allowing through-body communication. Here, RF propagation is analyzed in a saline phantom to characterize signal loss through free space when varying the distance between the transmitting and receiving antennas and the type and size of antennas, to find the highest received power to the lowest transmitted power. Two testing environments were constructed: dry and 0.9% saline. Four frequencies (400 MHz, 700 MHz, 900 MHz, and 2.5 GHz) and four antenna types (quarter-wave ground plane, horizontal half-wave dipole, single loop, and coiled loop) were implemented in the system.