Performance Comparison of Two Loop Antennas for Intracranial Implant-to-Implant Communications

We present the potential of implant-to-implant (I2I) communication with loop-type implantable antennas, conducting deep implant analysis through numerical simulations. Loop antenna dimensions make it a suitable candidate for I2I communication. Antenna dimensions are 13.3 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\times 2.5\times 1.5$</tex> mm and 8 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\times 2.5\times 1.3$</tex> mm including the silicone coating, for 915 MHz and 2450 MHz loop antennas, respectively. Two loop antenna cases operating in industrial, medical, and scientific bands, 915 MHz and 2450 MHz, are investigated. For I2I analysis, antennas are positioned 14.8 mm deep in the CSF layer and 75 mm deep in the brain of the ellipsoid 7 -layer human head model. Both antenna models poses reflection coefficient <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\vert S_{11}\vert)$</tex> below -10 dB. The maximum mutual coupling of implant antennas and combined gains of antennas are analyzed using the rotation antenna method. This method allows us to find the optimal alignment that maximizes the coupling and enhances communication efficiency between implant antennas.