Field-Circuit Combination Method for Solving the Detuning Problem of Magnetic Resonance Human Body Communication

The technological challenge to realize wearable medical devices is to ensure low power consumption and reliable transmission of communication. Magnetic resonance human body communication (MR HBC) provides ideas to improve the transmission effect. Although the coil's resonance properties have been proposed for MR HBC, the modeling and impedance matching for this method are still in the exploratory stage. However, different human impedances affect the coil resonance frequency to varying extents, leading to individual variability in the degree of magnetic coupling. This paper analyzes the influence of human tissues on the coil through finite element method (FEM) simulation modeling. This effect can be eliminated by employing a dual tunable capacitor matching method based on the field-circuit combination. By dynamically adjusting the values of the dual tunable capacitors in real-time, the human body and the coil can be tuned to a resonant state, effectively improving the degree of magnetic coupling. The results reveal that the proposed method enhances the communication gain by 38.91-42.02 dB at the preset frequency for different human tissues. In vivo experiments verify that the method eliminates the effect of different human impedances on the coil, which is of great significance for further improving the performance of MR HBC.