A Reconfigurable Impedance Matching Method for Magnetic Coupling-Based Near-Field Human Body Communication

Abstract

The interactions of medical devices within the body area network (BAN) have significantly alleviated the pressure on healthcare resources attributed to an aging society. However, the low-power, high-reliability wireless communications among these devices are susceptible to the influence of the human body. This article exploits the capacitive effects of human tissues to achieve precise and reconfigurable impedance matching in magnetic resonance coupling (MRC) human body communication (HBC) to minimize the adverse effects of the human body. First, the impact mechanism of the human body on MRC port impedance is analyzed in this article under the inductive near-field based on the dielectric dispersion of human tissues. This mechanism helps identify the quasistatic magnetic field within MRC, from which the resonance conditions of MRC are derived. A reconfigurable impedance matching method within a broad bandwidth is proposed using these conditions, and experiments on port impedance and transmission characteristics are conducted using an optimized variable parameter coil as the implementation medium. Results demonstrate that the proposed method can precisely tune within a range of 10 MHz under inductive near-field, confirming the reliability of the resonance conditions and matching methodology. After matching, the MRC exhibits only 12.5 dB at 13.56 MHz path loss over a 90 cm transmission distance, surpassing other methods by more than 52.8%. The optimized MRC provides an effective technical foundation for narrowband communication schemes for medical devices in the BAN.