Wideband Strongly Coupled Magnetic Human Body Communication for Low Rate Wireless Body Area Networks (BANs): A Numerical Analysis

Human Body Communication (HBC) is a novel and innovative transmission technique that utilizes human tissues as a medium for transferring physiological data. Recently, Magnetic HBC (MHBC) has been introduced, employing magnetic signals to facilitate data transfer through human tissue. In this paper, we design and optimize two concentric circular spiral coils for near-field resonance MHBC. These coils are used to validate, characterize, and compare signal transmission through various scenarios: the female left arm, the male left arm, the entire human body modeled as a conductor, and the human body modeled as a dry skin layer over a conductor, in comparison with transmission through an air medium. The analysis focuses on the frequency range of 314–316 MHz, as used in low-rate wireless personal area networks (WPANs). We analyzed the effects of coil spacing variation and load variation on signal transmission, incorporating a series-series resonant matching circuit. Additionally, we investigated the maximum power efficiency <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\eta)$</tex> at the resonant frequency f = 316 MHz with and without the lossy element <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{R}(\Omega)$</tex> for the air-channel magnetic resonance wireless power transfer system. The results confirmed that MHBC enhanced the transmission coefficient by more than 3 dB through both female and male arms within the desired frequency range. It also demonstrated a wideband -10 dB bandwidth exceeding 4 MHz, with an efficiency <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\eta)$</tex> greater than 99.8% at a coil spacing of d = 100 mm and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{Z}_{\mathrm{L}}=\mathbf{5 0} \boldsymbol{\Omega}$</tex>. The SAR analysis for both male and female arms is presented, showing values well below the specified limits of IEEE C95.3-2002.