A Physics-Based Digital Human Twin for Galvanic-Coupling Wearable Communication Links

Abstract

This paper presents a systematic characterization of wearable galvanic coupling (GC) channels under narrowband and wideband operation. A physics-consistent digital human twin maps anatomical properties, propagation geometry, and electrode-skin interfaces into complex transfer functions directly usable for communication analysis. Attenuation, phase delay, and group delay are evaluated for longitudinal and radial configurations, and dispersion-induced variability is quantified through attenuation ripple and delay standard deviation metrics versus bandwidth. Results confirm electro-quasistatic, weakly dispersive behavior over 10 kHz-1 MHz. Attenuation is primarily geometry-driven, whereas amplitude ripple and delay variability increase with bandwidth, tightening equalization and synchronization constraints. Interface conditioning (gel and foam) significantly improves amplitude and phase stability, while propagation geometry governs link budget and baseline delay. Overall, the framework quantitatively links tissue electromagnetics to waveform distortion, enabling informed trade-offs among bandwidth, interface design, and transceiver complexity in wearable GC systems.

Figures (9)

• Figure 1: Galvanic-coupling wearable link model showing the layered electrode structure (left), longitudinal Tx–Rx configuration with spacing $d_r$ and separation $d_l$ (center), and radial arm cross-section with tissue layers (right).
• Figure 2: Equivalent circuit with aggregated transmitter impedance $Z_{\mathrm{TX}}(f)$, open-circuit voltage $V_{\mathrm{oc}}(f)=Z_{\mathrm{tr}}(f)I_{\mathrm{TX}}(f)$, aggregated receiver impedance $Z_{\mathrm{RX}}(f)$, and load $Z_L(f)$. The red arrow denotes the injected current $I_{\mathrm{TX}}(f)$, while curved arrows indicate the differential voltages.
• Figure 3: Concentric-layer arm model
• Figure 4: Estimated CIR and normalized power delay profile (PDP) for longitudinal configuration.
• Figure 5: Digital human twin versus in-vivo measurements for galvanic coupling under (a) longitudinal and (b) radial electrode configurations. For each configuration, attenuation, phase delay $\tau_P$, and group delay $\tau_G$ are shown as mean and $\pm1\sigma$ across repeated acquisitions over the quasi-static band (0--100 kHz).