Human Skin Model From 15 GHz to 110 GHz.

Area of Science:

• Electromagnetics
• Biophysics
• Materials Science

Background:

• Accurate human skin models are crucial for wireless device compliance testing against absorbed power density (APD) limits.
• The stratum corneum (SC) layer significantly influences skin's impedance-matching and absorption characteristics.
• Existing models may not fully capture skin's dielectric properties across a wide frequency range.

Purpose of the Study:

• To develop a single macroscopic dielectric model for human skin that conservatively reproduces electromagnetic field absorption up to 110 GHz.
• To provide a reliable model for compliance testing of wireless devices in 5G and 6G bands.
• To enhance the accuracy of absorbed power density (APD) estimations.

Main Methods:

• Measured skin reflection coefficients in human volunteers from 15 to 43 GHz using open waveguide probes, complementing existing data up to 110 GHz.
• Analyzed reflection coefficient data statistically across various body regions with differing stratum corneum (SC) thickness.
• Derived dispersive two-layer dielectric models based on measured data and uncertainty analysis.

Main Results:

• Reflection coefficients in dB followed a normal distribution in regions with thin SC, enabling conservative model development.
• Non-normal distribution of reflection coefficients in thick SC regions (e.g., palms) was observed due to mechanical stress-dependent SC thickness.
• The derived models accurately represent skin's absorption and reflection properties with quantifiable uncertainty.

Conclusions:

• The developed macroscopic dielectric skin model accurately represents electromagnetic absorption up to 110 GHz.
• The models provide a conservative basis for demonstrating wireless device compliance with APD limits for 5G and 6G.
• Understanding SC variability is key for accurate dielectric modeling of human skin.