Parametric analysis of electromagnetic wave interactions with layered biological tissues for varying frequency, polarization, and fat thickness

TL;DR

This paper studies how electromagnetic waves interact with layered biological tissues at different frequencies and angles, revealing how fat thickness and polarization affect heating and reflection.

Contribution

A novel MATLAB framework integrating transmission line theory, dielectric modeling, and bioheat simulations to analyze EM wave interactions with layered tissues across ISM bands.

Findings

Significant superficial heating (up to 3.5°C) occurs at 5.8 GHz due to reduced penetration depth.

Subcutaneous fat modulates the balance between reflection and absorption depending on its thickness.

Polarization and angle influence the shape of reflection curves, including TM Brewster-like minima.

Abstract

Electromagnetic wave interaction with biological tissue is frequency-, angle-, and polarization-dependent, influencing both dosimetric parameters and resultant thermal effects. This work presents a comprehensive analysis across the major ISM bands (433, 915, 2450, and 5800 MHz) for transverse electric (TE) and transverse magnetic (TM) polarizations incident on a three-layer tissue model (skin–fat–muscle). A custom MATLAB code was developed to integrate the multilayer transmission line formalism, polarization-specific wave impedance modeling, Cole–Cole dielectric parameterization, and a finite difference method (FDM) solution of the Pennes bioheat equation. Simulations were performed for incident power density 50 W/\documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\hbox {m}^2$$\end{document} and fat thicknesses from 0.005 m to 0.03 m, over incidence angles 0 °C– 80 °C. Throughout the manuscript, reflection is reported strictly as a power quantity \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$R=|\Gamma |^2$$\end{document} rather than a field-amplitude coefficient. The thermal pipeline solves the steady-state Pennes equation in its direct \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\Delta T$$\end{document} form with consistent surface (Robin) and deep (Dirichlet) boundary conditions, and simulations are audited by an energy-conservation budget. Results indicate that while temperature increases remain below 0.4 °C at lower frequencies (433–915 MHz), significant superficial heating (up to 3.5 °C) occurs at 5.8 GHz due to reduced penetration depth, even at moderate exposure levels. The results demonstrate that subcutaneous fat acts as a low-loss impedance transformer whose thickness strongly modulates the balance between reflection and internal absorption, while polarization and angle primarily tune the detailed shape of angular reflection curves (including TM Brewster-like minima) at a given incident power. The analytical framework therefore complements voxel-based full-wave numerical models by providing fast, physically transparent trends across ISM bands that are directly relevant for preliminary assessment of wearable devices, implanted sensors, and compliance with radiofrequency safety limits.

Figures