Exposure Levels Induced in Curved Body Parts at mmWaves

Abstract

This study investigates the impact of the ear and the finger curvature on the electromagnetic (EM) power absorption and resulting heating to quantify the potential enhancement of the induced exposure levels compared to commonly used planar tissue models. The analysis is performed at millimeter-wave (mmW) frequencies upcoming for 5G and future generations, with a special attention to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$26 \,\mathrm{GHz}$</tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$60 \,\mathrm{GHz}$</tex-math></inline-formula> . A cylindrical model is used to calculate EM power density and heat in fingers (radii <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{a\leq }10 \,\mathrm{mm}$</tex-math></inline-formula> ) and EM power density in ears ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$1 \,\mathrm{mm}\boldsymbol{\leq a\leq }5 \,\mathrm{mm}$</tex-math></inline-formula> ). To compute the temperature rise in the ear, the model is modified to account for heat conduction in the tissue connecting the ear to the head. Our results show that for transverse electric (TE) polarization the maximal absorbed power density remains generally lower than for a planar interface (up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-38.2 \,\%$</tex-math></inline-formula> at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$26 \,\mathrm{GHz}$</tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-18.7 \,\%$</tex-math></inline-formula> at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$60 \,\mathrm{GHz}$</tex-math></inline-formula> ) and exceeds this value for transverse magnetic (TM) polarization (up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$72.3 \,\%$</tex-math></inline-formula> at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$26 \,\mathrm{GHz}$</tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$15 \,\%$</tex-math></inline-formula> at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$60 \,\mathrm{GHz}$</tex-math></inline-formula> ). The resulting heating is always higher than for the planar model. For the ear model ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{a=}1 \,\mathrm{mm}$</tex-math></inline-formula> ), the variations at steady state reach <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$93.11 \,\%$</tex-math></inline-formula> at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$26 \,\mathrm{GHz}$</tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$103.62 \,\%$</tex-math></inline-formula> at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$60 \,\mathrm{GHz}$</tex-math></inline-formula> .

Topics & Concepts