Scattering and Roughness Analysis of Indoor Materials at Frequencies from 750 GHz to 1.1 THz

Abstract

The problem of wave propagation and scattering at terahertz (THz) frequencies has become increasingly important, in particular for accurate modeling of future indoor wireless communication channels. The reflective properties of indoor materials with different surface roughness and dielectric constants are important to explore diffuse scattering for accurate channel modeling. First and foremost, a terahertz <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Swissto12</i> system is adopted to obtain the first ever transmission measurements for a wide choice of indoor material groups, such as <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">wood, plastic</i> , and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">brick</i> at frequencies from 750 GHz to 1.1 THz using up-conversion (frequency-domain) method. Both the reflection ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{11}$ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{22}$ </tex-math></inline-formula> ) and transmission coefficients ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{12}$ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{21}$ </tex-math></inline-formula> ) are measured using this novel and noninvasive electromagnetic technique. The inversion method based on Kramers–Kronig (K-K) relations is then applied to convert the calibrated scatter data into intrinsic material properties (i.e., refractive index, permittivity, absorption coefficient). Then, the surface topography of rough material samples is acquired using surface measurement instruments. Further, the optically smooth <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$(\sigma _{h} /\lambda \ll 1)$ </tex-math></inline-formula> materials are assorted as most to least rough based on Rayleigh roughness factor. Lastly, the ray tracer considering the Rayleigh-Rice (R-R) scattering model is employed to obtain the maximum achievable reflected paths of the above-mentioned indoor material samples at 300 GHz followed by their experimental validation.