Study On Influencing Factors Of Terahertz Wireless Communication Channel In Near-Earth Atmosphere

The increasing demand for high-speed wireless communications requires in-depth studies of broadband terahertz communication technology.The serious path loss of terahertz signals in the atmosphere is an important limit of the development of terahertz broadband communication technology.Therefore,the development and performance analysis of future ultra-high speed wireless communication systems require detailed studies of the attenuation characteristics of terahertz waves in the near-surface atmosphere.And an accurate atmospheric transmission channel model in terahertz band can be built up.In this paper,the attenuation mechanisms of terahertz wave in the near-Earth atmosphere are analyzed and studied,which include the absorption of polar molecules in the atmosphere,the scattering of aerosol particles,the scattering and absorption of vegetation and the reflection and scattering of building materials.Based on the formula of standard atmospheric parameters and the molecular spectral line parameters in HITRAN database,the absorption attenuation of polar molecules in the atmosphere are studied by the Van-Vleck Weisskopf method.The optical parameters of fog,haze and rain particles are determined by meteorological data and literature.Based on scale distribution spectrum,dielectric constant and complex refractive index of different particles,we studied the scattering attenuation of THz waves by aerosol particles under different meteorological conditions by using Mie and Rayleigh scattering theories according to different particle scale factors.Based on the simplified model of plant structure and theoretical path loss model,the scattering and absorption attenuation of terahertz waves in mixed channels composed of different types of plants and air were studied by changing the size and distribution of leaves and moisture content in the air.Based on the traditional Fresnel reflection formula and Kirchhoff scattering theory,the modified Fresnel equation was derived by introducing Rayleigh scattering factor to study the reflection and scattering attenuation of terahertz waves by building materials.Based on the above four aspects,a complete atmospheric transmission channel model of terahertz wave band was established,and the attenuation characteristics of terahertz wave in the nearsurface atmospheric environment were analyzed by numerical simulation.The position of strong absorption frequency point,weak absorption frequency point andwidth of transparent window with small attenuation were obtained.The accuracy of the established channel model was verified by comparing the measured data.This paper will help to solve the bottleneck of near-ground terahertz communication and provide theoretical supports for near planets,wireless local area network(WLAN)and short-range atmospheric communication technology.