Rain Attenuation in the Microwave-to-Terahertz Waveband

Abstract

In recent years, there has been increased interest in the terahertz waveband for application to ultra-high-speed wireless communications and remote sensing systems. However, atmospheric propagation at these wavelengths has a significant effect on the operational stability of systems using the terahertz waveband, so elucidating the effects of rain on propagation is a topic of high interest. We demonstrate various methods for calculating attenuation due to rain and evaluate these methods through comparison with calculated and experimental values. We find that in the 90 -225 GHz microwave band, values calculated according to Mie scattering theory using the Best and P-S sleet raindrop size distributions best agree with experimental values. At 313 and 355 GHz terahertz-waveband frequencies, values calculated according to Mie scattering theory using the Weibull distribution and a prediction model following ITU-R recommendations best agree with experimental values. We furthermore find that attenuation due to rain increases in proportion to frequency for microwave-band frequencies below approximately 50 GHz, but that there is a peak at around 100 GHz, above which the degree of attenuation remains steady or decreases. Rain-induced attenuation increases in proportion to the rainfall intensity.

Wireless communications beyond 5G: Uncertainties of terahertz wave attenuation due to rain

“…For example, M. Sekine et al [16] considered the Mie scattering theory for five raindrop-size distributions and determined that the Weibull distribution best describes the rain attenuation above 30 GHz. In a later work it was demonstrated that the Mie scattering theory with Best and P-S distributions provide the most suitable agreement with the experimental values in the 90-225 GHz range, while the ITU-R model and Mie scattering with the Weibull distribution leads to a better approximation at 313 and 355 GHz [17]. It could also be mentioned that both researches of the origins of raindrop size distributions [18] and search for the best empirical description of these distributions [19] continued well past the publication of the P.838-3 recommendation in 2005 and, Fig.…”

“…To our knowledge, a detailed theoretical study of such 'shot-noise' has not been performed up to now. However, a substantial dispersion of values is visible in the experimental data presented in [16] and [17]. Furthermore, such dispersion can be seen even in the case of the laboratory-controlled rain at extreme 50-400 mm/h rain rates with a relatively narrow Gaussian-like raindrop size distribution [20].…”

“…The classical scattering theory for plane wave radiation by absorbing sphere particles [21] is a widely used (including [4,16,17,20]) tool for a detailed analysis of the absorption in the THz range and also serves as a starting point for our calculations. The rain attenuation coefficient α within this theory is calculated as ,…”

“…therefore, alternative descriptions can and have to be discussed. The Weibull distribution will be considered further in our work in more detail, since it provides both the best percentage of the most successful approximations of raindrop-size distributions [19] and one of the most relevant THz attenuation approximations in [16] and [17].…”

Low‐loss frequency selective surface for multi‐band THz transmission measurement

“…There are many methods to evaluate the effects of these particles on THz transmission. Theoretically, the Mie theory or Rayleigh scattering method is frequently used to calculate the transmission loss due to these particles . Experimentally, THz time domain spectroscopy (THz‐TDS) and antenna system have been employed for in‐house and outdoor measurements, respectively.…”