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.
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