On the Use of Experimental Drop Size Distributions From Different Instruments in Millimeter-Wave Propagation Studies

Abstract

The attenuation produced by raindrops in millimeter-wave links relies on the Drop Size Distributions (DSD). However, empirical models dismiss this dependence and approximate the specific attenuation (γ (dB/km)) considering only the integrated rainfall rate (R (mm/h)). The use of empirical models is effective for relatively low frequencies but, as the frequency of interest becomes higher within the millimeter-wave range, empirical models lose accuracy. Moreover, the value of γ for a given R is expected to vary more than at lower frequencies, depending on the DSD. This paper aims to study this higher variability of γ, not incorporated in the current models, by calculating the specific attenuation γ from the experimental DSD measured by a vertical Doppler radar (MRR-2) and a Laser optical disdrometer (Thies Laser disdrometer) in periods of more than ten years. Both Ka-band and W-band have been considered for the calculations in order to understand the effect of increasing the frequency. Additionally, with the objective of evaluating the application of these techniques in propagation studies, the attenuation calculated from the DSD obtained from the above instruments has been compared to experimental values measured in a W-band terrestrial radio link at 75/85 GHz, yielding good results.