Rain Attenuation at Millimeter Waves in Different Climatic Zones Estimated from Drop Size Distributions

Rain attenuation at millimeter waves is progressively more influenced by the Drop Size Distributions (DSD). In this paper, DSD data collected in Madrid, Spain, with continental climate; Milan, Italy, with Mediterranean climate; and Kuala Lumpur, Malaysia, with tropical climate are used to study this effect. The first two sites use the same model of laser disdrometer whereas the equipment available at Kuala Lumpur is an impact disdrometer. Rain specific attenuation at different frequencies (30-300 GHz) as well as rainfall rate have been calculated. The data have then been used to assess the validity of the ITU-R Rec. P.838-3 model. Results show that the ITU-R model tends to underestimate the specific attenuation, and confirm a significant variability around its reference value obtained from the rainfall rate, with a similar extent in Madrid and Milan, and a different trend in Kuala Lumpur, attributed to the different disdrometer and to the tropical climate.