Rain Attenuation in Terrestrial and Satellite Communications Links

Abstract

Specific attenuation values from 1 to 1000 GHz are calculated by using the negative exponential, Best and Weibull raindrop-s ize distributions. It is shown that the Weibull distribution is a useful tool for rain attenuation calculations of cent'imeter, miVlimeter and submillimeter radio waves. The empirical relation A=aR between the specific attenuation A and the rainfall rate R is also tabulated for these three distributions. INTRODUCT IONIn the design of terrestrial and satellite communications links that operate at frequencies above IOGH 7, rain attenuation is an important characteristic. Especially, in millimeter and submillimeter wave links, raln attenuation is severe and greatly dependent on the various models of raindrop-size distribution.Laws and Parsons [1] measured the proportion of the total volume of water reaching the ground and proposed the median diameter Dm(1) m where the precipitation rate R is in mm/hr. To evaluate the drop size distribution with the Laws and Parsons data, the terminal velocity of the drops is used in the calculations [2,3]. Although their data were taken in old years 1938-1939 in Washington,D.C. on surface rain using the flour pellet method, currently it is recommended to use the Laws and Parsons data for rain attenuation and scattering calculations [4]. However, the Laws and Parsons distribution was determined only for drops D > 1 mm so that the behaviour of the distribution is incorrect for very small drops less than D = 1 mm that still contribute a major part of the rain attenuation in millimeter and submillimeter ranges-In 1972, Sander [5] measured the size distribution of raindrops in Berlin by means of the electrostatilc method and the results were quite similar to the Laws and Parsons data.Wickerts measured one-minute drop-size distribution of drizzle, wide spread rain and rain shower using a distrometer in 1977 and 1978 at 15Km zouth of Stockholm [6]. Especial-ly. he observed drizzle for 65 minutes in which small drops less than D=1 mm play an important role for rain attenuation at high frequencies above 100 GHz. by anaiyzing tihe above Laws ana farsuns' ,Sander and Wickertst data, we proposed the following Weibull distribution[7]:

Measurement of Rain Attenuation in Terahertz Wave Range

“…This distribution is retained for microwave and terahertz applications [10][11][12][13][14][15][16][17][18][19][20][21][22][23].…”

Rain Attenuation at Terahertz

“…Thawing of Pellets (Hail) 64500 R -0. This distribution is retained for microwave applications for drizzle, widespread rain, and shower rain cases [10][11][12][13][14][15][16][17][18][19][20][21][22].…”

Weibull Raindrop-Size Distribution and its Application to Rain Attenuation from 30 GHz to 1000 GHz

“…This distribution is retained for microwave applications for drizzle, widespread rain, and shower rain cases [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Sayama [16] calculated rain attenuation from Eq.…”