300 0,38 4,49 19,12 0,39 4,46 18,87 400 0,38 4,35 18,37 0,37 4,33 18,28 Calculation of Attenuation due to Clouds and Fog A calculation method is described in ITU-R 840-6 [5.5]: The specific attenuation within a cloud or fog can be written as: dB/km (5.12) : specific attenuation (dB/km) within the cloud c : specific attenuation coefficient ((dB/km)/(g/m3)) Kl : liquid water density in the cloud or fog (g/m3). M At frequencies of the order of 100 GHz and above, attenuation due to fog may be significant. Typical water content for different fog types are listed in table 5.5. Table 5.4: Typical liquid water density of fog types [5.5] Fog type Typical liquid density in g/m3 medium fog (visibility of the of 0.05 300 m) thick fog (visibility of the order of 0.5 50 m) A mathematical based on Rayleigh scattering, which uses a double-Debye model for the dielectric permittivity ( ) of water, can be used to calculate the value of for frequencies up to f Kl 1000 GHz: (dB/km)/(g/m3) (5.13) where is the frequency (GHz), and: f (5.14) The complex dielectric permittivity of water is given by: (5.15) (5.16) = 77.66 + 103.3 ( 1) (5.17) – 0 = 0.0671 (5.18) 1 = 3.52 (5.19) 2 = 300 / (5.20) T
300 0,38 4,49 19,12 0,39 4,46 18,87 400 0,38 4,35 18,37 0,37 4,33 18,28 Calculation of Attenuation due to Clouds and Fog A calculation method is described in ITU-R 840-6 [5.5]: The specific attenuation within a cloud or fog can be written as: dB/km (5.12) c : specific attenuation (dB/km) within the cloud Kl : specific attenuation coefficient ((dB/km)/(g/m3)) M : liquid water density in the cloud or fog (g/m3). At frequencies of the order of 100 GHz and above, attenuation due to fog may be significant. Typical water content for different fog types are listed in table 5.5. Table 5.4: Typical liquid water density of fog types [5.5] Fog type Typical liquid density in g/m3 medium fog (visibility of the of 300 m) 0.05 thick fog (visibility of the order of 50 m) 0.5 A mathematical based on Rayleigh scattering, which uses a double-Debye model for the dielectric permittivity ( f ) of water, can be used to calculate the value of Kl for frequencies up to 1000 GHz: (dB/km)/(g/m3) (5.13) where f is the frequency (GHz), and: (5.14) The complex dielectric permittivity of water is given by: (5.15) (5.16) 0 = 77.66 + 103.3 ( – 1) (5.17) 1 = 0.0671 (5.18) 2 = 3.52 (5.19) = 300 / T (5.20)
15-14-0310-19-003d-channel-modeling-document.docx