1、 Rec. ITU-R F.1404-1 1 RECOMMENDATION ITU-R F.1404-1*Minimum propagation attenuation due to atmospheric gases for use in frequency sharing studies between systems in the fixed service and systems in the broadcasting-satellite, mobile-satellite and space science services (Questions ITU-R 111/9, ITU-R
2、 113/9 and ITU-R 163/9) (1999-2002) The ITU Radiocommunication Assembly, considering a) that slant path attenuation between a terrestrial station and a space station (geostationary (GSO) or non-geostationary (non-GSO) resulting from absorption due to atmospheric gases including water vapour is an im
3、portant factor in frequency sharing studies between systems in the fixed service (FS) and systems in the broadcasting-satellite service (BSS), the mobile-satellite service (MSS) and space science service; b) that slant path attenuation depends on the distribution along the path of meteorological par
4、ameters such as temperature, pressure and humidity, and thus varies with the geographic location of the site, the month of the year, the height of an FS station above sea level and the elevation angle of the slant path; c) that such slant path attenuation can be estimated by the method described in
5、Annex 1 to Recommendation ITU-R P.676, but that it is desirable to provide a simple procedure to estimate the attenuation; d) that for the purpose of frequency sharing studies, it is necessary to define the parameters in the driest month at sea level for each climate area, based on Recommendation IT
6、U-R P.835; e) that slant path attenuation is a complicated function of the frequency and that for each frequency band a representative frequency giving the lowest attenuation should be chosen, recommends 1 that for frequency sharing studies between FS systems and BSS, MSS and space science service s
7、ystems in each frequency band, slant path attenuation resulting from absorption due to atmospheric gases including water vapour should be estimated at a representative frequency which gives the lowest attenuation in that band (see Note 1); 2 that the method of Annex 1 should be utilized for the esti
8、mation of slant path attenuation due to atmospheric absorption (see Notes 2, 3 and 4). NOTE 1 The information in this Recommendation is solely for the purpose of frequency sharing studies, because it deals with the slant path attenuation in the driest month. _ *This Recommendation should be brought
9、to the attention of Radiocommunication Study Groups 3 (Working Party (WP) 3J), 6 (WP 6S), 7 (WP 7D) and 8 (WP 8D). 2 Rec. ITU-R F.1404-1 NOTE 2 When more details are required, these may be obtained from Recommendation ITU-R P.676. NOTE 3 The information in this Recommendation is based on Recommendat
10、ion ITU-R P.676-3 (Geneva, 1997) and Recommendation ITU-R P.835-2 (Geneva, 1997). NOTE 4 Recommendation ITU-R SF.1395 presents approximate formulae of minimum slant path attenuation due to atmospheric absorption for the frequency bands shared by the FS and the FSS. ANNEX 1 Estimation of slant path p
11、ropagation attenuation due to atmospheric gases for use in frequency sharing studies between FS systems and BSS, MSS and space science service systems 1 Introduction Slant path attenuation between a terrestrial station and a space station (GSO or non-GSO) resulting from absorption due to atmospheric
12、 gases including water vapour is an important factor in frequency sharing studies between FS systems and BSS, MSS and space science service systems. The slant path attenuation depends on the distribution along the path of meteorological parameters such as temperature, pressure and humidity, and thus
13、 varies with the geographic location of the site, the month of the year, the height of an FS station above sea level and the elevation angle of the slant path and the operating frequency. The procedure for calculating the slant path attenuation is the line-by-line procedure given in Annex 1 to Recom
14、mendation ITU-R P.676. The detailed calculations of atmospheric attenuation may utilize local information of average water vapour content in the driest month and of other meteorological parameters along with the atmospheric models of Recommendation ITU-R P.835. Where this information is not availabl
15、e, the following results provide a simple procedure for estimating atmospheric attenuation. The formulae given in 2 consider each of the frequency bands which are allocated to the FS and one of the BSS, MSS or space science services on a shared basis and are presented for five representative geograp
16、hical areas of the world (northern and southern hemispheres). 2 Estimation of slant path attenuation For the purpose of this simplified estimation, an FS station is identified as being within one of three climate areas depending only on the latitude (absolute value) of the station: low-latitudes wit
17、hin 22.5 of the Equator; mid-latitudes greater than 22.5, but less than 45 from the Equator; high-latitudes of 45 or more from the Equator. Rec. ITU-R F.1404-1 3 Table 1 shows the climate parameters for each of these areas. Note that the sea-level water vapour density for the low-latitude area is lo
18、wer than that prescribed in Recommendation ITU-R P.835 corresponding to the dry season. The attenuation values for these areas have been determined as a function of the elevation angle of the actual transmission path from the FS station to the position of a space station (GSO or non-GSO). The numeri
19、cal formulae for atmospheric attenuation which approximate the theoretical values are given in the following sections, where: AL(h, ), AM(h, ) and AH(h, ): total atmospheric absorption loss (dB) for the low-latitude, mid-latitude and high-latitude areas, respectively; h and : FS antenna altitude abo
20、ve sea level (km) and elevation angle (degrees), respectively. TABLE 1 Parameters at sea level for the climate areas The method in Annex 1 to Recommendation ITU-R P.676 was used for integration. The height profiles of temperature, pressure and water vapour density as defined in Recommendation ITU-R
21、P.835 were used in calculating the loss. The approximation was carried out for 0 h 3 km and 0 90. The actual elevation angle may be determined from the elevation angle developed under free space propagation conditions using the method in Recommendation ITU-R F.1333. For actual elevation angles below
22、 0, the attenuation for 0 should be used. NOTE 1 In some situations, it may become necessary to estimate the attenuation at a specific frequency based on the following formulae. For example, if it is necessary to find the attenuation in the low-latitude area at 36.5 GHz, it is possible to estimate t
23、his attenuation as an interpolation of the attenuation at 36.0 GHz (see equation (9a) and that at 37.0 GHz (see equation (10a). However, for such interpolation to be accurate, the two adjacent representative frequencies should be reasonably close to each other. In addition, special caution is requir
24、ed near 22.24 GHz (water vapour resonance frequency) where the linear interpolation may not apply. 2.1 Frequency band 11.7-12.75 GHz In this frequency band, the attenuation is larger at higher frequencies and, therefore, the following formulae give the attenuation at 11.7 GHz. AL(h, ) = 3.84 / 1 + 0
25、.8598 + h (0.2815 + 0.3031 ) + 0.1148 h2 (1a) AM(h, ) = 3.23 / 1 + 0.7585 + h (0.4154 + 0.2232 ) (1b) AH(h, ) = 3.12 / 1 + 0.7487 + h (0.3792 + 0.2102 ) (1c) Climate area Temperature (K) Atmospheric pressure (hPa) Water vapour density (g/m3) Low-latitude 300.4 1 012.0 10.0 Mid-latitude 272.7 1 018.9
26、 3.5 High-latitude 257.4 1 010.8 1.23 4 Rec. ITU-R F.1404-1 2.2 Frequency band 18.6-18.8 GHz In this frequency band, the attenuation is larger at higher frequencies and, therefore, the following formulae give the attenuation at 18.6 GHz. AL(h, ) = 15.16 / 1 + 0.9258 + 0.03625 2+ h (0.2981 + 0.4352 )
27、 + h2(0.2429 + 0.1330 ) (2a) AM(h, ) = 7.98 / 1 + 0.9103 + h (0.2862 + 0.4112 ) + 0.1469 h2 (2b) AH(h, ) = 5.67 / 1 + 0.8172 + h (0.2017 + 0.3017 ) + 0.1057 h2 (2c) 2.3 Frequency band 21.2-21.4 GHz In this frequency band, the attenuation is larger at higher frequencies and, therefore, the following
28、formulae give the attenuation at 21.2 GHz. AL(h, ) = 38.08 / 1 + 0.8485 + 0.06485 2 0.002121 3+ 0.1669 10 44+ h (0.2934 + 0.3816 ) + h2(0.09441 + 0.1701 ) + 0.04082 h3 (3a) AM(h, ) = 16.70 / 1 + 0.8126 + 0.02719 2+ h (0.2395 + 0.2772 ) + h2(0.1180 + 0.08558 ) (3b) AH(h, ) = 9.66 / 1 + 0.6721 + 0.043
29、48 2+ h (0.07322 + 0.3655 ) + 0.1177 h2 (3c) 2.4 Frequency band 21.4-22.0 GHz In this frequency band, the attenuation is larger at higher frequencies and, therefore, the following formulae give the attenuation at 21.4 GHz. AL(h, ) = 40.39 / 1 + 0.8413 + 0.06418 2 0.002095 3+ 0.1646 10 44+ h (0.2871
30、+ 0.3732 ) + h2(0.09311 + 0.1638 ) + 0.03859 h3 (4a) AM(h, ) = 17.59 / 1 + 0.8066 + 0.02682 2+ h (0.2354 + 0.2699 ) + h2(0.1135 + 0.08342 ) (4b) AH(h, ) = 10.08 / 1 + 0.6205 + 0.04369 2+ h (0.06793 + 0.3605 ) + 0.1155 h2 (4c) 2.5 Frequency band 22.21-22.5 GHz In this frequency band, the attenuation
31、is at its maximum at 22.24 GHz due to water vapour resonance and lowest at 22.5 GHz and, therefore, the following formulae give the attenuation at 22.5 GHz. AL(h, ) = 47.88 / 1 + 0.78405 + 0.10659 2 0.0091566 3+ 0.30002 1034 0.40272 1055+ 0.18706 1076+ h (0.29782 + 0.30275 ) + h2(0.066824 + 0.17983
32、) + 0.038747 h3 (5a) AM(h, ) = 20.36 / 1 + 0.7223 + 0.06031 2 0.001980 3+ 0.1572 10 44+ h (0.2053 + 0.2374 ) + h2(0.1101 + 0.08933 ) (5b) AH(h, ) = 11.55 / 1 + 0.6073 + 0.04379 2+ h (0.05750 + 0.3490 ) + 0.1102 h2 (5c) Rec. ITU-R F.1404-1 5 2.6 Frequency band 23.6-24.0 GHz In this frequency band, th
33、e attenuation is smaller at higher frequencies and, therefore, the following formulae give the attenuation at 24.0 GHz. AL(h, ) = 40.20 / 1 + 0.8774 + 0.06742 2 0.002221 3+ 0.1759 10 44+ h (0.3193 + 0.4177 ) + h2(0.1014 + 0.1945 ) + 0.05008 h3 (6a) AM(h, ) = 17.88 / 1 + 0.8377 + 0.02861 2+ h (0.2587
34、 + 0.3070 ) + h2(0.1362 + 0.09479 ) (6b) AH(h, ) = 10.51 / 1 + 0.6504 + 0.04326 2+ h (0.08915 + 0.3870 ) + 0.1285 h2 (6c) 2.7 Frequency band 25.25-27.5 GHz In this frequency band, the attenuation is smaller at higher frequencies and, therefore, the following formulae give the attenuation at 27.5 GHz
35、. AL(h, ) = 22.73 / 1 + 0.9463 + 0.03455 2+ h (0.3232 + 0.4519 ) + h2(0.2486 + 0.1317 ) (7a) AM(h, ) = 11.96 / 1 + 0.8121 + 0.03055 2+ h (0.2619 + 0.4728 ) + 0.1490 h2 (7b) AH(h, ) = 8.77 / 1 + 0.8259 + h (0.2163 + 0.3037 ) + 0.1067 h2 (7c) 2.8 Frequency band 31.0-31.3 GHz In this frequency band, th
36、e attenuation is larger at higher frequencies and, therefore, the following formulae give the attenuation at 31.0 GHz. AL(h, ) = 19.54 / 1 + 0.9323 + 0.02553 2+ h (0.3416 + 0.4413 ) + h2(0.1980 + 0.08016 ) (8a) AM(h, ) = 11.76 / 1 + 0.81370 + 0.02033 2+ h (0.2740 + 0.3935 ) + 0.1203 h2 (8b) AH(h, )
37、= 9.52 / 1 + 0.8160 + h (0.2378 + 0.2722 ) + 0.08949 h2 (8c) 2.9 Frequency band 31.8-33.0 GHz In this frequency band, the attenuation is larger at higher frequencies and, therefore, the following formulae give the attenuation at 31.8 GHz. AL(h, ) = 19.55 / 1 + 0.9263 + 0.02442 2+ h (0.3399 + 0.4324
38、) + h2(0.1898 + 0.07463 ) (9a) AM(h, ) = 12.04 / 1 + 0.8112 + 0.01934 2+ h (0.2740 + 0.3825 ) + 0.1155 h2 (9b) AH(h, ) = 9.90 / 1 + 0.8140 + h (0.2401 + 0.2679 ) + 0.08673 h2 (9c) 2.10 Frequency band 36.0-37.0 GHz In this frequency band, the attenuation is larger at higher frequencies and, therefore
39、, the following formulae give attenuation at 36.0 GHz. AL(h, ) = 21.60 / 1 + 0.8102 + 0.05726 2 0.001887 3+ 0.1488 10 44+ h (0.2731 + 0.5166 ) + 0.1884 h2 (10a) AM(h, ) = 15.00 / 1 + 0.8197 + 0.01342 2+ h (0.3078 + 0.2651 ) + h2(0.07561 + 0.03399 ) (10b) AH(h, ) = 12.80 / 1 + 0.7376 + 0.01588 2+ h (
40、0.2185 + 0.2806 ) + 0.07660 h2 (10c) 6 Rec. ITU-R F.1404-1 2.11 Frequency band 37.0-38.0 GHz In this frequency band, the attenuation is larger at higher frequencies and, therefore, the following formulae give the attenuation at 37.0 GHz. AL(h, ) = 22.63 / 1 + 0.8064 + 0.05519 2 0.001808 3+ 0.1416 10
41、 44+ h (0.2740 + 0.4986 ) + 0.1789 h2 (11a) AM(h, ) = 16.03 / 1 + 0.8146 + 0.01315 2+ h (0.3044 + 0.2598 ) + h2(0.07308 + 0.03276 ) (11b) AH(h, ) = 13.85 / 1 + 0.7369 + 0.01556 2+ h (0.2197 + 0.2771 ) + 0.07495 h2 (11c) 2.12 Frequency band 39.5-40.0 GHz In this frequency band, the attenuation is lar
42、ger at higher frequencies and, therefore, the following formulae give the attenuation at 39.5 GHz. AL(h, ) = 26.03 / 1 + 0.7941 + 0.05051 2 0.001631 3+ 0.1259 10 44+ h (0.2739 + 0.4541 ) + 0.1562 h2 (12a) AM(h, ) = 19.39 / 1 + 0.8019 + 0.01254 2+ h (0.2957 + 0.2470 ) + h2(0.06718 + 0.03002 ) (12b) A
43、H(h, ) = 17.46 / 1 + 0.7615 + 0.01187 2+ h (0.2619 + 0.2041 ) + h2(0.05213 + 0.02735 ) (12c) 2.13 Frequency band 40.0-40.5 GHz In this frequency band, the attenuation is larger at higher frequencies and, therefore, the following formulae give the attenuation at 40.0 GHz. AL(h, ) = 26.87 / 1 + 0.7912
44、 + 0.04963 2 0.001599 3+ 0.1230 10 44+ h (0.2735 + 0.4451 ) + 0.1517 h2 (13a) AM(h, ) = 20.23 / 1 + 0.7993 + 0.01243 2+ h (0.2939 + 0.2444 ) + h2(0.06605 + 0.02951 ) (13b) AH(h, ) = 18.33 / 1 + 0.7608 + 0.01179 2+ h (0.2620 + 0.2033 ) + h2(0.05148 + 0.02706 ) (13c) 2.14 Frequency band 40.5-42.5 GHz
45、In this frequency band, the attenuation is larger at higher frequencies and, therefore, the following formulae give the attenuation at 40.5 GHz. AL(h, ) = 27.78 / 1 + 0.7880 + 0.04877 2 0.001566 3+ 0.1202 10 44+ h (0.2729 + 0.4361 ) + 0.1473 h2 (14a) AM(h, ) = 20.76 / 1 + 0.6980 + 0.04731 2 0.001508
46、 3+ 0.1157 10 44+ h (0.2497 + 0.3257 ) + 0.07995 h2 (14b) AH(h, ) = 18.92 / 1 + 0.6577 + 0.04678 2 0.001484 3+ 0.1139 10 44+ h (0.2200 + 0.2811 ) + 0.06507 h2 (14c) Rec. ITU-R F.1404-1 7 2.15 Frequency band 55.78-59.0 GHz In this frequency band, the attenuation is generally larger at higher frequenc
47、ies and, therefore, the following formulae give the attenuation at 55.78 GHz. AL(h, ) = 2 217.1 / 1 + 0.40513 + 0.011553 2 0.00046820 3+ 0.84110 1054 0.77381 1075+ 0.27719 1096+ h (0.089500 + 0.042363 + 00025474 2 0.41230 1053) + 0.0093864 h2 (15a) AM(h, ) = 2 338.1 / 1 + 0.43368 + 0.011352 2 0.0004
48、5777 3+ 0.81145 10 54 0.74110 1075+ 0.26432 1096+ h (0.10951 + 0.050614 + 0.00028913 2 0.47829 1053) + 0.0099073 h2 (15b) AH(h, ) = 2 414.2 / 1 + 0.44582 + 0.011815 2 0.00048462 3+ 0.87303 1054 0.80607 1075+ 0.28980 1096+ h (0.12263 + 0.054149 + 0.00032477 2 0.52680 1053) + 0.0087766 h2 (15c) In the band 55.78-56.26 GHz, in order to protect stations in the Earth e
