1、Rec. ITU-R SF.1395 1RECOMMENDATION ITU-R SF.1395*MINIMUM PROPAGATION ATTENUATION DUE TO ATMOSPHERIC GASESFOR USE IN FREQUENCY SHARING STUDIES BETWEEN THEFIXED-SATELLITE SERVICE AND THE FIXED SERVICE(Questions ITU-R 60/4, 250/4, ITU-R 116/9 and ITU-R 217/9)(1999)Rec. ITU-R SF.1395The ITU Radiocommuni
2、cation Assembly,consideringa) that slant path attenuation between a terrestrial station and a space station (geostationary or non-geostationary)resulting from absorption due to atmospheric gases including water vapour is an important factor in frequency sharingstudies between the fixed-satellite ser
3、vice (FSS) and the fixed service (FS);b) that slant path attenuation depends on the distribution along the path of meteorological parameters such astemperature, pressure and humidity, and thus varies with the geographic location of the site, the month of the year, theheight of an FS station above se
4、a level and the elevation angle of the slant path;c) that such slant path attenuation can be estimated by the method described in Annex 1 to Recommen-dation 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 st
5、udies, it is necessary to define the parameters in the driest month atsea level for each climate area, based on Recommendation ITU-R P.835;e) that slant path attenuation is a complicated function of the frequency and that for each frequency band arepresentative frequency giving the lowest attenuatio
6、n should be chosen,recommends1 that for frequency sharing studies between FSS and FS systems in each frequency band, slant path attenuationresulting from absorption due to atmospheric gases including water vapour should be estimated at a representativefrequency which gives the lowest attenuation in
7、that band (see Note 1);2 that the method of Annex 1 should be utilized for the estimation of slant path attenuation due to atmosphericabsorption (see Notes 2, 3 and 4).NOTE 1 - The information in this Recommendation is solely for the purpose of frequency sharing studies, because itdeals with the sla
8、nt path attenuation in the driest month.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 Recommendation ITU-R P.676-3 (Geneva, 1997) andRecommendation ITU-R P.835-2 (Geneva, 1997).NOTE 4 - Recom
9、mendation ITU-R F.1404 presents approximate formulae of minimum slant path attenuation due toatmospheric absorption for the frequency bands shared by the FS and the broadcasting-satellite, mobile-satellite andspace science services._*This Recommendation should be brought to the attention of Radiocom
10、munication Study Group 3 (Radiocommunication WorkingParty 3J).2 Rec. ITU-R SF.1395ANNEX 1Estimation of slant path propagation attenuation due to atmospheric gasesfor use in FSS/FS frequency sharing studies1 IntroductionSlant path attenuation between a terrestrial station and a space station (geostat
11、ionary or non-geostationary) resultingfrom absorption due to atmospheric gases including water vapour is an important factor in FSS/FS frequency sharingstudies. The slant path attenuation depends on the distribution along the path of meteorological parameters such astemperature, pressure and humidit
12、y, and thus varies with the geographic location of the site, the month of the year, theheight of an FS station above sea level and the elevation angle of the slant path and the operating frequency. Theprocedure for calculating the slant path attenuation is the line-by-line procedure given in Annex 1
13、 to Recommen-dation ITU-R P.676.The detailed calculations of atmospheric attenuation may utilize local information of average water vapour content in thedriest month and of other meteorological parameters along with the atmospheric models of Recommen-dation ITU-R P.835. Where this information is not
14、 available, the following results provide a simple procedure forestimating atmospheric attenuation.The formulae given in 2 consider each of the frequency bands which are allocated to FSS and FS on a shared basis andare presented for five representative geographical areas of the world (northern and s
15、outhern hemispheres).2 Estimation of slant path attenuationFor the purpose of this simplified estimation, an FS station is identified as being within one of three climate areasdepending only on the latitude (absolute value) of the station: low-latitudes within 22.5 of the Equator; mid-latitudes grea
16、ter than 22.5 , but less than 45 from the Equator; high-latitudes of 45 or more from the Equator.Table 1 shows the climate parameters for each of these areas. Note that the sea-level water vapour density for the low-latitude climate is lower than that prescribed in Recommendation ITU-R P.835 corresp
17、onding to the dry season. Theattenuation values for these areas have been determined as a function of the elevation angle of the actual transmissionpath from the FS station to the position of a space station (geostationary or non-geostationary). The numerical formulaefor atmospheric attenuation whic
18、h approximate the theoretical values are given in the following sections, where:AL(h, q ), AM(h, q ) and AH(h, q ): total atmospheric absorption loss (dB) for the low-latitude, mid-latitude andhigh-latitude areas, respectively;h and q : FS antenna altitude above sea level (km) and elevation angle (d
19、egrees),respectively.TABLE 1Parameters at sea level for the climate areasThe 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 P.835 were used in calculating the loss. Thea
20、pproximation was carried out for 0 h 3 km and 0 q 90 .Climate areaTemperature(K)Atmospheric pressure(hPa)Water vapour density(g/m3)Low-latitude 300.4 1 012.0 10.0Mid-latitude 272.7 1 018.9 3.5High-latitude 257.4 1 010.8 1.23Rec. ITU-R SF.1395 3The actual elevation angle may be determined from the el
21、evation angle developed under free space propagationconditions using the method in Recommendation ITU-R F.1333. For actual elevation angles below 0 , the attenuationfor 0 should be used.NOTE 1 - In some situations, it may become necessary to estimate the attenuation at a specific frequency based on
22、thefollowing formulae. For example, if it is necessary to find the attenuation in the low-latitude area at 18.5 GHz, it ispossible to estimate this attenuation as an interpolation of the attenuation at 17.7 GHz (see equation (4a) and that at18.8 GHz (see equation (5a). However, for such interpolatio
23、n to be accurate, the two adjacent representativefrequencies should be reasonably close to each other.2.1 Frequency band 10.7-11.7 GHzIn this frequency band, the attenuation is larger at higher frequencies and, therefore, the following formulae give theattenuation at 10.7 GHz.AL(h, q ) = 3.40 / 1 +
24、0.8356 q + h (0.2693 + 0.2753 q ) + 0.1002 h 2 (1a)AM(h, q ) = 3.01 / 1 + 0.7509 q + h (0.3991 + 0.2149 q ) (1b)AH(h, q ) = 2.98 / 1 + 0.7477 q + h (0.3737 + 0.2072 q ) (1c)2.2 Frequency band 11.7-12.75 GHzIn this frequency band, the attenuation is larger at higher frequencies and, therefore, the fo
25、llowing formulae give theattenuation at 11.7 GHz.AL(h, q ) = 3.84 / 1 + 0.8598 q + h (0.2815 + 0.3031 q ) + 0.1148 h 2 (2a)AM(h, q ) = 3.23 / 1 + 0.7585 q + h (0.4154 + 0.2232 q ) (2b)AH(h, q ) = 3.12 / 1 + 0.7487 q + h (0.3792 + 0.2102 q ) (2c)2.3 Frequency band 14.3-14.8 GHzIn this frequency band,
26、 the attenuation is larger at higher frequencies and, therefore, the following formulae give theattenuation at 14.3 GHz.AL(h, q ) = 5.59 / 1 + 0.9245 q + h (0.3063 + 0.3929 q ) + 0.1671 h 2 (3a)AM(h, q ) = 4.00 / 1 + 0.8411 q + h (0.2844 + 0.2832 q ) + 0.09031 h 2 (3b)AH(h, q ) = 3.63 / 1 + 0.7509 q
27、 + h (0.3973 + 0.2205 q ) (3c)2.4 Frequency band 17.7-18.8 GHzIn this frequency band, the attenuation is larger at higher frequencies and, therefore, the following formulae give theattenuation at 17.7 GHz.AL(h, q ) = 11.38 / 1 + 0.8601 q + 0.04510 q 2+ h (0.2342 + 0.6585 q ) + 0.2658 h 2 (4a)AM(h, q
28、 ) = 6.54 / 1 + 0.8994 q + h (0.2971 + 0.3762 q ) + 0.1322 h 2 (4b)AH(h, q ) = 4.95 / 1 + 0.8149 q + h (0.2205 + 0.2830 q ) + 0.09616 h 2 (4c)2.5 Frequency band 18.8-19.3 GHzIn this frequency band, the attenuation is larger at higher frequencies and, therefore, the following formulae giveattenuation
29、 at 18.8 GHz.AL(h, q ) = 16.17 / 1 + 0.9205 q + 0.03829 q 2+ h (0.2888 + 0.4380 q ) + h 2(0.2481 + 0.1380 q ) (5a)AM(h, q ) = 8.38 / 1 + 0.9117 q + h (0.2821 + 0.4201 q ) + 0.1500 h 2 (5b)AH(h, q ) = 5.87 / 1 + 0.8171 q + h (0.1962 + 0.3061 q ) + 0.1079 h 2 (5c)4 Rec. ITU-R SF.13952.6 Frequency band
30、 19.3-19.7 GHzIn this frequency band, the attenuation is larger at higher frequencies and, therefore, the following formulae give theattenuation at 19.3 GHz.AL(h, q ) = 19.17 / 1 + 0.9089 q + 0.04175 q 2+ h (0.2674 + 0.4401 q ) + h 2(0.2570 + 0.1485 q ) (6a)AM(h, q ) = 9.34 / 1 + 0.7790 q + 0.03929
31、q 2+ h (0.2256 + 0.4979 q ) + 0.1562 h 2 (6b)AH(h, q ) = 6.45 / 1 + 0.8152 q + h (0.1799 + 0.3163 q ) + 0.1141 h 2 (6c)2.7 Frequency band 27.0-27.5 GHzIn this frequency band, the attenuation is smaller at higher frequencies and, therefore, the following formulae give theattenuation at 27.5 GHz.AL(h,
32、 q ) = 22.73 / 1 + 0.9463 q + 0.03455 q2+ h (0.3232 + 0.4519 q ) + h 2(0.2486 + 0.1317 q ) (7a)AM(h, q ) = 11.96 / 1 + 0.8121 q + 0.03055 q2+ h (0.2619 + 0.4728 q ) + 0.1490 h 2 (7b)AH(h, q ) = 8.77 / 1 + 0.8259 q + h (0.2163 + 0.3037 q ) + 0.1067 h 2 (7c)2.8 Frequency band 27.5-29.5 GHzIn this freq
33、uency band, the attenuation is generally smaller at higher frequencies and, therefore, the following formulaegive the attenuation at 29.5 GHz.AL(h, q ) = 20.10 / 1 + 0.9428 q + 0.02816 q 2+ h (0.3417 + 0.4499 q ) + h 2(0.2165 + 0.09728 q ) (8a)AM(h, q ) = 11.51 / 1 + 0.8174 q + 0.02298 q 2+ h (0.273
34、4 + 0.4214 q ) + 0.1291 h 2 (8b)AH(h, q ) = 9.00 / 1 + 0.8202 q + h (0.2324 + 0.2825 q ) + 0.09510 h 2 (8c)2.9 Frequency band 37.5-40.5 GHzIn this frequency band, the attenuation is larger at higher frequencies and, therefore, the following formulae give theattenuation at 37.5 GHz.AL(h, q ) = 23.21
35、/ 1 + 0.8042 q + 0.05421 q 2 0.001771 q 3+ 0.1382 104q 4+ h ( 0.2743 + 0.4897 q ) + 0.1742 h 2 (9a)AM (h, q ) = 16.60 / 1 + 0.8121 q + 0.01302 q 2+ h (0.3027 + 0.2572 q ) + h 2(0.07186 + 0.03217 q ) (9b)AH(h, q ) = 14.44 / 1 + 0.7365 q + 0.01542 q 2+ h (0.2202 + 0.2754 q ) + 0.07416 h 2 (9c)2.10 Fre
36、quency band 40.5-42.5 GHzIn this frequency band, the attenuation is larger at higher frequencies and, therefore, the following formulae give theattenuation at 40.5 GHz.AL(h, q ) = 27.78 / 1 + 0.7880 q + 0.04877 q 2 0.001566 q 3+ 0.1202 104q 4+ h (0.2729 + 0.4361 q ) + 0.1473 h 2 (10a)AM(h, q ) = 20.
37、76 / 1 + 0.6980 q + 0.04731 q2 0.001508 q 3+ 0.1157 104q 4+ h (0.2497 + 0.3257 q ) + 0.07995 h 2 (10b)AH( h, q ) = 18.92 / 1 + 0.6577 q + 0.04678 q 2 0.001484 q 3+ 0.1139 104q 4+ h (0.2200 + 0.2811 q ) + 0.06507 h 2 (10c)Rec. ITU-R SF.1395 52.11 Frequency band 42.5-43.5 GHzIn this frequency band, th
38、e attenuation is larger at higher frequencies and, therefore, the following formulae giveattenuation at 42.5 GHz.AL(h, q ) = 32.19 / 1 + 0.7732 q + 0.04549 q 2 0.001445 q 3+ 0.1096 104q 4+ h (0.2687 + 0.3992 q ) + 0.1297 h 2 (11a)AM(h, q ) = 25.20 / 1 + 0.6884 q + 0.04608 q 2 0.001462 q 3+ 0.1117 10
39、4q 4+ h (0.2437 + 0.3107 q ) + 0.07470 h 2 (11b)AH( h, q ) = 23.56 / 1 + 0.6557 q + 0.04605 q 2 0.001457 q 3+ 0.1115 104q 4+ h (0.2216 + 0.2749 q ) + 0.06237 h 2 (11c)2.12 Frequency band 47.2-50.2 GHzIn this frequency band, the attenuation is larger at higher frequencies and, therefore, the followin
40、g formulae give theattenuation at 47.2 GHz.AL(h, q ) = 52.43 / 1 +0.7364 q + 0.03601 q 2 0.001099 q 3+ 0.8024 105q 4+ h (0.2642 + 0.2479 q ) + h 2(0.08130 + 0.02637 q ) (12a)AM(h, q ) = 47.00 / 1 + 0.7004 q + 0.03568 q 2 0.001081 q 3+ 0.7878 105q 4+ h (0.2527 + 0.1970 q ) + h 2(0.05539 + 0.03239 q )
41、 (12b)AH(h, q ) = 46.70 / 1 + 0.6872 q + 0.03637 q 2 0.001105 q 3+ 0.8087 105q 4+ h (0.2472 + 0.1819 q ) + h2(0.04858 + 0.03221 q ) (12c)2.13 Frequency band 47.9-48.2 GHzIn this frequency band, the attenuation is larger at higher frequencies and, therefore, the following formulae give theattenuation
42、 at 47.9 GHz.AL(h, q ) = 57.90 / 1 + 0.7262 q + 0.03534 q 2 0.001074 q 3+ 0.7826 105q 4+ h (0.2576 + 0.2382 q ) + h 2(0.07645 + 0.02443 q ) (13a)AM(h, q ) = 53.06 / 1 + 0.6962 q + 0.03555 q 2 0.001076 q 3+ 0.7840 105q 4+ h (0.2495 + 0.1940 q ) + h 2(0.05420 + 0.03176 q ) (13b)AH( h, q ) = 53.21 / 1
43、+ 0.6864 q + 0.03632 q 2 0.001103 q 3+ 0.8073 105q4+ h (0.2476 + 0.1812 q ) + h 2(0.04791 + 0.03191 q ) (13c)NOTE 1 - Although the band 47.9-48.2 GHz is part of the band 47.2-50.2 GHz, different formulae have been developedfor the band 47.9-48.2 GHz, because No. S5.552A of the Radio Regulations desi
44、gnates the band 47.9-48.2 GHz for useby high-altitude platform stations in the FS on a shared basis with the FSS (Earth-to-space). The slant path attenuationfrom the ground to a high-altitude platform station, at an altitude of 20 km or more, will be very similar to that on anEarth-space path of the same elevation angle.
