1、 Rec. ITU-R P.838-3 1 RECOMMENDATION ITU-R P.838-3 Specific attenuation model for rain for use in prediction methods (Question ITU-R 201/3) (1992-1999-2003-2005) The ITU Radiocommunication Assembly, considering a) that there is a need to calculate the attenuation due to rain from a knowledge of rain
2、 rates, recommends 1 that the following procedure be used. The specific attenuation R(dB/km) is obtained from the rain rate R (mm/h) using the power-law relationship: = kRR(1) Values for the coefficients k and are determined as functions of frequency, f (GHz), in the range from 1 to 1 000 GHz, from
3、the following equations, which have been developed from curve-fitting to power-law coefficients derived from scattering calculations: =+ =411021010loglogexplogjkkjjjcfmcbfak (2) =+ =5110210loglogexpjjjjcfmcbfa (3) where: f : frequency (GHz) k : either kHor kV : either Hor V. Values for the constants
4、 for the coefficient kHfor horizontal polarization are given in Table 1 and for the coefficient kVfor vertical polarization in Table 2. Table 3 gives the values for the constants for the coefficient Hfor horizontal polarization, and Table 4 gives the values for the constants for the coefficient Vfor
5、 vertical polarization. 2 Rec. ITU-R P.838-3 TABLE 1 Coefficients for kH j aj bj cj mk ck 1 5.33980 0.10008 1.13098 2 0.35351 1.26970 0.45400 3 0.23789 0.86036 0.15354 4 0.94158 0.64552 0.16817 0.18961 0.71147 TABLE 2 Coefficients for kV j aj bj cj mk ck 1 3.80595 0.56934 0.81061 2 3.44965 0.22911 0
6、.51059 3 0.39902 0.73042 0.11899 4 0.50167 1.07319 0.27195 0.16398 0.63297 TABLE 3 Coefficients for H j aj bj cj m c 1 0.14318 1.82442 0.55187 2 0.29591 0.77564 0.19822 3 0.32177 0.63773 0.13164 4 5.37610 0.96230 1.47828 5 16.1721 3.29980 3.43990 0.67849 1.95537 TABLE 4 Coefficients for V j aj bj cj
7、 m c 1 0.07771 2.33840 0.76284 2 0.56727 0.95545 0.54039 3 0.20238 1.14520 0.26809 4 48.2991 0.791669 0.116226 5 48.5833 0.791459 0.116479 0.053739 0.83433 Rec. ITU-R P.838-3 3 For linear and circular polarization, and for all path geometries, the coefficients in equation (1) can be calculated from
8、the values given by equations (2) and (3) using the following equations: 2/2coscos)(2+=VHVHkkkkk (4) () kkkkkVVHHVVHH2/2coscos2+= (5) where is the path elevation angle and is the polarization tilt angle relative to the horizontal ( = 45 for circular polarization). For quick reference, the coefficien
9、ts k and are shown graphically in Figs. 1 to 4, and Table 5 lists numerical values for the coefficients at given frequencies. 110102103105104103102101110CoefficientkHFIGURE 1k coefficient for horizontal polarization4 Rec. ITU-R P.838-3 Rec. ITU-R P.838-3 5 TABLE 5 Frequency-dependent coefficients fo
10、r estimating specific rain attenuation using equations (4), (5) and (1) Frequency (GHz) kH H kV V 1 0.0000259 0.9691 0.0000308 0.8592 1.5 0.0000443 1.0185 0.0000574 0.8957 2 0.0000847 1.0664 0.0000998 0.9490 2.5 0.0001321 1.1209 0.0001464 1.0085 3 0.0001390 1.2322 0.0001942 1.0688 3.5 0.0001155 1.41
11、89 0.0002346 1.1387 4 0.0001071 1.6009 0.0002461 1.2476 4.5 0.0001340 1.6948 0.0002347 1.3987 5 0.0002162 1.6969 0.0002428 1.5317 5.5 0.0003909 1.6499 0.0003115 1.5882 6 0.0007056 1.5900 0.0004878 1.5728 7 0.001915 1.4810 0.001425 1.4745 8 0.004115 1.3905 0.003450 1.3797 9 0.007535 1.3155 0.006691 1
12、.2895 10 0.01217 1.2571 0.01129 1.2156 6 Rec. ITU-R P.838-3 TABLE 5 (continued) Frequency (GHz) kH H kV V 11 0.01772 1.2140 0.01731 1.1617 12 0.02386 1.1825 0.02455 1.1216 13 0.03041 1.1586 0.03266 1.0901 14 0.03738 1.1396 0.04126 1.0646 15 0.04481 1.1233 0.05008 1.0440 16 0.05282 1.1086 0.05899 1.0
13、273 17 0.06146 1.0949 0.06797 1.0137 18 0.07078 1.0818 0.07708 1.0025 19 0.08084 1.0691 0.08642 0.9930 20 0.09164 1.0568 0.09611 0.9847 21 0.1032 1.0447 0.1063 0.9771 22 0.1155 1.0329 0.1170 0.9700 23 0.1286 1.0214 0.1284 0.9630 24 0.1425 1.0101 0.1404 0.9561 25 0.1571 0.9991 0.1533 0.9491 26 0.1724
14、 0.9884 0.1669 0.9421 27 0.1884 0.9780 0.1813 0.9349 28 0.2051 0.9679 0.1964 0.9277 29 0.2224 0.9580 0.2124 0.9203 30 0.2403 0.9485 0.2291 0.9129 31 0.2588 0.9392 0.2465 0.9055 32 0.2778 0.9302 0.2646 0.8981 33 0.2972 0.9214 0.2833 0.8907 34 0.3171 0.9129 0.3026 0.8834 35 0.3374 0.9047 0.3224 0.8761
15、 36 0.3580 0.8967 0.3427 0.8690 37 0.3789 0.8890 0.3633 0.8621 38 0.4001 0.8816 0.3844 0.8552 39 0.4215 0.8743 0.4058 0.8486 40 0.4431 0.8673 0.4274 0.8421 41 0.4647 0.8605 0.4492 0.8357 42 0.4865 0.8539 0.4712 0.8296 43 0.5084 0.8476 0.4932 0.8236 44 0.5302 0.8414 0.5153 0.8179 45 0.5521 0.8355 0.5
16、375 0.8123 46 0.5738 0.8297 0.5596 0.8069 47 0.5956 0.8241 0.5817 0.8017 48 0.6172 0.8187 0.6037 0.7967 Rec. ITU-R P.838-3 7 TABLE 5 (continued) Frequency (GHz) kH H kV V 49 0.6386 0.8134 0.6255 0.7918 50 0.6600 0.8084 0.6472 0.7871 51 0.6811 0.8034 0.6687 0.7826 52 0.7020 0.7987 0.6901 0.7783 53 0.
17、7228 0.7941 0.7112 0.7741 54 0.7433 0.7896 0.7321 0.7700 55 0.7635 0.7853 0.7527 0.7661 56 0.7835 0.7811 0.7730 0.7623 57 0.8032 0.7771 0.7931 0.7587 58 0.8226 0.7731 0.8129 0.7552 59 0.8418 0.7693 0.8324 0.7518 60 0.8606 0.7656 0.8515 0.7486 61 0.8791 0.7621 0.8704 0.7454 62 0.8974 0.7586 0.8889 0.
18、7424 63 0.9153 0.7552 0.9071 0.7395 64 0.9328 0.7520 0.9250 0.7366 65 0.9501 0.7488 0.9425 0.7339 66 0.9670 0.7458 0.9598 0.7313 67 0.9836 0.7428 0.9767 0.7287 68 0.9999 0.7400 0.9932 0.7262 69 1.0159 0.7372 1.0094 0.7238 70 1.0315 0.7345 1.0253 0.7215 71 1.0468 0.7318 1.0409 0.7193 72 1.0618 0.7293
19、 1.0561 0.7171 73 1.0764 0.7268 1.0711 0.7150 74 1.0908 0.7244 1.0857 0.7130 75 1.1048 0.7221 1.1000 0.7110 76 1.1185 0.7199 1.1139 0.7091 77 1.1320 0.7177 1.1276 0.7073 78 1.1451 0.7156 1.1410 0.7055 79 1.1579 0.7135 1.1541 0.7038 80 1.1704 0.7115 1.1668 0.7021 81 1.1827 0.7096 1.1793 0.7004 82 1.1
20、946 0.7077 1.1915 0.6988 83 1.2063 0.7058 1.2034 0.6973 84 1.2177 0.7040 1.2151 0.6958 85 1.2289 0.7023 1.2265 0.6943 86 1.2398 0.7006 1.2376 0.6929 8 Rec. ITU-R P.838-3 TABLE 5 (end) Frequency (GHz) kH H kV V 87 1.2504 0.6990 1.2484 0.6915 88 1.2607 0.6974 1.2590 0.6902 89 1.2708 0.6959 1.2694 0.68
21、89 90 1.2807 0.6944 1.2795 0.6876 91 1.2903 0.6929 1.2893 0.6864 92 1.2997 0.6915 1.2989 0.6852 93 1.3089 0.6901 1.3083 0.6840 94 1.3179 0.6888 1.3175 0.6828 95 1.3266 0.6875 1.3265 0.6817 96 1.3351 0.6862 1.3352 0.6806 97 1.3434 0.6850 1.3437 0.6796 98 1.3515 0.6838 1.3520 0.6785 99 1.3594 0.6826 1
22、.3601 0.6775 100 1.3671 0.6815 1.3680 0.6765 120 1.4866 0.6640 1.4911 0.6609 150 1.5823 0.6494 1.5896 0.6466 200 1.6378 0.6382 1.6443 0.6343 300 1.6286 0.6296 1.6286 0.6262 400 1.5860 0.6262 1.5820 0.6256 500 1.5418 0.6253 1.5366 0.6272 600 1.5013 0.6262 1.4967 0.6293 700 1.4654 0.6284 1.4622 0.6315 800 1.4335 0.6315 1.4321 0.6334 900 1.4050 0.6353 1.4056 0.6351 1 000 1.3795 0.6396 1.3822 0.6365
