where: fr: reference frequency a = 2 702 MHz for the band 14.4-15.35 GHz, and a = 2 800 MHz for the band 14.5-15.35 GHz n = 1, 2, . . . N14 with N14 ≤ 32 for the band 14.4-15.35 GHz n and N14 ≤ 30 for the band 14.5-15.35 GHz. The channel arrangement with fr = 11 701 MHz and a frequency spacing of 14 MHz is illustrated in Fig. 2; 3 that the preferred radio-frequency channel arrangement for medium-capacity digital fixed wireless systems operating with a 56 MHz channel spacing should be derived as follows: Let N56 be the number of RF channels; then the frequencies (MHz) of individual channels are expressed by the following relationships: lower half of the band: fn = fr + a + 56 n MHz upper half of the band: two options are possible for maintaining a common duplex separations with lower size channels arrangements: Option 1: f 'n = fr + 3 612 – 56 (N56 – n) MHz Option 2: f 'n = fr + 3 584 – 56 (N56 – n) MHz Option 1 should be used when corresponding 28 MHz arrangement provides N28 = 2 N56 channels, or when no lower channel arrangements are used. Option 2 should to be used when corresponding 28 MHz arrangement provides N28 = 2 N56 + 1 channels, fr : reference frequency a = 2 674 MHz for the band 14.4-15.35 GHz, and a = 2 772 MHz for the band 14.5-15.35 GHz n = 1, 2, . . . N56, with N56 ≤ 8 for the band 14.4-15.35 GHz and N56 ≤ 7 for the band 14.5-15.35 GHz. The channel arrangement with fr = 11 701 MHz and a frequency spacing of 56 MHz is illustrated in Fig. 3; FIGURE 1 Radio-frequency channel arrangement for radio-relay systems operating in the 15 GHz band: 28 MHz spacing
c) The centre frequencies of the 10 paired channels which allow RF channel bandwidths of greater than 10 MHz and less than or equal to 20 MHz are expressed by the following relationships: half of the band Cn = 14 490 + 20 n for n = 1 to 8 Cn = 14 650 + 20 n for n = 9 to 10 Upper half of the band C′n = 14 965 + 20 n for n = 1 to 8 C′n = 15 125 + 20 n for n = 9 to 10 where n is the channel number and Cn and C′n are the centre frequencies in MHz of the paired channels. d) The centre frequencies of the six paired channels which allow RF channels bandwidths of greater than 20 MHz and less than or equal to 30 MHz are expressed by the following relationships: Lower half of the band Dn = 14 485 + 30 n for n = 1 to 5 Dn = 14 655 + 30 n for n = 6 half of the band D′n = 14 960 + 30 n for n = 1 to 5 D′n = 15 130 + 30 n for n = 6 n is the channel number and Dn and D′n are the centre frequencies in MHz of the paired channels. e) The centre frequencies of the five paired channels which allow RF channels bandwidths of greater than 30 MHz and less than or equal to 40 MHz are expressed by the following relationships: half of the band En = 14 480 + 40 n for n = 1 to 4 En = 14 640 + 40 n for n = 5 Upper half of the band E′n = 14 955 + 40 n for n = 1 to 4 E′n = 15 115 + 40 n for n = 5 n is the channel number and En and E′n are the centre frequencies in MHz of the paired channels. f) The centre frequencies of the four paired channels which allow RF channels bandwidths of greater than 40 MHz and less than or equal to 50 MHz are expressed by the following relationships: Lower half of the band Fn = 14 475 + 50 n for n = 1 to 3 Fn = 14 645 + 50 n for n = 4 Upper half of the band F′n = 14 950 + 50 n for n = 1 to 3 F′n = 15 120 + 50 n for n = 4 where n is the channel number and Fn and F′n are the centre frequencies in MHz of the paired channels.