1、 Rec. ITU-R BO.1445 1 RECOMMENDATION ITU-R BO.1445 IMPROVED PATTERNS FOR FAST ROLL-OFF SATELLITE TRANSMIT ANTENNAS OF THE REGIONS 1 AND 3 BSS PLANS OF RR APPENDIX S30 (Question ITU-R 93/11) (2000) Rec. ITU-R BO.1445 The ITU Radiocommunication Assembly, considering a) that Resolution 532 (WRC-97) (Wo
2、rld Radiocommunication Conference (Geneva, 1997) invites ITU-R to study the possibilities to improve the efficiency of the Appendix S30 Plan of the RR by taking due account of the technical progress; b) that the existing RR Appendix S30 Regions 1 and 3 satellite transmitting antenna patterns with ro
3、ll-off in the main beam can be improved to reflect technical progress; c) that the use of antennas with improved radiation patterns will lead to a more efficient use of the radio spectrum and the GSO, recognizing a) that the adoption of improved satellite transmitting antenna patterns with fast roll
4、-off in the main beam does not prevent the use of other antennas that have been coordinated or will be coordinated in the future on the basis of different patterns; b) that the next competent conference may include these patterns into Annex 5 of RR Appendix S30, recommends 1 to use the improved sate
5、llite antenna co-polar and cross-polar patterns with fast roll-off in the main beam as provided in Annex 1, for elliptical beams of fast roll-off when such fast roll-off antenna is required, e.g. in studies in accordance with Resolution 532 (WRC-97). 2 Rec. ITU-R BO.1445 ANNEX 1 1445-013530252015105
6、04045101110102ABCG2G1G2G2G2G1Relativeantennagain(dB)Off-axis angle, (degrees)FIGURE 1Improved fast roll-off satellite transmittingantenna patterns for Regions 1 and 3Improved fast roll-off co-polar (Curve A defined as G below)Regions 1 and 3 transmitting co-polar (Curve G2) Improved fast roll-off cr
7、oss-polar (Regions 1 and 3 transmitting cross-polar) (Curve B) Regions 1 and 3 transmitting fast roll-off co-polar (Curve G1)Curve C (minus the on-axis gain) Note 1 The diagram gives the example curves in case of a satellite antenna beamwidth of 0= 1.2 (circular).FIGURE 1 1445-01 Curve A: co-polar r
8、elative gain ()21,min GGG = (dB): where: ()201/12 =G for 0 (/0) 0.5 200112Gf7Gf7Gf7Gf7Gf8Gf6Ge7Ge7Ge7Ge7Ge8Ge6=minBxG for 0.5 1.45 ()axisonGG=1after intersection with Curve C ()202/12 =G for 0 1.58 0302=G for 1.58 03.16 0()axisonGG=2after intersection with Curve C Curve B: cross-polar relative gain
9、(dB): Gf7Gf7Gf8Gf6Ge7Ge7Ge8Ge6+ 1log40400for 0 0.33 033 for 0.33 01.67 0()axisonG after intersection with Curve C Curve C: minus the on-axis gain (Curve C in this Figure illustrates the particular case of an antenna with an on-axis gain of 42.773 dBi) where: : off-axis angle (degrees) 0: cross-secti
10、onal half-power beamwidth in the direction of interest (degrees) Bmin: 0.6 for Regions 1 and 3 Gf7Gf7Gf8Gf6Ge7Ge7Ge8Ge6=0minBx 15.0 The relationship between the maximum gain of an antenna and the half-power beamwidth can be derived from the expression: baGmax84327= where: a and b are the angles (degrees) subtended at the satellite by the major and minor axes of the elliptical cross-section of the beam; an antenna efficiency of 55% was assumed.
