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.
