1、 Rec. ITU-R S.1844 1 RECOMMENDATION ITU-R S.1844 Cross-polarization reference gain pattern for linearly polarized very small aperture terminals (VSAT) for frequencies in the range 2 to 31 GHz (2009) Scope This Recommendation provides a cross-polarization reference gain pattern that, in the absence o
2、f particular information concerning the cross-polarization radiation pattern of a linearly polarized very small aperture terminal (VSAT) earth station antenna, should be used as a reference for interference calculations involving VSAT earth stations in the fixed-satellite service and stations of oth
3、er services sharing the same frequency band, as well as coordination studies and interference assessment between systems in the fixed-satellite service. The ITU Radiocommunication Assembly, considering a) that, for studies of mutual interference between radiocommunication-satellite systems and betwe
4、en earth stations of such systems and stations of other services sharing the same frequency band, it may be necessary to use a single cross-polarization radiation pattern for the very small aperture terminal (VSAT) earth station antenna; b) that, for coordination studies and for the assessment of in
5、terference between VSAT earth stations and space stations, a cross-polarization radiation pattern for the angular region near the main beam based on the envelope of the peak power of the side lobes in this region may be appropriate; c) that the use of antennas with the best achievable cross-polariza
6、tion radiation patterns will lead to the most efficient use of the radio-frequency spectrum and the geostationary-satellite orbit, noting a) that increased utilization of the orbital arc has resulted in the widespread use of very small aperture antennas, recommends 1 that, in the absence of particul
7、ar information concerning the radiation pattern of the linearly polarized very small aperture terminal antenna for the earth station involved, a single reference radiation pattern should be used for coordination and interference studies involving linearly polarized VSAT earth stations in the fixed-s
8、atellite service and stations of other services sharing the same frequency band; 2 Rec. ITU-R S.1844 2 that the following cross-polarization reference gain pattern should be used for linearly polarized VSAT antennas with a diameter-to-wavelength (D/) less than 100, for different angles between the d
9、irections considered and the axis of the main beam (boresight direction), for frequencies in the range 2 to 31 GHz: Gx() = Gmax 25 dBi for 0 0.3 Gx() = Gmax 20 dBi for 0.3 20 Gx() = Gmax 20025.0DdBi for 20 SXPGx() = 23 20 log dBi for SXP 7 Gx() = 20.2 16.7 log dBi for 7 26.3 Gx() = 32 25 log dBi for
10、 26.3 48 Gx() = 10 dBi for 48 180 where: Gmax: antenna maximum gain (in the boresight direction) = 22log10DD: antenna diameter (m) : wavelength (m) : efficiency as a fraction 0.3: angular limit of the 0.3 dB co-polar beamwidth = 10.95 /D 20: angular limit of the 20 dB co-polar beamwidth = 89.44 /D SXP: angle of intersection between: F1() = Gmax 20025.0Dand F2() = 23 20 log and can be approximated by the following expression: 99.0101=DSXP
