1、Rec. ITU-R F.1248 1RECOMMENDATION ITU-R F.1248*LIMITING INTERFERENCE TO SATELLITES IN THE SPACE SCIENCE SERVICESFROM THE EMISSIONS OF TRANS-HORIZON RADIO-RELAY SYSTEMSIN THE BANDS 2 025-2 110 MHz AND 2 200-2 290 MHz(Questions ITU-R 118/7 and ITU-R 113/9)(1997)Rec. ITU-R F.1248The ITU Radiocommunicat
2、ion Assembly,consideringa) that the World Administrative Radio Conference for Dealing with Frequency Allocations in Certain Parts ofthe Spectrum (Malaga-Torremolinos, 1992) (WARC-92) added on a co-primary basis with existing fixed and mobileservices, allocations to the space research, space operatio
3、n and Earth exploration-satellite services (space scienceservices) in the bands 2 025-2 110 MHz and 2 200-2 290 MHz;b) that trans-horizon radio-relay systems may operate in the bands 2 025-2 110 MHz and 2 200-2 290 MHz;c) that Recommendation ITU-R F.698 addresses the general problems of sharing betw
4、een the space services andtrans-horizon radio-relay systems;d) that No. 2509A of the Radio Regulations (RR) (RR No. S21.7) notes the difficult sharing conditions withtrans-horizon radio-relay systems and urges administrations to keep to a minimum the number of trans-horizon systemsin certain bands,
5、including the bands 2 025-2 110 MHz and 2 200-2 290 MHz;e) that limits on the emissions of trans-horizon radio-relay systems are required in order to prevent harmfulinterference to space science services satellites operating in the bands stated in a),recommends1 that in the band 2 025-2 110 MHz, the
6、 power spectral density at the input to the transmitting antenna of a trans-horizon radio-relay system (except for existing systems on existing routes) should not exceed 6 dB(W/MHz) in order tosatisfy the sharing criteria set forth in Recommendation ITU-R SA.1274 (see Note 1 and Annex 1);2 that in t
7、he band 2 200-2 290 MHz, the e.i.r.p. spectral density of the emission of a trans-horizon radio-relaysystem (except for existing systems on existing routes) should conform to the values and conditions given inRecommendation ITU-R F.1247 (see Note 1);3 that this Recommendation provides the latest inf
8、ormation prepared by the ITU-R as referred to inrecommends 1 of Recommendation 100 (Rev.WRC-95) (see Note 2).NOTE 1 For the purpose of this Recommendation, an existing system on an existing route is regarded as one alreadyplanned before the closure of the third ITU Radiocommunication Assembly (Genev
9、a, 1997) and brought into servicebefore 1 January 2000.NOTE 2 Recommendation 100 (Rev.WRC-95), in its recommends 1, states that administrations for the assignment offrequencies to new stations in systems using tropospheric scatter, take into account latest information prepared by ITU-Rto ensure that
10、 systems established in the future use a limited number of certain frequency bands._*This Recommendation was developed jointly by Radiocommunication Study Groups 7 and 9, and any future revision should alsobe undertaken jointly.2 Rec. ITU-R F.1248ANNEX 1Statistics of interference to low-orbiting sat
11、ellites from the emissions of a singletrans-horizon radio-relay station in the band 2 025-2 110 MHz1 IntroductionThis Annex summarizes the results of computer simulations to determine the statistics of interference to low-orbitingsatellites from the emissions of a single trans-horizon radio-relay st
12、ation. Several cases were evaluated. In a typical case,a single trans-horizon station was located at a specified latitude. The antenna was positioned at an elevation angle of 1and at an azimuth angle of 0 to 350 in 10 steps. Interference to a low-orbiting satellite for each azimuth angle of thetrans
13、-horizon station transmitting antenna was calculated in 3 s increments over a simulated period of 30 days. Theoutput of the simulation was the cumulative probability of interference as a function of interference power density level.The major parameters used in the simulations are listed in Table 1.T
14、ABLE 1Summary of the parameters used in the simulations2 ResultsResults were obtained for a satellite in an orbit that is characteristic of Earth observing satellites (an altitude of 800 kminclined by 98.6 with respect to the equatorial plane) and for a satellite in an orbit that is typical of the i
15、nternationalspace station (an altitude of 350 km inclined by 57.1 with respect to the equatorial plane). The results are given inFigs. 1 through 4. Each curve in the figure corresponds to a particular azimuth angle of the trans-horizon transmittingantenna.Figure 1 shows that the level of interferenc
16、e at the 0.1% criterion given in Recommendation ITU-R SA.1274 is exceededby about 7 dB. Similarly, Figs. 2, 3 and 4 show that the interference level at the 0.1% criterion is exceeded by about10 dB, 11 dB and 16 dB, respectively. Thus, the power spectral density at the input to the antenna of a trans
17、-horizonradio-relay station needs to be reduced by about 15 dB from the value of 21.3 dB(W/MHz) used in the simulations to avalue of 6 dB(W/MHz).Trans-horizon station ValueTransmitter power density (dB(W/MHz) 21.3Antenna gain (dBi) 45Reference radiation pattern Recommendation ITU-R F.1245Elevation a
18、ngle (degrees) 1Azimuth angle (degrees) 0-350Azimuth angle step size (degrees) Station latitude (degrees) Station latitude (degrees)101040Low-orbiting satellite Altitude/inclination (km/degrees) Altitude/inclination (km/degrees)800/98.6350/57.1Receiving antenna gain (dBi) 0Sharing criteriaRecommenda
19、tion ITU-R SA.1274 147 dB(W/MHz), 0.1%Simulation Duration (days) Time step (s) Operating frequency (MHz)3032 050Rec. ITU-R F.1248 31248-01 160 150 140 130 120 110Probability(%) interference exceedsXInterference power density, X (dB(W/MHz)100.0010.001.000.100.010.00FIGURE 1Probability of interference
20、 to a low-orbiting satellite in an 800 km orbitinclined by 98.6 from a trans-horizon station with differentazimuth angles located at 10 latitude FIGURE 11248-01 = xx cm1248-02 160 150 140 130 120 110FIGURE 2Probability of interference to a low-orbiting satellite in an 800 km orbitinclined by 98.6 fr
21、om a trans-horizon station with differentazimuth angles located at 40 latitudeProbability(%) interference exceedsXInterference power density, X (dB(W/MHz)100.0010.001.000.100.010.00FIGURE 21248-02 = xx cm4 Rec. ITU-R F.12481248-03 160 150 140 130 120 110FIGURE 3Probability of interference to a low-o
22、rbiting satellite in a 350 km orbitinclined by 57.1 from a trans-horizon station with differentazimuth angles located at 10 latitudeProbability(%) interference exceedsXInterference power density, X (dB(W/MHz)100.0010.001.000.100.010.00FIGURE 31248-03 = xx cm1248-04 160 150 140 130 120 110FIGURE 4Pro
23、bability of interference to a low-orbiting satellite in a 350 km orbitinclined by 57.1 from a trans-horizon station with differentazimuth angles located at 40 latitudeProbability(%) interference exceedsXInterference power density, X (dB(W/MHz)100.0010.001.000.100.010.00FIGURE 41248-04 = xx cmRec. IT
24、U-R F.1248 53 Summary and conclusionsFor the case of a single trans-horizon radio-relay system interfering with low-orbiting satellites in the band2 025-2 110 MHz, it was found that the power spectral density at the input to the transmitting antenna should be limitedto a value on the order of 6 dB(W/MHz). An appropriate reduction in this value should be made if there are more thanone co-channel trans-horizon system on the surface of the Earth._
