1、 Rec. ITU-R RS.1628 1 RECOMMENDATION ITU-R RS.1628*, *Feasibility of sharing in the band 35.5-36 GHZ between the Earth exploration-satellite service (active) and space research service (active), and other services allocated in this band (Question ITU-R 233/7) (2003) The ITU Radiocommunication Assemb
2、ly, considering a) that the frequency band 35.5-36 GHz is allocated to the Earth exploration-satellite service (EESS) (active) and space research service (SRS) (active) on a primary basis with No. 5.551A of the Radio Regulations (RR); b) that the 35.5-36.0 GHz band is also allocated to the meteorolo
3、gical aids service and radiolocation service on a primary basis; c) that ITU-R studies have shown that sharing of the 35.5-36 GHz band is feasible between terrestrial radars and precipitation radars, spaceborne radar altimeters and scatterometers, as shown in Annex 1; d) that ITU-R studies have show
4、n that stations from the fixed service allocated by RR No. 5.549 in the 35.5-36 GHz band are protected from emissions from EESS precipitation radars as shown in Annex 2; e) that a bandwidth of up to 500 MHz is needed for the wideband altimeter to precisely measure altitude, recommends 1 that in orde
5、r to ensure compatibility between radiolocation service and EESS (active) and SRS (active), the mean pfd at the Earths surface from the spaceborne active sensor generated at any angle greater than 0.8 from the beam centre should not exceed 73.3 dB(W/m2) in any 2 GHz band; 2 that compatibility with t
6、he fixed service is assured without any additional constraints on the EESS (active) as shown in Annex 2. *This Recommendation should be brought to the attention of Radiocommunication Study Groups 8 and 9. *Radiocommunication Study Group 7 made editorial amendments to this Recommendation. 2 Rec. ITU-
7、R RS.1628 Annex 1 Compatibility of spaceborne active sensors with radiolocation systems operating in the 35.5-36 GHz band 1 Introduction The frequency band 35.5-36 GHz is allocated to the EESS (active), space research (active), radiolocation and meteorological aids services on a primary basis. Altho
8、ugh the 35.5-36 GHz band is allocated for meteorological aids, there is no known use of the band by this service. ITU-R studies have shown that sharing between spaceborne active sensors and radiolocation systems in the band 35.5-36 GHz is feasible. This Recommendation presents the results of simulat
9、ions to evaluate the levels of potential interference between spaceborne active sensors and radiolocation stations in the 35.5-36 GHz band. 2 Approach 2.1 Overview A dynamic interference model was developed using a commercial interference simulation tool. Interference statistics were collected for i
10、nterference from spaceborne active sensors into radiolocation systems and from radiolocation systems into spaceborne active sensors. 2.2 Spaceborne active sensor models Table 1 lists the parameters of the spaceborne active sensors included in the simulations. These sensors include altimeters and pre
11、cipitation radars that are planned to be implemented in constellations of three to nine satellites. For the purposes of these simulations, a Walker delta pattern was assumed for each active sensor constellation with the parameters listed in Table 1. In the absence of specific antenna side-lobe patte
12、rns for any of the active sensors, the antenna beam for each sensor was modelled using a parabolic antenna beam with a peak gain and 3 dB beamwidth as specified in Table 1. The antenna side-lobe patterns were modelled by a capped Bessel function which simulated an envelope of the antenna side-lobe p
13、eaks calculated for the standard circular aperture model using the following formula: 212)sin()sin(2)(=DDJDG A gain floor was set at 10 dBi for each antenna pattern. Rec. ITU-R RS.1628 3 TABLE 1 Spaceborne active sensor model characteristics 2.3 Radiolocation models This analysis modelled two radiom
14、etric imaging radar station types, two instrumentation radar (metric) station types and one seeker radar station type. The characteristics of these modelled systems are provided in Table 2. In the absence of a reference antenna pattern for radiolocation stations in this band, the same capped Bessel
15、function pattern and 10 dBi gain floor was used for the radiolocation stations as was used with the spaceborne active sensors. For the cases where the antenna beam was elliptical (e.g. the imager systems), the capped Bessel function was ellipticized to achieve the desired beamwidths across the princ
16、ipal axes of the beam. Type of sensor Altimeter Precipitation radar System name O-AltiKa O + P-AltiKa TRMM follow-on/GPM PR-2 O + P-AltiKa Altitude (km) 800 650 400 750 650 Inclinaison 98.6 98.0 70.0 70.0 98.0 Number of satellites 3 8 9 9 8 Number of planes 3 4 3 3 3 3 4 Satellites per plane 1 2 3 3
17、 3 3 2 Delta longitude 120 90 120 120 120 120 90 Inter-plane phasing 120 45 36 36 36 36 45 Antenna pointing Nadir Nadir 37 azimuth sweep at 250/s Nadir 28 azimuth sweep at 250/s Nadir Nadir Peak gain (dBi) 48.90 54.30 55.00 55.00 57.00 57.00 54.30 3 dB beamwidth (degrees) 0.78 0.42 0.50 0.50 0.50 0.
18、50 0.42 Bandwidth (MHz) 480.00 480.00 5.30 5.30 5.30 5.30 4.40 Peak power (W) 2.0 2.0 200.0 200.0 200.0 200.0 2.0 Duty cycle (%) 42.2 42.2 10.9 20.0 10.9 20.0 27.0 Average power (dBW) 0.73 0.73 13.39 16.02 13.39 16.02 2.68 4 Rec. ITU-R RS.1628 TABLE 2 Characteristics of radiolocation systems in the
19、35.5-36 GHz band 2.4 Interference model A simulation model was developed to calculate the cumulative distribution function (CDF) of the interfering power levels produced by spaceborne active sensors interfering with radiolocation stations on Earth, and the interfering power levels produced by ground
20、-based radiolocation stations interfering with spaceborne active sensors. Interference statistics were also collected during each simulation run, including the worst-case interference power, the percentage of time the interference power exceeded the specified interference criteria, and the duration
21、of the longest interference event exceeding the specified interference criteria. Radiolocation system type Parameter Imager 1 Imager 2 Metric 1 Metric 2 Seeker Sensor type Passive Active Active Active Active Modulation Pulse Pulse Pulse Linear frequency modulation Compression ratio 200 Pulse width (
22、s) 0.05 0.25 0.05 10 Tx peak power (kW) 0.5 135 1 0.001 Pulse repetition frequency (kHz) 30 1 50 10 RF bandwidth 80 10 101 12 Antenna gain 35 dBi 30 52 51 28.7 Beamwidth (degrees) 0.5 3.0 0.75 10 0.25 0.25 0.5 0.5 4.4 4.4 Rx IF bandwidth (MHz) 2 GHz 40 6 185 100 Noise temperature (K) 850 Noise figur
23、e (dB) 4,5 10 10 5 Rx sensitivity (dBm) 81 95 78 93 Tuning Fixed Fixed Fixed Frequency hop Fixed Rec. ITU-R RS.1628 5 The interference power level I (dBW) was calculated using the following equation: ()atmrttLOTRGRfGPI += )log(2044.32)log(10log10 where: Pt: interferer transmitter power (W) : interfe
24、rer duty cycle (i.e. pulse duration times pulse repetition rate) Gt: interferer antenna gain in direction of victim station (dBi) f : victim station receive frequency (MHz) R : slant range between interferer and victim station (km) Gr: victim station antenna gain in direction of interferer (dBi) OTR
25、 : receiver on-tune rejection (dB) = 10 log(Br/ Bt) for Br15 Receiver IF bandwidth (MHz) 28/1.3 Receiver noise figure (dB) 7 Receiver thermal noise (dBW) 137 Nominal short-term interference (dBW) (% time) 123 (0.01%) Nominal long-term interference (dBW) 147 Rec. ITU-R RS.1628 23 2 Analysis methodolo
26、gy Same as Annex 1. No duty cycle was considered for the precipitation radars in the simulations. Should this parameter be considered, an additional 5 to 10 dB margin should be added to the margin found in 3. 3 Analysis results 3.1 P-P fixed service systems Simulations were performed for one single
27、EESS system, and one P-P fixed service receiver over a 24-hour period. Thirty-five different azimuth angles (from 0 to 350 with a 10 step) and an elevation angle of 5 were considered for the fixed service receiver antenna. Figure 22 shows the results obtained for all EESS systems and all fixed servi
28、ce antenna azimuth. 1628-22200 190 130180 170 160 150 140 120 11010101102103104105101102Pr (dBW)FIGURE 22Received power CDFProbability(%)Figure 22 shows that there is a 20 to 45 dB margin between the CDF curves and the protection criteria, depending on the system considered. Even if several differen
29、t EESS satellites were present (percentage multiplied by the number of EESS systems), the margin would remain in the order of 24 Rec. ITU-R RS.1628 15 to 20 dB. It is not currently possible to increase the peak power of EESS (active) systems by such a value and therefore is no need to impose any con
30、straint to the EESS (active) or SRS (active) in this band to protect the P-P fixed service links. 3.2 P-MP FS systems Simulations were performed for one single EESS system, and one P-MP fixed service receiver over a 24-hour period. Thirty-five different azimuth angles (from 0 to 350 with a 10 step)
31、and an elevation angle of 5 were considered for the fixed service receiver sectorial antenna. Figure 23 shows the results obtained for all EESS systems and all fixed service antenna azimuth. 1628-23200 190 130180 170 160 150 140 120 11011010101102103104105101102Pr (dBW)FIGURE 23Received power CDFPro
32、bability(%)Figure 23 shows that there is a 15 to 40 dB margin between the CDF curves and the protection criteria, depending on the system considered. Even if several different EESS system satellites were present (percentage multiplied by the number of EESS service systems), the margin would remain i
33、n the order of 10 to 15 dB. It is not currently possible to increase the peak power of EESS (active) systems by such a value, there is no need to impose any constraint to the EESS (active) or SRS (active) in this band to protect the P-MP fixed service links. Rec. ITU-R RS.1628 25 4 Summary Simulatio
34、ns have been performed and have shown that there is no problem of sharing between the fixed service and the EESS (active) and SRS (active) in the 35.5-36 GHz band. Simulation results show: a minimum 20 dB margin between the maximum interference and the protection criterion in a P-P receiver; a minim
35、um 15 dB margin between the maximum interference and the protection criterion in a P-MP receiver. This margin should again be increased by 10 log (d.c.), where d.c. is the duty cycle of spaceborne precipitation radars. In view of these margins, there is no need to impose any constraint to the EESS (active) or SRS (active) for the protection of the fixed service in the 35.5-36 GHz band.
