1、 Rep. ITU-R RS.2094 1 REPORT ITU-R RS.2094 Studies related to the compatibility between Earth exploration-satellite service (active) and the radiodetermination service in the 9 300-9 500 MHz and 9 800-10 000 MHz bands and between Earth exploration-satellite service (active) and the fixed service in
2、the 9 800-10 000 MHz band (2007) TABLE OF CONTENTS Page 1 Introduction 3 2 EESS (active) 3 2.1 Applications 3 2.2 Parameters. 3 3 Radiodetermination services. 5 3.1 Applications 5 3.2 Parameters. 5 4 Fixed service. 11 4.1 Applications 11 4.2 Parameters. 11 5 Interference analysis. 12 5.1 Analysis St
3、udy No. 1: Assessment of potential interference from the radiodetermination service to active spaceborne sensors operating in the 9 300-9 500 MHz band and 9 800-10 000 MHz band 12 5.1.1 Analysis approach 12 5.1.2 Analysis results 16 5.1.3 SAR interference mitigation techniques 19 5.1.4 Analysis conc
4、lusion . 20 5.2 Analysis Study No. 2: Assessment of the potential for interference from ground based meteorological radars into the EESS (active) in the band 9 300-9 500 MHz 21 5.2.1 EESS (active) simulated parameters 21 5.2.2 Meteorological radar simulated parameters. 21 5.2.3 Results 21 5.2.4 Conc
5、lusion . 23 2 Rep. ITU-R RS.2094 Page 5.3 Analysis Study No. 3: Assessment of maximum interference levels from the EESS (active) into the radiolocation service in the bands 9 300-9 500 MHz and 9 800-10 000 MHz . 23 5.3.1 Analysis approach 23 5.3.2 Analysis results 23 5.3.3 Discussion of interference
6、 mitigation 25 5.3.4 Analysis conclusion . 25 5.4 Analysis Study No. 4: Analysis of potential interference from the EESS (active) into ground-based meteorological radars operating in the radiolocation service in the band 9 300-9 500 MHz. 25 5.4.1 Preliminary analysis. 26 5.4.2 Additional factors to
7、mitigate interference to meteorological radars. 30 5.4.3 Conclusion Re-evaluating data from the preliminary analysis . 34 5.5 Analysis Study No. 5: Compatibility studies between the EESS (active) and the fixed service in the 9 800-10 000 MHz band 36 5.5.1 Analysis approach 36 5.5.2 Analysis results
8、40 5.5.3 Analysis conclusion . 44 6 Examples of spaceborne SAR interference mitigation techniques. 45 6.1 Example 1: Selection of emission characteristics for interference mitigation of active spaceborne sensors in EESS (active) for use in the 500 MHz bandwidth near 9.6 GHz. 45 6.1.1 Selection of EE
9、SS (active) characteristics for interference mitigation 45 6.1.2 Analysis conclusion . 47 6.2 Example 2: Interference mitigation technique using active spaceborne sensor SAR3 antenna in EESS (Active) for use in 500 MHz bandwidth near 9.6 GHz 47 6.2.1 Technical characteristics of wideband active spac
10、eborne sensor SAR3 antenna 47 6.2.2 Technical characteristics of terrestrial radar system 49 6.2.3 Receive power profiles at terrestrial stations . 49 6.2.4 Analysis conclusion . 51 7 Summary and conclusion 51 8 Supporting documents 51 Rep. ITU-R RS.2094 3 1 Introduction The purpose of this Report i
11、s to summarize the results of the studies related to the compatibility between Earth exploration-satellite service (EESS) (active) and the radiodetermination service in the 9 300-9 500 MHz and 9 800-10 000 MHz bands and between EESS (active) and the fixed service in the 9 800-10 000 MHz band. 2 EESS
12、 (active) 2.1 Applications In 2007 there are five synthetic aperture radars (SAR) that are planned to operate in the band near 9.6 GHz. These include the SARs found on board the four satellites of a constellation as commissioned by the Italian Space Agency (ASI) but not yet launched; and one SAR lab
13、elled “SAR3” that is currently under consideration by the United States National Aeronautics and Space Agency (NASA). The SARs operating near 9.6 GHz would be controlled via ground command to turn on and off as required to view only specific areas on the earth due to power constraints of the spacecr
14、aft. This mode of operation results in the SAR transmitting for 10% to 20% of the time. Another mode of operation is the spotlight mode. In the spotlight mode, a look angle is selected between 20 and 44, and data will typically be collected by taking 49 to 65 sub-swaths of 20 km in range by 0.35 km
15、in azimuth. This data can then be put into a mosaic of the sub-swaths in azimuth to process a 20 km by 20 km image. 2.2 Parameters Technical characteristics of spaceborne active sensors in the frequency band 9 300-10 000 MHz are given in Table 1, the SAR1 antenna gain pattern is given in Table 2, th
16、e SAR2 antenna gain pattern is given in Table 3 and the SAR3 antenna gain pattern is given in Table 4. TABLE 1 Technical characteristics of proposed SAR Parameter SAR1 SAR2 SAR3 Orbital altitude (km) 400 619 506 Orbital inclination (degrees) 57 98 98 RF centre frequency (GHz) 9.6 9.6 9.6 Peak radiat
17、ed power (W) 1 500 5 000 25 000 Pulse modulation Linear FM chirp Linear FM chirp Linear FM chirp Chirp bandwidth (MHz) 10 400 450 Pulse duration (s) 33.8 10-80 1-10 Pulse repetition rate (pps) 1 736 2 000-4 500 410-515 Duty cycle (%) 5.9 2.0-28.0 0.04-0.5 Range compression ratio 338 60 Horizontal (a
18、zimuth) Gh(h ) = 0 612.2(h )2Gh(h ) = 12 Gh(h ) = 0 27.0 (h ) Gh(h ) = 35 h1.3 Beam pattern G() = Gv(v ) + Gh(h ), 3 max TABLE 3 SAR2 antenna gain pattern near 9.6 GHz Pattern Gain G() (dBi) as a function of off-axis angle (degrees) Angular range (degrees) Vertical (elevation) Gv(v ) = 46.0 0.835(v
19、)2Gv(v ) = 31.0 Gv(v ) = 26.0 Gv(v ) = 10.0 v30 Horizontal (azimuth) Gh(h ) = 0 444.5(h )2Gh(h ) = 16 Gh(h ) = 20.0 (h ) h 0.7 Beam pattern G() = Gv(v ) + Gh(h ), 3 max Rep. ITU-R RS.2094 5 TABLE 4 SAR3 antenna gain pattern near 9.6 GHz Pattern Gain G() (dBi) as a function of off-axis angle (degrees
20、) Angle range (degrees) Vertical (elevation) Gv(v) = 42.5 9.92(v)2Gv(v) = 31.4 0.83 vGv(v) = 10.5 0.133 v0 30 Horizontal (azimuth) Gh(h) = 0.0 9.07(h)2Gh(h) = +1.9 12.08 hGh(h) = 48 0 4.13 Beam pattern G() = Gv(v) + Gh(h) 3 Radiodetermination services 3.1 Applications The band 8 500-10 500 MHz is us
21、ed by many different types of radars on ground-based, transportable, shipboard, and airborne platforms. Radiodetermination functions performed in this frequency range include airborne and surface search, ground-mapping, terrain-following, navigation (both aeronautical and maritime), and meteorologic
22、al (both airborne and ground-based). 3.2 Parameters The radiodetermination radar characteristics were provided in reference 1. Characteristics were provided for ten airborne radar systems, nine shipborne radar systems, and eight beacon/ground-based radar systems that operate in the 8 500-10 500 MHz
23、band. A set of representative radar systems that operate in the 9 300-10 000 MHz band were selected for the following studies and their characteristics are listed in Tables 5, 6, and 7. TABLE 5 Characteristics of airborne radiodetermination radars in the 8 500-10 500 MHz band Characteristics System
24、A1 System A2 System A3 Function Search and track radar (multifunction) Airborne search radar Ground-mapping and terrain-following radar (multifunction) Tuning range (MHz) 9 300-10 000 8 500-9 600 9 240, 9 360 and 9 480 Modulation Pulse Pulse Non-coherent frequency-agile pulse-position modulation Pea
25、k power into antenna (kW) 17 143 (min) 220 (max) 95 Pulse widths (s) and Pulse repetition rates 0.285; 8 200 to 23 000 pps 2.5; 0.5 400 and 1 600 pps 0.3, 2.35, and 4 2 000, 425 and 250 pps, resp. Maximum duty cycle 0.0132 0.001 0.001 6 Rep. ITU-R RS.2094 TABLE 5 (continued) Characteristics System A
26、1 System A2 System A3 Pulse rise/fall time (s) 0.01/0.01 0.02/0.2 0.1/0.1 Output device Travelling wave tube Tunable magnetron Cavity-tuned magnetron Antenna pattern type Pencil Fan Pencil Antenna type Planar array Parabolic reflector Flat-plate planar array Antenna polarization Linear Linear Circul
27、ar Antenna main beam gain (dBi) 32.5 34 28.3 Antenna elevation beamwidth (degrees) 4.6 3.8 5.75 Antenna azimuthal beamwidth (degrees) 3.3 2.5 5.75 Antenna horizontal scan rate 118 scans/min 6 or 12 rpm Up to 53 scans/min Antenna horizontal scan type (continuous, random, sector, etc.) Sector: 60 (mec
28、hanical) 360 (mechanical) Sector: 60 (mechanical) Antenna vertical scan rate 59 scans/min Not applicable Up to 137 scans/min Antenna vertical scan type Sector: 60 (mechanical) Not applicable Sector: +25/40 (mechanical) Antenna side-lobe (SL) levels (1st SLs and remote SLs) 7.5 dBi at 15 Not specifie
29、d 5.3 dBi at 10 Antenna height Aircraft altitude Aircraft altitude Aircraft altitude Receiver IF 3 dB bandwidth (MHz) 3.1; 0.11 5 5.0, 1.8 and 0.8 Receiver noise figure (dB) Not specified Not specified 6 Minimum discernible signal (dBm) 103 107; 101 101 Total chirp width (MHz) Not applicable Not app
30、licable Not applicable RF emission bandwidth (MHz) 3 dB 20 dB 3.1; 0.11 22.2; 0.79 0.480; 2.7 1.5; 6.6 (Frequency and pulsewidth dependent) 100 to 118 102 to 120 Rep. ITU-R RS.2094 7 TABLE 5 (end) Characteristics System A7dSystem A8 System A10 Function Navigation Search (radiolocation) weather Weath
31、er avoidance, ground mapping, search Tuning range (MHz) Frequency agile pulse-to-pulse over 340 MHz 9 250-9 440, frequency-agile pulse-to-pulse, 20 MHz steps Preheat pulse: 9 337 and 9 339 (precedes each oprtl pulse) Operational pulse: 9 344 Modulation Linear FM pulse FM pulse Pulse Peak power into
32、antenna 50 kW 10 kW 26 W (14 dBW) Pulse width (s) and Pulse repetition rate 10 approx. 380 pps 5 and 17 2 500, 1 500, 750, and 400 pps (all pulse widths) 9 337 and 9 339 MHz: 1-29 s at 2 200-220 pps (dithered) for all pulse widths;9 344 MHz: 1.7-2.4, 2.4-4.8, 4.8-9.6, 17, 19, and 29 s at 2 200-220 p
33、ps (dithered) Maximum duty cycle 0.004 0.04 9 337 and 9 339 MHz: 0.0649 344 MHz: 0.011 (with 17 s pulses) Pulse rise/fall time (s) 0.1/0.1 0.1/0.1 9 337 and 9 339 MHz: 0.3/0.29 344 MHz: 0.5/0.5 Output device Travelling wave tube Travelling-wave tube IMPATT diode Antenna pattern type Pencil/Fan Fan P
34、encil Antenna type Parabolic Reflector Slotted array Flat array Antenna polarization Horizontal Vertical and horizontal Horizontal Antenna main beam gain (dBi) 34.5 32 29 Antenna elevation beamwidth (degrees) 4.0 9.0 1 where: T: chirped pulse width (s) Bc: transmitter chirped bandwidth during the pu
35、lse width, T (Hz) BR: receiver 3 dB bandwidth. For the selected meteorological radar bandwidth of 10 MHz, and the selected SAR chirp pulse width of 10 s, the OTR is zero. The simulations used a value of 0 dB for the FDR. 5.4.1.4 Analysis results Since the ability of the ground-based meteorological r
36、adar to mitigate the SAR interference is unknown at the time the initial results were obtained, the generic I/N of 6 dB was used as a reference. The generic 6 dB I/N is associated with a continuous wave (CW) or noise-like interference signal and it may not be applicable to a space borne SAR signal d
37、ue to its chirped pulsed nature. It should be noted that the radar used in this analysis and other types of ground-based meteorological radars that are operating in this band may not contain interference mitigation techniques that are described in Recommendation ITU-R M.1372 for eliminating the effe
38、cts of pulsed interference. The initial results, as presented, should not be used to determine compatibility based on signal processing. 28 Rep. ITU-R RS.2094 5.4.1.5 Radar volume scan results Table 18 presents the results for the volume scan simulations. The time durations are independent of the ma
39、ximum I/N value. The durations provide some insight into how long a radar operator may experience interference from a SAR before any processing gain or mitigation techniques are applied to the analysis results. Table 18 also presents the data for an I/N threshold of = +10 dB, to provide insight into
40、 how the results will be affected by the radars potential ability to mitigate the effects of interference at levels greater than an I/N of 6 dB. As with the I/N = 6 dB level, the +10 dB level has no significance and was just selected to illustrate the point that as the radar can withstand a higher i
41、nterference level, the number of interference occurrences and the interference durations change. Within the United States of America, ground-based meteorological radars operating in this band are generally used for atmospheric research and other applications that can and do withstand some periods of
42、 pulsed interference. Other administrations may have more stringent protection requirements for radars operating in 9 300-9 500 MHz. TABLE 18 Volume scan simulation results 5/s rotation Radar location Max I/N (dB) Longest duration above I/N = 6 dB (s) Average duration above I/N = 6 dB(s) Number of I
43、/N 6 dB occurrences over 23 day period Longest duration above I/N = +10 dB(s) Average duration above I/N = +10 dB (s) Number of I/N+10 dB occurrences over 23 day period Low latitude 23.8 0.55 0.34 225 0.40 0.22 139 Mid latitude 27.3 2.50 0.38 366 0.35 0.22 231 High latitude 24.6 0.55 0.34 488 0.40 0
44、.22 371 20/s rotation Low latitude 23.9 0.15 0.09 853 0.10 0.06 523 Mid latitude 24.2 2.5 0.10 1321 0.10 0.06 836 High latitude 24.2 0.15 0.09 2205 0.01 0.06 1330 The results presented in Table 18 indicate that the ground-based meteorological radar may experience maximum I/N values on the order of 2
45、4 to 27 dB when operating in a typical volume scan mode. A limited number of simulations were also run to confirm the number of interference occurrences was directly proportional to the number of SARs used in the simulation. The results showed the number of occurrences was reduced by a factor of 4 w
46、hen a single SAR was used, but the peak levels and durations remained approximately the same. Rep. ITU-R RS.2094 29 5.4.1.6 Radar sector volume scan results Table 19 present the results with the radar simulated operating in a sector volume scan mode. In the sector scan mode none of the radar receive
47、r characteristics change. The antenna is moved in a pattern as shown in Fig. 11. The simulations were run for only the 45 latitude location. TABLE 19 Sector scan simulation results (45 latitude) 5/s rotation 20/s rotation 60 sector start/end azimuth Max I/N (dB) Longest duration aboveI/N = 6 dB (s)
48、Average duration aboveI/N = 6 dB (s) Max I/N (dB) Longest duration above I/N = 6 dB (s) Average duration above I/N = 6 dB (s) North sector (330 to 60) 24.0 2.50 0.36 28.3 2.50 0.10 East sector (60 to 120) 23.6 2.50 0.37 24.3 2.50 0.10 Southeast sector (105 to 165) 24.1 2.50 0.38 23.0 2.50 0.10 5.4.1
49、.7 Radar spotlight mode results Table 20 present the results with the radar simulated operating in a spotlight mode. Ground-based meteorological radars operated in the band 9 300-9 500 MHz for atmospheric research will periodically be used in a spotlight mode, where a point in the atmosphere is illuminated for a long period of time. During this operation, the antenna elevation and azimuth do not change. Simulations were run with the radar placed at the 45
