1、ITU-R RECMN*S* Lob8 94 m 4855232 0523476 383 I 422 Rec. ITU-R S.1068 RECOMMENDATION ITU-R S. 1068 FIXED-SATELLITE AND RADIOLOCATION/RADIONAVIGATION SERVICES SHARING IN THE BAND 13.75-14 GHz (Question ITU-R 79/4) ( 1994) The ITU Radiocommunication Assembly, considering a) that the World Administrativ
2、e Radio Conference for Dealing with Frequency Allocations in Certain Parts of the Spectrum (Malaga-Torremolinos, 1992) (WARC-92) allocated the frequency band 13.75-14 GHz to the fixed-satellite service (FSS) on a primary basis; b) c) radiolocation and radionavigation services in order to allow these
3、 services to share this band; d) the values given in RR No. 855A and report its outcome; e) f) g) that this band is also allocated to the radiolocation and radionavigation services on a primary basis; that the Footnote No. 855A of the Radio Regulations (RR) restrictions were placed on the FSS and th
4、at the WARC-92 in Resolution No. 112 invited the ex-CCIR to conduct the necessary studies with respect to that digital and analogue TV-FM carriers in the FSS are sensitive to interference from radars; that studies have been performed to ascertain the effects of radar interference to these carrier ty
5、pes; that the highest average e.i.r.ps of known existing radars operating in the band 13.75-14 GHz is 59 dBW, recnmmetis 1. protection of carriers in the FSS fiom existing radars with a maximum average e.i.r.p. of 59 dBW; 2. that the minimum earth station antenna diameter of 4.5 m is consistent with
6、 the minimum e.i.r.p. requirement of 68 dBW for FSS networks and also minimizes the possibilities of unacceptable interference to the radionavigation and radiolocation services; that the minimum value of any emission from an earth station of 68 dBW e.i.r.p. is appropriate for the 3. maximum values e
7、mployed in FSS networks; 4. FSS networks; that the maximum value of any emission from an earth station of 85 dBW e.i.r.p. is consistent with the that the methods and criteria given in Annex 1 be used to compute and assess the interference from radars to 5. sharing criteria in Annex 1. that the desig
8、n of new transmitters in the radiolocation/radionavigation services should be consistent with the ANNEX 1 Sharing criteria between radiolocationiradionavigation services and the fixed-satellite service 1. interference from radar into FSS Measurements reflecting very severe interference from radars i
9、n the band were conducted in order to assess its impact on some FSS digital carriers as well as to analogue TV carriers. IT-R RECMN*S= Lb 94 I 4855212 0523477 018 I Rec. ITU-R S.1068 423 1.1 Measurements of interference into digital FSS camers The interference was measured into Intelsat intermediate
10、 data rate (IDR) digital carriers operating at 2 Mbits, 8 MbWs and 45 Mbii/s and using FEC rate 3/4. The interfering radars were assumed to operate in a range of the pulse repetition frequencies (PRF) of 1 kHz to 100 kHz. It was also assumed that the interference occurs during the “clear sky” condit
11、ions, i.e. that the noise level on the link is very low compared to the interference, and consequently, its impact is insignificant. The results of the measurements of the BER versus the duty cycle 6 are shown in Fig. 1 for all the three digital carriers measured and for PRF = 1 kHz. The results for
12、 other PRFs show similar behaviour. Having in mind that radar interference is a short time event, a degradation up to BER = lo4 is acceptable. Using the results of the measurements, the C/Z values corresponding to BER = lo4 were determined and converted into the permissible peak radar e.i.r.ps. (e.i
13、.r.ps of the FSS carrier of 68 dBW, 74 dBW and 81.5 dBW for 2 Mbii/s, 8 Mbits and 45 Mbit/s carriers, respectively). A composite envelope of the results is shown in Fig. 2 together with the (59 -log 6) (dBW) limit imposed by the RR. 1.2 Measurements of interference into analogue TV carriers The C/Z
14、ratios for “just perceptible interference” into a NTSC, 20 MHz TV carrier were recorded for PRFs of 1 kHz, 10 kHz and 100 kHz, and for duty cycles up to about 3%. The carrier-to-noise ratio of the TV carrier was set at 18 dB. The results are presented in Fig. 3. Following the same procedure as above
15、 for IDR carriers, a composite envelope of the maximum permissible peak radar e.i.r.ps was then derived for a TV carrier e.i.r.p. of 77 dBW and presented in Fig. 4. 2. Sharing criteria The following criteria are based on the analysis in 5 3 and 4 and are consistent with the expected radar emissions
16、from the radars described in 5 3. 2.1 Short-term criterion for FSS digital IDR carriers The necessary short-term criterion for sharing between the FSS digital carriers and radars was obtained as an envelope of the maximum permissible peak radar e.i.r.ps towards FSS geostationary satellites determine
17、d for various FSS carriers as indicated in 5 1. The following expression provides a good approximation of the envelope: e.i.r.pp (dBW) = 59 + 15 log i + 0.5 PRF (kHz) / 6 (%)I (1) Taking into account the peak radar e.i.r.p. limit defined by the FR and the above developed criterion, the short-term sh
18、aring criteria can be defined as: c 59 - 10 log 6 (%)/ loo or I 59 + 15 log i + 0.5 PRF (kHz) / 6 (%)I for more than 99.98% of any month and 99.996% of any year li e.i.r.p.p (dBW) I whichever is less. The criteria are shown in Fig. 2. 424 ITU-R RECMN*S* 1068 74 m 4855232 0523478 T54 m Rec. ITU-R S.1
19、068 FIGURE 1 BER versus duty cycle for PRF of 1 kHz a) 2 Mbit/s IDR carrier Duty cycle, 6 (%) b) 8 Mbit/s IDR carrier ,n-2 lu t 10- AL I I 5 2 5 2 5 2 5 2 10- 1 10 Duty cycle, 6 (%) c) 45 Mbit/s IDR carrier Duty cycle, 6 (%) A E: CII=4dB A F CII=SdB 0 G: CI1 = 6 dB ITU-R RECMNaS. LObB 94 = 48552L2 O
20、523479 990 W 425 Rec. ITU-R S.1068 FIGURE 2 Interference criteria for IDR carriers 10- -2 5 lo-2 10- 1 Duty cycle, 6 (%) A: PRF= 1 K F PRF=115K B: PRF= 1.5K G PRF=130K C: PRF= 3 K H: PRF = 160 K D: PRF= 6K I: PRF= 100 K E: PRF= 10 K e.i.r.p. I59 + 15 log I + 0.5 PRF (kHz)/G (%)I dBW For iDR carriers
21、, 2 Mbit/s to 45 Mbit/s, QPSK, rate 314 FEC, BER = i x io6 e.i.r.p. I 59 - 10 log 6 (%)/100 dBW (RR No. 855A) 10 lo2 2.2 Long-term criterion for FSS digital ZDR carriers The mask in Fig. 5 provides the long-term criterion for FSS digital IDR carriers for radar duty cycles up to about 10%. The peak r
22、adar e.i.r.p. at point A should be computed using equation (2). The percentage of time at point A is: (For BW = 36 MHz, t% = T%) 36 T(%) BW(MHz) t(%) = T = 0.004% is emissions over the year, allowance is maintained. the overall annual allowance. However, in the case of non-uniform distribution of ra
23、dar the worst month percentage should not exceed 0.02% provided that the overall annual ITU-R RECMN*S. Lab8 94 M 4855232 0523480 602 = 426 2 5 Rec. ITU-R S.1068 FIGURE 3 Radar interference into anabgue TV (C/I for ?just perceptible interfrence? into NTSC, 20 MHz TV) L 10- io- Duty cycle, (%) 2 1 FIG
24、URE 4 interference criteria for analogue FM-TV carriers 5 2 5 I o A: PRF= 1 kHz A B: PRF= 10kHz o C: PRF= 100 kHz 10 A: PRF= B: PRF= 1K 3K C: PRF= 10 K D: PRF= 15 K G: PRF= 100 K e.i.r.p. I52 - (1.25)?0gPRF(kHz) (5 log (%)/1001) + 30 log l + 0.001 PRF (kHz)/G (%)I For just perceptible interference t
25、o analogue FM-TV carriers e.i.r.p. I59 - 10 log S (%)/iO dBW dBW (RR No. 855A) E: PRF= 130 K F: PRF = 160 K ITU-R RECMN*S* Lab most of which are mounted on ships. These radars have a number of operating modes which include both scanning and tracking modes. Various duty cycles (6), pulse repetition f
26、requencies (PRF) and peak e.i.r.ps are used. The higher levels of interference to an FSS satellite will be intermittent and will be present a very small percentage of time. Analyses of the per cent of time versus peak e.i.r.p. levels have been made and are described in the following paragraphs. Two
27、models are analysed, a global situation and a quasi-stationary situation. 3.2 The global situation The peak e.i.r.p. as a function of time is determined by the following factors: a) Antenna main-lobe patterns e.i.r.p. = e.i.rpmm - 20 log (sin K 0) / K e) dBW where: 0 : angle from peak gain, and K: a
28、ppropriate constant for each antenna pattern. The first side-lobe levels are at least 17 dB below the peak gain. The maximum e.i.r.p. in the scanning mode is 74 dBW and in the tracking mode is 79 dBW. There are several antenna patterns on these radars. b) Operational modes For the scanning modes, th
29、e operation with respect to azimuth and elevation angles is defined. The radars scan in azimuth by elevation segments. The time per radar in each segment is summed at each e.i.r.p. level to arrive at a total time in which the satellite is within a given e.i.r.p. contour. For the tracking mode the az
30、imuth and elevation angles are assumed to be random. c) Radar operating times The purpose and use of these radars is such that the per cent of time that the radar is operating is very small as compared to total time. The average time per radar is less than 1% for the scanning mode and less than O. 1
31、 % for the tracking mode. This applies to both land-based and ship-based radars. d) Co-frequency operation The radar frequency assignments are nearly uniform over the 600 MHz of allocated bandwidth. ITU-R RECMNXS. LObB 94 W 4855212 0523483 311 = Rec. ITU-R S.1068 429 Thus, the probability of Co-freq
32、uency operation per radar (Pc) is taken as: P, = BW600 where BW is the interfered-with bandwidth (MHz) and is greater than 2 MHz. e) Number and distribution of operational radars It is assumed that the radars are uniformly distributed on the Earths surface and that one-third are visible to a satelli
33、te; approximately 200. The results of combining the above factors for the global situation, including both scanning and tracking mode, are shown in Fig. 6 for peak e.i.r.p. values from 57 dBW to 79 dBW and for a 36 MHz interfered-with bandwidth. Since the overall probability is dominated by time fac
34、tors, the probability is expressed as per cent of time. The per cent of time can be considered to be proportional to bandwidth. 3.3 Quasi-stationary situation For the ship-based radars it is fairly common to have a cluster of ships. Because of mutual radar interference problems the frequencies are w
35、idely separated, i.e. only one frequency in a 72 MHz transponder. It is assumed that the radar is Co-frequency in the interfered-with bandwidth and that the radar location has a very low elevation angle with respect to the satellite. This is the condition for the highest e.i.r.ps from the radars. Th
36、e results of the analysis of this situation are also shown in Fig. 6 for values of e.i.r.p. from 57 dBW to 79 dBW. This case is also applicable to a land-based radar. 3.4 Peak e.i.r.p. versus time beyond first side-lobe The following rationale is used to estimate the peak e.i.r.p. versus time functi
37、on beyond the first side-lobe. The portion of time that a satellite is within an antenna gain contour is proportional to I2. The side-lobe envelope gain is assumed to be proportional to l/12.5 which is also proportional to the e.i.r.p. Thus the e.i.r.p. versus time function is proportional to l/t.25
38、 or -12.5 log t (dB) where tis time. The lowest e.i.r.p. value is based on the smallest DIA. 3.5 Overall envelope function Overall envelope functions can be developed which cover the cases shown in Fig. 6 as follows: I 79 dBW; (7a) 2 79 - 50000 (36 T/ BW) dBW; (7b) 2 74.14 - 1428 (36 T/BW dBW; (7c)
39、2 33 - 12.5 log (36 T/ BW) dBW; (74 2 45 dBW; 0.11% ,. :E$?: 4. ITU-R RECMN*S* 1068 94 4855212 0523485 194 Rec. ITU-R S.1068 43 1 Interference to FSS satellites 4.1 General Measurements have been made as described in 5 1.1 and 1.2 of the effects of pulsed radars on IDR and FM-TV carriers and short-t
40、erm criteria have been developed for these cases. These short-term criteria are shown in Figs. 2 and 4. Short-term is taken as implying values in the order of 0.01 to 0.04% or less. Another factor to be considered is transponder saturation due to the peak radar e.i.r.p. Interference to IDR carriers,
41、 FM-TV carriers and transponder saturation is addressed in the following paragraphs. 4.2 Interference to ZDR carriers The worst known case scanning mode for these radars with respect to the IDR carrier criterion in Fig. 2 is characterized by a maximum (6) of 3%, a minimum (PRF) of 60 kHz, a maximum
42、pulse duration of 0.5 ps and a peak e.i.r.p. of 74 dBW. Using these values in the equations shown in Fig. 2 results in an e.i.r.p. criterion value of 74.6 dBW and a maximum allowable peak e.i.r.p. of 74.2 dBW in accordance with RR No. 855A. It is noted that the e.i.r.p. criterion is only a function
43、of the pulse duration. The worst known case tracking mode is characterized by a maximum (6) of 1%. a minimum (PRF) of 45 kHz and a peak e.i.r.p. of 79 dBW. Again using these values in the Fig. 2 equations results in an e.i.r.p. criterion of 79.6 dBW and a maximum allowable peak e.i.r.p. of 79 dBW in
44、 accordance with RR No. 855A. Thus the KR No. 855A limits are satisfied and the sharing criteria (e.g. Fig. 2) are met for IDR carriers and for radar emissions from radars described in 0 3. 4.3 Interference to FM-TV carriers The worst known case scanning mode for these radars with respect to the FM-
45、TV carrier criterion in Fig. 4 is characterized by a maximum (6) of 3%, a minimum (PRF) of 15 kHz, and a maximum pulse duration of 2 ps. The reason that this case is different than for the IDR carriers is that the 2 ps pulse is PSK modulated such that the pulse duration is effectively about 0.2 ps a
46、nd as noted above, the IDR criterion is a function of pulse duration. However, in the FM-TV criterion equation (Fig. 4) only one term involves pulse duration. For the case considered here an order of magnitude change in the pulse duration has a negligible effect on the criterion value. From the crit
47、erion equation of Fig. 4, the criterion value is 62 dBW. For the tracking mode the value is 67 dBW. The per cent of time is determined by the 62 dBW value in equation (7c). For a 30 MHz carrier, 62 dBW is exceeded 0.0071% of the time; for a 20 MHz carrier, 62 dBW is exceed 0.0047% of the time; and f
48、or a 17 MHz carrier, 0.004% of the time. Thus, for the FM-TV case the criterion is met for 99.99% of the time for radars described in 5 3. 4.4 Transponder saturation If the peak radar e.i.r.p. plus the desired carriers e.i.r.p. cause transponder saturation, suppression of the desired carriers and ot
49、her deleterious effects take place. From Fig. 6, it would appear that the transponder saturation e.i.r.p. should be set to accommodate a 74 dBW pulse with acceptable degradation so that transponder saturation would occur a very small percentage of the time; an operating time of 0.0001% for a 36 MHz transponder or 0.0002% for a 72 MHz which are 0.000001% and O.OooOo2% for actual emissions. 432 Rec. ITU-R S.1068 4.5 Long-term interference to IDR carriers From Fig. 7, values of peak e.i.r.p. of 57 dBW or less might be considered long-term interference. From
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