1、ITU-R RECIINUS. SERIES 45 m 4855232 0527837 936 m Rec. ITU-R S.1151 111 SECTION 4E: FREQUENCY SHARING BETWEEN NETWORKS OF THE FZXED-SATELLITE SERVICE AND THOSE OF OTHER SPACE FL4DIOCOMMUNICATIONS SYSTEMS RECOMMENDATION ITU-R S.1151* SHARING BETWEEN THE INTER-SATELLITE SERVICE INVOLVING GEOSTATIONARY
2、 SATELLITES IN THE FIXED-SATELLITE SERVICE AND THE RADIONAVIGATION SERVICE AT 33 GHz (Question ITU-R 213/4) (1995) The ITU Radiocommunication Assembly, considering a) radionavigation service; that the frequency band 32-33 GHz is allocated on an equal basis to the inter-satellite service (ISS) and to
3、 the b) that the band may be used for links between satellites of the fixed-satellite service (FSS); c) services, supplemented by reasonable assumptions where information is lacking; such information as is available in existing -R texts regarding the technical characteristics of the two d) that inte
4、r-satellite links of various path lengths should be taken into account; e) the content of Recommendation ITU-R M.496; f) and that protection and sharing criteria exist for this service (Recommendation ITU-R SA.578); that the space research service (deep space) (space-to-Earth) shares the band 32-32.
5、3 GHz on a primary basis 8) allocation to the space research service; that analysis and conclusions concerning sharing in the band 32-32.3 GHz should take into account the h) the analysis contained in Annex 1, recommends 1 maximum geocentric separation angle of the two ends of the inter-satellite li
6、nk should not exceed 90“; that to avoid the requirement of power limitations to emissions of the ISS and the radionavigation service, the 2 should be accomplished by means of the following criteria: that, whenever it is not practicable to observe the angular limitation in 0 1, sharing between these
7、two services 2.1 satellites should be limited to the values given by curve B of Fig. 2; for emissions of the ISS, the maximum power flux-density (pfd) at the Earths surface from geostationary 2.2 should be limited to: for continuous wave emissions of the radionavigation service, the e.i.r.p. density
8、 of individual transmitters A - 43 - 10 log D dB(W/MHz), for separation angles of 5 140“ where A is the aggregate e.i.r.p. spectral density given by Fig. 2 and D is the estimated geographical density of radionavigation transmitters per km2 simultaneously active in any 1 MHz band, taking into account
9、 future needs and averaged over the temtory of the administration concerned or over an area of lo6 km2, whichever is less (see Annex 1 to Recommendation ITU-R M.496). NOTE 1 -recommends 2.2 is restricted to continuous wave emissions. Further study is required for pulsed radionavigation systems. Info
10、rmation on pulsed systems is given in Annex 2. * This Recommendation should be brought to the attention of Radiocommunication Study Group 8. 1TU-R RECMN*S- SERIES 95 4855232 0527838 872 = 112 Rec “U-R S.1151 Receiver system noise temperature T (K) 10 log T Receive, transmit antenna diameter (m) Rece
11、ive, transmit antenna gain (dBi) ANNEX 1 ISL RN 31 30 2 54 50 35 (airborne) - Sharing criteria between inter-satellite links connecting geostationary satellites in the fured-satellite service and the radionavigation service at 33 GHz Receive noise power per MHz (dB(W/MHz) (referred to antenna port)
12、Carrier-to-noise ratio dB) 1 Introduction In the near term there may be a need for a limited form of inter-satellite link having a relatively short inter-satellite spacing and operating between about 15 and 33 GHz. At the World Administrative Radio Conference (Geneva., 1979) (WARC-79) a band in this
13、 range was allocated to the ISS (32-33 GHz), shared with the radionavigation service. The feasibility of sharing between inter-satellite links of geostationary satellites in the FSS and the radionavigation service is considered below. -138 -1 39 25 - 2 It is assumed that the links would probably be
14、few in number, would be used for relatively short inter-satellite distances to minimize transit-time delay, and, if required soon, would rely as much as possible on existing spacecraft technology. Parameters which might represent typical links are presented in Table 1. The links considered here are
15、assumed to connect satellites at varying orbital separations, to employ tracking antennas of 2 m diameter and to operate at a carrier- to-noise ratio of 25 dB such that the inter-satellite link contributes a relatively small part of the allowable channel noise. Characteristics of inter-satellite lin
16、ks in the frequency range 32-33 GHz Required carrier at receiver (dB(WA4Hz) Maximum permissible interference level, below noise (dB) TABLE 1 Assumed characteristics of inter-satellite link (ISL) and radionavigation service (RN) -1 13 -10 -10 Maximum permissible unwanted signal level (dB(W/MHz) Combi
17、ned tracking loss (dB) -148 -149 - 1 Path loss (Earth-to-space geostationary orbit) (dB) Half power beamwidth (ISL) (degrees) 215 - 0.32 - From the values derived, it is possible to assess the levels of interference caused to, and received from, the radionavigation services. ITU-R RECMNrS. SERIES 95
18、 = 4855232 0527839 709 W RW. ITU-R S.1151 113 It is recognized that the link considered in Table 1 is only one possible design of an inter-satellite link, and other designs involving techniques such as FM remodulation have also been postulated. However, such links would be characterized by a lower t
19、ransmitter power density and probably a lower susceptibility to interference, so it is considered that the characteristics given represent a sufficiently conservative case. 3 Characteristics of the radionavigation service at 32-33 GHz It is not possible to predict, with precision, the technical char
20、acteristics that will be adopted for systems in the radionavigation service. However, certain assumptions have had to be made and they are detailed in Table 1 for continuous wave systems. Two antenna gains have been postulated, one for ground and one for airborne installations. These characteristics
21、 are used in the following analyses to arrive at the recommends for continuous wave radionavigation systems. 4 Interference from inter-satellite links to the radionavigation service The interference from an inter-satellite link is considered in terms of power flux-density at the Earths surface. Ther
22、e are two factors contributing to this pfd, firstly the power per MHz into the inter-satellite service link antenna (PT) which is proportional to the inter-satellite link distance, and secondly the off boresight gain G(6) (see Recommen- dation -R S.672) towards the Earth of the transmitting antenna.
23、 Both of these are dependent upon the separation angle cp (see Fig. 1) and it can be shown that the pfd on the surface (pfdIsL) is approximately equal to: PfdisL = PT(P) + G(8) - 10 log (4a d2) dB(W/(m2 . MHz) where: P(cp) : power (dB(W/MHz) delivered to the satellite G(6): gain (dB) relative to tha
24、t of an isotropic radiator, of the ISL satellite antenna in an off-axis direction tangential to the Earths surface d: path distance from the satellite to the Earths surface in the direction 6 (m). Since the required value of P(cp) is determined by the power level needed at the input to the receiver
25、at the other end of the inter-satellite link (typically -1 12 dB(W/MHz), then: PT(P) = -112 + 2010g(h/4L) + 2 X Go dB(W/(m2 a MHz) where: : wavelength (m) L : Go : length of the ISL (m) on-axis gain of each ISL satellite antenna (dBi). Combining these factors, and expressing L and 6 in terms of cp t
26、he power flux-density for the worst case (low angle of arrival) becomes: and results in the expression: 8a x 4.22 x lo7 sin (p/2) h 163 - p z - 25 log ( o.32 ) - 330 dB(W/(m2 MHz) ITU-R RECMNxS. SERIES 95 = 4855232 0527820 420 W 114 Ra. ITU-R S.1151 FIGURE 1 Inter-saeiiie Pnk 0 : off boresight angle
27、 r : tangential angie (constant) cp : separationangle ;#$i Figure 2 shows the pfd estimate from the characteristics assumed and over separation angles from 40“ to 160“. Note that the term used above for off-beam antenna gain reduces to -10 dB for a satellite separation angle cp of 46.6. This results
28、 in the flattening and discontinuity shown in Fig. 2. FIGURE 2 Criteria for the case of interference between an inter-saeliie link and the radionavigation service 30 40 50 60 70 80 90 100 110 120 130 140 150 160 180 Separation angle, p (degrees) Curves A: radionavigation service to inter-satellite l
29、ink (e.ir.p.m-) B: inter-satellite link to radionavigation service (pfd 1s) ITU-R RECMN+S. SERIES 95 W 4855232 0527823 367 W RW. ITU-R S.1151 115 5 interference from the radionavigation service will depend mainly on the receiving antenna gain of the inter-satellite link in the direction of the Earth
30、 G (e), and the e.i.r.p. from the radionavigation service. Interference from the radionavigation service to inter-satellite links Assuming that the total interference power must be limited to one tenth of the receiver system noise, then a carrier to overall interference ratio of 35 dB would be appro
31、priate (compared with 25 dB carrier-to-noise ratio). Thus for these conditions the maximum e.i.r.p., e.i.r.p.RNmax from the radionavigation service can be estimated for different separation angles, thus: e.i.r.p.mmar = path loss - maximum permitted interference - G (0) 215 - 148 - G(0) 163 - (P =13
32、+ 25lOg( 0.32 ) dB(W/MHz) Figure 2 shows the maximum e.i.r.p. for separation angles from 40 to 160 6 Results From the curves in Fig. 2 it can be seen that a given pfd limitation to protect the radionavigation service places a maximum value on the permissible separation angle of the inter-satellite l
33、ink. Conversely the maximum link separation angle to which the inter-satellite links may be limited determine the maximum permissible e.i.r.p. limitation on the radionavigation service. 6.1 Inter-satellite link to the radionavigation service Taking an antenna gain value of 50 dB and a noise power fi
34、gure of -139 dB(W/MHz) for the radionavigation service, this would give a limit of -155 dB(W(m2 . MHz) on the inter-satellite link, leading to an angular Separation limit of 140“. 6.2 Radionavigation service to inter-satellite link From 0 6.1 a maximum separation angle of 140“ would give an aggregat
35、e e.i.r.p. limitation of about 60 dBW 7 Conclusion for continuous wave systems in the radiolocation service It is concluded that there will be no interference problems for either service for short links (separation angle up to 90). For long links, the satellite link is more capable of causing or rec
36、eiving interference, and based on the assumed characteristics of Table 1 it appears that it may be necessary to limit separation angles to about 140“. ANNEX 2 Pulsed radionavigation system characteristics The characteristics of an airborne pulsed radionavigation system have been identified and the c
37、haracteristics are given in Table 2. The peak pulse power of these systems exceeds the e.i.r.p. limits in recommends 2, but the average e.i.r.p. is much lower than these limits; i.e. a low duty cycle. Analyses need to be made in order to assess the interference to ISL links. ITU-R RECMNaS. SERIES 95
38、 4855232 0527822 2T3 116 RW. ITU-R SA51 TABLE 2 Characteristics of an airborne puked radionavigation system Emission 17M4PN (fixed mode) 117MPON (agile mode) Power output 38.6 kW (peak pulse power) Output device Inverted CO-axial magnetron Servo controlled Transmitting and receiving antenna Antenna
39、type: Simple beam (Antenna 1) Scan: Vertical -29“ to +lo“, mechanical Horizontal i135 at 7,13 or 21 r.p.m. Gain: 41.1 dBi 23.1 dBi at 1.1 o off-axis in azimuth 17.2 dBi at 1.4“ off-axis in elevation Polarity: Horizontal or LHC Beamwidth (degrees): 0.8 H, 1.0 V Tuning Fixed - 9 channels spaced at 100
40、 MHz; agile (spread spectrum) over 100 MHz Puise characteristics Rate: 1 600p.p.s. Width: 0.2s (Unmodulated pulses) Antenna pattern type: cosec2.cosine() (Antenna 2) Scan: Vertical -29“ to +lo“, mechanical Horizontal f135 at 7, 13 or 21 f.p.m. Gain: 35.2dBi 30.1 dBi at -3 1 O elevation 23.1 dBi at -3“ elevation Polarity: Horizontal or LHC Beamwidth (degrees): 0.8 H proportional to coseG.cosine() from -3 to -31 V Note that cosec2.cosine is a generic pattern description used for many radars.
