ITU-R SA 1015-1-2007 Bandwidth requirements for deep-space research《太空研究中带宽的要求》.pdf
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1、 Rec. ITU-R SA.1015-1 1 RECOMMENDATION ITU-R SA.1015-1 Bandwidth requirements for deep-space research (Question ITU-R 209/7) (1994-2007) Scope This Recommendation presents bandwidth requirements for the space research service (deep space), to be taken into account in band allocations to space resear
2、ch service (deep space) in the future. The technical basis for these bandwidth requirements is also explained. The ITU Radiocommunication Assembly, considering a) that maximum symbol rates required for deep-space telecommunications in both space-to-Earth and Earth-to-space directions, have been well
3、 established (see Annex 1) for the foreseeable future; b) that, utilizing currently practicable techniques, the corresponding required bandwidths have been established; c) that the required width of allocated bands is influenced by the requirements of individual links and by the number of links that
4、 are simultaneous within the beamwidth of a deep-space research earth station antenna; d) that, in the future, the bandwidth required for some telecommunication functions of deep-space research may be reduced by utilizing newer techniques, recommends 1 that band allocations for deep-space research s
5、hould take into account the bandwidth requirements listed in Annex 1; 2 that all feasible steps that will reduce the required bandwidth should be considered for future telecommunication systems for deep-space research. Annex 1 Bandwidth requirements for deep-space research 1 Introduction The total b
6、andwidth suitable for deep-space telecommunications is a function of the required symbol rates, the number of spacecraft links in each mission, the number of missions, and the extent to which frequencies may be shared without mutual interference. 2 Rec. ITU-R SA.1015-1 2 Link bandwidth Earth-to-spac
7、e and space-to-Earth bandwidths are governed by the required telemetering symbol rates, and by the required precision of angular and ranging measurements. Needed symbol rates and corresponding bandwidths for the different functions projected to be used in deep-space research are summarized in Table
8、1. TABLE 1 Maximum required symbol rates and bandwidths for a deep-space mission Direction and function Symbol rate (Msymbol/s) RF bandwidth (MHz) Earth-to-space Telecommand 00 0.002 0 00.040(1)Computer programming 0 00.2 0.8 Voice 0 00.045 0 0.18 Television 30 120 Ranging 100(2)400 Space-to-Earth M
9、aintenance telemetering 1.2(3)4.8 Scientific data 600(4)1 200(5)Voice 00 0.27(3)00 1.08 Television 60(4)240 Ranging 100(2)400 (1)Typically a sub-carrier will be used. (2)The unit is MHz for sinewave ranging and Mchip/s (mega chips per second) for pseudo-noise (PN) ranging. (3)Assuming rate 1/6 error
10、 correction code will be used. (4)Assuming rate 1/2 error correction code will be used. (5)Assuming QPSK modulation will be used. The extremely precise navigation technique using very long baseline interferometry (VLBI) requires the transmission of tones widely spaced from the carrier. Typically the
11、 spacing may vary from 1/200 to 1/600 of the spacecraft transmitted frequency and the relative power of these tones to the carrier is typically 15 dB. Transmission of these tones will not be continuous. Therefore, spectral line separation of frequency tones used in VLBI need not be considered a dete
12、rminant of required bandwidth. Spacecraft design simplicity, reliability and optimum performance of the telecommunications links have led to the use of bi-phase modulation with residual carrier as the traditional deep-space technique for the transmission of information. To pass a periodic square mod
13、ulation waveform with no more than 0.3 dB loss, the bandwidth must include the fifth harmonic of the modulating square wave. For the telemetering signal, the radio-frequency bandwidth must be wide enough to pass the fifth harmonic of the sub-carrier frequency plus two and half times the symbol rate.
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