1、6 CCIR VOLUME*IV-L 70 4855232 O507862 5 e.* . .-*_ Rec. 352-4 4B2: Performance and availability - RECOMMENDATION. 352-4 HYPOTHETICAL REFERENCE CIRCUIT FOR SYSTEMS USING ANALOGUE TRANSMISSION IN THE FIXED-SATELLITE SERVICE (Question 24) (1963-1970-1974-1978-1982) The CCIR, CONSIDERING (u) that it is
2、desirable to establish a hypothetical reference circuit for active fixed-satellite systems to afford guidance to designers of equipment and systems for use in telephone and television networks; (b) that only high-altitude satellites are being used or planned; (c) that with such satellites it will be
3、come possible for most connections to be made with one satellite link, with occasional need for two links in tandem, particularly for television; (d) that the oyera11 performance of each satellite link depends only to a small extenf on the great circle distance between the earth stations; (e) that,
4、to overcome fading, earth stations may operate in site diversity configurations, requiring terrestrial interconnection links between pairs of antennas; (f) that satellite-to-satellite links are likely to be used in the fixed-satellite service, UNANIMOUSLY RECOMMENDS .1. that a hypothetical reference
5、 circuit for systems in the fixed-satellite service using analogue transmission should consist of one Earth-space-Earth link in which the space portion may contain one or more satellite-to- satellite links. 2. that for earth stations not connected in site diversity the input to this circuit should c
6、orrespond to the input of the modulator carrying out the translation from the baseband to the radio-frequency carrier and the output should correspond to the output of the demodulator carrying out the reverse operation; 3. hypothetical reference circuit; that links between these earth stations and t
7、heir associated switching centres should not be included in this Satellite link 43 Earth station Earth station Space station in the fixed-satellite service, or space stations in that service interconnected by satellite-to-satellite links FIGURE I - Hypothetical reference circuit for analogue transmi
8、ssion Rec. 352-4 7 4. that, for site diversity earth stations, the hypothetical reference circuit shall also include the necessary terrestrial links- and where appropriate additional modulation and/or demodulation equipment; the terrestrial/ satellite system interface should then be assumed to be situated at the baseband, after the diversity switching point: 5. switching centres, should not be included in the hypothetical reference circuit. that terrestrial links between the site diversity switching points of such earth stations and the associated
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