1、BRITISH STANDARD BS EN 60835-3-7:1996 BS7573-3.7: 1996 IEC835-3-7: 1995 Methods of measurement for equipment used in digital microwave radio transmission systems Part 3: Measurements on satellite earth stations Section 3.7: Figure-of-merit of receiving system The European Standard EN60835-3-7:1995 h
2、as the status of a BritishStandard ICS 33.060.30BSEN60835-3-7:1996 This BritishStandard, having been prepared under the directionof the Electrotechnical Sector Board, was published underthe authority of the Standards Board and comes into effect on 15 February1996 BSI01-2000 The following BSI referen
3、ces relate to the work on this standard: Committee reference EPL/12 Draft for comment91/22366DC ISBN 0 580 24956 5 Committees responsible for this BritishStandard The preparation of this BritishStandard was entrusted to Technical Committee EPL/12, Radio communication, upon which the following bodies
4、 were represented: British Broadcasting Corporation British Radio and Electronic Equipment Manufacturers Association British Telecommunications Plc ERA Technology Ltd. Institution of Electrical Engineers Radio, Electrical and Television Retailers Association Radiocommunications Agency Amendments iss
5、ued since publication Amd. No. Date CommentsBSEN60835-3-7:1996 BSI 01-2000 i Contents Page Committees responsible Inside front cover National foreword ii Foreword 2 Text of EN60835-3-7 3 List of references Inside back coverBSEN60835-3-7:1996 ii BSI 01-2000 National foreword This BritishStandard has
6、been prepared by Technical Committee EPL/12 and is the English language version of EN60835-3-7:1995 Methods of measurement for equipment used in digital microwave radio transmission systems Part3:Measurements on satellite earth stations Section3.7 Figure-of-merit of receiving system published by the
7、 European Committee for Electrotechnical Standardization (CENELEC). It is identical with IEC835-3-7:1995, published by the International Electrotechnical Commission (IEC). BS EN60835 is published in three Parts. The other Parts are: Part 1: Measurements common to terrestrial radio-relay systems and
8、satellite earth stations; Part 2: Measurements on terrestrial radio-relay systems. Some of the many Sections of the three Parts have appeared under the number BS7573, of the same generic title. This section of BS EN60835 describes several methods of measuring the figure-of-merit (G/T) of the receivi
9、ng systems of earth stations. Reference is required to BS EN60835-1-2:1995 when using this Section of BSEN60835. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a Brit
10、ish Standard does not of itself confer immunity from legal obligations. Cross-references International Standard Corresponding BritishStandard EN60835-1-2:1993 (IEC835-1-2:1992) BS EN60835 Methods of measurement for equipment used in digital microwave radio transmission systems. Part 1: Measurements
11、common to terrestrial radio-relay systems and satellite earth stations. Section 2:1995 Basic characteristics Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, theEN title page, pages2 to16, an inside back cover and a back cover. This standard has been updat
12、ed (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN60835-3-7 May1995 ICS 33.060.30 Descriptors: Radiocommunications, telecommunications, communication equipment,
13、 digital technics, earth station, microwave frequencies, receivers, quality, measurements Englishversion Methods of measurement for equipment used in digital microwave radio transmission systems Part 3: Measurements on satellite earth stations Section7: Figure-of-merit of receiving system (IEC835-3-
14、7:1995) Mthodes de mesure applicables au matrial utilis pour les systmes de transmission numrique en hyperfrquence Partie3: Mesures applicables aux stations terriennes de tlcommunications par satellite Section7: Facteur de qualit du systme de rception (CEI835-3-7:1995) Meverfahren fr Gerte in digita
15、len Mikrowellen-Funkbertragungssystemen Teil3: Messungen an Satelliten-Erdfunkstellen Hauptabschnitt7: Gtezahl des Empfangssystems (IEC835-3-7:1995) This European Standard was approved by CENELEC on 1995-05-15. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipu
16、late the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CENELEC member. This European Standar
17、d exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has the same status as the official versions. CENELEC members are the national
18、 electrotechnical committees of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and UnitedKingdom. CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisatio
19、n Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B-1050 Brussels 1995 Copyright reserved to CENELEC members Ref.No.EN60835-3-7:1995EEN60835-3-7:1995 BSI 01-2000 2 Foreword The text of document12E(CO)169, future edition1 of IEC835-3-7, prepa
20、red by SC12E, Radio relay and fixed satellite communication systems, of IECTC12, Radiocommunications, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN60835-3-7 on1995-05-15. The following dates were fixed: Annexes designated “normative” are part of the body of the sta
21、ndard. Annexes designated “informative” are given for information only. In this standard, Annex ZA is normative and Annex A and Annex B are informative. Annex ZA has been added by CENELEC. Contents Page Foreword 2 Introduction 3 1 Scope 3 2 Normative references 3 3 Definition and general considerati
22、ons 3 4 Indirect method of measurement 4 5 Direct method of measurement using a radio star 4 5.1 General considerations 4 5.2 Method of measurement 4 5.3 Correction factors 5 5.3.1 Correction for atmospheric attenuation (C 1 ) 5 5.3.2 Correction for the angular extension of the radio star (C 2 ) 5 5
23、.3.3 Correction for the change of radio-star flux density with time (C 3 ) 5 Page 5.3.4 Correction for frequency dependence of flux density of the radio star (C 4 ) 5 5.3.5 Correction for the polarization of radio-star flux 6 5.4 Presentation of results 6 5.5 Details to be specified 6 5.6 Error anal
24、ysis 6 6 Direct method of measurement using a remote source 6 6.1 General considerations 6 6.2 Method of measurement 6 6.2.1 Measurement procedures 7 6.2.2 Calculation of G/T 7 6.3 Presentation of results 7 6.4 Details to be specified 7 Annex A (informative) Radio star and atmospheric loss data 13 A
25、nnex B (informative) Bibliography 14 Annex ZA (normative) References to international publications with their corresponding European publications 15 Figure 1 Typical G/T measurement arrangement using i.f. precision variable attenuator 8 Figure 2 Typical G/T measurement arrangement using r.f. precisi
26、on variable attenuator 9 Figure 3 Typical G/T measurement arrangement using a test down-converter 10 Figure 4 Simplified arrangement for direct G/T measurement 11 Figure 5 Linearity and signal ratio 12 Figure A.1 Correction factor for the angular extension of radio stars 14 Table A.1 Characteristics
27、 of radio stars 13 Table A.2 Atmospheric attenuation, zenithal loss 13 latest date by which the ENhas to be implemented at national level by publication of an identical national standard or by endorsement (dop)1996-02-15 latest date by which the national standards conflicting with the EN have to be
28、withdrawn (dow)1996-02-15EN60835-3-7:1995 BSI 01-2000 3 Introduction The quantity G/T represents the figure-of-merit of an earth station for satellite communication applications. Two measurement principles may be used in the measurement of the G/T of an earth station, using both direct and indirect
29、measurement methods. The direct method measures the combined characteristics of the antenna and the receiver and can be carried out using a radio star or other remote transmitter as a suitable signal source. In the indirect method, the antenna gain and receiver equivalent noise temperature are measu
30、red separately and the G/T is calculated from the two measurements. The choice between the indirect method, which is of low accuracy, and of the higher accuracy, but more complex, direct method, mainly depends on the type of satellite earth station under test. 1 Scope This section of IEC835-3 descri
31、bes several methods of measuring the figure-of-merit (G/T) of the receiving systems of earth stations. 2 Normative references The following normative documents contain provisions which, through reference in this text, constitute provisions of this section of IEC835-3. At the time of publication, the
32、 editions indicated were valid. All normative documents are subject to revision, and parties to agreements based on this section of IEC835-3 are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. Members of IEC and ISO maintain
33、registers of currently valid International Standards. IEC835-1-2:1992, Methods of measurement for equipment used in digital microwave radio transmission systems Part1: Measurements common to terrestrial radio-relay systems and satellite earth stations Section2: Basic characteristics. IEC835-3-2, Met
34、hods of measurement for equipment used in digital microwave radio transmission systems Part3: Measurements on satellite earth stations Section2: Antenna. (under consideration) ITU-R Recommendation574-3:1990, Use of the decibel and the neper in telecommunications. 3 Definition and general considerati
35、ons The figure-of-merit (G/T) of a satellite earth station is a logarithmic quantity which is related to the antenna power gain G, given in decibels, and the absolute temperature T, given in kelvins, by the following expression: This definition is in accordance with that given in Recommendation ITU-
36、R574-3. The indirect method (see clause4) is generally usable with all receiving systems, taking into account the lower measurement accuracy of the method, and is the most feasible method for receiving systems with small and medium-size antennas. In these cases, the expected G/T of the receiving sys
37、tems does not result in a sufficiently large Y-factor to enable the direct method to be used. The indirect method may also be used for earth stations with large antenna systems, either when the tracking capability of the antenna is limited or a suitable remote source does not exist. The direct metho
38、d using a radio star (see clause5) is the preferred method, with maximum accuracy for large antenna systems. NOTEIf the higher accuracy, more complex, direct method is preferred, specialized knowledge and experience is necessary to carry out the measurement. The direct method using a remote source a
39、nd reference antenna is also possible for relatively small antennas (see clause6). The measurement should always be carried out with clear sky conditions so as to eliminate the effects of rain, snow, cloud, fog, etc. G/T=G10log 10(T/1K) dB/K (1)EN60835-3-7:1995 4 BSI 01-2000 4 Indirect method of mea
40、surement The indirect measurement uses separate measurements of antenna gain G and system noise temperatureT to calculate G/T. For measurement of G, refer to IEC835-3-2. For measurement of T, refer to IEC835-1-2 (future amendment1). 5 Direct method of measurement using a radio star 5.1 General consi
41、derations When the direct method of measurement using a radio star is carried out, the determination of the figure-of-merit is based on the measurement of the Y-factor, using the following calculation: The Y-factor is defined as the ratio of the measured noise power when the antenna is pointed towar
42、ds the radio star to that measured when the antenna is pointed towards the background sky at the same elevation angle. 5.2 Method of measurement Three different test arrangements can be used depending on which equipment contributions to the figure-of-merit have to be determined, as detailed in the f
43、ollowing table: According to the test arrangements of Figure 1 and Figure 2, the measurement is carried out by pointing the antenna first to the background sky at an elevation angle corresponding to that of the chosen radio star and noting the reading of the power meter connected to the i.f. output.
44、 The antenna is then pointed, at the same elevation angle, to the chosen radio star, thereby causing the noise power to increase. The output noise power is reduced to its original value by adjusting the r.f. or i.f. attenuator. The Y-factor is then given by the difference in decibels between the two
45、 attenuator settings. The measurement can also be accomplished using a scanning technique, which is capable of indicating the maximum noise power by sweeping the antenna over the position of the radio star. When using the scanning technique, the Y-factor is normally measured by reading two power lev
46、els with the same attenuator setting. According to the test arrangement of Figure 3, the down-converter normally used in the earth station, i.e.the operational down-converter, may be replaced by a test down-converter which has a much improved gain stability. This will eliminate the effects of gain v
47、ariations during the antenna pointing or scanning procedure. The two noise powers are read from the power meter connected to the i.f. output of the test down-converter. The minimum elevation angles for the G/T measurement should be limited because of the effect of refraction and atmospheric absorpti
48、on at low elevation angles. Following the above measurement, the G/T is calculated by substituting into equation(2) the measured Y-factor, the wavelength corresponding to the receiving frequency and the flux density of the chosen radio star as given in Table A.1. The calculated G/T value has to be c
49、orrected by applying the appropriate correction factors as given in the following subclause. G/T=10log 10 (8;k/2 2 S) (Y1) dB/K (2) where k is the Boltzmann constant,1,38 10 23Ws/K; 2 is the wavelength; S is the spectral power flux density of the radiation from the radio star at the frequency at the time of the measurement (Wm 2 Hz 1 ); Y is the measured Y-factor. Test arrangement Contributions Figure 1, using i.f. attenuator Figure 2, using r.f. attenuator Figure 3, using test down-converter Antenna feed,
