BS EN 60835-2-7-1995 Methods of measurement for equipment used in digital microwave radio transmission systems - Measurements on terrestrial radio-relay systems - Diversity switchi.pdf

1、BRITISH STANDARD BS EN 60835-2-7:1995 BS7573-2.7: 1995 IEC835-2-7: 1994 Methods of measurement for equipment used in digital microwave radio transmission systems Part 2: Measurements on terrestrial radio-relay systems Section 2.7 Diversity switching and combining equipment The European Standard EN60

2、835-2-7:1994 has the status of a BritishStandard UDC 621.396.6:629.783:621.317.08BSEN 60835-2-7:1995 This BritishStandard, having been prepared under the directionof the ElectrotechnicalSector Board, was published under the authorityof the Standards Boardand comes into effect on 15October1995 BSI01-

3、2000 The following BSI references relate to the work on this standard: Committee reference EPL/12 Draft for comment 91/29836 DC ISBN 0 580 24805 4 Committees responsible for this BritishStandard The preparation of this BritishStandard was entrusted to Technical Committee EPL/12, Radio communication,

4、 upon which the following bodies were represented: British Broadcasting Corporation British Radio and Electronic Equipment Manufacturers Association British Telecommunications plc Institution of Electrical Engineers Radio, Electrical and Television Retailers Association Radiocommunications Agency Th

5、e following bodies were also represented in the drafting of the standard, through subcommittees: ERA Technology Ltd. Amendments issued since publication Amd. No. Date CommentsBSEN 60835-2-7:1995 BSI 01-2000 i Contents Page Committees responsible Inside front cover National foreword ii Foreword 2 Tex

6、t of EN 60835-2-7 3 List of references Inside back coverBSEN 60835-2-7:1995 ii BSI 01-2000 National foreword This Section of BS EN60835 has been prepared by Technical Committee EPL/12 and is the English language version of EN60835-2-7:1994 Methods of measurement for equipment used in digital microwa

7、ve radio transmission systems Part2: Measurements on terrestrial radio-relay systems Section7:Diversity switching and combining equipment, published by the European Committee for Electrotechnical Standardization (CENELEC). It is identical with IEC835-2-7:1994 published by the International Electrote

8、chnical Commission (IEC). BS EN60835 is published in three Parts. The other Parts are: Part 1: Measurements common to terrestrial radio-relay systems and satellite earth stations; Part 3: Measurements on satellite earth stations. Some of the many Sections of the three Parts have appeared under the n

9、umber BS7573, of the same generic title. 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 British Standard does not of itself confer immunity from legal obligations.

10、Cross-references Publication referred to Corresponding BritishStandard BS EN60835 Methods of measurement for equipment used in digital microwave radio transmission systems Part1 Measurements common to terrestrial radio-relay systems and satellite earth stations EN60835-1-2:1992 Section1.2:1995 Basic

11、 characteristics EN60835-1-4:1995 Section1.4:1995 Transmission performance EN60835-2-5:1995 Part2 Measurements on terrestrial radio-relay systems Section2.5:1995 Digital signal processing sub-system Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, the EN t

12、itle page, pages2 to18, an inside back cover and a back cover. This standard has been updated (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 EN60835-2-7 August 19

13、94 UDC 621.396.6:629.783:621.317.08 Descriptors: Radiocommunications, telecommunications, communication equipment, earth stations, radio-relay systems, microwave frequencies, measurements, characteristics English version Methods of measurement for equipment used in digital microwave radio transmissi

14、on systems Part2: Measurements on terrestrial radio-relay systems Section7: Diversity switching and combining equipment (IEC 835-2-7:1994) Mthodes de mesure applicables au matriel utilis pour les systmes de transmission numrique en hyperfrquence Partie 2: Mesures applicables aux faisceaux hertziens

15、terrestres Section 7: Equipement de diversit par commutation et combinaison (CEI835-2-7:1994) Meverfahren for Gerte in digitalen Mikrowellen-Funkbertragungs-systemen Teil 2: Messungen an terrestrischen Richtfunksystemen Hauptabschnitt 7: Gerte-einrichtungen fr Schalt- und Kombinationsdiversity (IEC

16、835-2-7:1994) This European Standard was approved by CENELEC on1994-03-08. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bib

17、liographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CENELEC member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibil

18、ity 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 electrotechnical committees of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Nether

19、lands, Norway, Portugal, Spain, Sweden, Switzerland and UnitedKingdom. CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B-1050 Brussels 1994 Copyri

20、ght reserved to CENELEC members Ref. No. EN 60835-2-7:1994 EEN 60835-2-7:1994 BSI 01-2000 2 Foreword The text of document 12E(CO)149, as prepared by Subcommittee12E: Radio-relay and fixed satellite communications systems, of IEC Technical Committee12: Radiocommunications, was submitted to the IEC-CE

21、NELEC parallel vote in April1993. The reference document was approved by CENELEC as EN60835-2-7 on8 March 1994. The following dates were fixed: Annexes designated “normative” are part of the body of the standard. In this standard, Annex ZA is normative. Contents Page Foreword 2 Introduction 3 1 Scop

22、e 3 2 Normative references 3 3 Switching diversity 3 3.1 General considerations 3 3.2 Isolation between the ports of a diversity switch 4 3.3 Delay difference between diversity channels 4 3.4 Switching due to the BER alarm 4 3.5 Synchronization time 5 4 Combining diversity 5 4.1 General consideratio

23、ns 5 4.2 BER/receiver input level characteristic 5 4.3 In-band amplitude dispersion characteristic 6 4.4 BER/phase difference characteristic 7 4.5 Fading signatures 7 Annex ZA (normative) Other international publications quoted in this standard with the references of the relevant European publicatio

24、ns 17 Figure 1 Base-band switching equipment used in diversity systems 8 Page Figure 2 Arrangement for measuring the tolerable delay difference by a variable r.f.delay line 9 Figure 3 Arrangement for measuring the tolerable delay difference by a variable base-band delay line 9 Figure 4 Arrangement f

25、or measuring base-band switching equipment functions due to BER 10 Figure 5 Arrangement for measuring the synchronization time 10 Figure 6 Simplified block diagrams of diversity combining equipment 11 Figure 7 Arrangements for measuring the BER/receiver input level characteristic 12 Figure 8 Example

26、 of a BER/receiver input level characteristic 13 Figure 9 Arrangement for measuring in-band amplitude dispersion characteristic 13 Figure 10 In-band amplitude dispersion characteristic 14 Figure 11 Arrangement for measuring the BER/combiner entry points phase difference characteristic 14 Figure 12 A

27、rrangements for measuring the signature of a combining system 15 Figure 13 Example of signature curves as a function of level difference %P (positive delay) 16 latest date of publication ofan identical national standard (dop)1995-07-01 latest date of withdrawal ofconflicting national standards (dow)

28、1995-07-01EN 60835-2-7:1994 BSI 01-2000 3 Introduction The availability of a radio-relay link for service may be influenced by the reliability of the equipment itself and by propagation conditions. Fading due to multipath propagation arises from interfering paths refracted in a stratified atmosphere

29、. Since all the interfering paths are delayed relative to the direct path, multipath fading results in frequency-dependent amplitude and group-delay variations, in addition to variations in the received signal level (flat fading). One way to overcome the propagation effects is by transmitting or rec

30、eiving the signals over two (or more) diversity channels, as described in CCIR Report376-6 (seeclause5 of this section). Diversity reception is based upon the fact that radio signals arriving at the receiving site by separate paths and/or at different frequencies have partially correlated impairment

31、s. Therefore the effects of flat fading and/or multipath propagation upon the time during which the link is available for service may be decreased by suitably switching or combining the outputs of the diversity receivers. The following types of diversity systems are in general use: frequency and cro

32、ss-band diversity systems: these diversity arrangements use different frequencies in the same band or different frequency bands; space diversity systems: these use a single transmitting antenna and two or more receiving antennas. 1 Scope This section of IEC835-2 deals with measurements for diversity

33、 equipment used in digital microwave systems. For the purpose of this section, diversity equipment is assumed to consist of the circuits for switching and/or combining the diversity channels, excluding the channel equipment itself, i.e.transmitters, receivers, modulators, demodulators, etc.although

34、these may also be involved in the measurements. 2 Normative references The following normative documents contain provisions which, through reference in this text, constitute provisions of this section of IEC835-2. At the time of publication, the editions indicated were valid. All normative documents

35、 are subject to revision, and parties to agreements based on this section of IEC835-2 are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. I

36、EC835-1-2:1992, Methods of measurement for equipment used in digital microwave radio transmission systems Part1: Measurements common to terrestrial radio-relay and satellite earth stations Section2: Basic characteristics. IEC835-1-4:1992, Methods of measurement for equipment used in digital microwav

37、e radio transmission systems Part1: Measurements common to terrestrial radio-relay and satellite earth stations Section4: Transmission performance. IEC835-2-5:1993, Methods of measurement for equipment used in digital microwave radio transmission systems Part2: Measurements on terrestrial radio-rela

38、y Section5: Digital signal processing subsystem. IEC835-2-8:1993, Methods of measurement for equipment used in digital microwave radio transmission systems Part2: Measurements on terrestrial radio-relay Section8: Adaptive equalizer. CCITT Recommendation G.703:1972, Physical/electrical characteristic

39、s of hierarchical digital interfaces. CCITT Recommendation752:1992, Diversity techniques for radio-relay systems. 3 Switching diversity 3.1 General considerations In all diversity switching sub-systems, equipment alarm signals are fed to a logic circuit which generates a switch-drive signal. Switch-

40、over from one channel to the other may be monitored by an internal test point. In the following, all the test arrangements described will be assumed to include hit-less switching equipment as shown in Figure 1a. In the case of hit-less base-band switching equipment, a circuit compares the two input

41、signals and aligns one of them with the other.EN 60835-2-7:1994 4 BSI 01-2000 When making measurements, a high isolation between each of the paths is necessary to avoid degrading the BER, for example not less than20dB. In addition the following should be observed: all measurements should be made for

42、 several specified settings of the equipment controls provided for adjustments of the switch-over conditions; step attenuators should not be used in order to avoid momentary interruption of the signal when the attenuation is altered; to avoid unnecessary switching in many two-channel switching equip

43、ments, the switch retains its last position, even if the original conditions in the failed channel are restored. The measurement methods which follow are also applicable to such “no switch-back” type systems. 3.2 Isolation between the ports of a diversity switch Diversity switching equipment has two

44、 or more input ports and one output port, so it is necessary to measure the isolation between the input port which is not in use and the input port which is in use. Attenuation measurements should be carried out in accordance with IEC835-1-2. 3.3 Delay difference between diversity channels 3.3.1 Gen

45、eral considerations For satisfactory diversity operation, a switching circuit which does not cause excessive transmission impairment during switch-overs is required. To achieve this the delay difference between the two bit streams, %E, needs to be shorter than the pulse duration time T, for example

46、one-third of T, T/3. In high-capacity systems %E may become greater than the tolerable delay time difference due to the variation of the propagation delay-time. In such cases automatic delay-time compensation is needed. The maximum tolerable delay-time difference, %E max , at which switch-over is po

47、ssible without loss of synchronization or bit-slip, has to be greater than the largest expected delay-time difference between diversity channels. 3.3.2 Method of measurement The arrangements for measuring the limits of the tolerable delay-time difference are shown in Figure 2and Figure 3. Figure 2re

48、presents a transmit-receive section including an r.f.variable delay. Automatic switch-over is initiated by decreasing the r.f.input level. Attenuators RF-1 and RF-2 in Figure 2 are first adjusted to obtain nominal receiver input levels. The delay %E is adjusted to zero, and the position of the diver

49、sity switch, for example channel1, is noted. Then the r.f.input level in channel1 is decreased until switch-over to channel2 occurs at a specified BER. During switch-over neither clock synchronization loss nor bit-slip is allowed. The same procedure is then repeated for channel2. The measurement is then repeated by increasing the delay %E up to a value %E maxwhen bit-slip or synchronization loss occurs. The tolerable delay difference can also be measured by the test arrangement shown in Figure 3,