1、CENELEC ENxb0835-2-7 94 3404583 OLbL74b 3TL BS EN 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 EN 60835-2-7 : 1994 has th
2、e status of a British Standard UDC 621 396 6 629 783 621 317 08 60835-2-7 : 1995 BS 7573 : Section 2.7 : 1995 1994 IEC 835-2-7 : - CENELEC ENab0835-2-7 94 m 3404583 OLbL747 238 m Amd. No. Date BS EN 60835-2-7 : 1995 Text affected Committees responsible for this British Standard The preparation of th
3、is British Standard was entrusted to Technical Committee EPU12, Radio communidon, upon which the following bodies were represented: British Broadcasting Corporation British Radio and Electronic QuiPrnent ManufactureIs Association British Telecommunications pic Institution of Electrical Engineers Rad
4、io, Electrical and Television Retailem Association Radiocommunications Agency The following bodies were also represented in the drafting of the standard, through subcommittees: ERA Technology Ltd. This British Standard, having been prepared under the direction of the Electrotechnicai Sector Board, w
5、as published under the authority of the Standards Board and comes into effect on 15 October 1995 O BSI 1995 The following BSI references relate to the work on this standard Committee reference EPU12 Draft for comment 91/29836 DC I I - ISBN O 680 24805 4 I I CENELEC EN*b0835-2-7 94 3404583 OLbL748 17
6、4 = BS EN 60836-2-7 : 1996 Contents Page Committees responsible Inside front cover National foreword ii Foreword 2 Text of EN 608352-7 3 i CENELEC EN*b0835-2-7 94 D 3404583 0163749 O00 D BS EN 60835-2-7 : 1996 National foreword This Section of BS EN 60835 has been prepared by Technical Committee EPI
7、12 and is the English language version of EN 60835-2-7 : 1994 Methods of measurement for equipment used in digital mimave dio tmnsrnission systems Part 2: Measurements on terrestrial dio-relay systems Section E Diversity switching and combining equipment, published by the European Committee for Elec
8、trotechnicd Standadhation (CENELEC). It is identical with IEC 8352-7 : 1994 published by the Internatiorxd Electrotechnicai Commission (JEC). BS EN 60835 is published in three Parts. The other Parts are: Part 1 Measurements mmn to terrestrial dio-relay systems and sateiiite earth statians Part 3 Mea
9、surements on sateliite earth stations Some of the my Sections of the three Parts have appeared under the number BS 7573, of the same generic titie. Cross-references Publication referred to Corresponding British Standard BS EN 60835 Methods of measurement for equipment used in digital microwave di0 t
10、mm.iSsion systems Part 1 Measurements comnwn to terrestrial dio-rehy systems and sutdite earth stations Section 1.2 : 1995 Basic chamteristics Section 1.4 : 1995 lkmsmission perfomme Part 2 Measurements on terrestrial dio-rehy systems Section 2.5 : 1995 Digital signal processing sub-system EN 608351
11、-2 : 1992 EN 6083514 : 1995 EN 608352-5 : 1995 Compliance with a British Standard does not of itself confer immunity from legal obiigations. CENELEC ENsb0835-2-7 94 = 3404583 OLbL750 822 EUROPEAN STANDARD NORME EUROPENW EUROP NORM EN 60835-27 August 1994 UDC 62 1.396.6629.783:62 1.3 17.08 Descriptor
12、s: 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 transmission systems Part 2: Measurements on terrestrial
13、 radierelay systems Section 7: Diversity switching and combining equipment (IEC 8352-7 : 1994) Mthodes de mesure applicables au matriel utilis pour les Systemes de transmission numrique en hyperfrquence Partie 2: Mesures applicables aux faisceaux hertziens terrestres Section 7 Equipement de diversit
14、 par MeBverfahren fr Gerte in digitalen Mikrowellen-Funkbertragungs-Systemen Teil 2: Messungen an terrestrischen Richtfunksystemen Hauptabschnitt 7: Gerte-einrichtungen fr Schalt- und Kombinationsdiversity commutation et combinaison (CE1 8352-7 : 1994) (IEC 8352-7 : 1994) This European Standard was
15、approved by CENELEC on 199403138, CENELEC members are bound to comply with the CENKENELEC 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 bibliographical references concerning such na
16、tional 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 anguage made by trmation under the responsibility of a CENELEC member into its own language
17、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, Netherlands, Norway, Portugal, Spain, Sweden, Switze
18、rland and United Kingdom. CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Centrai Secretariat: rue de Stassart 35, B-1060 Brussels O 1994 Copyright reserved to CENELEC members Ref. NO. EN
19、 60835-2-7 : 1994 E CENELEC ENsb0835-2-7 94 3404583 OLbL75L 7b9 m Page 2 EN 60835-2-7 : 1994 Foreword The kxt of document 12E(C0)149, as prepared by Subcommittee 12E Radio-relay and ked satellite communidons systems, of IEC Technical Committee 12: Radiocommunications, was submitted to the IEC-CENELE
20、C parallel vote in Aprii 1993. The reference document was approved by CENELEC as EN 608352-7 on 8 March 1994. The foilowing dates were kd - latest date of publication of an identical national standard (dop) 1995-07-01 latest date of withdrawal of conflicting national standards (dow) 1995-07-01 - Ann
21、exes designated normative are part of the body of the standard. In this standard, annex ZA is normative. CENELEC EN+b0835-2-7 94 3404583 OLbL752 bT5 Page 3 EN 60835-2-7 : 1994 CONTENTS FOR E WOR D INTRODUCTION Clause Scope . Normative references . Switching diversity 3.1 General considerations . 3.2
22、 Isolation between the ports of a diversity switch . 3.3 3.4 Switching due to the BER alarm . 3.5 Synchronization time . Combining diversity 4.1 General considerations . 4.2 BERreceiver input level characteristic . 4.3 In-band amplitude dispersion characteristic 4.4 BER/phase difference characterist
23、ic . Delay difference between diversity channels . 4.5 Fading signatures 2 5 6 6 7 7 7 7 8 9 10 10 11 12 13 13 Annex ZA (normative) Other international publications quoted in this standard with the references of the relevant European publications 26 Figures 1 Base-band switching equipment used in di
24、versity systems 15 2 3 4 Arrangement for measuring the tolerable delay difference by a variable r.f. delay line . 16 Arrangement for measuring the tolerable delay difference by a variable Arrangement for measuring base-band switching equipment functions base-band delay line 17 due to BER 17 5 Arrang
25、ement for measuring the synchronization time : 18 6 Simplified block diagrams of diversity combining equipment . 19 7 Arrangements for measuring the BEWreceiver input level characteristic . 20 8 Example of a BERheceiver input level characteristic 21 CENELEC EN*b0835-2-7 94 m 3404583 OLbL753 531 m Pa
26、ge 4 EN 60836-2-7 : 1994 Figures Pages 9 Arrangement for measuring in-band amplitude dispersion characteristic . 22 1 O In-band amplitude dispersion characteristic . 22 11 Arrangement for measuring the BEFVcombiner entry points phase difference characteristic , . 23 12 Arrangements for measuring the
27、 signature of a combining system 24 13 Example of signature curves as a function of level difference AP (positive delay) . 25 CENELEC EN+b0835-2-7 94 3404583 OLbL754 478 Page 5 EN 60835-2-7 : 1994 INTRODUCTION The availability of a radio-relay link for service may be influenced by the reliability of
28、 the equipment itself and by propagation conditions. Fading due to multipath propagation arises from interfering paths refracted in a stratified atmosphere. Since all the interfering paths are delayed relative to the direct path, multipath fading results in frequency- dependent amplitude and group-d
29、elay variations, in addition to variations in the received signal level (flat fading). One way to overcome the propagation effects is by transmitting or receiving the signals over two (or more) diversity channels, as described in CCIR Report 376-6 (see clause 5 of this section). Diversity reception
30、is based upon the fact that radio signals arriving at the receiving site by separate paths and/or at different frequencies have partially correlated impairments. Therefore the effects of flat fading and/or multipath propagation upon the time during which the link is available for service may be decr
31、eased by suitably switching or combining the outputs of the diversity receivers. The following types of diversity systems are in general use: - frequency and cross-band diversity systems: these diversity arrangements use-dif- ferent frequencies in the same band or different frequency bands; - space
32、diversity systems: these use a single transmitting antenna and two or more receiving antennas. - CENELEC EN*b0835-2-7 94 3404583 OLbL755 304 Page 6 EN 60835-2-7 : 1994 METHODS OF MEASUREMENT FOR EQUIPMENT USED IN DIGITAL MICROWAVE RADIO TRANSMISSION SYSTEMS Part 2: Measurements on terrestrial radio-
33、relay systems Section 7: Diversity switching and combining equipment 1 Scope This section of IEC 835-2 deals with measurements for diversity 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 co
34、mbining the diversity channels, excluding the channel equipment itself, .e. transmitters, receivers, modulators, demodulators, etc. al- though these may also be involved in the measurements. 2 Normative references The following normative documents contain provisions which, through reference in this
35、text, constitute provisions of this section of IEC 835-2. At the time of publication, the editions indicated were valid. All normative dpcuments are subject to revision, and parties to agreements based on this section of IEC 835-2 are encouraged to investigate the possibility of applying the most re
36、cent editions of the normative documents indicated below. Members of IEC and IS0 maintain registers of currently valid International Standards. IEC 835-1 -2: 1992. Methods of measurement for equipment used in digital microwave radio transmission systems - Part 1: Measurements common to terrestrial r
37、adio-relay and satellite earth stations - Section 2: Basic characteristics IEC 835- 1-4: 1992, Methods of measurement for equipment used in digital microwave radio transmission systems - Part I: Measurements common to terrestrial radio-relay and satellite earth stations - Section 4: Transmission per
38、formance IEC 835-2-5: 1993, Methods of measurement for equipment used in digital microwave radio transmission systems - Part 2: Measurements on terrestrial radio-relay - Section 5: Digital signal processing subsystem IEC 835-2-8: 1993, Methods of measurement for equipment used in digital microwave r
39、adio transmission systems - Part 2: Measurements on terrestrial radio-relay - Section 8: Adaptive equalizer CCITT Recommendation G. 703: 1972, PhysicaUelectrical characteristics of hierarchical digital interfaces CCITT Recommendation 752. 1992, Diversity techniques for radio-relay systems CENELEC EN
40、*b0835-2-7 94 m 3404583 OLbL75b 240 m Page 7 EN 60835-2-7 : 1994 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-over from one channel to the other may be monitor
41、ed 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 la. In the case of hit-less base-band switching equipment, a circuit compares the two input signals and aligns one of them with the other. Wh
42、en making measurements, a high isolation between each of the paths is necessary to avoid degrading the BER, for example not less than 20 dB. In addition the following should be observed: - all measurements should be made for several specified settings of the equipment controls provided for adjustmen
43、ts 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 equipments, the switch retains its last position, even if the original condit
44、ions 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 or more input ports and one output port, so it is necessary to measure t
45、he isolation between the input port which is not in use and the in- put port which is in use. Attenuation measurements should be carried out in accordance with IEC 835-1 -2. 3.3 Delay difference between diversity channels 3.3.1 General considerations For satisfactory diversity operation, a switching
46、 circuit which does not cause excessive transmission impairment during switch-overs is required. To achieve this the delay difference between the two bit streams, AT, needs to be shorter than the pulse duration time T, for example one-third of T, T/3. in high-capacity systems AT may become greater t
47、han 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, AT, at which switch-over is possible without loss of synchronization or bit-slip, has to be greater than
48、 the largest expected delay-time difference between diversity channels. CENELEC EN+60835-2-7 94 M 3404583 01b1357 187 M Page 8 EN 60835-2-7 : 1994 3.3.2 Method of measurement The arrangements for measuring the limits of the tolerable delay-time difference are shown in figures 2 and 3. Figure 2 repre
49、sents 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 Ar is adjusted to zero, and the position of the diversity switch, for exam- ple channel 1, is noted. Then the r.f. input level in channel 1 is decreased until switch-over to channel 2 occurs at a specified BER. During switch-over neither clock synchronization loss nor bit-slip is allowe
