1、BRITISH STANDARD BS EN 60835-2-8:1996 BS 7573-2.8: 1996 IEC 835-2-8: 1993 Incorporates Amendment No. 1 toBS EN 60835-2-8: 1996 Methods of measurement for equipment used in digital microwave radio transmission systems Part 2: Measurements on terrestrial radio-relay systems Section 2.8 Adaptive equali
2、zer The European Standard EN60835-2-8:1993, together with its amendmentA1:1996 has the status of a British Standard ICS 33.060.30BSEN 60835-2-8:1996 This British Standard, having been prepared under the directionof the Electrotechnical Sector Board, was published underthe authority of the Standards
3、Board and comes intoeffect on 15February1996 BSI 03-2000 The following BSI references relate to the work on this standard: Committee reference EPL/12 Draft for comment 91/29837 DC ISBN 0 580 25173 X Committees responsible for this British Standard The preparation of this British Standard was entrust
4、ed to Technical Committee EPL/12, Radio communication, upon which the following bodies were represented: British Broadcasting Corporation British Radio and Electronic Equipment Manufacturers Association British Telecommunications plc ERA Technology Ltd. Institution of Electrical Engineers Radio, Ele
5、ctrical and Television Retailers Association Radiocommunications Agency Amendments issued since publication Amd. No. Date Comments 9598 September 1997 Indicated by a sideline in the marginBSEN 60835-2-8:1996 BSI 03-2000 i Contents Page Committees responsible Inside front cover National foreword ii F
6、oreword 2 Text of EN 60835-2-8 5 List of references Inside back coverBSEN 60835-2-8:1996 ii BSI 03-2000 National foreword This British Standard has been prepared by Technical Committee EPL/102 (formerly EPL/12) and is the English language version of EN60835-2-8:1993 Methods of measurement for equipm
7、ent used in digital microwave radio transmission systems Part2: Measurements on terrestrial radio-relay systems Section 8: Adaptive equalizer, including amendment A1:1996, published by the European Committee for Electrotechnical Standardization (CENELEC). It is identical with IEC835-2-8:1993, includ
8、ing amendment No.1:1996, published by the International Electrotechnical Commission (IEC) and is part of a series. BS EN 60835 is published in three Parts. The other Parts are: Part 1: Measurements common to terrestrial radio-relay systems and satelliteearth stations; Part 3: Measurements on satelli
9、te earth stations. This Section of BSEN60835-2 covers measurements pertaining to the adaptive equalizers used in digital microwave radio-relay systems. These measurements are intended to characterize the system equalizer in the presence of selective fading and may also be performed on systems withou
10、t adaptive equalizers. To take account of those properties of the system which are especially influenced by the use of frequency and/or time domain equalizers, the results of measurements performed on the system are presented by so-called signatures. Additional measurements provide further means to
11、characterize the performance of the system. It is expected that other Sections of the IECPublication835 will be published as identical British Standards, subject to their harmonization by CENELEC. Some Sections of this British Standard have already been published as Sections of BS7573. A British Sta
12、ndard 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. Summary of pages This document comprises a front cover
13、, an inside front cover, pagesi andii, theEN title page, pages2 to 20, 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
14、EUROPENNE EUROPISCHE NORM EN 60835-2-8 July 1993 + A1 March 1996 UDC 621.396.7:621.317.083 Descriptors: Radiocommunications, telecommunications, communication equipment, earth stations, radio-relay systems, microwave frequencies, measurements, characteristics English version Methods of measurement f
15、or equipment used in digital microwave radio transmission systems Part 2: Measurements on terrestrial radio-relay systems Section 8: Adaptive equalizer (includes amendment A1:1996) (IEC 835-2-8:1993 + A1:1996) Mthodes de mesure applicables au matriel utilis pour les systmes de transmission numrique
16、en hyperfrquence Partie2: Mesures applicables aux faisceaux hertziens terrestres Section8: Egaliseur auto-adaptif (inclut lamendement A1:1996) (CEI 835-2-8:1993 + A1:1996) Meverfahren fr Gerte in digitalen Mikrowellen-Funkbertragungssystemen Teil2: Messungen an terrestrischen Richtfunksystemen Haupt
17、abschnitt8: Adaptive Entzerrer (enthltnderung A1:1996) (IEC 835-2-8:1993 + A1:1996) This European Standard was approved by CENELEC on1993-07-06. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status o
18、f 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 Standard exists in three official versions (English, French, German). A v
19、ersion 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 electrotechnical committees of Austria, Belgium, Denmark, Finland
20、, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normu
21、ng Central Secretariat: rue de Stassart 35, B-1050 Brussels 1993 Copyright reserved to CENELEC members Ref. No. EN 60835-2-8:1993 + A1:1996 EEN 60835-2-8:1993 BSI 03-2000 2 Foreword The text of document12E(CO)146, as prepared by subcommittee12E, Radio relay and fixed satellite communication systems,
22、 of IEC technical committee12, Radiocommunications, was submitted to the IEC-CENELEC parallel vote inNovember1991. The reference document was approved by CENELEC asEN60835-2-8 on6July 1993. The following dates were fixed: Foreword to amendment A2 The text of12E/255/FDIS, future amendment1 to IEC835-
23、2-8:1993, prepared 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 amendmentA1 to EN60835-2-8:1993 on1996-03-05. The following dates were fixed: Contents Page Foreword 2 1
24、Scope 5 2 General 5 2.1 Frequency domain equalizer 5 2.2 Time domain equalizer 5 2.3 Evaluation of system parameters influenced by the equalizers 6 3 Outage signature 7 3.1 Definition and general considerations 7 3.2 Measurement method 7 3.3 Presentation of results 8 3.4 Details to be specified 8 4
25、Return signature 8 4.1 Definition and general considerations 8 4.2 Measurement method 8 4.3 Presentation of results 8 4.4 Details to be specified 8 5 Measurements of dynamic fading effects 9 5.1 Definition and general considerations 9 5.2 Method of measurement 9 5.3 Presentation of results 9 5.4 Det
26、ails to be specified 9 6 Recovery time 10 6.1 Definition and general considerations 10 6.2 Measurement method 10 6.3 Presentation of results 10 6.4 Details to be specified 10 7 Additional measurements 11 7.1 Outage signature with flat fading 11 7.2 Outage signature with interfering adjacent channels
27、 11 Annex A (informative) Bibliography 20 Figure 1 Linear distortion and crosstalk in a QAM system caused by multipage fading 11 Figure 2 Block diagram of a linear baseband equalizer 11 Figure 3 Basic arrangement for the measurement of signatures 12 Figure 4 Example of an outage signature 12 Figure
28、5 Example of an outage signature with possible unusual signature values 13 Figure 6 Presentation of the signature, minimum phase and non-minimum phase, on the same ordinate scale 13 Figure 7 Example of the return signature 14 latest date of publication ofan identical national standard (dop) 1994-07-
29、01 latest date of withdrawal ofconflicting national standards (dow) 1994-07-01 latest date by which the amendment has to be implemented at national level by publication of an identical national standard or by endorsement (dop) 1996-12-01 latest date by which the national standards conflicting with t
30、he amendment have to be withdrawn (dow) 1996-12-01EN 60835-2-8:1993 BSI 03-2000 3 Page Figure 8 Arrangement for the measurement of recovery time 14 Figure 9 15 Figure 10 Schematic for the measurement of dynamic fading effects 16 Figure 11a Illustration of sweep waveform for the measurement of the sy
31、stem sensitivity to dynamic fading: sweep of the notch effect frequency 17 Figure 11b Graphical representation of the relative system sensitivity to dynamic fading: sweep of the notch offset frequency 18 Figure 12a Illustration of sweep waveform for the measurement of the system sensitivity to dynam
32、ic fading: sweep of the relative echo amplitude 18 Figure 12b Graphical representation of the relative system sensitivity to dynamic fading: sweep of the relative echo amplitude 194 blankEN 60835-2-8:1993 BSI 03-2000 5 1 Scope This section of IEC835-2 deals with measurements pertaining to the adapti
33、ve equalizers used in digital microwave radio-relay systems. These measurements are intended to characterize the system equalizer in the presence of selective fading and may also be performed on systems without adaptive equalizers. To take account of those properties of the system which are especial
34、ly influenced by the use of frequency and/or time domain equalizers, the results of measurements performed on the system are presented by so-called signatures. Additional measurements provide further means to characterize the performance of the system. 2 General The performance of a digital radio-re
35、lay link may be influenced by multipath propagation 1 1) . This is especially true in the case of high capacity multi-state QAM systems. In addition to reducing the received signal level, i.e.“flat fading”, multipath propagation results in linear distortion, i.e.“dispersive fading”, producing amplit
36、ude and phase distortion. Multistate modulation systems are especially vulnerable to this form of fading see835-2-4: Part 2: Measurements on terrestrial radio-relay systems Section4: Transmitter/receiver (in preparation). For a system operating under multipath propagation conditions the vulnerabilit
37、y of the time-variant channel to linear distortion is of utmost importance. In the majority of high-capacity line-of-sight digital radio-relay systems, adaptive equalizers are used to counteract “dispersive fading” in order to decrease outages. The following types of equalizers are generally in use:
38、 frequency-domain equalizers, which are mainly, but not necessarily, implemented at i.f, and time-domain equalizers, which are mainly, but not necessarily, implemented at baseband. 2.1 Frequency domain equalizer It is the purpose of a frequency domain equalizer to correct the power density spectrum
39、of the received signal, which, for example, can be analyzed with the aid of a bank of band-pass filters. Since there is usually no major redundant information in the transmitted signal, it is not possible to gain any information about the phase or group delay distortion of the channel; only the atte
40、nuation distortion can be recognized properly. In some cases, the equalization network is of the minimum-phase type where the phase and magnitude responses are linked to each other via the Hilbert transform. If the channel distortion is also of the minimum-phase type, then by equalizing the magnitud
41、e response the phase response is equalized as well. If the channel distortion is of the non-minimum phase type, for example in the case of two-path propagation where the weaker signal arrives before the stronger signal at the receiver site, the phase distortion may be increased and in some cases eve
42、n doubled when the attenuation is equalized. This is the basic shortcoming of such a frequency domain equalizer. Its main advantage, however, is that it will operate correctly, with certain limitations, without any need for a recovered carrier signal (for synchronous demodulation), or for a recovere
43、d timing signal (formaking correct timing decisions). Therefore, in contrast to time domain equalization systems, lock-in/lock-out properties need not be investigated. 2.2 Time domain equalizer It is the purpose of a time domain equalizer to achieve an intersymbol-interference-free (ISI-free) pulse
44、shape at the input of the decision circuitry, although the channel itself may cause a considerable amount of ISI due to multipath propagation. Basically, time domain equalizers optimize the eye-opening either in the worst-case sense, i.e.by using the zero-forcing algorithm, or in the minimum-mean-sq
45、uare-error (MMSE) sense, i.e.using the MMSE algorithm 2. For proper operation, they require at least a correctly recovered timing signal. On the other hand, it is possible for the carrier- and timing-recovery circuits to take advantage of the operation of the equalizer by using the already equalized
46、 signal for the control of these loops. 1) The figures in square brackets refer toAnnex A.EN 60835-2-8:1993 6 BSI 03-2000 By looking at the pulse response of the channel, time domain equalizers are usually capable of counteracting both minimum and non-minimum phase channel distortion. In general, mu
47、ltipath propagation causes not only distortion in the I-I path and in the Q-Q path but also cross-talk contamination between the quadrature signals in a QAM system, (seeFigure 1). Therefore the time domain equalizer, if realized at baseband, shall have equalizing circuits not only in the I-I and Q-Q
48、 path, but also in the I-Q and Q-I path (seeFigure 2). If this equalizer is realized at i.f., only two equalization networks may be used and it may be possible to have only two independent controls. 2.3 Evaluation of system parameters influenced by the equalizers To evaluate the properties of a radi
49、o-relay system with respect to selective fading the important concept of the so-called signature is widely used. It is based on a two-path (two-ray) propagation model3. Due to peculiarities which occur in connection with equalizers, several variants of signature measurements are usually performed in addition to the basic signature measurement given in IEC835-2-4. In IEC835-2-4, the signature is defined as the locus in the relative echo-amplitude versus notch offset-frequency plane or in the notch de
