1、61580-3 : 1997 Methods of measurement for waveguides Part 3. Variation of group delay * * rn The European Standard EN 615803 : 1997 has the status of a British Standard ICs 33.120.10 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW BS EN 615803 : 1997 Amd.No. National foreword
2、_- - Date %xt affected -. . . _. - - _ . _I - -. . . - This British Standard is the English language version of EN 61580 3 : 1937 Tl is identical with IEC 61580-3 : 1997. The UK participation in its preparation was entrusted by Technical CoiiimiLtct. EPIJ46, Cables, wires and waveguides, r.f. connec
3、tors and accessories for communication and signalling, to Subcommittee EPU46/2, Connectors anuiti waveguides, which has the responsibility to: - aid enquirers to understand the text; - present to the responsible internationallEuropean committee any enqiiii-h i on the interpretation, or proposais for
4、 change, and keep the l.W interests informed - monitor related intemational and European developments and proir!iilgaw them in the UK A list of organizations represented on this subcommittee can be obtained :)II rqucsi to its secretary. From 1 January 1997, all IEC publications have the number 60000
5、 added to the old number. For instance, IEC 27-1 has been renumbered as IEC 60027-1. For R pci.i:ct of time during the change over from one numbering system to the other, publications may contain identifiers from both systems. Cross-references Attention is dram to the fact iftat CEN and CENELEC Stan
6、dards normally Ucliick an annex which lists nonnative references to international publications with their corresponding European publications. The British Standards which inqhmcnt these international or European publications may be found in the BSI Standards Catalogue under the section entitled Inkr
7、national standasds Correspondencr Index, or by using the Find facility of the BSI Standards Electronic Catalogue Compliance with a British Standard does not of itself confer immunity from legal obligations. This British Standard, having been prepared under the direction of theElectrotechnical Sector
8、 Board, was published under the authority of the Standards Board and comes into effect on 15 December 1997 O BSI 1997 BN O 580 28870 6 Summary of pages This document comprises a front cover, an inside front cover, the EN title page. pages 2 to 9, a blank page, an inside back cover and a back cover.
9、STD-BSI BS EN LL580-3-ENGL L777 = lb24bb7 Obb54D5 686 E EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 61580-3 October 1997 ICs 33.120.10 English version Methods of measurement for waveguides Part 3: Variation of group delay (IEC 61 580-31997) Mthodes de mesure appliques aux guides dondes Meve
10、rfa hren fr Ho hlleiter Teil 3: nderung der Gruppeniaufzeit Partie 3: Variation du temps de groupe (CE1 61 580-3: 1997) (IEC 61 580-3:1997) This European Standard was approved by CENELEC on 1997-10-01. CENELEC members are bound to comply with the CENKENELEC Internal Regulations which stipulate the c
11、onditions 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 Standard exists i
12、n three officiai versions English, French, German). A version in any othw 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 officiai versions. CENELEC members are the national eiectrotech
13、nical committees of Austria, Belgium, Damark, Fmlrnd, France, Gennany, Greece, Iceland, Ireland, Italy, Luxembourg, NethariandS. Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisation Electrotech
14、nique Europisches Komitee fr Elektrotechnische Normung Centrai Secretariat: rue de Stassart 35, B - 1050 Brussois 1997 CENELEC - All rights of exploitation in any form and by any means reserved warldwklo for CENELEC mambom. Ref. No. EN 61 580-3:1997 E - STD-BSI BS EN bL5O-3-ENGL 1997 Lb24bb9 Obb540b
15、 512 Page 2 EN 61580-3 : 1997 Foreword The text of document 46B/224/FDIS, future edition 1 of IEC 61 580-3, prepared by SC 468, Waveguides and their accessories, of IEC TC 46, Cables, wires, waveguides, R.F. connectors, and accessories for communication and signalling, was submitted to the IEC-CENEL
16、EC parallel vote and was approved by CENELEC as EN 61 580-3 on 1997-1 0-01. The following dates were fixed: - latest date by which the EN has to be implemented at national levei by publication of an identical national standard or by endorsement with the EN have to be withdrawn - latest date by which
17、 the national standards conflicting (dop) 1998-07-01 (dow) 1998-07-01 Endorsement notice The text of the international Standard IEC 61580-3:1997 was approved by CENELEC as a European Standard without any modification. Page 3 EN 61580-3 1997 CONTENTS Clause 1 Scope and object 2 General 3 Principle 4
18、Test Set-up 4.1 Test set-up 1 4.1.1 Test equipment . 4.1.2 Procedure 4.1.3 Expression of results . 4.2 Test Set-up 2 4.2.1 Test equipment . 4.2.2 Procedure 4.2.3 Expression of results . 5 Requirements . Figures 1 Test Set-up 1 2 Test set-up 2 . . Page 4 4 4 5 5 6 7 7 7 8 9 9 9 6 8 Q BSI 1997 STD-BSI
19、 BS EN b1580-3-ENGL 1997 W Lb24bb9 ObbSYnB 395 Page 4 EN 61580-3 : 1997 METHODS OF MEASUREMENT FOR WAVEGUIDES - Part 3: Variation of group delay 1 Scope and object This part of IEC 61580 is applicable to the variation of group delay of a wave propagated in waveguide or waveguide assemblies. The obje
20、ctive of the test procedures given below is to characterize the group delay variation of a wave propagated in waveguide or waveguide assemblies. 2 General Group delay variation of a waveguide versus frequency, describes the variations of the derivative or the slope of the phase characteristic within
21、 the bandwidth. Group delay variation, often referred to as group delay distortion also, is found in all waveguide with wave propagation modes having a non-linear dependence of frequency on wavelength. Furthermore, dimensional variations along waveguide, single or multiple reflections, filter struct
22、ures, multi-mode propagation, etc. can cause additional group delay variations. Signals of non-zero bandwidth transmitted through media exhibiting large group delay variations can be altered in such a way that, in the extreme case, the information contained in the bandwidth cannot be restored. 3 Pri
23、nciple Three main measurement principles are currently used: a) static numerical differentiation; b) AM measurement; c) FM measurement. Methods a) and c) require expensive and/or complicated test equipment, therefore assembling a test set-up from single components can not be recommended. However, de
24、dicated test equipment does provide accurate group delay variation measurements with convenient data presentation. Method b) can be assembled from current RF-laboratory test equipment. For the test, an unmodulated or modulated RF-signal is sent through the waveguide under test (WUT). At the output,
25、the phase of the RF signal (or of the demodulated signal) is compared with the reference phase at the input of the WUT. Page 5 EN 61580-3 : 1997 Group delay variation is then derived using computation formula: or signal processing based on the where 7 is the group delay in seconds; As is the variati
26、on of. group delay; $I is the transmission phase in radians; w is the frequency in radians; f is the frequency in hertz. NOTE - The comparison of group delay variation measurements obtained by direct phase measurement (and subsequent computation) with test results from a modulated carrier method may
27、 be difficult. Compensation for the modulation bandwidth in respect to the discrete step-tidth in the computation routine for group delay calculation may be necessary. 4 Testset-up Two test Set-ups are described below. Figure 1 describes a test set-up to be used for any of the methods a), b), or c)
28、allowing direct measurement of group delay variation. Figure 2 describes a test set-up to be used for method b). It can be assembled from standard laboratory test equipment. Additional computation for deriving the correct group delay values is necessary. 4.1 Test set-up 1 This test set-up uses a net
29、work analyzer which directly measures the phase at two closely spaced frequencies and then computes the slope (approximation of the derivative). REMARK - Attention should be paid to the interval between the two frequencies (called “aperture). Increasing the aperture tends to average out fine grain v
30、ariations in the group delay data because the fine grain variations in the phase data are lost. Errors will occur when there is more than 180“ of phase shift between adjacent frequency points. However, for el% resolution uncertainty, one must maintain 21“ phase shift between frequency points. STD-BS
31、I BS EN bL580-3-ENGL 1777 W Lb24bb7 ObbSLiLO T43 RF generator Page 6 EN 61580-3 : 1997 - - WUT L . I Frequency meter u Variable attenuator Network analyzer Figure 1 - Test Set-up 1 4.1 .1 Test equipment The test equipment according to figure 1 consists of: RF-generator low-pass filter isolator direc
32、tional couplers attenuator load network analyzer REMARKS: (see remark 1) (see remark 2) (see remark 3) (see remark 4) (see remark 5) (see remark 6) (see remark 7) 1) The generator should have a sufficient frequency accuracy for the measure to be performed. In the most of cases a synthetizer should b
33、e necessary. 2) May be omitted depending on the level of harmonics. 3) May be omitted where the return loss of the coaxial to waveguide transition is better than 26 dB. 4) Directivity 40 dB. Main line return loss 26 dB. 5) Optional, depending on network analyzer. 6) Load; return loss better than 40
34、dB. 7) Some network analyzers provide built-in generator and directional couplers. If available, built-in error correction routines should be used. * * GY - STD.BSI BS EN b1.580-3-ENGL 1997 Lb24bb9 Obb54LL 98T m Page 7 EN 61580-3 : 1997 4.1.2 Procedure - If applicable, perform network analyzer calib
35、ration according to the manufacturers instructions. - Connect the two test ports of the test equipment together to establish a calibration line. This calibration line serves not only for measuring the group delay variation but also checks for the absolute delay produced by the electrical length of t
36、he WUT. - Insert the WUT. Offset the network analyzer to compensate for the absolute delay if necessary. - Record the group delay variation of the WUT. Caution: For group delay variation measurements in the Nanosecond-range, the test ports of the instrumentation must be very closely matched to the s
37、pecified characteristic impedance or waveguide dimension. 4.1.3 Expression of results The group delay variation can be read as a function of frequency directly from the recorded curve. 4.2 Test Set-up 2 The RF carrier is amplitude modulated and the group delay variation is measured as a function of
38、the distortion of the envelope of the modulated signal. After passing through the WUT, the modulated signal is demodulated (detector). In the phase comparator, the demodulated signal and the reference signal produce an output signal according to the following formula: -1 X A4 7(0) = - 2xxk where z i
39、s the group delay in seconds; A# is the variation of phase of modulation in radians; fm is the frequency of the modulation in hertz. NOTE - Fast variations in the group delay response of the WUT can be averaged out, if the modulation frequency is too large. Therefore, different modulation frequencie
40、s should be used during the measurements. REMARKS - A medium amplitude modulation factor (-50 %) has to be chosen. If the modulation factor is too small, the response will be poor; if it is too large, it could lead to phase distortions in the modulator/detector used. Page 8 EN 61580-3 : 1997 -%- 111
41、)- - 1 WUT Variable generator Figure 2 - lest Set-up 2 comparator Detectar 4.2.1 Test equipment The test equipment according to figure 2 consists of: swept RF-generator low-pass filter (see remark 1) amplitude modulator (see remark 2) isolator (see remark 3) variable attenuator (see remark 4) detect
42、or (see remark 5) reference generator (see remark 6) phase comparator (see remark 6) recorder REMARKS: 1) May be omitted depending on the level of harmonics. 2) The amplitude modulator should be free from phase modulation. 3) May be omitted where the return loss of the coaxial to waveguide transitio
43、n is better than 26 dB and if the detector is sufficiently linear over RF amplitude variation range. 4) Optional, depending on network analyzer. 5) The linearity of the detector in respect to RF-amplitude variations must be carefully checked. 6) The reference generator and phase comparator may be re
44、placed with a low frequency network analyzer. Page 9 EN 61580-3 : 1997 4.2.2 Procedure - Connect the two test ports of the test equipment together and calibrate for the proper scale of the curve. Record the group delay variation, if any, produced by the test equipment. Ensure that the variable atten
45、uator exhibits a constant group delay when adjusted. - Insert the WUT. If necessary, compensate for the loss of the WUT by adjusting the variable attenuator. - Record the group delay variation of the WUT. REMARK - Depending on the construction of the phase detector and the absolute delay introduced
46、by the WUT, the slope of the displayed group delay variation may appear inverted relative to the previously recorded Cali bration. - For group delay variation measurements in the nanosecond range, the test ports of the instrumentation must be very closely matched to the specified characteristic impe
47、dance or waveguide dimension. 4.2.3 Expression of results The group delay variation can be read as a function of frequency directly from the recorded plot. 5 Requirements Compliance with the relevant specification. * m * BS EN 61580-3 : 1997 IEC 61580-3 : 1997 BSI 389 Chiswick High Road London w4 4A
48、L BSI - British Standards Institution BSI is the independent national body responsible for preparing British Standards. It presents the UK view on standards in Europe and at the international level. It is incorporated by Royal Charter. Contract requirements A British Standard does not purport to inc
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