1、STD-BSI BS EN b1580-9-ENGL 1777 m 1b2qbb7 0587230 703 BRITISH STANDARD . . . . . . . -. . . - . . . . -. . -. . I Methods of measurement for waveguides Part 9. Reflection coefficient at retangular waveguide interfaces * * m The European Standard EN 61580-9 : 1996 has the status of a British Standard
2、 ICs 33.120.10 m BS EN 61580-9 : 1997 IEC 1580-9 : I1996 STD-BSI BS EN bL580-9-ENGL I997 3b2VbbS 0587233 8liT M AmdNo. Date BS EN 61580-9 : 1997 Text affected Committees responsible for this British Standard The preparation of this British Standard was entrusted by Technical Committee EPU46, Cables,
3、 wires and waveguides, RF connectors and accessories for communication and signalling, to Subcommittee EPU46/2, RF connectors and waveguides, on which the following bodies were represented: AEA Technology BEAMA Electrical Cable and Conductor Accessory Manufacturers British Non-Ferrous Metals Federat
4、ion British Telecommunications plc Federation of the Eleclmnics Industry Ministry of Defence National Supervisory inspectorate Society of Cable Television Engineers This British Standard, having been prepared under the direction of the Electrotechnid Sector Board, was published under the authority o
5、f the Standards Board and comes into effect on 15 February 1997 O BSI 1997 The following BSI references relate to the work on this standard Committee reference EPU42 Draft for comment 96203429 DC ISBN O 580 26941 8 I STD-BSI BS EN bL580-7-ENGL 1777 m Lb29bb7 058FZ12 78b m - BS EN 61580-9 : 1997 _ Co
6、ntents Committees responsible Page Inside fmnt cover National foreword ii Foreword 2 Text of EN 61580-9 3 O BSI 1997 i STD-BSI BS EN bL58KGNGL 1797 Lb24bbTO5872L3 bL2 = BS EN 61680-9 : 1997 National foreword This British Stanard has been prepared by Subcommittee EPL/46/2 and is the English language
7、version of EN 61580-9 : 1996 MeuLods of measurement for waveguides - Part 9: b) lateral displacement between the waveguide axes in either the H or E plane; c) angular misalignment between the waveguide axes. 2 Normative reference The following normative document contains provisions which, through re
8、ference in this text, constitute provisions of this part of IEC 1580. At the time of publication, the edition indicated was valid. All normative documents are subject to revision, and parties to agreements based on this part of IEC 1580 are encouraged to investigate the possibility of applying the m
9、ost recent edition of the normative document indicated below. Members of IEC and IS0 maintain registers of currently valid International Standards. IEC 154: Flanges for waveguides 3 List of symbols Let: a = basic inside width of the waveguide; b = basic inside height of the waveguide; hc = cut-off w
10、avelength; Aal Ab = deviations from the basic internal waveguide dimensions; AaO, Abe = linear displacements between the waveguide axes. = waveguide wavelength; hg The above symbols are illustrated in figure 1. In addition, let: Pa = reflection coefficient due to changes in waveguide width; Pb = ref
11、lection coefficient due to changes in waveguide height; PH = reflection coefficient due to H-plane displacement; PE = reflection coefficient due to E-plane displacement. e STD-BSI BS EN b158-p7TENL 1777 m 1b2bbT0587218 LT4 m Page 5 EN 61580-9 : 1996 4 Effect of dimensional changes and axial dlspacem
12、ent 4.1 Combination of mismatches For small dimensional changes, pa and Pb are due to the resistive mismatches between the waveguides, the shunt susceptances being negligible. lhe reflection coefficients due to displacements, pH and pE, are due to shunt susceptances and consequently in phase quadrat
13、ure with (pa + Pb). The total mismatch due to the combination of dimensional changes and axial displacement is therefore: NOTES 1 lhe highest value of reflection coefficient for axially aligned waveguides is when a and b are at extreme tolerances and a waveguide with dimensions (a + Aa), (b - Ab) ma
14、tes with a waveguide with dimensions (a - Aa), (b + Ab)- 2 susceptance. p and PE have opposite signs, p being due to an inductlve susceptance and PE to a capacitive 4.2 Theoretical considerations In the IEC 154 series of standards, the following formula is given for the maximum reflection due to the
15、 combination of dimensional changes and lateral displacement for rectangular waveguides: 1 R = lolog, 4,9348 kg X 7,8957 x Av2 - a3 where R is the reflection loss. Equation (2) can be re-written in terms of reflection coefficients as follows: 1 R= 10 log,o - P2 i Ag2 x Aa 4,9348 hg X Aae2 7,8957 x A
16、b#2 - a3 v therefore p = J 4a3 +% + (3) .e. Equation (3a) is identical to equation (1). STD-BSI BS EN bL580-7-ENGL 1977 LbZqbb9 0587237 O30 Page 6 EN 61580-9 : 1996 The separate factors in equation (3a) can be expressed as follows: Ab b Pb =- 4,9348 hg x Aa.2 “s (*J (6) =x - a3 2a kc PH - 4.3 Determ
17、ination of reflection coefficients These may be determined either by use of equations (4) to (7) or by means of the graphs shown in figure 2 where the reflection coefficients are expressed as percentages. For Pb the ordinate of figure 2 may be used directly as pb is independent of frequency. For pa,
18、 pH and pE the ordinate takes into account the frequency of operation. NOTES 1 mid-band values for pa and pH. For mid-band operation of a waveguide kcA, approximates to unity and the ordinate gives the approximate Ao Io 2 For waveguides with a 2:1 aspect ratio -I - and the ordinate gives the approxi
19、mate mid-band value of pE, 4.4 Summary Equation (2) has been accepted by the IEC for the determination of reflection loss (.e. return loss) between two rectangular waveguide flanges in the IEC 154 series of flange standards. These standards contain tables of reflection loss based. on the criterion t
20、hat the maximum allowable displacement between waveguide flanges should not degrade the inherent return loss due to waveguide dimensional tolerances by more than 1 dB. This leads to a maximum value for Aa, of 0,0175a for a waveguide tolerance of 1d500. For the larger sizes of waveguide this gives a
21、worst-case value of return loss of approximately 40 dB. STD-BSI BS-EN bL580-9-ENGL 1777 Lb2Vbb 0587220 852 Page 7 EN 61580-9 : 1996 5 Angular misalignment between waveguide flanges For a rotation of 4“ between the flanges of two identical rectangular waveguides, with aspect ratios of 2:1, the follow
22、ing approximate expression may be used to determine the mid-band value of reflection coefficient: pt = 0,5 sin2 9 (8) where pt is due to the effect of an inductive susceptance. Equation (8) may be used for values of 9 up to 45“ but p, varies with aspect ratio and also varies inversely with frequency
23、. STD-BSI BS EN bL580-9-ENGL 1777 Lb24bb7 0587223 777 Page 8 EN 61580-9 : 1996 Aa Guide Balde n 1 waveguideN1 - Guide Bande no 2 waveguide N 2 b a I, J Fig la - Variations des dimensions intrieureslchange internal dimensiais plan WH piane Plan OE plane fig 1 b - piacement latrai des axes des guidesl
24、lateral displacement beivuwn weguides axes fig lc - caiage angulaire des axes des guidedAngular msaligiment betwen waveguides Figure 1 - Illustration des discontinuits dans la section Illustration of section discontinuities 100 10 1 Page 9 EN 61580-9 : 1996 0,001 0,Ol 1 Figure 2 - Graphiques pour dt
25、erminer le coefficient de rflexion Graphs for determination of reflection coefficient STD-BSI BS EN bL5O-7-ENL 1777 W LbELibb7 057223 561 Page 10 EN 61580-9 : 1996 Annex ZA (normative) Normative references to international publications with their corresponding European publications This European sta
26、ndard incorporates by dated or undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text and the publications are listed herealter. For dated references, subsequent amendments to or revisions of any of these publications apply t
27、o this European Standard oniy when incorporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies (including amendments). NOTE. When an international publication has been modified by common modifications, indicated by (mod), the relevant
28、 EN/HD applies. Publication Year Title EC 154 series finges for waveguides EN/ED Year EN 60154-1 1994 HD 129 series O BSI 1997 BS EN 61580-9 : 1997 List of references See national foreword. * * m O BSI 1997 BS EN 61580-9 : 1997 IEC 1580-9 : 1996 BSI 389 Chiswick High Road London w4 4AL BSI - British
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