ASTM D2520-2013 Standard Test Methods for Complex Permittivity (Dielectric Constant) of Solid Electrical Insulating Materials at Microwave Frequencies and Temperatures to 1650oC《在微.pdf

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1、Designation: D2520 13Standard Test Methods forComplex Permittivity (Dielectric Constant) of Solid ElectricalInsulating Materials at Microwave Frequencies andTemperatures to 1650C1This standard is issued under the fixed designation D2520; the number immediately following the designation indicates the

2、 year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 These test methods cover the determination of relat

3、ive(Note 1) complex permittivity (dielectric constant and dissipa-tion factor) of nonmagnetic solid dielectric materials.NOTE 1The word “relative” is often omitted.1.1.1 Test Method A is for specimens precisely formed to theinside dimension of a waveguide.1.1.2 Test Method B is for specimens of spec

4、ified geometrythat occupy a very small portion of the space inside a resonantcavity.1.1.3 Test Method C uses a resonant cavity with fewerrestrictions on specimen size, geometry, and placement thanTest Methods A and B.1.2 Although these methods are used over the microwavefrequency spectrum from aroun

5、d 0.5 to 50.0 GHz, each octaveincrease usually requires a different generator and a smaller testwaveguide or resonant cavity.1.3 Tests at elevated temperatures are made using specialhigh-temperature waveguide and resonant cavities.1.4 This standard does not purport to address all of thesafety concer

6、ns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2A893/A893M Test Method for Complex Dielec

7、tric Constantof Nonmetallic Magnetic Materials at Microwave Fre-quenciesD150 Test Methods for AC Loss Characteristics and Permit-tivity (Dielectric Constant) of Solid Electrical InsulationD1711 Terminology Relating to Electrical Insulation3. Terminology3.1 Definitions of Terms. For definitions of te

8、rms used inthis test method, refer to Terminology D1711.3.2 Definitions of Terms Specific to This Standard:3.2.1 neper, na division of the logarithmic scale whereinthe number of nepers is equal to the natural logarithm of thescalar ratio of either two voltages or two currents.NOTE 2The neper is a di

9、mensionless unit. 1 neper equals 0.8686 bel.With Ixand Iydenoting the scalar values of two currents and n being thenumber of nepers denoted by their scalar ratio, then:n 5 lnelxly!where:lne= logarithm to base e.3.2.2 For other definitions used in these test methods, referto Terminology D1711.4. Sign

10、ificance and Use4.1 Design calculations for such components as transmis-sion lines, antennas, radomes, resonators, phase shifters, etc.,require knowledge of values of complex permittivity at oper-ating frequencies. The related microwave measurements sub-stitute distributed field techniques for low-f

11、requency lumped-circuit impedance techniques.4.2 Further information on the significance of permittivity iscontained in Test Methods D150.4.3 These test methods are useful for specificationacceptance, service evaluation, manufacturing control, andresearch and development of ceramics, glasses, and or

12、ganicdielectric materials.TEST METHOD ASHORTED TRANSMISSIONLINE METHOD5. Scope5.1 This test method covers the determination of microwavedielectric properties of nonmagnetic isotropic solid dielectric1These test methods are under the jurisdiction of ASTM Committee D09 onElectrical and Electronic Insu

13、lating Materials and is the direct responsibility ofSubcommittee D09.12 on Electrical Tests.Current edition approved May 1, 2013. Published August 2013. Originallyapproved in 1966. Last previous edition approved in 2001 as D252001 which waswith drawn in 2010 and reinstated in May 2013. DOI: 10.1520/

14、D2520-132For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive,

15、PO Box C700, West Conshohocken, PA 19428-2959. United States1materials in a shorted transmission line method. This testmethod is useful over a wide range of values of permittivityand loss (1).3It is suitable for use at any frequency wheresuitable transmission lines and measuring equipment are avail-

16、able. Transmission lines capable of withstanding temperaturesup to 1650C in an oxidizing atmosphere can be used to holdthe specimen.6. Summary of Test Method6.1 For an isotropic dielectric medium, one of Maxwellscurl equations is writtencurl H 5 j*0E (1)assuming exp (jt) time dependence,where:* = re

17、lative complex permittivity,0= (absolute) permittivity of free space, and =2f, f being the frequency.The notation used will be as follows:* 5 2j“ 5 1 2 jtan! (2)where:tan = “/, = real part, and“ = imaginary part.The value of * is obtainable from observations that evaluatethe attenuation and waveleng

18、th of electromagnetic wave propa-gation in the medium.6.2 The permittivity of the medium in a transmission lineaffects the wave propagation in that line. Obtain the dielectricproperties of a specimen by using a suitable line as a dielectricspecimen holder. The electromagnetic field traveling in oned

19、irection in a uniform line varies with time, t, and with distancealong the line, , as exp (jt 6 ) where is the propagationconstant.Assuming that the metal walls of the line have infiniteconductivity the propagation constant of any uniform line ina certain mode is 5 2 c222 *22!12(3)where:c= cut-off w

20、avelength for the cross section and themode in question,( = c/f ) = wavelength of the radiation in free space, and* = relative complex permittivity of the nonmag-netic medium.Since * is complex, is complex, that is, 5 1j (4)the field dependence on distance is therefore of the form eej. The wave atte

21、nuation is in nepers per unit length; isthe phase constant, =2/gwhere gis the guide wavelengthin the line. The method of observing and by impedancemeasurements and of representing the behavior of a linecontaining a dielectric by means of the formalism of transmis-sion line impedance will be outlined

22、 briefly (1).6.3 Impedance Representation of the Ideal ProblemTheimpedance representation of the ideal problem is illustrated byFig. 1 for a uniform line terminated by a short. In Fig. 2 adielectric specimen of length dsis supposed to fill completelythe cross section of the line and be in intimate c

23、ontact with theflat terminating short. The impedance of a dielectric filled lineterminated by a short (1), observed at a distance dsfrom theshort (at what is defined as the input face of the specimen) isZin5 j02tanh2ds! (5)where 0is the permeability of free space and of the materialand 2is given by

24、Eq 2, using the dimensions of the line aroundthe specimen.6.4 Impedance Measurement:6.4.1 The object of the measurement is to obtain theimpedance at the input face of the specimen for evaluation ofthe unknown 2in Eq 4 which in turn allows K* to be evaluatedin Eq 2. The impedance in question is measu

25、red by a travelingprobe in a slotted section of the line. As illustrated schemati-cally in Fig. 1 and Fig. 2, the position of an electric node, thatis, an interference minimum of the standing wave, is observed,and also the “width,” , of this node is observed. is thedistance between two probe positio

26、ns on either side of the nodeposition where the power meter indicates twice the power3The boldface numbers in parentheses refer to the list of references appended tothese test methods.FIG. 1 Standing Wave Established Within Empty Shorted WaveguideD2520 132existing at the node minimum. The voltage st

27、anding wave ratiodenoted by r (r = VSWR) is obtained from by the equation(see gs, Section 11)r 5 (6)NOTE 3Refer to Appendix X2 and Appendix X3 for additionalcomments on errors and refinements in the method to improve accuracy.Also refer to Refs (1-4) for information on air gap corrections and use of

28、standard materials to reduce errors and improve accuracy.When r is small, a correction is necessary (5). The loadimpedance at a phase distance u away from an observedelectric node having VSWR = r isZmeas5 Z011 2 jrtanu!r 2 jtanu! (7)where Z01= j0/1= f0gassuming the line is uniform andlossless.6.4.2

29、It remains to determine r and u correctly, taking intoaccount losses of the line and nonuniformity due to tempera-ture differences, then to equate Zmeasand Zinfrom Eq 6 and Eq4, and finally to lay out a convenient calculation scheme for *.The measuring procedure for obtaining r and u is discussed in

30、Section 10.7. Significance and Use7.1 This test method is useful for quality control andacceptance tests of dielectric materials intended for applicationat room and substantially higher temperatures. Dielectricmeasurement capabilities over wide ranges of temperature andover wide, continuous ranges o

31、f frequency provide significantusefulness of this method for research and development work.8. Apparatus8.1 See Fig. 3 for a block diagram of equipment compo-nents. Some characteristics of the component in each block areas follows:8.1.1 GeneratorStable in power and frequency with lowharmonic output.8

32、.1.2 Square-Wave Modulator1.0 kHz output or fre-quency required for VSWR meter.8.1.3 Frequency MeterHeterodyne or cavity absorption;uncertainty 1 part in 104.8.1.4 Isolator30-dB isolation, and having an outputVSWR of less than 1.15.FIG. 2 Standing Wave Established Within Shorted Waveguide After Inse

33、rtion of SpecimenFIG. 3 Block Diagram of Apparatus Used to Perform the Measurement of Dielectric Properties by the Short Circuit Line MethodD2520 1338.1.5 Slotted SectionA slotted waveguide section andcarriage capable of measuring gross distances to 0.025 mm(0.001 in.) and small distance to 0.0025 m

34、m (104in.) (fornode width). A micrometer head is required; it is to moveparallel to the axis of the line.8.1.6 ProbeAdjustable for depth. The detector must besquare law (6) if one uses the voltage-decibel scale of thestanding wave ratio (SWR) meter. The detector must beoperated in the square law reg

35、ion.And, in particular, the crystaldetectors will comply with the square law, if they are notoverdriven. The law of a crystal is checked commonly byadding a good rotating-vane microwave attenuator.8.1.7 VSWR MeterReadable in decibels.8.1.8 Temperature Isolation SectionIncludes a bend.8.1.9 Cooling S

36、inkSufficient conduction to water or airstream to maintain suitable temperature and waveguide dimen-sions.8.1.10 Waveguide Specimen HolderPlatinum-20 % rho-dium for 1650C; platinum for temperature 1300C; copper orsilver for lower temperatures within their abilities to withstandthermal damage and cor

37、rosion. Length shall be sufficient tohave a main transition region of temperature of the order of gin extent and still keep sample temperature uniform to 5C.8.1.11 Tube FurnacePlatinum-wound tube furnace to ac-cept test section, and maintain a 50-mm (2-in.) length at aconstant temperature 65C up to

38、1650C.8.2 The so-called slope of the attenuation characteristic ofthe slotted line is to be normal, that is, the VSWR is changingby the expected amount in going from one node to anotherwhile looking into a shorted termination. Items 8.1.5, 8.1.8,and 8.1.10 shall have initial dimensions plus differen

39、tialexpansions at the temperature of a junction so that the changein dimensions is less than 0.25 mm (0.01 in.). The dielectricholder shall slope downward at 45 to 90 to maintain specimenagainst termination. Termination shall be flat to 0.010 mm(0.0004 in.) and perpendicular to axis of waveguide wit

40、hin60.05.At 9 GHz, the tolerance on transverse dimensions shallbe 60.075 mm (0.003 in.).9. Sampling9.1 Determine the sampling by the applicable materialspecification.10. Test Specimen10.1 The transverse dimensions of the specimen shall be0.05 6 0.025 mm (0.002 6 0.001 in.) less than those of thetran

41、smission line. The front and back faces shall be parallelwithin 0.01 mm (0.0004 in.) and perpendicular to the axis ofthe transmission line within 6 0.05. The corners of thespecimen are slightly rounded so the end surface seats flatagainst the termination with no air film between the surfaces.The len

42、gth, ds, shall be suitable for the measurement; a lengthof 1 mm (0.04 in.) shall be used in 1 by 23-mm (0.04 by0.9-in.) rectangular waveguide. For high loss materials thelength is controlled by the electrical criterion given for n tan in 12.2.2.11. Procedure11.1 Impedance measurements are required i

43、n the emptyline (Fig. 1), and with the specimen in place (Fig. 2). Thefrequency of the source and the temperature distribution of theline are to be the same for both observations. With no specimen(Fig. 1) read the position 1of a voltage minimum (a node), ona scale of arbitrary origin; also measure t

44、he separation betweenpositions either side of 1where the power is +3.01 dB fromthe minimum. This is the width 1of the node. Likewisemeasure this analogous 2and 2with the specimen againstthe termination (Fig. 2). As an additional check measurement,in one case measure the distance between two adjacent

45、 nodes.This distance is gs/2, where gsis the guide wavelength in theslotted section.12. Calculation12.1 Measurements Transformed to Input Face ofSpecimenWhen measurements are made at elevatedtemperatures, the guide width and the guide wavelength, g,vary because of the temperature gradient between th

46、e heatedsection and the cool (room temperature) slotted section. For-tunately the argument of the tangent in Eq 6 is obtainable,assuming the change in gis not abrupt. The correct argumentisu 5 2N2 2 dgh6 22 1gs! # (8)where ghis calculated for the empty heated dielectric holdersection from the dimens

47、ions duly adjusted for thermal expan-sion. In Eq 7 the plus sign is used if the scale for increasesaway from the short, the minus sign if the opposite. N is thesmallest integer 0, 1, etc., that makes u positive. To calculateghuse the general equationgh225 222 c22(9)where: = c/f = free space waveleng

48、th, andc= cutoff wavelength calculated from the dimensions.For the TE10mode rectangular guide discussed below, c=2a* where a* is the wide dimension. It remains to find the (width of the node) that would have been measured at the faceof the specimen. The node width 1without the specimen isassumed to

49、arise from the attenuation factor of the empty line,and can be treated as if it increased smoothly with distancefrom the short. The width contribution accumulated due toattenuation in going from the sample face to the place 2whereit is observed is 1(L2 ds)/L1where Liis the total length ofpath, i = 1 or 2, to the shorting termination and dsis the lengthof the specimen. The node width , transformed to the sam