SAE ARP 1705C-2017 Coaxial Test Procedure to Measure the RF Shielding Characteristics of EMI Gasket Materials.pdf

1、_ 6$(7HFKQLFDO6WDQGDUGV%RDUG5XOHVSURYLGHWKDW7KLVUHSRUWLVSXEOLVKH GE6$(WRDGYDQFHWKHVWDWHRIWHFKQLFDODQGHQJL neering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising tKHUHIURPLVWKHVROHUHVSRQVL

2、ELOLWRIWKHXVHU SAE reviews each technical report at least every five years at which time it may be revised, reaffirmed, stabilized, or cancelled. SAE invites your written comments and suggestions. Copyright 2017 SAE International All rights reserved. No part of this publication may be reproduced, st

3、ored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: +1 724-776-4970 (outside USA) Fax: 724-776-079

4、0 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE values your input. To provide feedback on this Technical Report, please visit http:/standards.sae.org/ARP1705C AEROSPACE RECOMMENDED PRACTICE ARP1705 REV. C Issued 1981-06 Revised 2017-02 Superseding ARP1705B Coaxial Test Procedu

5、re to Measure the RF Shielding Characteristics of EMI Gasket Materials RATIONALE ARP1705 was revised from Revision B to C to increase the accuracy of the test fixture and increase the frequency range to 18 GHz. TABLE OF CONTENTS 1. SCOPE . 2 1.1 Purpose 2 1.2 Background 2 2. REFERENCES . 2 2.1 Appli

6、cable Documents . 2 2.2 Definitions . 3 2.2.1 TRANSFER IMPEDANCE 3 2.2.2 SHIELDING EFFECTIVENESS (EMC) 3 2.2.3 SHIELDING QUALITY 3 3. BASIS FOR TEST METHOD . 4 3.1 Electromagnetic (EM) Wave 4 3.2 Induced Currents in Barrier (Surface Current Density) 4 3.3 Seams and Gasketed Joints 4 3.4 Transfer Imp

7、edance of a Joint . 4 3.5 Measurement of Transfer Impedance 4 3.6 Use of Transfer Impedance in Equipment Design . 5 3.7 Penetration of an EM Wave through an EMI Gasketed Joint 5 4. TEST FIXTURES . 6 4.1 Fixture Assemblies . 7 4.1.1 Fixture 1705A . 7 4.1.2 Fixture 1705C . 7 4.1.3 Fixture 1705C assemb

8、ly notes (see figure C12) 7 4.2 Maximum Gasket Dimensions . 7 4.2.1 Fixture 1705A . 7 4.2.2 Fixture 1705C . 7 4.3 Test Set-Up 7 4.4 Dynamic Range 8 5. NOTES . 8 5.1 Revision Indicator . 8 SAE INTERNATIONAL ARP1705 (2) test the relative value of joint surfaces as related to the gasket under test; and

9、 (3) test the ability of gaskets and gasketed joint surfaces to survive hostile environmental conditions. 2. REFERENCES 2.1 Applicable Documents The following publications form a part of this document to the extent specified herein. The latest issue of SAE publications shall apply. The applicable is

10、sue of other publications shall be the issue in effect on the date of the purchase order. In the event of conflict between the text of this document and references cited herein, the text of this document takes precedence. Nothing in this document, however, supersedes applicable laws and regulations

11、unless a specific exemption has been obtained. 1. ARP1173, Test Procedure to Measure the R.F. Shielding Characteristics of E.M.I. Gaskets, July 1975. 2. 5DGLDWHG )LHOG 6WUHQJWK 0HWKRG IRU 0HDVXUHPHQWRIWKH5)6KLHOGLQJ however when more than one penetration, leak or gasketed joint is of concern in a gi

12、ven local region, then the phase of the transfer impedance of each becomes significant so that the individual leakages may be combined to determine the severity of the total leakage. 3.7 Penetration of an EM Wave through an EMI Gasketed Joint When a radiated EM wave is impinged on a metallic shieldi

13、ng barrier, a current (surface current density in amperes per meter) is generated in the material. When the current flows across a gasketed maintenance cover as illustrated in Figure 1, a voltage e is generated across the gasket. The value of e is equal to the current in amperes/meter times the impe

14、dance of the joint (transfer impedance in ohm-meters). The transmitted EM fields (ET and HT) illustrated in Figure 1 are generated by the voltage across the gap and have the characteristics of a low impedance slot antenna. The radiated power can be estimated from the example of Figure 1 as follows:

15、ET | 2e / 2S R = JS ZT / S R (Eq. 3) HT | ET O / 2S R(377) R O /2S = ET / 377 R t O /2S SAE INTERNATIONAL ARP1705& Page 6 of 32 Figure 1 - Penetration of EM wave through EMI gasketed maintenance cover where: JS = current due to EM Wave striking barrier (A/m) | HI e = voltage across gasket = JSZT (Vo

16、lts) ZT = Transfer impedance of gasketed joint (:-m) 4. TEST FIXTURES Appendix B Figures B1 through B12 illustrate the construction of the 1705A test fixture. Appendix C Figures C1 through C11 illustrate the construction of the 1705C test fixture. The frame members of both fixtures are made from 606

17、1-T6 DOXPLQXP)RUTXDOLWFRQWUROSXUSRVHVWKHVKLHOGLQJTXDOLWRIWKHJDVNHWXQGHUWHVWLVSHUIRUPHG XVLQJJROGSODWHG -T6 aluminum contact joint surfaces. For shielding quality testing of the gasketed joint surfaces and for testing the effects of the various hostile environments illustrated in Appendix A and B, th

18、e contact joint surfaces are to be manufactured from the materials to be used in actual application and plated with the proposed surface coating. SAE INTERNATIONAL ARP1705& Page 7 of 32 4.1 Fixture Assemblies 4.1.1 Fixture 1705A Figure B1 illustrates the gasket assembly under test (consisting of a b

19、ase plate, a gasket and contact plate). The spacing between the two plates is controlled with non-conductive spacers where the compression of the gasket is to be that recommended by the gasket manufacturer (or as dictated by the design of the equipment). The contact plate is fastened to the base pla

20、te with 3-1/4 - 20 nylon (non-conductive) cap screws. This assembly is EM bonded to the receiver plate with an EMI gasket imbedded in the edge of the receiver plate and held in place with two toggle clamps. Current is brought into the fixture via the input connector assembly consisting of a modifier

21、 type N connector and 50 : resistor assembly. The voltage measured across the gasket is performed using the output connector assembly consisting of a modified type N connector and an output pin assembly. The description of the 50 : resistor is contained in the notes of Figure B5. The frame assembly

22、(including the toggle clamps) is illustrated on the Figure B8 and contained in the notes. 4.1.2 Fixture 1705C Figure C1 the gasket assembly under test (consisting of 50 : input assembly, input receiver cap, test sample under test, simple holder contact plate, output receiver base and receiver pin as

23、sembly.) The degree of compression of the gasket under test is controlled by the sample holder. Current is brought into the test fixture via input 50 : connector assembly. The voltage measured across the gasket is performed using the output connector assembly. 4.1.3 Fixture 1705C assembly notes (see

24、 Figure C12). 4.2 Maximum Gasket Dimensions 4.2.1 Fixture 1705A Figure B13 illustrates a contact plate which has the maximum gasket dimensions outlined on it. These maximum outside dimensions are as follows: Square Gasket - 3.40 inches Circular Gasket - 4.0 inches Thickness - 0.50 inch 4.2.2 Fixture

25、 1705C The maximum outside diameter (OD) of the gasket under test is 0.75 inch (19 mm), minimum ID = 0.37 inch (9 mm) and a maximum height of 3/16 inch (5 mm). 4.3 Test Set-Up Figure B14 illustrates the setup to be used in the performance of the testing. This consists of the following: 1. The curren

26、t to be delivered to the transfer impedance test fixture is obtained by connecting the output of the signal source to the receiver input port, measuring the voltage and dividing by 50. 2. The voltage across the gasket is measured by connecting the signal source to the transfer impedance input connec

27、tor and the output connector of the fixture to the receiver. As noted, to obtain the required dynamic range to accurately measure the transfer impedance of the gasket under test it may be required to add an amplifier to the output of the signal generator. A pre-amplifier may also be required to be a

28、dded to the output of the test fixture. SAE INTERNATIONAL ARP1705& Page 8 of 32 4.4 Dynamic Range For many good gasket materials, the transfer impedance may be as low as a few micro-ohms-meters - that is, a few micro-ohms per meter length. Therefore, the receiver should be capable of measuring signa

29、l levels as low as 140 dB, below the output of the signal generator. This typically requires the use of a 1 W broadband power amplifier driven by the swept frequency signal generator, a low-noise broadband preamplifier in front of the receiver may also be required. 5. NOTES 5.1 Revision Indicator A

30、change bar (l) located in the left margin is for the convenience of the user in locating areas where technical revisions, not editorial changes, have been made to the previous issue of this document. An (R) symbol to the left of the document title indicates a complete revision of the document, inclu

31、ding technical revisions. Change bars and (R) are not used in original publications, nor in documents that contain editorial changes only. PREPARED BY SAE COMMITTEE AE-4, ELECTROMAGNETIC COMPATIBILITY SAE INTERNATIONAL ARP1705& Page 9 of 32 APPENDIX A - TEST PROCEDURE A.1 SCOPE This procedure establ

32、ishes an accurate method of grading the EM shielding quality of the EMI/RFI gasket materials and EMI/RFI gasketed joints. The frequency range is 10 kHz to 1.0 GHz for fixture 1705A and 10 kHz to 18.0 GHz for fixture 1705C. 1. Obtaining the current delivered to the ZT fixture is required for all test

33、ing and is obtained as follows: a. Attach the output of the signal generator (with 50 : output) to the input to the receiver, using tracking generator. b. Record the current delivered to the test fixture (i.e., divide the recorded voltage obtained above by 50 : or subtract 34 dB if recording is expr

34、essed in dB). 2. Quality assurance testing of EMI gaskets. This consists of measuring the shielding quality of the gaskets under test using flat, low contact resistance, gold plated aluminum joint surfaces, and sufficient force to compress the gaskets to WKHPDQXIDFWXUHUVVSHFLILHGGHIOHFWLRQ7KHFRQGLWL

35、RQVXQGHUZKLFKWKHJD skets are to be tested are: a. Production quality gaskets using test fixture 1705A and 1705C. b. Using test fixture 1705A and production quality gaskets subjected to appropriate transportation and storage environmental conditions as applicable to system requirements (see Table A1)

36、. 3. Obtain the shielding quality of EMI gasketed joints. This consists of measuring the shielding quality of gasketed joints using the gasket material under test and flat joint surfaces, where the material and surface finish is that which is to be used during normal operation. The conditions under

37、which gasketed joints are to be tested are: a. Production quality gaskets using joint materials and surfaces of concern. Applicable for test fixture 1705A and 1705C. b. Using test fixture 1705A and production quality gaskets using joint materials and surface finishes of concern where the gaskets and

38、 joints are subjected to hostile appropriate environmental conditions as applicable to system requirements (see Table A2). A.2 REQUIREMENTS 1. The gasket materials under test are to be placed between a set of appropriate joint surfaces. The maximum size of the sample and sample placement is illustra

39、ted in Figure 13 and 4.2.2. 2. The testing is to be performed using receivers, spectrum analyzers or network analyzers in a sweep mode. A tracking generator is to be used to obtain a continuous sweep of data over the frequency range of interest. 3. In testing for the shielding quality of the gaskete

40、d joints, the test plates are to be manufactured and plated from the materials identical to that to be used during actual application of the system concern. SAE INTERNATIONAL ARP1705& Page 10 of 32 A.3 TEST PROCEDURE A.3.1 General The testing is to be performed on sample coupons. During the performa

41、nce of the test, the following considerations are to be observed. 1. In performing the quality control testing on the gaskets, the joint test surfaces are to be gold plated 6061-T6 aluminum. 2. In performing the shielding quality testing on gasketed joints, the joint surfaces are to be of the same m

42、aterial and finish as to be used during normal operation. 3. Prior to beginning the testing, the joint surfaces are to be cleaned of all contaminants with denatured alcohol or equivalent solvent. A.3.2 Specific Testing A.3.2.1 Obtain amplitude of current spectrum (required for all testing). 1. Attac

43、h the output of the signal generator to the input to the receiver and obtain the amplitude of the current (divide the received voltage by 50, or in dB subtract 34 dB from the dB voltage received). A.3.2.2 Shielding Quality Testing of EMI Gaskets 1. Place the gasket coupon under test between gold pla

44、ted joint surface and compress the gasket material to the deflection amount specified by the manufacturer of the gasket under test (this is performed by using non-conductive washers or spacers between tKHEDVHDQGFRQWDFWSODWHVRI$WHVWILWXUHRUWKHDSSURSULDWHLQVXODWHGVDPSOHKROGHURI C test fixture). 2. Set

45、 up the test fixture with the signal generator connected to the input port and the receiver connected to the output port. 3. Set the output power level of the signal source to the same level as used in A.3.2.1, and scan over the frequency range of interest. Observe the voltage amplitude spectrum obt

46、ained by the receiver. 4. Convert the reading to ohm-meters using the methodology of Section A.4. A.3.2.3 Transfer Impedance Testing of EMI Gasketed Joints 1. Place the gasket coupon under test between the joint surface plates. 2. Set up the test fixture with the signal generator connected to the in

47、put port, and the receiver connected to the output port. 3. Set the output power level of the signal source to the same level as used in A.3.2.1, and scan over the frequency range of interest. Observe the voltage amplitude spectrum obtained by the receiver. 4. Convert the reading to ohm-meters using the methodology of Section A.4. SAE INTERNATIONAL ARP170