SAE ARP 6248-2016 Stripline Test Method to Characterize the Shielding Effectiveness of Conductive EMI Gaskets up to 40 GHz.pdf

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1、_ 6$(7HFKQLFDO6WDQGDUGV%RDUG5XOHVSURYLGHWKDW7KLVUHSRU t is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefrom, is

2、the sole rHVSRQVLELOLWRIWKHXVHU 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 2016 SAE International All rights reserved. No part of this publication may

3、be reproduced, stored 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)

4、 Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/ARP6248 AEROSPACE RECOMMENDED PRACTICE ARP6248 Issued 2016-02 Stripline Test Method to Character

5、ize the Shielding Effectiveness of Conductive EMI Gaskets up to 40 GHz RATIONALE This new standard is intended to provide a test method to characterize the shielding effectiveness of conductive EMI gaskets, up to the frequency of 40 GHz. FCC recently published EMC emission limits up to this frequenc

6、y. At this moment (February 2015), standardized methods are only available up to a maximum frequency of 18 GHz. Methods addressing small samples of gaskets are limited up to 10 GHz and are not giving a shielding effectiveness value, but a related parameter called transfer impedance. This standard wi

7、ll directly provide shielding effectiveness values up to 40 GHz, and will also be applicable for small samples of conductive EMI gaskets. A more detailed rationale concerning the validity of some standards is given in Appendix C of this document. INTRODUCTION Due to the impact of higher and higher f

8、requencies, characterization of shielding materials and components is needed up to the frequency range as occurring in actual electronic applications and products. Consequently, FCC recently published EMC emission limits up to the frequency of 40 GHz. In more, the direct radiated effects of small su

9、bassemblies and components such as the ones found on a PCB are becoming important. For this reason, an appropriate SE characterization of small in-circuit enclosures and the accompanying shielding gaskets at frequencies above 1 GHz is needed. 7KHVWDQGDUG,(6WGLVDJXLGDQFHGRFXPHQWRQFKRRVLQJDSSURSULDWHW

10、HV WPHWKRGVIRUFRQGXFWLYH(0,JDVNHWVand refers to the standardized methods such as MIL-DTL-83528C, ARP1173, and ARP1705. MIL-DTL-83528C and ARP1173 are dealing with SE measurements up to 18 GHz, but the methods proposed in these standards are not applicable for samples of small shielding components. T

11、he standard ARP1705B is dealing with the related parameter transfer impedance for conductive EMI gaskets up to the frequency of 10 GHz. But there is no clear and firm relationship between transfer impedance of conductive gaskets and the forthcoming shielding effectiveness. A method overcoming these

12、problems is proposed in this document, and is furthermore also in line with the recently published standards IEC 61967-8 and IEC 62132-8 on the characterization of integrated circuits for EMI emission and immunity. SAE INTERNATIONAL ARP6248 Page 2 of 25 TABLE OF CONTENTS 1. SCOPE 3 1.1 Purpose . 3 1

13、.2 Background . 3 2. REFERENCES 3 2.1 Applicable Documents 3 2.1.1 SAE Publications . 4 2.2 Other References and Publications 4 2.3 Definitions . 4 3. BASIS OF THE TEST METHOD 5 4. TEST Fixture . 6 4.1 Fixture Assembly . 6 4.2 Maximum Gasket Dimensions 9 4.3 Test Set-Up . 10 4.4 Dynamic Range . 10 5

14、. NOTES 12 5.1 Acronyms of Organizations . 12 5.2 Acronyms of Subjects . 12 5.3 Revision Indicator 12 APPENDIX A TEST PROCEDURE . 13 APPENDIX B CONSTRUCTION DETAILS AND FIGURES . 14 APPENDIX C DETAILED RATIONALE FOR THIS MEASURING PROCEDURE 23 APPENDIX D ALTERNATIVE VERSION OF A NON-CONDUCTIVE CLAMP

15、ING PLATE 25 FIGURE 1 PRINCIPLE SETUP OF THE STRIPLINE METHOD IN ORDER TO CHARACTERIZE ICS (LEFT) AND THE RESULTING STRIPLINE METHOD FOR GASKETS (RIGHT) . 5 FIGURE 2 OVERALL VIEW OF THE STRIPLINE SETUP 5 FIGURE 3 SCHEMATIC FIGURE OF A DIRECTIONAL COUPLER . 5 FIGURE 4A GLOBAL VIEW OF THE COMPLETE SET

16、UP . 6 FIGURE 4B EMBEDDED MICROSTRIP IN THE BASE PLATE 6 FIGURE 4C THE STRIPLINE, AND INSULATING SURFACES ON TOP OF THE BASE PLATE 7 FIGURE 4D THE CLAMPING PLATE IN ORDER TO COMPRESS THE GASKET UNDER TEST 7 FIGURE 4E TYPICAL SIZE OF A SAMPLE OF GASKET TO BE TESTED 7 FIGURE 5 POSITION OF THE 4 COAXIA

17、L PANEL SOCKET CONNECTORS WITH RESPECT TO THE SETUP, AND EXAMPLE OF PANEL SOCKET CONNECTOR 7 FIGURE 6A DETAILS FOR FIXING THE CLAMPING PLATE (UPPER) ON THE GND BASE PLATE (LOWER) . 8 FIGURE 6B DETAILS OF THE POSITIONING TAPS FOR THE CLAMPING PLATE 9 FIGURE 7 DETAILED VIEW SHOWING THE NON-CONDUCTIVE

18、SPACERS, TO CONTROL THE COMPRESSION OF THE GASKET . 9 FIGURE 8 DIMENSIONS OF THE SQUARE GASKET SAMPLES . 9 FIGURE 9 SCHEMATIC OVERVIEW OF THE TEST SETUP, FROM GENERATOR/AMPLIFIER TO THE RECEIVER 10 FIGURE 10A NOISE FLOOR OF THE RECEIVER AND THE COUPLING OF THE OPEN STRUCTURE, WITHOUT AND WITH A 30 d

19、B GAIN AMPLIFIER . 11 FIGURE 10B RESULTING DYNAMIC RANGE (DR) WITHOUT AND WITH A 30 dB GAIN AMPLIFIER . 11 SAE INTERNATIONAL ARP6248 Page 3 of 25 1. SCOPE 1.1 Purpose The purpose of this procedure is to establish a technique for reliably and repeatedly measuring the RF shielding characteristics of E

20、MI conductive gasket materials and EMI conductive gaskets. Depending on the materials used for the construction of the measuring setup, the EMI conductive gaskets can be characterized against various joint surfaces. This standard will directly provide shielding effectiveness values up to 40 GHz, and

21、 will also be applicable for small samples of conductive EMI gaskets. 1.2 Background MIL-DTL-83528C and ARP1173 are existing methods for accomplishing the goals expressed in 1.1, but are limited to an upper frequency of 18 GHz. Both methods consists of a larger (MIL-DTL-83528C) or smaller (ARP1173)

22、enclosure with an open window in one of the metallic walls of the enclosure. A solid metal clamping plate is used to close the window, and to clamp the gasket under test between this clamping plate and the enclosure wall. The gasket is placed around the periphery of the window. A source is placed wi

23、thin the enclosure and a receiving antenna located outside the enclosure. Beside the limited frequency range, there is the fact that the utility of data from measurements made using these techniques is limited, since the results depend upon the dimensions and construction of the enclosure, the detai

24、ls of the antennas used for both source and receiver, the size of the open window, the measuring environment (such as the location of the measuring enclosure in or outside a shielded room), as well as the performance of the gasket under test. Since the data is so dependent upon the test setup, it ca

25、nnot be accurately used in equipment design analysis. ARP1705 is using another measuring test setup in order to define a parameter related to the shielding effectiveness of EMI conductive gaskets. The method was originally limited to an upper frequency of 1 GHz and has recently been expanded up to 1

26、0 GHz. Although there is a close relationship between the global conductivity of the complete system of the two surfaces and the clamped gasket in between and the provided shielding effectiveness, there is no firm one-to-one relationship which makes it not possible to be accurately used in equipment

27、 design analysis. The stripline test method presented in this document offers an attractive alternative to any of the radiated field methods and to the transfer impedance method for evaluating EMI conductive gaskets, over a wide frequency range from 100 MHz up to 40 GHz in one measuring sweep. The m

28、ethod yields data which are directly related to the design and test procedures of small subassemblies, shielding compartments and cavities of larger systems, and components such as the ones found on a PCB. Additional theory can be found in the publications referenced in 2.2 of this document. The str

29、ipline test method offers a great repeatability for evaluating EMI conductive gaskets, and has the advantage of requiring no specific measuring environment and less laboratory equipment such as antennas, and is very compact and easy to handle. It is also a broadband measuring setup, covering a frequ

30、ency range from 100 MHz up to 40 GHz at once. By allowing a lower dynamic range, the lower frequency limit is even below 100 MHz. 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

31、apply. The applicable issue 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 applicab

32、le laws and regulations unless a specific exemption has been obtained. SAE INTERNATIONAL ARP6248 Page 4 of 25 2.1.1 SAE Publications Available from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or +1 724-776-4970 (outside USA), www.sa

33、e.org. ARP1173 Test Procedure to Measure the R.F. Shielding Characteristics of E.M.I. Gaskets ARP1705 Coaxial Test Procedure to Measure the RF Shielding Characteristics of EMI Gasket Materials ARP1705B Coaxial Test Procedure to Measure the RF Shielding Characteristics of EMI Gasket Materials 2.2 Oth

34、er References and Publications 2.2.1 ,(6WG - ,(*XLGHIRUWKH Electromagnetic Characterization of Conductive Gaskets in the Frequency Range of DC to 18 GHz,(November 2008. 2.2.2 MIL-DTL-83528C - *HQHUDO6SHFLILFDWL on for Gasketing Material, Conductive, Shielding Gasket, Electronic, Elastomer, EMI/RFI,

35、. 2.2.3 J. Catrysse et al. 7RZDUGV D JOREDO D pproach for the FKDUDFWHULDWLRQ RI ,&V DQG RQ ERDUG VKLHOGLQJcomponents,3URFHHGLQJV(0&(XURSH:URFODZ September 2010. 2.2.4 -&DWUVVHHWDO(SDQGLQJWKHVWULSOLQHPHDVXULQJVHWXS for the characterisation of conductive gaskets up to 40 GHz,Proceedings IEEE EMC Inte

36、rnational Symposium 2012. 2.2.5 J. Catrysse et al., “A measuring setup for the characterisation of in circuit conductive gaskets up to 40 GHz,Proceedings EMC Europe 2012, Roma, September 2012. 2.2.6 J. Catrysse et al.7KHLPSRUWDQFHRIFRQWLQXRXVDQGKRPRJHQHRXVJDVNHWFRQGXFWLYLWXSWR *+,3URFHHGLQJVEMC Euro

37、pe 2013, Brugge, September 2013. 2.2.7 D. Pissoort et al., “Correlating the High-Frequency shielding performance of on-board gaskets when measured using a stripline or reverberation room method,“ Proceedings IEEE EMC International Symposium 2014. 2.2.8 B. Koerber et al. ,&-stripline: A QHZ SURSRVDO

38、IRU VXVFHSWLELOLW DQG HPLVVLRQ WHVWLQJ RI ,&V , 3URFHHGLQJVEMCcompo 2007. 2.2.9 IEC 61967-8 ed. 1, Integrated Circuits - measurements of electromagnetic emissions - part 8: measurement of radiated emissions - IC stripline method. 2.2.10 IEC 62132-8 ed. 1, Integrated Circuits - measurements of electr

39、omagnetic immunity - part 8: measurement of radiated immunity - IC stripline method. 2.3 Definitions 2.3.1 SHIELDING EFFECTIVENESS (EMC) For a given external source, the ratio of the electric of magnetic field strength at a point before and after the placement of the shield in position (IEEE Standar

40、d Directory of Electrical and Electronic Terms, p. 528, 1972). For the purpose of this measurement methodology, it is referred to the standard MIL-DTL-83528C (clause 4.5.12) which uses a same approach: “Shielding Effectiveness is defined as the ability of a gasket to electrically bond a test cover p

41、anel to an enclosure flange such that radiated RF is attenuated.“ Consequently, the results of this measurement methodology includes contributions from the gasket material itself as well as the clamping plate. SAE INTERNATIONAL ARP6248 Page 5 of 25 3. BASIS OF THE TEST METHOD Based on work by B. Koe

42、rber, a test methodology has been standardized for emission and susceptibility testing of ICs: IC stripline method (IEC 61967-8 ed. 1 and IEC 62132-8). See also References 2.2.8 through 2.2.10. The method is based on putting a stripline over a PCB board with a full GND layer, so that susceptibility

43、or emission of an integrated circuit may be characterized. The principle of the setup is sketched in Figure 1. Figure 1 - Principle setup of the stripline method in order to characterize ICs (left) and the resulting stripline method for gaskets (right) By replacing the IC under test by a 50 ohm micr

44、ostrip, and a plate to clamp and compress a gasket to the chassis of the system, a basically matched measuring setup is obtained. Principally, matching is not an essential issue in this concept, but it will avoid the occurrence of high standing waves over the whole frequency range, although good mat

45、ching is only obtained in the lower frequency range. A picture of the setup is shown in Figure 2. Figure 2 - Overall view of the stripline setup Both the microstrip and the stripline have one load of 50 ohm, so that the setup may be considered as a 2-port circuit. The open structure can be modelled

46、as a set of two asymmetrical coupled lines, with a common reference GND conductor, as sketched in Figure 3. Figure 3 - Schematic figure of a directional coupler GND layer Active stripline SAE INTERNATIONAL ARP6248 Page 6 of 25 It is a well-known characteristic of these geometries that sharp uncoupling at one of the ports may occur at a given frequency. This means that some sharp resonant effects may occur in the measurement graphs, and they should be disregarded with respect to the characteristic properties of the gasket.