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1、ANSI C63.7-1988 guide for construction of open area test sites for performing radiated emission measurements October 31. 1988 SH12237 Authorized licensed use limited to: Peking University. Downloaded on December 26,2010 at 16:19:18 UTC from IEEE Xplore. Restrictions apply. Authorized licensed use li
2、mited to: Peking University. Downloaded on December 26,2010 at 16:19:18 UTC from IEEE Xplore. Restrictions apply. ANSI C63.7-1988 American National Standard Guide for Construction of Open Area Test Sites for Performing Radiated Emission Measurements Accredited Standards Committee On Electromagnetic
3、Compatibility, C63 accredited by the American National Standards Institute Secretariat Institute of Electrical and Electronics Engineers, Inc Approved June 16, 1988 American National Standards Institute Published by The Institute of Electrical and Electronics Engineers, Inc 345 East 47th Street, New
4、 York, NY 10017, USA Authorized licensed use limited to: Peking University. Downloaded on December 26,2010 at 16:19:18 UTC from IEEE Xplore. Restrictions apply. American National Standard Approval of an American National Standard requires verification by ANSI that the requirements for due process, c
5、onsensus, and other criteria for approval have been met by the standards developer. Consensus is established when, in the judgment of the ANSI Board of Standards Review, substantial agreement has been reached by directly and materially affected interests. Substantial agreement means much more than a
6、 simple majority, but not necessarily unanimity. Consensus requires that all views and objections be considered, and that a concerted effort be made toward their resolution. The use of American National Standards is completely voluntary; their existence does not in any respect preclude anyone, wheth
7、er he has approved the standards or not, from manufacturing, marketing, purchas- ing, or using products, processes, or procedures not conforming to the standards. The American National Standards Institute does not develop standards and will in no circumstances give an interpretation of any American
8、National Standard. Moreover, no person shall have the right or authority to issue an interpretation of an American National Standard in the name of the American National Standards Institute. Requests for interpretations should be addressed to the secretariat or sponsor whose name appears on the titl
9、e page of this standard. CAUTION NOTICE: This American National Standard may be revised or withdrawn at any time. The procedures of the American National Stand- ards Institute require that action be taken to reaffirm, revise, or withdraw this standard no later than fwe years from the date of approva
10、l. Purchasers of American National Standards may receive current information on all standards by calling or writing the American National Standards Institute. Copyrght 1988 by The Institute of Electrical and Electronics Engineers, Inc 345 East 47th Street, New York, NY 10017, USA No part o f this pu
11、blication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior written permission o f the publisher. Authorized licensed use limited to: Peking University. Downloaded on December 26,2010 at 16:19:18 UTC from IEEE Xplore. Restrictions apply. Foreword (This
12、Foreword is not part of ANSI C63.7-1988.) ANSI C63.4, Methods of Measurement of Radio-Noise Emissions from Low-Voltage Electrical and Elec- tronic Equipment in the Range of 10 kHz to 1 GHz, has undergone several revisions since the original document covering methods of measurement was produced in 19
13、40. While many improvements were made in the standard from time to time, the reproducibility of measurements of radiated interference from one test site to another has not been completely satisfactory. In 1982 a concerted effort was organized in Subcommittee One of the Accredited Standards Committee
14、 C63, to determine how the technique could be improved. Evidence showed that the variability was due, in part, to inadequate a) control of site ground plane conductivity, flatness, site enclosures, effects of surrounding objects, and certain other site construction features, b) accounting for antenn
15、a factors, associated cabling, and balun and device under test characteristics, and c) consideration of mutual coupling effects between the device under test and the receiving antenna and their images in the ground plane. Accordingly ANSI C63.4 is being revised, and ANSI C63.5, Standard Calibration
16、of Antennas Used for Radiated Emission Measurements in Electromagnetic Interference (EMI) Control, and C63.6, Guide for the Computation of Errors in Open Area Test Site Measurement, are in preparation to provide additional information. This document provides guidance information on the construction
17、of a suitable test site. At the time this document was approved, members of Task Group on Open Area Test Sites were as follows: D. N. Heirman A. A. Smith, Jr Edwin L . Bronaugh, Chairman s. Linkwitz G. Dash L. A. Wall R. A. Magnuson At the time that the Accredited Standards Committee on Electromagne
18、tic Compatibility, C63 approved this standard it had the following membership: Ralph M. Showers, Chairman Edwin L. Bronaugh, Vice Chairman Fred Huber, Secretary Organization Represented Aeronautical Radio,Inc American Council of Independent Laboratories, Inc Association of American Railroads . Assoc
19、iation of Home Appliance Manufacturers. . Association of Telecommunication Attorneys. . AT when preceded by B, they correspond to the bibliography i n Section 9. 2This ANSI-approved standard is unavailable at the time of this publication. When published, it will become part of the references of this
20、 standard. 3ANSI publications, wher available, may be purchased from the Sales Department, American National Standards Institute, 1430 Broadway, New York, NY 10018. 2 ANSI C63.5-1988, Standard for Calibration of Antennas Used for Radiated Emissions Measure- ments in Electromagnetic Interference (EMI
21、) Control.2 4. General Considerations Paragraph 4.1 of 11 lists general conditions for test sites and in particular open area test sites (OATS). To summarize, radiated emission tests can be performed in an open, flat area character- istic of cleared, reasonably level terrain. Alternate sites might i
22、nclude a raised platform, roof-top site, an open area such as a large factory floor, relatively clear of obstructions that could adverse- ly affect the measurements, or an effectively absorber-lined shielded room which is also free of undesired reflections from the walls and ceiling. The preferred t
23、est site is an OATS which is inter- nationally recognized as the standard for making radiated emission measurements (see B3). Such open area sites should be void of buildings, electric lines, fences, trees, etc, and free of under- ground cables, pipelines, etc, except when using a metallic groundpla
24、ne which isolates the adverse effects of such underground metallic objects. Services to operate the equipment under test (EUT) and the cabling to the receive antenna should be trenched into the earth if no metallic ground plane is used. The following describes key recommendations for site selection,
25、 ground plane, instrumentation and EUT services, and all-weather covers. These recommendations have been used by several OATS users to ensure adequate test sites. 5. Obstruction-Free Area An obstruction-free area surrounding the EUT and field strength measuring antenna is required. The obstruction-f
26、ree area should be free from sig- nificant scatterers of electromagnetic fields, and should be large enough so that scatterers outside the obstruction-free area will have little effect on the fields measured by the field strength measuring antenna. The definitive test of the 6 Authorized licensed us
27、e limited to: Peking University. Downloaded on December 26,2010 at 16:19:18 UTC from IEEE Xplore. Restrictions apply. obstruction-free area is to perform normalized site attenuation measurements indicated in 11. Since the magnitude of the field scattered from an obstruction depends on many factors (
28、size of the obstruction, distance from the EUT and receiv- ing antenna, orientation with respect to the EUT and receiving antenna, conductivity and permit- tivity of the obstruction, frequency, etc), it is impossible to specify an obstruction-free area which is necessary and sufficient for all appli
29、ca- tions. However, a reasonable guide is given in the following paragraphs. The size and shape of the obstruction-free area are dependent upon the measurement distance and whether or not the EUT will be rotated. If the site is equipped with a turntable, the recom- mended obstruction-free area is an
30、 ellipse with the receiving antenna and EUT at the two foci and having a major axis equal to twice the mea- surement distance and a minor axis equal to the product of the measurement distance and the square root of three (see Fig 1). For this ellipse, the path of the undesired ray reflected from any
31、 object on the perimeter is twice the length of the direct ray path between the foci. Twice the length implies that the scattered signal at the boundary will be at least 6 dB down from the direct signal between the EUT and receiving antenna and hence have a minimal impact on the direct path measurem
32、ent. If a large EUT is installed on the turntable, the obstruction-free area must be ANSI C63.7-1988 expanded so that the obstruction clearance distances exist from the perimeter of the EUT. The effects of test site construction including inadequate obstruction-free area, improper groundplane constr
33、uction and sizing, and other site defects are discussed in (B2 and B6. If the site is not equipped with a turntable, that is, the EUT is stationary, the recommended obstruction- free area is a circular area such that the radial distance from the boundary of the EUT to the boundary of the area is equ
34、al to the measurement distance multiplied by one and one-half (see Fig 2). In this case, the receiving antenna will be moved about the EUT and the 1.5 times the mea- surement separation distance will provide a clear area behind the antenna away from the EUT equivalent to that in Fig 1. The terrain w
35、ithin the obstruction-free area should be flat, but does not have to be horizontal. Small slopes needed for adequate drainage may be acceptable. (See 6.2 for a discussion of flatness requirements.) 6. GroundPlane 6.1 Size and Shape of Ground Plane. The size and shape of the reflecting surface, or gr
36、ound plane, are dependent upon the measurement geometry and whether or not the EUT can be Fig 1 Obstruction-Free Area for OATS with a Turntable 4 MAJOR DIAMETER 2 R 0 / / / / / R/2 ANTENNA / . I MINOR DIAMETER = f l R 7 Authorized licensed use limited to: Peking University. Downloaded on December 26
37、,2010 at 16:19:18 UTC from IEEE Xplore. Restrictions apply. ANSI C63.7-1988 GUIDE FOR CONSTRUCIION OF OPEN AREA TEST SITES / / / / BOUNDARY OF OBSTRUCTION-FREE /AREA / / / I .- Fig 2 Obstruction-Free Area for OATS with Stationary E U T . rotated. In general, the reflecting surface is con- tained who
38、lly within the obstruction-free area. However, it is prudent to construct the ground plane so that it may be extended in a l l directions if needed. For a site equipped with a turntable, the theo- retically minimum ground plane size and shape is that of the first Fresnel ellipse. See Appendix A for
39、a discussion of Fresnel ellipses, Fig A1 and footnote for a descriptive picture, and Table 1 for dimensions of several representative ellipses. Practical experience indicates that rectangular ground planes having length and width dimen- sions substantially less than the Fresnel ellipse dimensions sh
40、own in Table 1 are satisfactory, For example, 3 shows a 6 m X 9 m ground plane for making 3-m measurements. Table 1 indicates that at 30 MHz the ellipse is 9.9 m X 9.5 m which for certain areas of the ellipse is larger than the rec- tangular 6 m X 9 m size (which is generally ade- quate for measurem
41、ents). In fact, the Fresnel ellipse is also larger than the obstruction-free area in Fig 1. The Fresnel ellipse dimensions should, therefore, be used only as a guide and the adequacy of an actual ground plane should be determined using the site characterization pro- cedure and acceptability criterio
42、n given in l. Again, it may be prudent to have the capability to extend the ground plane up to the dimensions of the Fresnel ellipse. If the site is not equipped with a turntable and the receiving antenna must be moved around the EUT, a circular ground plane is recommended. The radius of the ground
43、plane derived by rotat- ing the first Fresnel ellipse about the source focal point is given by R = Xo+X1 where Xo = distance from the closest point of the EUT to the center (midway between the two foci) of the first Fresnel ellipse XI = length of semi-major axis of Fresnel ellipse (see Table 1) For
44、example, for a 3-m measuring distance, use of the calculated Fresnel ellipse major axis from Table 1 in the above equation (R = 1.4 + - = 6.35m) results in a ground plane that is larger than the obstruction-free area radius given in Elg 2 at a frequency of 30 MHz, that is, 1.5 m X 3 m = 4.5 m. 9.9 2
45、 8 Authorized licensed use limited to: Peking University. Downloaded on December 26,2010 at 16:19:18 UTC from IEEE Xplore. Restrictions apply. FOR PERFORMING RADIATED EMISSION MEASUREMENTS ANSI C63.7-1988 Table 1 Dimensions for Several Representative Measurement Conditions Ellipse Ellipse Center Axe
46、s (m) (Mk) (m) Major Minor (Note 2) (m) (m) R hl hz =1 2 Yl XO (Note 1) 100 5.9 5.3 1.2 lo00 4.0 3.4 1 .o 10 30 2 4 16.3 13.0 4.9 100 12.4 8.0 4.7 lo00 10.6 5.6 4.5 Measurement Antenna Distance Frequency Heights 3 30 1 4 9.9 9.5 1.4 30 30 2 6 34.6 19.1 14.4 100 29.2 11.4 13.5 1000 24.6 6.6 11.8 NOTE
47、S (1) The dimensions of the first Fresnel ellipse calculated for the 3-m measurement dis- tance at 30 MHz are larger than the recommended obstruction-free area ellipse dimensions in Fig Al. See 6.1 for further discussion. (2) X” i s the distance from the position of the EUT to the center of the firs
48、t Fresnel ellipse. (See Fig Al.) 6.2 Smoothness of Ground Plane. The Rayleigh roughness criterion described in Appendix B pro- vides a useful estimate of maximum allowable rms ground plane roughness (see Fig Bl)? Some examples for representative geometries are given in Table 2. For most practical te
49、st sites, especially for 3-m separation applications, up to 4.5 cm (1.8 in) of “valleys” are not significant. Clearly, any site reasonably graded would meet this cri- terion. The obvious exceptions would be raised ground planes where the edge would probably exceed the 4.5 cm. For those cases, site attenu- ation measurements as described in l would have to be measured to determine the impact of exceeding the roughness criterion. As can be seen in Table 2, the roughness for the 10-m and 30-m separations is not as restrictive as that for