A Comparison of the First Three Editions of CISPR 22

In order to comply with FCC Part 15 and CISPR 22, the differences between the current version of CISPR 22 and the version used by FCC must be understood.

For a decade and a half, CISPR 22 (standard number 22 of the International Special Committee on Radio Interference of the International Electrotechnical Commission [IEC]) has been the dominant international standard for radiated- and conducted-emissions testing. It is very much a living document, as it has moved through three editions since it first appeared in 1985. Several intermediary versions, containing specific modifications, have been used in conjunction with the various editions and have typically been incorporated into the next formal edition. The first set of these modifications was referred to as the central office (CO) papers because they were logged and issued by the CISPR central office in Geneva (they are also referred to as the draft international standards papers). In the same way, the current (third) edition, published in 1997, assimilated amendments published in 1995 and 1996, and work continues toward a fourth edition of CISPR 22.

Meanwhile, a general worldwide trend toward regulatory harmonization of electromagnetic interference (EMI) and other requirements continues, driven largely by a desire to reduce regulatory barriers to trade. For example, Donald Heirman traces the convergence of ANSI C63.4 with CISPR 22 over the last 10 years and believes that it's now possible to show product compliance with either procedure.¹ William Hurst also examines regulatory harmonization by comparing conducted- and radiated-emission limits between FCC and CISPR 22.²

Regulatory harmonization reduces the testing burden for affected products by removing the need for redundant testing, the removal of which decreases time to market. However, situations such as that in the United States, where obsolete versions of CISPR 22 are still referenced, delay harmonization and increase time to market. In fact, the FCC EMI rules in 47 CFR Part 15 still incorporate one of the intermediary versions of CISPR 22. Sections 15.107 and 15.109 currently refer to the first (1985) edition of CISPR 22 as modified by the CO papers as an alternative to following unique FCC procedures.^3–5 This presents a problem, however, because the 1985 edition is no longer in print and the CO papers are not generally available.

To facilitate greater harmonization, it is helpful to first understand the differences between versions of CISPR 22. This article seeks to clarify the differences that separate the current edition and the one used by FCC. The methodology used was first to show that the version quoted in Part 15 is substantially identical to the second edition, then to compare the second and third editions. For the purposes of this analysis, it is adequate to compare the second and third editions of CISPR 22, rather than comparing the third edition to the first edition plus the CO papers, because:

• After a careful examination of the CO papers and their impact on the second edition, it seems clear that the relevant changes proposed in the CO papers were substantively incorporated into the second edition (see Table I). The only exceptions were as follows: editorial changes, which did not affect the substance of the changes but did affect the wording and clarity of the changes, their location in the second edition, or references to updated standards; implicit exclusion, including two occasions (relating to conducted and radiated emissions in CO paper no. 9) in which language that would explicitly exempt regulation of certain frequency ranges is implicit in the second edition; and irrelevant exclusion, including proposed language (to include telephone PABX equipment as Class B equipment, CO paper no. 12) that does not appear in the second edition of CISPR 22 and is largely irrelevant (because Class B is designated to residential equipment, and PABXs are seldom installed in homes).
• A comparison of the first and second editions of CISPR 22 (see sidebar) shows that all additional changes not covered in the CO papers are insignificant or irrelevant to the issue at hand.
• FCC's report and order that modified Part 15 to include the language referring to the first edition of CISPR 22 plus the CO papers was issued very near to the publication date of the second edition.⁶ The report and order appeared in the Federal Register for October 1, 1993, and the second edition of CISPR 22 is dated December 1993.^7,8 Due to the brevity of the interim period, it is unlikely that additional modifications came out during this period.
• Art Wall (Policy & Rules Div., Office of Engineering and Technology, FCC) affirmed that the second edition was predominant by telling me in private correspondence: "The CISPR central office documents referenced in the FCC Rules are actually the documents contained in CISPR 22 (second edition). Look at page 5 of the second edition. At the time the rules were adopted, the second edition had not been released. Unfortunately, we have [not] yet gotten around to updating the rules....I have the original documents, but I don't think they are needed, since all are contained in the second edition of CISPR 22."

Paper No.	Pub. date	Description of proposed change to CISPR 22 Ed. 2	How it appears in CISPR 22 Ed. 2
2	Dec. 1986	a. In preface, delete references to CISPR publications 7B (1975) and 11 (1975).	"Normative References" section added instead of preface. References included CISPR publication 11 (1990) but not 7B.
		b. Modify wording in Section 7 interpreting RFI limits relating to significance of limits, tests required, and statistical compliance (the 80/80 rule).	Became Section 8, "Interpretation of CISPR radio disturbance limit." Language nearly identical to that proposed, with additional small changes. Specifically, reference was made to equipment instead of appliance. Several editorial differences were also made (e.g., a reference to CISPR 16 in the CO paper was moved to the "Normative References" section in Ed. 2).
		c. Open-area test site ground-plane requirements and physical layout specified (changed reference point for determining antenna-to-equipment distance).	Section 10.3 of Ed. 1 became 11.3 in Ed. 2. Language in CO paper editorially modified but substantively identical in Ed. 2. Drawing of ground plane (Figure 3) changed in Ed. 2 to as shown in CO paper.
5	Jan. 1988	In section 7.1.2 of wording proposed in CO paper no. 2, this paper proposed deleting the words: "for type approved appliances" when referring to that for which the RE limits are significant.	Wording in question appears in Section 8.1.2 of Ed. 2. Proposed deletion appears as "for equipment..." and may be more editorial than substantive.
9	May 23, 1990	a. Increase frequency range specified in "Scope" from 0.15–1000 MHz to 9 KHz–400 GHz and specify that no limits apply outside this range.	Shown in "Scope" as written, with minor editorial changes from CO paper./TD>
		b. Add note in Section 4.1 explicitly saying that no CE limits apply for 9–150 kHz.	Language does not appear in Ed. 2. However, while not explicitly included, it is implicit because frequency range covered is specified.
		c. Add note to Section 5 explicitly saying that no RE limits apply for 0.15–30MHz.	Language does not appear in Ed. 2. However, while not explicitly included, it is implicit because frequency range covered is specified.
		d. Change quasi-peak RE limits for 30-m measurements of Class A equipment (Table III of Section 5).	Changed as proposed (became Table 3 in Section 6).
		e. Replace language in Section 8 on dealing with ambient noise.	Change as proposed with additional editorial revision (became Section 9).
		f. Add language after that existing in Section 10.3.4 regarding applicability of measurements from large equipment at site of installation.	Changed as proposed (became last paragraph in Section 11.3.6).
11	Aug. 23, 1991	Replace language in Section 2.1 defining information technology equipment (ITE) and excluded equipment.	Changed as proposed, with additional editorial revision (became Section 3.1).
12	Aug. 23, 1991	Replace language in Section 3 classifying and defining A and B classes of ITE.	Changed as proposed, with editorial revision, except telecom PABXs and auxiliary connected equipment were dropped from the list of Class B equipment and Class B was designated as equipment intended for domestic environments (appears in Section 4).
13	Aug. 23, 1991	Replace language in Section 9.3 specifying the ground plane for terminal-voltage measurements, including ground-plane dimensions and distance from EUT.	Changed as proposed, with additional editorial revision (became Section 10.3). This also affected the language in Section 11.2.1 describing antenna-to-EUT distance.
14	Aug. 23, 1991	a. Replace language in Section 10.3.1 through 10.3.3 defining physical and other requirements for open-area RE-measurement sites, and acceptance criteria for site attenuation measurements.	Changed as proposed, with additional editorial revision. (Section 10.3 became 11.3 in Ed. 2.)
		b. Insert new annex specifying site attenuation measurements for alternate test sites, including use of broadband antennas.	Changed as specified, with additional editorial revision. (Annex appears as normative Annex A in Ed. 2.)

Table I. Summary of changes proposed by CISPR/G in the central office (CO) papers referenced in 47 CFR Sections 15.107 and 15.109.

Comparing the Second and Third Editions

The third edition of CISPR 22 contains much more detail than the second edition. New annexes were added and coverage of telecommunications equipment testing was expanded. In the third edition, telecom equipment is regarded as a type of information technology equipment, to the extent that it is subject to certain conducted-emissions tests. Many procedures in the second edition were expanded or elaborated upon, clarifying test methodology and reducing interpretive variability. What follows is a comparison of differences between the second and third editions of CISPR 22.⁹ Most editorial, nontechnical, or other revisions that do not significantly affect substance are not included below on a case-by-case basis. This comparison is interpretive; that is, interpretations of the changes are given rather than a verbatim listing of the changes. References to the affected sections, figures, or tables were made to assist readers who need exact wording differences.

Normative. Annexes B and C are new in the third edition and form an integral part of CISPR 22. Annex B covers the decision tree for peak detector measurements, and Annex C covers possible test setups for common-mode measurements.

Informative. Annexes D and E were also added. Annex D describes the schematic diagrams of impedance stabilization networks (ISNs), and Annex E covers parameters of signals at telecommunications ports.

Normative References. The normative references list (Section 2) was revised and updated as follows:

• Standards for plugs and sockets were changed from IEC 83:1975 to IEC 60083:1997.
• IEC 61000-4-6:1996, Part 4 (EMC test techniques) and Section 6 (conducted immunity) were added.
• Reference to CISPR 16:1987 (measuring apparatus and methods) was dropped. However, a reference to this document was retained with the table of k-values used in the 80/80 rule statistics in Section 7 of the third edition.
• Reference to CISPR 16-2 Part 2 (measuring apparatus and methods) was updated to the 1996 edition.
• CCITT V.24:1993 was dropped.
• ISO/IEC 11801:1995 (customer premises cabling for IT) was added.
• Reference to CISPR 16-1:1993 Part 1 (RF disturbance and immunity apparatus) was retained without change.

Disturbance Power Limits. "Limits for disturbance power" (second edition, Section 7) was dropped (this was the absorbing clamp test used in certain countries). This resulted in a downward shift in the section numbering scheme from Section 7 on. For example, the material in Section 8 of the second edition appears in Section 7 of the third edition, and so forth.

EUT Configuration. The EUT configuration during testing was significantly revised (Sections 8.1 and 10.4 in the third edition). The requirement to maximize the emissions by manipulating cables or equipment configuration was eliminated in favor of configurations that were "consistent with typical applications." The need to document the configuration so it can be reproduced was retained. Procedures for determining typical configurations for modular equipment or systems of several pieces of equipment were clarified. Detailed examples of configurations for PCs, their peripherals, and point-of-sale terminals were added. Specific requirements for testing separately marketed PC boards (e.g., PC adapter cards or the equivalent) in representative hosts were added.

A new subsection (8.1.1) discusses the determination of maximum emission configuration for both conducted and radiated measurements. The subsection references 11 new drawings (Figures 4–14) describing typical initial equipment and cable placement. These drawings, one each for conducted disturbance (Section 9.3) and radiated disturbance (Section 10.4), are also referenced in new equipment setup sections. The subsection specifies separation distances between equipment and both vertical and horizontal ground reference planes.

EUT Operation. EUT operation during both conducted and radiated testing is detailed in a new section (8.2 in the third edition) that includes advice on computer test programs, rules for operating visual display devices, and parameters for the operation of facsimile devices and telephone sets. Again, the fundamental requirement seems to be intended for typical operation, but EUT exercising should "permit detection of all system disturbances" and "generate the greatest level of emission" or "full disturbance potential."

Conducted-Disturbance Measurement. In the measurement of conducted disturbances (Section 9 in the third edition), a recommendation was added that measurements be performed in a screened enclosure. Also, the use of a peak detector as an alternative to the quasi-peak (QP) or average detectors was permitted to reduce test time. However, in disputed cases, the QP or average detector methods and limits take precedence. The decision tree is elaborated in Annex B.

Telecom Port Disturbance. New telecommunications port conducted-disturbance tests were added to the third edition (Tables 3 and 4 in Section 5, Section 9.5, and Annexes C, D, and E). Telecom ports are defined as ports intended for connection to telecommunications networks, which include the public-switched telephone network and local-area networks. Conducted measurements are limited to common mode. Anyone anticipating doing these measurements should make a detailed study of the limits, ISN specifications, and annexes.

Each telecom port is connected to an ISN, typical auxiliary equipment, or an appropriate simulator. (In the case of a simulator, the actual common-mode impedance represented must be measured and stated in the test report.) Annex D includes general performance parameters for suitable ISNs (Section 9.5.2 of the third edition). Schematic diagrams are also shown in the annex (an "informative" annex, such that the ISNs described are only suggested designs). Two alternative methods for conformance testing using ISNs are offered (Sections 9.5.1.1 and 9.5.1.2), with the second alternative designated for Category 3 and Category 5 data cables. The principal difference in these alternatives appears to be the longitudinal (i.e., common mode) conversion loss specified for the ISNs. When ISNs are not suitable, other alternative common-mode measurement methods are given in normative Annex C.

New telecom port disturbance limits are given (Tables 3 and 4) and must be met in addition to previously existing limits for mains (ac) ports (Tables 1 and 2). To comply, equipment with telecom ports can meet either of the specified voltage and current limits for asymmetric-mode disturbance, except that both limits must be met when using a new current and voltage probe method described in Annex C (Section C.1.3). Guidelines for test traffic levels are given (Section 9.5.3).

Test Reports. Test reports need only include the six highest conducted and radiated emissions of all EUT emissions within 20 dB of the limits (Sections 9.6 and 10.5 of the third edition, respectfully).

Multiple Line Cords. For EUTs with multiple line cords, language was added (Section 9.2e in the third edition) specifying that line cords not under test may be connected to a multiple outlet, which must then be connected to another artificial mains network (AMN) separate from the AMN used for the line cord under test.

Open-Area Test Sites and Screened Enclosures. To clarify conducted-emissions measurements at open-area test sites or screened enclosures, a sentence was added (Section 9.3, "Ground Planes," of the third edition), specifying the distance to the horizontal ground plane as 0.4 m. Otherwise, the language in this section is identical in both editions. (The 0.4-m distance in CISPR 22 varies from the distance required by the test methods in ANSI C63.4:1992. The 0.4-m distance brought CISPR 22 into line with other CISPR standards that also specify this distance.)

Equipment Requirements. Equipment requirements in the third edition refer to later versions of CISPR 16. For example, rather than referencing CISPR 16, the third edition requires measuring receivers to operate in accordance with CISPR 16-1 and 16-2. Similarly, the third edition requires the use of AMNs defined in CISPR 16-1, Clause 11.3. The description of the AMN and EUT configuration appears to be the same in both editions, with clarity provided by the new EUT configuration drawings (see "EUT configuration," above).

For radiated-disturbance measurements, receivers with peak detectors and passbands in accordance with Clauses 2 and 3 of CISPR 16-1 are permitted instead of QP detectors (introduction to Section 10 of the third edition). However, in disputed cases (e.g., high emissions) QP measurements take precedence.

Conclusion

International regulatory harmonization will clearly be enhanced by the use of international standards such as CISPR 22, but without deviations, as it is highly unlikely that deviations will be accepted uniformly everywhere. For example, CENELEC has adopted a version of CISPR 22, with deviations, as EN 55022:1998 for Europe (effective 2001), whereas China has adopted the third edition of CISPR 22 without deviations (effective December 1, 1999, but with a delayed adoption of the telecom port measurements).

Industry and consumers are better served by a single, worldwide set of technical requirements implemented with a reasonable transition period to allow industry to catch up without delaying new product development. As a suggestion, a reasonable transition period for information technology products or platforms would be no less than 2 years. This would help prevent regulatory compliance from becoming a moving and continuously changing target for product development teams.

Although undesirable, deviations are not unexpected. Indeed, its originators expected adoption of CISPR 22 with national deviations. In the foreword of the 1985 edition, it says, "all National Committees should adopt the text of the CISPR recommendations for their national rules insofar as national conditions will permit. Any divergence between the CISPR recommendations and the corresponding national rules should, as far as possible, be clearly indicated in the latter." However, the EN version (EN 55022), with its reduced and modified requirements, may be of limited usefulness in practice, because it seems likely that most other countries with regulation regimes in place will, over time, switch to the latest version. China's recent adoption of the third edition without deviations is one example.

Harmonization of national standards to international standards, without deviation, will reduce barriers to trade and minimize time to market. The time and place to address specific issues with a standard (such as the discomfort over the third edition's telecom port tests) are in the standard's originating committee, because useful standards are living standards—under continual revision.

Differences between the first (1985) and second (1993) editions of CISPR 22, in addition to the changes proposed by the CISPR/G central office papers Structure. The organization of the two documents differs. For example, the second edition adds separate sections for scope, normative references, and definitions, incorporating some of the material contained in the preface of the first edition. Section Numbering. The organizational changes forced changes in section numbering throughout the document. In general, material after Section 3 in the first edition appears in a section of the second edition numerically increased by one. References. Additional references were added or updated. For example, a reference to CISPR 16 (1975) in the first edition was updated to the 1987 version in the second edition, and a reference to CCITT V.24 (1993) was added. Definitions. Several definitions were clarified or updated. For example, the definition of ITE was expanded, and EUT is used in the second edition instead of test unit. Terminal interference became conducted disturbance, and radiated interference became radiated disturbance. Measuring Distance. Class A radiated-disturbance measuring distance was changed from 30 m to 10 m, and the limits were proportionally changed by approximately the amount (10 dB) calculated by the difference in the distances and assuming a 1/r E-field relationship. This change also affects Section 11.3.6 of the second edition, changing the distance for user installation testing to 10 m. For small products, where the 1/r E-field relationship is valid over the 10–30-m range, this change makes the measurement more convenient but does not significantly change the requirement burden. AMNs. In Section 10.2, "Artificial Mains Network," of the second edition, the following new paragraph appears: "Conducted disturbance is measured between the phase lead and the reference ground, and between the neutral lead and the reference ground. Both measured values shall be within the appropriate limits." Although not included in the first edition, this description was probably intended but not explicitly stated. Therefore, it seems safe to assume that it was included in the second edition to provide clarity rather than to describe a significant change. High Ambient Signals. In Section 11.4, "Measurement in the presence of high ambient signals," of the second edition, a new alternative method appears that was not in the first edition or the CO papers: "b) In the frequency bands where the ambient noise values of clause 9 are exceeded (measured values higher than 6 dB below the limit), the disturbance values of the EUT may be interpolated from the adjacent disturbance values. The interpolated value shall lie on the curve describing a continuous function of the disturbance values adjacent to the ambient noise." This is not a requirement ("may be interpolated") but is presented as an advisory comment or helpful note. It merely expands upon situations described in the first edition. Consequently, it seems safe to conclude that it does not constitute a significant change.

References

1. Donald N Heirman, "ANSI C63.4 and CISPR 22—Harmony at Last?" in Proceedings of the IEEE EMC Symposium (Austin: IEEE EMC Society, 1997), pp. 112–117.

2. William S Hurst, "Comparison of FCC Limits with CISPR Limits," CCL Engineering Note 290, September 1993. Communications Certification Laboratory, Salt Lake City, UT; cited October 10, 2000; available from Internet: http://www.cclab.com/engnotes/eng290.htm.

3. "FCC Rules for Radio Devices," Code of Federal Regulations, 47 CFR Part 15, August 7, 1998.

4. CISPR 22:1985, "Limits and Methods of Measurement of Radio Interference Characteristics of Information Technology Equipment," International Special Committee on Radio Interference (CISPR), Geneva, 1985.

5. "Amendments to CISPR Publication 22, Limits and Methods of Measurement of Radio Interference Characteristics of Information Technology Equipment," a.k.a. "CISPR/G Central Office Papers," numbers 2 (1985), 5 (1988), 9 (1990), and 11–14 (1991). International Electrotechnical Commission (IEC), Geneva.

6. "Harmonization of Digital Device Standards with International Standards," Federal Communications Commission GEN Docket no. 92-152, FCC 93-421, Federal Register 58, no. 189 (October 1, 1993): pp. 51247–51250.

7. "Digital Devices: Harmonization with CISPR," FCC Docket 92-152, released July 30, 1992, published October 1, 1993.

8. CISPR 22:1993, 2nd ed., "Limits and Methods of Measurement of Radio Disturbance Characteristics of Information Technology Equipment," IEC, CISPR, Geneva, December 1993.

9. CISPR 22:1997, 3rd ed., "Information Technology Equipment—Radio Disturbance Characteristics—Limits and Methods of Measurement," IEC, CISPR, Geneva, November 1997.

Scott Roleson, PE, is a telecom and EMC engineer for Hewlett-Packard (San Diego, CA). He can be reached at scott_roleson@hp.com.

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