Ghery S. Pettit, NCE
President, Pettit EMC Consulting LLC
CISPR 32, “Electromagnetic compatibility of multimedia equipment – Emission requirements” was first published in 2012. This standard came about due to a major development in consumer electronics, the digital television receiver.
The CISPR is a special committee of the IEC. CISPR stands for the French words for the Special Committee on Radio Interference. CISPR publishes a number of EMC standards used for a variety of product families. This article will discuss only a very small portion of the standards published by CISPR.
From a CISPR perspective, prior to the development and wide scale use of digital TV receivers, television receiver manufacturers had a single emissions standard to deal with. CISPR 13 provides limits and methods of measurement for emissions from broadcast receivers. Likewise, computer manufacturers had a single emissions standard to deal with. CISPR 22 provides limits and methods of measurement for emissions from information technology equipment (ITE), also known as computers and their peripheral devices. These two standards are independent of each other and provide different limits and methods of measurement, as well as different configurations for the equipment under test. A significant difference noted by television manufacturers in the configuration area was the requirement in CISPR 22 to investigate the impact of cables connected to multiple I/O ports, something not required in CISPR 13.
When digital television receivers were developed the manufacturers found that they now had two standards to deal with for emissions. A digital television receiver has both a broadcast receiver and a computer in the same box. Hence, both CISPR 13 and CISPR 22 applied to the product. As the limits and test methods differed between the two standards each had to be addressed separately. Needless to say, this added time and cost to the qualification process. Managers don’t tend to look kindly on things that add time and cost to the development process, especially when they see no benefit. As a result, efforts began in CISPR to address this matter.
Addressing the matter of emissions standards for digital television receivers was complicated by the fact that CISPR 13 was maintained in CISPR Subcommittee E (Broadcast receivers) and CISPR 22 was maintained in CISPR Subcommittee G (ITE). If you need to either find a way to coordinate two standards, or write a new one, having two separate subcommittees is not the most efficient way to go about the task. In the end, CISPR/E and CISPR/G were merged in 2001, forming the new CISPR Subcommittee I (Electromagnetic compatibility of information technology equipment, multimedia equipment and receivers). CISPR/E and CISPR/G ceased to exist with the creation of CISPR/I. CISPR/I initially had 4 working groups. WG1 was tasked with the maintenance and updating of CISPR 13 (emissions) and CISPR 20 (immunity) for broadcast receivers. WG3 was tasked with the maintenance and updating of CISPR 22 (emissions) and CISPR 24 (immunity) for ITE. WG2 was tasked with the creation of the new multimedia equipment emissions standard, CISPR 32 and WG4 was tasked with the creation of the new multimedia equipment immunity standard, CISPR 35. WG1 and WG3 were dissolved at the end of 2012 and any continuing work on the old standards was folded into WG2 for emissions and WG4 for immunity.
Writing the new standards was not simply a matter of merging two existing documents. Over the years of work on creating CISPR 32 various ideas were proposed and discussed, both within WG2 and by the national committees. Several Committee Drafts (CD) were circulated to the national committees for comments before the final form of the standard emerged. A Committee Draft for Vote (CDV) was circulated and voted in 2010. A large number of comments were received with the national committee votes. These were considered in WG2 and the Final Draft International Standard (FDIS) was circulated and voted in the 4th quarter of 2011. This FDIS was successful and CISPR 32, Edition 1.0 was published in January 2012.
CISPR 32:2012 (1st Edition)
While its structure is different, CISPR 32 more closely resembles CISPR 22 (ITE) than it does CISPR 13 (Broadcast receivers). The limits, for the most part, are those contained in CISPR 22. Power line and telecommunications port conducted emissions limits are specified over the same 150 kHz to 30 MHz range, measured using the same techniques and equipment as in CISPR 22 and using the same limits. Likewise, radiated emissions limits are specified over the same frequency range of 30 MHz to as high as 6 GHz, with the same measurement techniques as in CISPR 22 and, again, using the same limits. CISPR 32 also adds radiated emissions limits from FM receivers at the fundamental and harmonics of the local oscillator frequency. The first edition further changed from calling out specific conducted emissions requirements on telecommunications ports as called out in CISPR 22 to, instead, providing limits for “asymmetric mode conducted emissions” which are applicable to wired network ports, optical fiber ports with metallic shield or tension members and antenna ports. Additional limits are provided for “conducted differential voltage emissions” for TV broadcast receiver tuner ports with an accessible connector, RF modulator output ports and FM broadcast receiver tuner ports with an accessible connector. This final set of limits is only provided at class B levels.
Under the rules of the IEC, a standard may only be amended twice before a new edition must be published. And, corrigenda issued to correct errors in published standards count as amendments. Members of CISPR/I were quick to note that the IEC Central office had made some seemingly harmless changes between the FDIS that was voted by the national committees and the published form for CISPR 32:2012 that weren’t so harmless. In fact, they had the effect of rendering three critical tables in the standard unusable due to changes to or deletion of notes.
The first corrigenda issued for CISPR 32 made an editorial correction to the French version of the standard. The second corrigenda corrected the errors that had been introduced by the IEC Central Office when they created the published form of CISPR 32:2012. As a result, CISPR 32 had been amended twice by August 2012. When further additions were proposed for CISPR 32 they resulted in the 2nd Edition of the standard, rather than an amendment.
CISPR 32, 1st Edition, provided for performing radiated emissions testing at an Open Area Test Site (OATS), either with or without a weather protection cover, an RF semi-anechoic chamber or a Free Space OATS (FSOATS). Unlike CISPR 22, which provide guidance on testing of radiated emissions below 1000 MHz at distances other than 10 meters for certain class B devices, CISPR 32 explicitly provides limits at 3 meters, as well as limitations on the suitability of test sites chosen for these different measurement distances. It also limits the use of an FSOATS to testing at frequencies above 1 GHz.
CISPR 32:2015 (2nd Edition)
What was changed with the publication of CISPR 32, 2nd Edition, with it came out in March 2015? The 2nd Edition of CISPR 32 provides a number of clarifications, new test methods and guidance on testing additional product types.
CISPR 32, 2nd Edition, adds limits and other guidance for testing radiated emissions below 1 GHz in a Fully Anechoic Room (FAR). Limitations and clarifications for the use of a FAR for radiated emissions testing below 1 GHz are provided in Table A1.4 and include the limitation that this facility may only be used for testing table-top EUTs. The tables providing limits for radiated emissions were all amended to cover the different types of measurement facilities. Limits are now provided for an OATS/SAC at 10 or 3 meters and for a FAR at 10 or 3 meters, both for class A and class B equipment.
A new table, A.7, was added to provide requirements for outdoor units of home satellite receiving equipment. This table includes limits for radiated emissions over the frequency range of 30 MHz to 18 GHz, the only limits above 6 GHz in CISPR 32. A whole new annex, Annex H, was added as an informative annex to provide supporting information on the measurement of outdoor units of home satellite receiving systems.
Annex I was added as an informative annex to provide information on other test methods, such as the Gigahertz Transverse ElectroMagnetic (GTEM) chamber and a ReVerberation Chamber (RVC). Annex I points out that information on these two test facilities is provided for information purposes and that meeting the limits in Annex I does not constitute compliance with CISPR 32.
In addition, when CISPR 32, 2nd Edition, was published a number of the dated references in section 2 of the standard were updated, as well. New figures were added, definitions were updated and other changes made throughout the standard. These changes are far too numerous to detail in this article.
How do I know what has changed?
The IEC makes it easy to see what has changed when a new edition of a standard is published. For additional cost you can purchase the Redline Version of the standard which shows all the changes and additions in red ink. There is a disclaimer in the forward stating that the Redline version is not an official IEC standard and is intended only to show you what has changed. The disclaimer states that “Only the current version of the standard is to be considered the official document.” A cynic would note that this disclaimer also has the effect, if taken to heart, of increasing sales of the standard. For a company needing multiple copies of the standard the author would recommend that a small number of Redline versions be purchased and that the version of the standard needed be purchased in quantity. And, the IEC does facilitate multiple copy purchases by giving quantity discounts on the electronic versions. A 20 copy license, for example, may be purchased for the price of 4 individual copies. Plan your purchases accordingly.
What is coming in the future?
CISPR/I WG2 is looking at a number of potential updates and changes to CISPR 32 over the next number of years. CISPR/I/510/DC was published on June 26, 2015 based on issues discussed in the May 2015 meeting of CISPR/I WG2 and includes a number of items to be considered for future work on CISPR 32. National committee comments on this DC were due by August 28, 2015 and work was begun at the CISPR/I WG2 meeting in Stresa, Italy on October 1, 2015. This article was written before the August 28 deadline, so it can’t be said here how any of these items will be handled. A description of some of the items is provided to give the reader an idea of what may or may not happen in the future.
The first part is a list of 8 items to be considered for inclusion in a corrigendum to make editorial changes to the standard. None of the proposals would change the meaning of the standard and would serve to clarify some points that have caused questions.
The second part of the Document for Comment (DC) details a list of 10 issues to be discussed and considered for short term work. Any or all of these items could appear in a future amendment to CISPR 32:2015. Some of these items include the possibility of modifying the wired network port requirements to only require current measurements when a telecom interface has a defined spectral mask; considering the use of the RMS Average detector as an option or as an informative annex; clarification on the need, or lack thereof, for additional insulation on top of the ground plane when interconnecting cables are already insulated; considering improving the termination of cables leaving a FAR; considering modification of the measurement methodology and limits above 1 GHz; and considering clarifying how to assess the coupling of a wanted radio signal (and its harmonics) to the line under test during conducted emissions measurements
The third part of this DC provides 11 items to be considered for long term work. While not all the items are listed here, key items that may be of interest include the termination of cables leaving the measurement area; consideration of using the Amplitude Probability Distribution (APD) method as an alternative above 1 GHz; consider what exercising image is appropriate for new display technologies; to consider if Annex I (RVC and GTEM) should be moved to the main body of the document; and consider the inclusion of the full approach of CISPR 16-4-2 on measurement instrument uncertainty.
Please note that none of these items noted in CISPR/I/510/DC constitute firm changes to CISPR 32. They are only items for consideration and discussion, initially in CISPR/I WG2 and then CISPR/I as a whole. Simple items could show up in CISPR 32 in a few years, more significant and/or controversial items could take even more time. Consider that it took 11 years from the formation of CISPR/I until CISPR 32 was first published. Change in CISPR documents can take a long time. For a really bad example, consider that work started on the creation of CISPR 35 (the immunity complement to CISPR 32) at the same time and that standard has not yet been agreed. There is hope that CISPR 35 will ultimately be published in the first half of 2016, but it remains to be seen how that will turn out.
I’ve discussed, at a high level, what is in CISPR 32, both 1st and 2nd Editions. Keep in mind that like all CISPR (for that matter, all IEC) documents, CISPR 32 is only so many words on paper. Unless and until a regulator adopts it into their national regulations it means nothing. For example, CISPR 32:2012 has been adopted in the EU as EN 55032:2012 and must be used in place of EN 55013 and/or EN 55022 for all products placed on the market in the EU (regardless of when first declared compliant with the EMC Directive) by March 5, 2017. As of the time of the writing of this article, nothing has been said in the list of harmonized standards about EN 55032:2015, so we must wait and see about the new edition.
CISPR 32 is an important standard for manufacturers of multimedia equipment (including digital television receivers) and provides a unified approach for demonstrating a reasonable level of control of emissions from these products to product other users of the radio spectrum. Products already compliant with the requirements in CISPR 22 should see no impact on their design due to the switchover to CISPR 32 in the near future.