A M E R I C A N C O U N C I L OF I N D E PE N D E NT L A B OR A TOR I E S
EMC Standards Alert
Vol. 1 No. 2
Timely Updates on
Critical Standards
Edited by
Don Heirman,
Chair of IEC/
CISPR & ANSI ASC C63®
Editorial Board
Harry H. Hodes - Acme Testing Co.
Doug Kramer - NCEE
October 2009
Latest Test Lab Cost Impacts This edition of the ACIL EMC Standards
Alert focuses on the latest planned major changes in the areas of EMC Measurement
Uncertainty (which will affect nearly every ISO/IEC 17025-accredited EMC Test
Lab), Antennas for “Special Tests” (that will also affect nearly every ISO/IEC
17025-accredited EMC Test Lab), and, the latest news on the status of CISPR 32
(which will be a topic of extreme concern for any EMC Test Lab that tests ITE and/
or Consumer Broadcast Receivers and other Audio/Video Equipment, because it will
replace both CISPR 22 and CISPR 13). We also list two major EMC Standards that
have been recently published, and we summarize recent and upcoming EMC-related
Standards meetings that may be of interest to our members.
Mike Violette - Washington Labs
EMC Measurement Instrumentation Uncertainty The International
In this issue
Special Committee on Radio Interference (CISPR) is now updating the CISPR 16-42 standard on the application of measurement instrumentation uncertainty (MU) in
product compliance measurements. CISPR 16-4-2 is increasingly being invoked on a
mandatory basis in the standards that are applicable to product compliance testing.
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Latest Test Lab Cost
impacts
EMC Instrumentation MU
Antennas for special tests
What is CISPR 32
Recently published standards
EMC Workshops
Upcoming Meetings
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The latest versions of CISPR 22 and CISPR 11 (discussed in the last Standards
Alert) now have mandatory requirements to address MU. The major components of
MU that have to be considered are for radiated emission measurements between 30
MHz and 1000 MHz. How will this affect EMC Test Labs? (Note: conducted emissions are also addressed in CISPR 16-4-2 but this discussion will focus only on radiated emission measurements between 30 MHz and 1000 MHz).
Note that the MU is based on those quantities that affect the results of the measurement, not on the tolerance or deviations of each component in the measurement
chain. At times, the only way to determine this is with repeated measurements
(―Type A‖ uncertainty), where the test setup is torn down and rebuilt, looking at
variations of the quantity under consideration on the measured emissions. That
quantity variation is then entered into the uncertainty calculation. Tolerances have
to be converted into an uncertainty using the probability distribution function of
these tolerances over the likely ranges of the tolerances. The default is to use a rectangular probability distribution that says that all possible values of the quantity are
possible with equal probability. For example, in the case of an EMI receiver input
having an amplitude tolerance of +/- 2 dB, it is generally assumed that the actual
reading can be anywhere in this tolerance range which is captured with the rectangular distribution function.
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A M E R I C A N C O U N C I L OF I N D E PE N D E NT L A B OR A TOR I E S
Typical MU Quantities
MagniCISPR 16-4-2: 2003
tude of
Impact
(30 MHz to 1000 MHz, 3 meter separation,
Log periodic antenna array, horizontal polari- on overzation. [Applicable to OATS or semiall MU
anechoic Chambers]
(dB)
Receiver
lowering the pulse responses of the EMI Receiver (or
spectrum analyzer-based system) uncertainties when they
are aligned and calibrated (as it is unlikely that a new
EMI receiver or spectrum analyzer-based system with
significantly better MU specifications will be affordable).
What is coming next? The most recent proposal for updat-
Reading
0.1
Sine-wave voltage accuracy
0.5
Pulse amplitude response
0.87
Pulse response variation w/rep. freq.
0.97
Noise floor (OATS testing)
0.25
Cable
Attenuation between receiver & antenna
0.05
Mismatch at ends of cable
0.67
Antenna
Factor
1.0
Frequency interpolation
0.17
Variation with height
0.17
Directivity
0.29
Phase center
0.58
Cross-polarization response
0.52
Balance
0.0
Test Facility
Site imperfections
1.63
Test separation distance from EUT
0.17
Support table height (table top EUTs)
0.05
MU (Ucispr) calculation (k=2 coverage factor; 95 percent confidence level)

5.2 dB
ing CISPR 16-4-2 is contained in CISPR/A/848/CD. This
committee draft document had many national committee comments (113 with 22 of them defined as technical), and was
discussed at the CISPR Subcommittee A meeting in late September 2009. The CISPR/A/848/CD document proposes to
add the following layers in the MU input tables:.
 Radiated emissions between 1 GHz and 18 GHz
 Radiated emissions using a fully absorber lined room
(FAR)—30 MHz to 1000 MHz
 Impact of antenna tilting and near field effects when
measuring at a 3 meter separation (0.5 dB)
 Effect of the material used as table top (0.5 dB)
In addition, the Ucispr for the situation noted in the table is
5.2 dB. When considering all the measurement geometries
and polarizations, the worse case Ucispr is 5.2 dB considering
the receiving antenna tilted towards the largest emission
source at 3 meter separation as the antenna is raised between 1
and 4 meters. However, in accordance with the CISPR/
A/848/CD document, if tilting is not used, Ucispr increases
only by a tenth of a dB for horizontal polarization, but for
vertical polarization, Ucispr will become 6.3 dB for 3 meter
separation with no tilting and only 5.3 dB with it. Thus, as far
as MU is concerned, tilting the antenna (boresighting or aiming at the noise source) is insignificant for horizontal polarization and will become 1.1 dB for vertical polarization—again
for the case of 3-meter separation and 200 MHz to 1 GHz.
The ability to gain back this dB (by having an articulated antenna positioner on the mast) has to be considered traded-off
against its cost for getting a reduced MU. Note that there may
be other reasons for tilting or boresighting, such as if one or
more relevant test standards regularly employed by the EMC
Lab, requires it.
Looking at the values of the contributors to the MU in the
table, it is clear that the lab has to focus on:
Antennas for special tests Besides making radiated
 Reducing test site imperfections (i.e. getting the NSA/
VSA to be well inside the +/- 4 dB tolerance);
 getting the MU of various antenna characteristics reduced
[either by selecting an antenna with inherently lower
(better) uncertainties or by specifying an antenna calibration method to be used by the antenna calibration laboratory that has lower MU];
 decreasing the mismatch at the ends of cables by using
precision attenuators;
emission measurements, antennas are used for special tests,
like determining normalized site attenuation, and now, determining the effect on measured EUT emissions of the material
of tabletops upon which the EUT is placed. Presently, CISPR
16-1-4 Clause 5.9 states that from 30 MHz to 1000 MHz, the
antenna needed for determining effects of tabletops on radiated emissions measurements is a ―shortened‖ biconical antenna which covers at least 200 MHz to 1000 MHz (the effects from 30 MHz to 200 MHz are considered to be negligible), and whose tip to tip length (i.e., the size of the antenna
A M E R I C A N C O U N C I L OF I N D E PE N D E NT L A B OR A TOR I E S
normal to the measurement direction) has to be less than 40
cm. This measurement is performed with the transmit and
receive antennas only horizontally polarized.
There is a national committee voting document passed with
95% approval earlier this year, and a final draft international
standard in preparation to replace the current CISPR 16-1-4
with a new edition 3.0. The new document includes the requirements in amendment 2 of Edition 2 and adds more requirements. Of particular interest is the requirement for determining table top effects (for tables tops greater than 15 cm)
from 1 GHz to 18 GHz, as well as specifying the antennas
used for making this determination.
The ―good news‖ is that there is no change to the procedure
for table top effects between 30 MHz and 1 GHz and that the
proposed antenna specifications for the 1-18 GHz frequency
range are identical to the requirements for the antenna or antennas used for the Site VSWR (SVSWR) validation tests
between 1 GHz and 18 GHz. (The SVSWR antenna specification is already contained in CISPR 16-1-4 Clause 8.2.2.1).
The “bad news” then is that if the final draft international
standard passes (which is expected) and there are no significant changes from the present text, the labs will need to purchase the special shortened biconical antenna for table top
effects below 1 GHz. The “good news” is that since there is
already a requirement for site validation above 1 GHz that
has to be met, there is no additional antenna to purchase for
table top effect testing above 1 GHz.
It is noted that the effect of the table top material is not to be
added (or subtracted depending on the effect) to the product
emission measurement. Instead the measurement uncertainty
shall be added to the test lab overall measurement instrumentation uncertainty. The calculation of what to add is shown in
the present edition of 16-1-4 and has not changed for the proposed next edition. Also since the requirement for measurement antennas above 1 GHz is that they be calibrated, linearly
polarized, the lab can use either the SVSWR antenna or those
normally used such as double-ridged guide horns, rectangular
wave guide horns, etc. as described in 4.6 of 16-1-4.
To summarize, EMC Test Labs that have to measure product
emissions above 1 GHz (which includes nearly all EMC Test
Labs), a set of one or more antennas will be required for the
SVSWR validation above 1 GHz (the characteristics of which
are specified in great detail in Clause 8.2.2.1 of CISPR 16-14). This same set of antennas will now additionally be used to
evaluate the effects of tabletops on radiated emissions measurements from 1 – 18 GHz There is at present no plan to
―tighten up‖ the specification on the shortened Biconical Antenna used to evaluate the effects of tabletops on radiated
emissions measurements from 30 MHz to 1000 MHz.
What is in CISPR 32 (which is geared to replace
CISPR 22 and CISPR 13)? First of all CISPR 32,
“Electromagnetic compatibility of multimedia equipment Emission” is meant to combine CISPR 22 (Edition 6) and
CISPR 13 (Edition 4) which impact ITE and broadcast receiver compliance testing, respectively. CISPR 32 is now a
committee draft (CIS/I/295/CD) which is subject to change,
and hence will not replace CISPR 22 and CISPR 13 until well
into 2011. However, it is good to look now at the challenges
CISPR 32 might present for EMC test labs, because the philosophy was to start with a clean sheet of paper as to both
emission measurements and associated limits for ―multimedia
equipment‖ which is essentially any ―black box".
The main normative text of the Committee Draft [CD] CISPR
32 is only 20 pages long. It addresses products that have ports
through which ―electromagnetic energy enters or leaves‖ the
product. Examples of these ports are: Fiber, RF modulator
output, Broadcast receiver tuner, enclosure, infra-red, antenna,
AC mains power, DC power, wired network and signal/control. This means that the test lab will have to have
suitable terminations to connect to these ports via the typical
connecting system. Plug in modules or any modules must be
tested in at least one representative host system. Either the
customer needs to provide the appropriate host system or the
test lab has to have one that is suitable. This latter alternative
is likely to be costly, and hence the test lab should be sure to
have the customer provide the host. Measurement uncertainty
is still the instrumentation MU, and only has to be calculated.
The CD did not say what to do with it, nor does it even require putting it in the test report.
Listing the annexes where most of the normative actions are
contained is helpful in seeing what will be required when this
standard is accepted for use.
Annex A:
Test requirements This covers the usual
set up topics but shows a clear use of a fully absorber lined
room (FAR) which references CISPR 16-1-4, Clause 5.8, for
the FAR facility validation requirements and CISPR 16-2-3,
Clause 7.2.9.2 for the test procedures, and CISPR 16-1-4,
clause 8.2 for a free space open area test site (FSOATS). It
then gives requirements in EUT size that can be tested in a
FAR, for example in Table A1. Test Labs should consider
converting their semi-anechoic room into a FAR to take advantage of this test method or to have a FAR if that is specified by the manufacturer or regulator. The radiated (30 MHz
to 6 GHz) and conducted emission limits are then found in
tables. There are relaxed radiated emission limits for broadcast satellite outdoor systems and FM receiver local oscillator
emissions. A wide range of requirements are then cited for
wired network ports, RF input/output ports, broadcast receiver
tuner ports using screened and unscreened cables, and fiber
ports designed for use with fibers having a metallic screen or
member.
A M E R I C A N C O U N C I L OF I N D E PE N D E NT L A B OR A TOR I E S
Annex B: Exercising the EUT during measurements and specification of test signals
Recently published EMC Standards of Interest
This annex provides how ports should be exercised for many
different port types such as audio, video (there are several
display images shown) and other signals. The requirement is
to generate signals corresponding to the most complex image
listed in table B1. Note that only one of the choices is the
usual ―H‖ pattern that may or may not be scrolled depending
on what is supported. Digital broadcast signals are also addressed.
C63.10-2009 - “Standard for Testing Unlicensed Wireless
Devices” was published on 10 September.
C63.4 - 2009 - “Methods of Measurement of Radio-Noise
Emissions from Low-Voltage Electrical and
Electronic Equipment in the Range of 9 kHz to
40 GHz” was published on 15 September.
Annex C: Measurement procedures, instrumentation and supporting information This annex provides additional information not contained in Annex A. It
describes in more detail what is called out from the CISPR 16
-x-y series of standards for instrumentation specifications,
general measurement procedures and also specific measurement procedures. It also covers such topics as antennas, ambient, boundary of the EUT system for determining the separation distance to the receiving antenna (it is different than
that of the straight line string method in ANSI C63.4), prescan and ―Formal‖ measurements (we call them ―final‖ measurements in ANSI C63.4), and other general measurement
procedures. These procedures are illustrated by a major flow
chart for selecting wired network port measurements. Telecom port measurements are identified in much detail as are
receiver tuner and RF modulator output ports (covering 30
MHz to 2.15 GHz). Normalized NSA values for 5 meter
separation are then presented (which are not contained in
ANSI C63.4) and apply to OATS and semi-anechoic chambers (SAC).
The remainder of the annexes are quite detailed. They will be
reviewed in the next edition of the ―ACIL EMC Standards
Alert.” For your information, the titles of the annexes are
listed below:
Annex D: Arrangement of EUT and Associated
Equipment
Annex E: Guidance for emission measurements using CISPR 16 methods
Annex F: Test report content summary
Annex G: Support information for the measurement
procedures defined in Clause C.3.1 (Screened or unscreened wired network port)
Annex H: Alternative test methods with limits for
the enclosure port
Annex I: Supporting information for the measurement of outdoor units of broadcast satellite receivers
Annex J:
Screening effectiveness measurement
method for receivers
Both these standards are very valuable for those that test to
FCC and other regulatory requirements from ITE to UWB and
new wireless technology. IEEE offers a discount for IEEE
members to purchase these standards. To order, click on:
http://standards.ieee.org/ then click on ―Shop‖. Once there,
type in the standard number, e.g. C63.10 in the ―search the
IEEE shop‖ window on the right and then click enter. Prices
and further ordering information are listed on the web page.
EMC Workshops
C63.10:
A two-day workshop on the use of C63.10 is being
held at UL in Research Triangle Park on November 4 - 5,
2009. For information and registration, go to the iNARTE
home page (www.narte.org) at the top and click on the workshop title. Space is usually available to attend even the week
before.
High Power Electromagnetic Effects: Another twoday workshop will be held at Washington Laboratories on
December 16-17, 2009 on new developments in high power
electromagnetic effects on products. There will be information presented on the standardized way in which these tests
are to be performed in this era of purposeful equipment damage. The ad and registration for this workshop will be posted
on the iNARTE web site soon.
Upcoming Meetings
ANSI ASC C63® Subcommittee 3 (International Standardization) is meeting at the National Institute of Standards
and Technology in Boulder, CO on 20 October 2009. The
scope of the SC3 meeting is found on the ASC C63® website:
http://www.c63.org/documents/sc_3/sc_3.htm . The full series
of ASC C63® meetings in Boulder is found at this URL:
http://www.c63.org/upcomingmeetingschedule.htm
These are open meetings with a nominal meeting fee charged.
For test labs, it is an excellent way to see the many standards
amendments underway that will or may impact their lab
ACIL 72nd Annual meeting October 24-26, 2009,
Gaylord Opryland Resort, Nashville, TN www.acil.org
The information contained in this newsletter is current based on sources as of the date of electronic publication, is the sole opinion of its editor, Don Heirman. ACIL
is not responsible for its content.