Another Busy Standards Time in Fort Lauderdale
We could hardly take a breath without running into a standards discussion at our annual EMC symposium in Fort Lauderdale. Some came from workshops, some from scheduled meetings, and some from ad hoc chats.
The standards activity started even before the start of the symposium; in fact, the Friday and Saturday before. The Accredited Standards Committee C63® held its usual workshops on July 23–24. This year it was again a Friday workshop on ANSI C63.4 which is the FCC referenced emission measurement standard for information technology equipment. On Saturday, the workshop addressed ANSI C63.5 on antenna calibration and provided an introduction to using time domain techniques for antenna calibration as well as investigating test site anomalies in the site validation process. For more info on C63®, visit www.c63.org
The C63.4 workshop was presented by Don Heirman of Don HEIRMAN Consultants and Bob Hofmann of Hofmann EMC Engineering. It focused on the differences between the 2003 and 2009 editions. The 2009 edition adds the following:
- Tables of LISN impedances (in addition to the plots in the 2003 edition) with and without the use of extension cords between the EUT power connection of the LISN and the end of the extension cord where the EUT connects its power plug
- Clarifying in Annex B the LISN calibration process
- What must appear on video displays during emission testing
- Variation in antenna cable loss as a function of significant temperature variation at the test site
- Precautions in using spectrum analyzers, which appear in clause 4.2.2 and Annex H
- Informative annexes for step-by-step testing procedures have been omitted, because those were mostly duplicative of the normative procedures in the main text
- Ensured that the standards not under the control of Accredited Standards Committee (ASC) C63® were dated to guarantee the acceptance of the versions that are referenced, whereas the ASC C63® standards were undated because ASC C63® would be voting their acceptance
- Added information on the effects of materials used to construct EUT support tables and antenna masts
- Condensed the information about absorbing clamp calibration and use, as well as the artificial hand, as these continue to be in limited use
- Retained the Clause 13 requirements for emission measurements of intentional radiators
- Introduced site validation specifications above 1 GHz from CISPR 16-1-4:2007, while still allowing use of absorber material on the ground plane for an open area test site (OATS) and semi-anechoic chambers in a particular configuration and with particular absorber performance without any further site validation measurements
- For measurement methods above 1 GHz, retain the provisions of ANSI C63.4-2003 with no change
|PHOTOS BY RICHARD GEORGERIAN
|Team problem solving during the ANSI C63.4 workshop held in Fort Lauderdale, prior to the EMC 2010 Symposium.
Changes being considered for the next edition of ANSI C63.4 in 2012 include the following:
- Remove measurement methods for intentional radiators (clause 13) since they are now covered by C63.10
- Revise the measurement method for emissions above 1 GHz; this would be limited to unintentional radiators
- Revisit site validation methods above 1 GHz
- Further describe scrolling H pattern requirements for large screen TV receivers as well as those used as computer monitors
- Add measurement uncertainty based on C63.23 if published
- Move antenna calibration requirements to C63.5
- Move site validation requirements to new standard if one is published covering different approaches (potential publication is C63.25)
- Add information on the various versions of the average detectors and review average measurement method using a reduced VBW
The next day Don, Zhong Chen of ETS-Lindgren and Mike Windler of UL presented what is covered in ANSI C63.5 on antenna calibration, the proposed changes for a 2012 edition and the use of time domain techniques to determine test site qualifications, especially above 1 GHz. This last session also showed the efficacy in finding where necessary improvements must be made to meet the site validation requirements.
Topics covered in the C63.5 portion of the workshop included:
- General test conditions for calibrating an antenna
- Standard site method (SSM) also known as the three antenna method
- Reference antenna method where specific construction techniques give predictable antenna factors
- Calibration geometry specifics that differ for antennas calibrated for use in compliance testing and those used in test site validation
- Specific biconical antenna calibration and the differences in those with 50 or 200 ohm baluns
- Determining the measurement uncertainty for the various antenna calibration methods in the standard
|Instructor Bob Hofmann presents the ANSI C63.4 workshop session on instrumentation.
||Lead instructor Don Heirman presents the ANSI C63.4 measurements session during the workshop.
|Lead instructor Don Heirman reviews an ANSI C63.4 problem solution with a student.
||Zhong Chen presents general test conditions for antenna calibration during the ANSI C63.5 workshop.
Also reviewed were the areas being investigated for the next edition of the standard ANSI C63.5. Below is a sample of those considerations:
- Clarify text as needed in annex H in section 5.1 on the use of free space antenna factor (FSAF) and near-FSAF in section 5 and annex G
- New text covering standard gain horn antennas above 1 GHz where either use the physical dimensions for reference with some S11 electrical check to assure working horn antennas or incorporate what cal labs use for horn antennas above 1 GHz (extrapolation, etc)
- Add free space corrections for dipole antennas similar to the Japan Voluntary Control for Interference (VCCI) and the International Electrotechnical Commission (IEC)
- Add vertical Ed_max to annex A
- Add limits to vertical vs. horizontal 1m ratio for hybrid antennas
- Add minimum frequency resolution for calibrations
- Reinstate sentence on biconical antennas - “Antenna factors obtained for biconical dipole antennas using the SSM that are used for either product testing or NSA testing shall be corrected to free space values using the correction factors provided in Annex G,” as in the 2004 edition
- Develop text for complex fit of log periodic antennas
- Develop text for time-domain gating for free-space AFs (i.e. reduction of reflections)
- Add measurement uncertainty estimates (either in this standard or in the uncertainty standard)
- Expand reference antenna options
The time domain method portion of the workshop focused on site validation. Note that this work is now part of the standards work on the subject given the draft number of C63.25. In advance of publication, the following information was presented to show the usefulness of this technique.
- Measurements can be done with a swept frequency vector network analyzer
- Converting from frequency to time domain using the inverse Fourier transform is extremely easy and fast with modern computational hardware and software
- Conversions are done “on the fly” using time domain reflectometry (TDR) equipped Vector Network Analyzers (VNAs)
- Procedure is basically analogous to testing of products:
- Place a transmitting antenna on the turntable with a receiving antenna at the 3-meter measurement location
- Measure the response (voltage and phase converted to voltage and time) every 6 degrees of turntable azimuth
- The proposed TDR method is similar to taking a radar measurement of your site
- The results are the amplitude, distance and angle of any reflections
- The amplitude of the reflections is measured relative to the direct path thus making them a direct measurement of error introduced by the site
|Mike Windler (seated with back to camera) and Zhong Chen (standing far left) demonstrate the way in which site anomalies affect validation using time domain techniques in the C63.5/Time Domain workshop.
|Students and instructors posed for a photo following the ANSI C63.5/Time Domain workshop. Instructors included (seated from left) Zhong Chen of ETS-Lindgren, Bob Hofmann of Hofmann EMC Engineering, Don Heirman of Don HEIRMAN Consultants, and Mike Windler of UL.
The workshop then concluded with the following:
- The same test site will have the same performance when measured with TDR and the IEC/CISPR Site VSWR (SVSWR) technique in CISPR 16-1-4 if the SVSWR measurement is done with continuous antenna movement (not in specific increments now in the SVSWR procedure)
- The TDR method will be faster and will yield diagnostic information (frequency, azimuth and distance to reflections—and hence show where the test site has to be improved to meet the validation specification) that SVSWR does not
On Monday, which was the start of the technical program of the Symposium in Fort Lauderdale, the morning brought together meetings on standards including a presentation to the members of the EMC Society Board of Directors that attended the luncheon sponsored this year by the Standards Advisory and Coordination Committee (SACCom). The luncheon was attended by SACCom members as well as members of the Representative Advisory Committee (RAC). RAC has other non-EMC Society committees that are not doing EMC standards work while the SACCom focuses on hearing from representatives of non-EMC Society standards committees around the world. The chair of SACCom is Werner Schaefer of CISCO and your author is the secretary. For more info on SACCom, visit http://ewh.ieee.org/soc/emcs/standards/saccomindex.html
The main EMC Society standards committee is the Standards Development Committee (SDCom). Andy Drozd is the chair and his secretary is Ed Hare of ARRL. Below is a glimpse of the list of standards. The status of each was discussed over two parts of the committee meeting (the first part was on Monday morning and the second was on Wednesday morning).
1.1 Std 1391 – In-situ measurement of ISM equipment
1.2 Std 1872 – Measurement of spurious radiation from FM/TV receivers
1.3 Std 2993 – Measuring shielding effectiveness
1.4 P299.14 – Shielding effectiveness, dimensions 0.1-2m
1.5 Std 3775 – Spurious emission from land-mobile transmitters
1.6 Std 4736 – EM site survey to 10 GHz
1.7 Std 4757 – Measurement of field disturbance sensors
1.8 Std 11288 – RF absorber evaluation
1.9 Std 11409 – Measuring emissions from video-display terminals
1.10 Std 130210 – Characterization of conductive gaskets
1.11 Std 130911 – Calibration of field sensors
1.12 P1309 Amd12 – Calibration of field sensors
1.13 P156013 – Measurement of RFI filtering capability
1.14 P1597.114 – Validation of EM computer modeling
1.15 P1597.215 – EM computer modeling applications
1.16 P164216 – Intentional EMI
1.17 P168817 – Module EMI testing
1.18 P177518 – BPL emissions testing/immunity testing and limits
1.19. P2030 – Smart Grid Standardization
1.20. PXXX – Resolution of Power Line Gap Noise Interference
For more information on the status of each of these projects, see the SDCom web site: http://ewh.ieee.org/soc/emcs/standards/sdcom/sdcomminutes.html
An interesting discussion during the Monday meeting involved the need for a project to discuss the measurements (and limits) of power line frequency harmonics as it should apply to North America, especially that of the U. S. and Canada which share the power grid of North America. Due to the very different power grid (using a 60 Hz system) in North America, the international standards on harmonics IEC61000-3-2 (using less than or equal to 16 Amps per phase for 50 Hz systems) and IEC61000-3-12 (using more than 16 Amps and less than or equal to 75 Amps per phase) needs to be adapted. After a discussion on the need as voiced by Canadian manufacturers, an ad hoc committee was established to draft an IEEE Project Authorization Request (PAR). Subsequent to the meeting, an SDCom electronic ballot was conducted and PARs for the study on adapting the 3-2 and 3-12 work were approved and given the IEEE numbers of P1836 and P1837, respectively. The ad hoc committee is now populating the working group as well as recommending a chair and co-chair for this work.
In addition to these standards meetings, there were project meetings on some of the above standards, including:
- P299.1 (two different four-hour meetings)
There were even other international standards meetings on these topics:
- IEC 61000-4-22 (use of reverberation chamber testing techniques) task force meeting
- G46 EMC Subcommittee meeting
- IEC 61000-4-21 (use of TEM chamber testing techniques) task force meeting
In conclusion, the amount of standards activity continues to be extensive and occupies much of the time of our EMC Society symposia. That remains very encouraging for the health of EMC standards in our Society.
1 IEEE 139 – IEEE Recommended Practice for the Measurement of Radio Frequency Emission from Industrial, Scientific, and Medical (ISM) Equipment Installed on User’s Premises
2IEEE 187 – IEEE Standard on Radio Receivers: Open Field Method of Measurement of Spurious Radiation from FM and Television Broadcast Receivers
3IEEE 299 – IEEE Standard Method for Measuring the Effectiveness of Electromagnetic Shielded Enclosures
4P299.1 – Standard Method for Measuring the Shielding Effectiveness of Enclosures and Boxes Having All Dimensions between 0.1 m and 2 m
5IEEE 377 – IEEE Recommended Practice for Measurement of Spurious Emission from Land-Mobile Communication Transmitters
6IEEE 473 – IEEE Practice for an Electromagnetic Site Survey (10 kHz to 10 GHz)
7IEEE 475 – IEEE Standard Measurement Procedure for Field Disturbance Sensors, 300 MHz to 40 GHz
8IEEE 1128 – IEEE Recommended Practice for RF Absorber Evaluation in the Range of 30 MHz to 5 GHz
9IEEE 1140 –1994 (R1999) - IEEE Standard for the Measurement of Electric and Magnetic Fields from Video Display Terminals (VDTs) from 5 Hz to 400 kHz
10IEEE 1302 – IEEE Guide for the Electromagnetic Characterization of Conductive Gaskets in the Frequency Range DC to 18 GHz
11IEEE 1309 – IEEE Standard Method for the Calibration of Electromagnetic Field Sensors and Field Probes, Excluding Antennas, from 9 kHz to 40 GHz
12Amendment 1 to IEEE Standard Method for the Calibration of Electromagnetic Field Sensors and Field Probes, Excluding Antennas, from 9 kHz to 40 GHz: Probe Characteristics, Use and Measurement Uncertainty: Probe Use
13IEEE P1560 – Methods of Measurement of Radio Frequency Interference Filter Suppression Capability in the Range of 100 Hz to 40 GHz
14 P1597.1 – Standard for Validation of Computational Electromagnetics (CEM) Computer Modeling and Simulation
15P1597.2 – Recommended Practice for Computational Electromagnetics (CEM) Computer Modeling and Simulation Applications
16 P1642 – Recommended Practice for Protecting Public Accessible Computer Systems from Intentional EMI
17P1688 – Standard for Module Electromagnetic Interference (EMI) Testing
18P1775 – Standard for Broadband Powerline Communication Equipment – Electromagnetic Compatibility (EMC) Requirements – Testing and Measurements Methods EMC
Please check the C63® website – www.C63.org – after January 2011 for more information about scheduled ANSI C63® workshops in 2011.