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June 2011 IN Compliance 3

CONTENTS

FEATURE ARTICLES

10 EMI Shielding Thermoplastic CompoundsDramatic Cost Reductions for Electronic Device Protection

Neil Hardwick

20 Eliminating the Need forExclusion Zones in Nuclear Power Plants

Philip F. Keebler

32 Rethinking the Role ofPower and Return Planes

Glen Dash

40 Effects of a Wire Beneath the Ground Plane on Antenna Coupling through a Slot

Takehiro Morioka and Kazuhiro Hirasawa

DEPARTMENTS

4 News IN Compliance

8 The iNARTE Informer

46 The Future of EMC Engineering The Need for Energy Conservation

47 Business News

49 Shielding Marketplace

50 Events

50 Compliance Marketplace

4 IN Compliance June 2011

FCC Orders $1.6 Million Fine for Junk Faxes

The Federal Communications Commission (FCC) has ordered a Florida travel and vacation marketing company to pay over $1.6 million in forfeiture penalties for sending unsolicited faxes.

The Forfeiture Order cites Mexico Marketing, based in Orlando, FL, for delivering 290 unsolicited fax advertisements for travel services to 80 separate consumers. The Order follows the issuance of a Citation against the company in 2006, and three separate Notices of Apparent Liability for Forfeiture, issued in 2007 and 2008. In each instance, the company failed to respond to the Commission’s communications.

The Telephone Consumer Protection Act of 1991 makes it “unlawful for any person within the United States…to use any telephone facsimile machine, computer, or other device to send, to a telephone facsimile machine, an unsolicited advertisement.”

Violations of the FCC regulations regarding these so-called junk faxes typically result in monetary fines of up to $10,000 per violation. In this case, the Commission cited Mexico Marketing for willful and repeated violations of its junk fax regulations, levying $10,000 fines for each of the 55 instances in which the company sent faxes after receiving requests to stop, and an additional $4500 for each of the remaining 235 faxes sent.

The complete text of the Commission’s Forfeiture Order against Mexico Marketing is available at http://www.fcc.gov/Daily_Releases/Daily_Business/2011/db0412/FCC-11-48A1.pdf .

FCC Proposed Rule Changes Regarding Signal Boosters

Continuing its efforts to expand mobile broadband access, the Federal Communications Commission (FCC) has proposed changes to its rules regarding the deployment and use of signal boosters.

Although more than 98% of the U.S. population now has access to advanced wireless services, the Commission notes that coverage gaps in mobile broadband services persist, particularly in rural areas. In addition, consistent access to mobile broadband services can be an issue in office buildings, educational campuses and healthcare facilities where reliable communications are essential. The Commission believes that the broader deployment of signal boosters can mitigate service gaps in difficult-to-serve geographies and environments.

Issued in April 2011, the Commission’s Notice of Proposed Rulemaking (NPRM) proposes to modify current rules to allow individuals and certain entities to operate “consumer signal boosters,” consistent with its radiofrequency (RF) exposure rules, and within parameters that would prevent or control interference with other operators. Specifically, the FCC seeks comments on the following issues related to the expanded use of signal boosters:

y Whether newly introduced signal boosters should be required to register with a national signal booster clearinghouse prior to operation;

y How signal boosters already in service should be treated under the proposed regulations;

y When the new signal booster requirements should come into effect.

The Commission’s NPRM regarding signal boosters is available at http://www.fcc.gov/Daily_Releases/Daily_Business/2011/db0406/FCC-11-53A1.pdf .

Lorie NicholsPublisher & Editor

(978) [email protected]

Sharon SmithDirector of Sales(978) 873-7722

[email protected]

Barbara KovalchekMedia Consultant(978) 846-1656

[email protected]

Erin C. FeeneyDirector of Media Services

(978) [email protected]

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Contents may not be reproduced in any form without the prior

consent of the publisher.While every attempt is made to provide

accurate information, neither the publisher nor the authors accept any

liability for errors or omissions.

Magazine

NEWS IN COMPLIANCE

http://www.fcc.gov/Daily_Releases/Daily_Business/2011/db0412/FCC-11-48A1.pdf













FCC Launches New Website

The Federal Communications Commission (FCC) has announced the beta release of its newly overhauled website, the first major revision in over a decade.

The overhaul is intended to improve and simplify the Commission’s website experience for consumers, government, public safety agencies and the business community. The website includes a number of new features, including agency blogs, multimedia and links to social media outlets.

According to the Commission, the new website is based on an open-source, cloud-hosted, scalable architecture that makes it more user-friendly while enabling more efficient and cost-effective updating and revisions in the future.

The beta version of the FCC’s overhauled website is available at http://beta.fcc.gov. The Commission says that it expects to make revisions to the beta site through the remainder of 2011 in response to comments and suggestions from the public.

Readers can obtain regular updates and information on the new website by following Steven Van Roekel, the FCC’s Managing Director, on Twitter at @stevenvfcc.

EU Sets Eco-Design Requirements for Electric Fans

The Commission of the European Union (EU) has issued a regulation implementing new energy efficiency requirements for fans driven by electric motors.

The regulation, which was published in April 2011 in the Official Journal of the European Union, is considered an implementation measure under the EU’s Eco-Design Directive, 2009/125/EC. That directive gives the Commission the authority to establish minimum efficiency standards for those

“energy-related products representing significant volume of sales and trade, having significant environmental impact and presenting significant potential for improvement in terms of their environmental impact without entailing excessive costs.”

The new energy efficiency requirements for electric fans, which come into effect beginning on January 1, 2013, are defined in Sections 1 and 2 of Annex I of the regulation. Compliance with the requirements is calculated following the methods described in Annex II of the regulation.

The complete text of the Commission’s regulation regarding the eco-design of electric fans is available at http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2011:090:0008:0021:EN:PDF .

EU Commission Revises Standards List for R&TTE Directive

The Commission of the European Union (EU) has published an updated list of standards that can be used to demonstrate compliance with the essential requirements of Directive 1999/5/EC, covering radio equipment and telecommunications terminal equipment (R&TTE).

DILBERT © 2008 Scott Adams. Used By permission of UNIVERSAL UCLICK. All rights reserved.

The new FCC website

includes a number

of new features,

including agency blogs,

multimedia and links to

social media outlets.

NEWS IN COMPLIANCE

http://beta.fcc.gov

http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2011:090:0008:0021:EN:PDF



6 IN Compliance June 2011 www.incompliancemag.com

According to the Directive, ‘radio equipment’ is defined as any product capable of communication via emission and/or reception of radio waves. ‘Telecommunications terminal equipment’ is any device intended to be connected directly or indirectly to the public telecommunications network. The scope of the Directive also includes certain medical devices and active implantable medical devices.

The extensive list of CENELEC and ETSI standards was published in April 2011 in the Official Journal of the European Union, and replaces all previously published standards lists for the Directive.

The revised list of standards can be viewed at http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:C:2011:118:0001:0034:EN:PDF .

Updated List of Standards Released for EU’s Directive on General Product Safety

The Commission of the European Union (EU) has published an updated list of standards that can be used to demonstrate compliance with the essential requirements of its Directive 2001/95/EC, related to general product safety.

The EU’s General Product Safety Directive covers “any product…which is intended for consumers or likely, under reasonably foreseeable conditions, to be used by consumers even if not intended for them, and is supplied or made available, whether for consideration or not, in the course of a commercial activity, and whether new, used or reconditioned.” The Directive is intended to ensure the general safety of products beyond those specific safety issues addressed in other product directives, such as the Machinery Directive, the EMC Directive, or the R&TTE Directive.

The list of CEN standards was published in April 2011 in the Official Journal of the European Union, and replaces all previously published standards lists for the Directive.

The revised list of standards is available at http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:C:2011:115:0005:0008:EN:PDF .

New List of Standards for the EU’s Machinery Directive

The Commission of the European Union (EU) has issued an updated list of standards that can be used to demonstrate compliance with the essential requirements of its Directive 2006/42/EC, also known as the Machinery Directive.

The EU’s Machinery Directive defines the essential health and safety requirements for a wide range of products, including: machinery and partly completed machinery; lifting accessories; chains, ropes and webbing; interchangeable equipment; removable mechanical transmission devices; and safety components.

The Directive’s scope specifically excludes electrical and electronic

products covered under Directive 73/23/EEC (the so-called Low Voltage Directive), including household appliances, audio and video equipment, informational technology equipment and ordinary office machinery.

The extensive list of CEN and CENELEC standards for the Machinery Directive was published in April 2011 in the Official Journal of the European Union, and replaces all previously published standards lists for the Directive.

The revised list of standards can be viewed at http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri= OJ:C:2011:110:0001:0057:EN:PDF . (A correction to the standards list is available at http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:C:2011:127:0015:0015:EN:PDF .)

Aquarium Heaters Recalled Due to Fire, Laceration Hazards

United Pet Group of Cincinnati, OH has announced the recall of about 1.2 million of its Marineland Stealth and Stealth Pro aquarium heaters manufactured in China and Italy.

The company reports that a wiring problem can cause the aquarium heaters to overheat or break during normal use, potentially damaging the aquarium by causing the glass to break, and posing a fire and laceration hazard to consumers. United Pet says that it has received 38 reports of fires resulting in property damage, and 45 reports of broken aquarium glass. The company has also received one report of a consumer injury.

The recalled aquarium heaters were sold in pet stores nationwide and through various websites from January 2004 through February 2011 for between $20 and $300.

The EU has released updated lists of standards for

the R&TTE Directive, the General Product Safety Directive and

the Machinery Directive.

NEWS IN COMPLIANCE


http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:C:2011:118:0001:0034:EN:PDF













More information about this recall is available at http://www.cpsc.gov/cpscpub/prerel/prhtml11/11202.html?tab=recalls .

Recalled Satellite Communicator Can Lose Emergency Communications Capability

Spot LLC of Covington, LA has recalled about 15,400 of its Spot Satellite Communicators manufactured in China.

According to the company, the Communicator’s internal voltage regulator can stop working, resulting in the inability of the Communicator to transmit messages and tracking information in emergency situations.

Spot LLC has received two reports of product failure in temperatures below 40 degrees (Fahrenheit), but there have not been any reports of injuries related to the recalled Communicators.

The affected Communicators were sold through Cabela’s, Bass Pro Shops, REI, L.L. Bean, and other retailers nationwide from July 2010 through March 2011 for $549.

Additional details about this product recall are available at http://www.cpsc.gov/cpscpub/prerel/prhtml11/11735.html .

Box Fans Recalled Due to Fire Hazard

Lasko Products, Inc. of West Chester, PA is recalling about 4.8 million of its

box fans manufactured in the United States.

Lasko reports that a potential electrical failure in the fan’s motor poses a fire hazard to consumers. The company says that it has received seven reports of fires associated with motor failures, including two house fires and one barn fire, which resulted in extensive property damage. However, there have been no reports of injuries.

The recalled box fans were sold through mass merchandisers nationwide from July 2002 through December 2005 for between $12 and $25.

More details about this recall are available at http://www.cpsc.gov/cpscpub/prerel/prhtml11/11183.html .

Navigate the IN Compliance library with just a

Download a pdf index of all of IN Compliance Magazine’s editorial to make accessing past information a snap. Use the pdf index to locate an article, column or letter, and then find the piece in your own library or simply click to access the article on our website.

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NEWS IN COMPLIANCE

http://www.cpsc.gov/cpscpub/prerel/prhtml11/11202.html?tab=recalls



http://www.cpsc.gov/cpscpub/prerel/prhtml11/11735.html




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The iNARTE InformerProvided by the International Association for Radio, Telecommunications and Electromagnetics

HEADQUARTERS NEWSLast month we reported that the Board of Directors of both iNARTE and RABQSA had voted in favor of a motion to affiliate. This month we can report that the final Affiliation Agreement has been signed by the Presidents of both organizations at a special meeting of the iNARTE Board of Directors on May 6th.

The combination of these two groups results in the largest global personal certification organization, having 15,000 certificate holders in countries all around the world.

The affiliation process is now underway and during the next 12 months administration of the various programs and schemes will be shared between the two teams, so that within a year from now the groups will be able to fully merge. However, the name and identity of iNARTE will be preserved within the new organization, and the status of iNARTE certificate holders will remain unchanged.

Given the increased political and financial strength that this larger organization will have, we plan for a number of new iNARTE Certification programs to be introduced in the near future and for existing programs to be strengthened, adding further value for our certificate holders.

The American Society for Quality, ASQ, is the controlling body for the new organization. Headquartered in Milwaukee, WI, ASQ is a global community of experts and the leading authority on quality with over 85,000 members worldwide. ASQ supports membership services and business operations around the globe; both directly and through its work with ANSI, ANAB and RABQSA, and now also with iNARTE.

This affiliation raises the profile of iNARTE and our certificate holders in the global community. Joining the ASQ, ANSI, ANAB, RABQSA family, introduces iNARTE into the upper echelon of international regulatory organizations and industry associations and will provide new opportunities for significant growth.

GET READY FOR EMC DESIGN ENGINEER CERTIFICATION IN 2011At a special meeting between iNARTE and representatives of Japanese industry leaders during the Asia Pacific EMC week, APEMC 2011, on Jeju Island, South Korea. The formal agreement on the structure and administration of our EMC Design Engineer Certification was signed. We will now begin to publish the details on our web site, so that all who are interested have enough time to register for examination, or recognition under a Grandfather scheme, before the IEEE EMCS 2011 in Long Beach. After EMCS 2011, the new examination will be available at all the iNARTE authorized test centers.

This certification is intended to demonstrate a candidate’s knowledge of the fundamentals to be observed in designing for EMC compliance. Therefore the examination element of the program will not be the usual open book format.

Michael Hayden, iNARTE’s President, and Peter Holtmann, President and CEO of RABQSA, ink the final Affiliation Agreement


http://www.narte.org


Candidates can bring only their own prepared notebook and a simple scientific calculator to the examination room.

SOMETHING NEW FOR THE MIL STD COMMUNITYIn cooperation the Washington Laboratories Academy, http://www.wll.com/academy, iNARTE has developed a new certification specifically for the Engineers and Technicians involved with testing and designing for compliance to the MIL STDs – Certified MIL STD EMC Specialist. The requirements for certification are similar to the structure of our traditional EMC certification program, but not quite as demanding:

y Complete the application, with registration fee

y Provide three references; one from a supervisor and two from peers.

y Provide evidence of post secondary education in Engineering or a Physical Science.

y Provide work history supporting six (6) years related experience (may include education years).

y Achieve a 70% grade in a four (4) hour, open book examination.

y Write five (5) new questions similar to those in the examination

The examination will consist of 48 questions, but only 40 are to be answered. Half of the 48 questions will be taken from the MIL STDs and the remainder will be from other EMC fundamentals, such as Antennas, Amplifiers, Filters, Shielding and Bonding.

MIL STD practitioners who have not yet attained 6 years of related experience should still take the examination. Upon passing they will be awarded an Associate Certification as a MIL STD EMC Specialist, which will automatically be upgraded when the 6 years have been reached.

The MIL STD examination will be available at any time and from any of iNARTE’s authorized test centers worldwide; simply register at the iNARTE web site. Alternatively, Washington Laboratories Academy will offer both the full iNARTE EMC Engineer or Technician Examinations and the new MIL STD EMC Specialist examination immediately following each of their series of MIL STD 461F workshops, the dates of which appear in this article.

REGISTER FOR CERTIFICATION EXAMSDon’t forget the following events that offer candidates a chance to take the iNARTE certification examinations without added proctoring fees.

WASHINGTON LABORATORIES ACADEMY – MIL-STD 461F Workshop, June 14th-17th, 2011, September 13th -16th, 2011, November 14th-17th, 2011, March 13th-16th, 2012

IEEE EMCS 2011 – Long Beach, CA iNARTE workshop on August 15th, examinations on August 19th

EOS/ESD 2011 – Anaheim, CA iNARTE examinations on September 16th

IEEE PSES 2011 – San Diego, CA iNARTE examinations on October 13th

Candidates can register in advance at the iNARTE web site to examine at any event for any of the programs that we offer. At the event, candidates can register until the day before the exam, but only for the discipline related to the event. n

QUESTION OF THE MONTHLast month we asked:

If 10 V is applied across the ends of a 1mm diameter copper wire 100 m long, find the current and electrical field over the length of the wire.

The conductivity of the copper = 5.7x107 Siemens/m.

A) 4.5 A, 0.1 V/m

B) 4.5 mA, 100 V/m

C) 9 A, 0.1 V/m

D) 9 mA, 100 V/m

The correct answer is A) 4.5 A, 0.1 V/m.

The question this month is :

A logic power supply de-coupling circuit utilizes a 0.01mF decoupling capacitor with an internal inductance of 2nH connected in series with a printed circuit board trace with a inductance of 12nH. At what frequency is the impendence of the de-coupling circuit growing larger with increasing source frequency?

A) 13.5MHz

B) 189.5kHz

C) 10.7MHz

D) 1.35MHz

http://www.wll.com/academy


EMI ShieldingThermoplastic Compounds

Dramatic Cost Reductions for Electronic Device Protection

OVERVIEW OF EMI SHIELDING COMPOUNDSElectromagnetic radiation that adversely affects device performance is generally termed EMI (ElectroMagnetic Interference). Interference takes many forms such as distortion on a television, disrupted/lost data on a computer, or “crackling” on a radio broadcast. Many electronic devices not only emit electromagnetic fields which might cause interference in other systems, but they are also susceptible to stray external fields which could affect its performance. As a result, they must be shielded to ensure proper performance.

Currently, the FCC regulates EMI emission between 30 MHz and 2 GHz, but does not specify immunity to external interference. As device operating frequencies increase (applications over 10 GHz are becoming common), their wavelengths decrease proportionally, meaning that EMI can escape/enter very small openings (for example, at a frequency of 1 GHz, an opening must be less than 1/2”).

Neil Hardwick, RTP Company



Dramatic Cost Reduct ions for E lectronic Device Protect ion FEATURE

The trend toward higher operating frequencies therefore is helping drive the need for more EMI shielding. As a reference point, computer processors operate in excess of 250 MHz and some newer portable phones operate at 900 MHz. Additional EMI background information is provided in an EMI Primer at the end of this article.

Shielding is the use of conductive materials to reduce EMI by reflection or absorption. Shielding electronic products successfully from EMI is a complex problem with three essential ingredients: a source of interference, a receptor of interference, and a path connecting the source to the receptor. If any of these three ingredients is missing, an interference problem cannot exist.

Traditional EMI Shielding

Metals (due to their inherent conductivity) traditionally have been the material of choice for EMI shielding. While effective in terms of shielding, metals can be heavy and bulky solutions to the design challenge of EMI. In recent years, there has been a tremendous surge in plastic resins (with conductive coatings or fibers) replacing metals due to the manufacturing flexibility, durability and weight reduction of plastic components. Even though plastics are inherently transparent to electromagnetic radiation, advances in conductive coatings, conductive fibers and compounding techniques have allowed design engineers to take advantage of the merits of plastics while enhancing EMI shielding effectiveness.

Advantages of Thermoplastics vs. Metals

In general, Thermoplastics deliver significant advantages over Metals. As related to EMI shielding, these include:

y Weight reduction – important in portable systems

y Design freedom – allows complex contours, part consolidation, and fastening options

y Cost effective – suitable for higher volumes (needed to offset tooling investment) and reduces assembly costs.

y Good physical properties – Inherently corrosion resistant and durability as well as high strength to weight ratio.

COMPETITIVE OPTIONS FOR EMI SHIELDING WITH THERMOPLASTICSThere are many alternative approaches for EMI shielding with thermoplastics. For purposes of this article, only the most popular approaches will be highlighted. A Business Communications Company industry report estimated that the plastics shielding sector will account for 37% ($156 million) of the total United States EMI shielding market ($422

million). The European market is substantially larger (due to more stringent agency standards) and the Asian market is even bigger due to the sheer volume of electronic systems assembled in that region.

EMI Shielding Compounds (Plastics filled with Conductive Fibers)

Over the past few years, EMI Shielding Compounds have arrived on the market by incorporating EMI shielding fiber technology (both Stainless Steel and Nickel Coated Graphite) into thermoplastic compounds. As the plastic resin is insulative, these conductive fibers (with a high aspect ratio) create a conductive network within the resin. Performance of conductive fiber filled compounds is maximized by utilizing special long fiber manufacturing techniques and cube (dry) blending metal fiber bundles in order to minimize conductive fiber damage.

Fiber properties are summarized in Table 1 for the most common fiber fillers for EMI shielding compounds:

Foils and Conductive Fabrics

A metal foil or conductive fabric applied to plastic is labor intensive and ideal only for low volume and simple geometry designs. Without higher volumes (justify tooling investment) or cost minimization objectives, these applications would not be appropriate for EMI Shielding Compounds.

On-Board Shielding

Using a simple metallic inner shield to isolate EMI at the most basic level (Printed Circuit Board, or “On-Board” Shielding) may reduce the requirements for shielding enclosures. EMI Shielding Compounds may be more appropriate than on-board shielding when weight savings, secondary operation reduction, and/or design complexity are desirable attributes.

Plastics with a Conductive Coating

Within Conductive Coatings, there are three significant coating technologies (vacuum metallization, electroless plating, and conductive paints). For the purposes of this

Stainless Steel Ni-Coated Graphite

Cost Less than NCG More than Stainless Steel

Fiber Loading Typically 0.75% - 1.50% vol. Typically 6% - 12% wt.

Typically 6% - 15% wt.

Physical Properties Minimal effect on compound. Reduced impact strength.

Improved over base resin. Reduced impact strength.

Dimensional Stability Little effect Some shrinkage due to reinforcement

Fiber Ductile Rigid

Table 1


FEATURE Dramatic Cost Reduct ions for E lectronic Device Protect ion

article, these three coating technologies will not be compared versus each other. Rather, this article will help the reader become familiar with the competitive processes, advantages and disadvantages, and opportunities for EMI Shielding Compounds.

The three major coating processes are briefly discussed below. Conductive paints are the most common method of applying a conductive surface coating to plastics, but vacuum metallization is gaining ground due to its high quality control. An example of process costs is discussed in a section below.

Vacuum Metallization

y Multiple stage process that deposits a layer of aluminum on plastic in the absence of air.

y Size limitations due to vacuum chamber

Electroless Plating

y Multiple stage chemical process deposits a thin layer of copper (high conductivity and SE) and overplates it with nickel (corrosion inhibition and a good surface for painting).

y Not all plastics can be plated

y Offers best shielding of coatings

Conductive Paints

y Contain particles of silver, copper, or nickel dispersed in an acrylic, vinyl, epoxy, or urethane binder. For general shielding, nickel/acrylic paints have captured major share of market.

y Automated spraying systems apply the coating with a high degree of consistency and repeatability

y Market for paints is highly competitive and two major suppliers of conductive paints offer good technical support services

y Most plastics can be painted (PPO and Nylon do not coat well)

Comparing the Plastic Shielding Alternatives

The advantages and disadvantages EMI Shielding Compounds and Conductive Coatings are summarized in Table 2.

While it is rather easy to compare the advantages and disadvantages, it is difficult to compare the shielding capabilities as EMI Shielding Compounds shield primarily by a different mechanism (absorption) than Conductive Coatings (reflection).

EMI Shielding Compounds Conductive Coatings

Durability Integral property within protective plastic y Can flake or scratch off during handling, shipping and assembly.

y Scratching the coating may create slot antenna (shield failure and EMI leakage).

y May delaminate during thermal cycling and other adhesion problems.

Consistency Uniform EMI/RFI shielding throughout the part (even in sharp corners)

y Difficult to coat uniform thickness. y Difficult to measure conductive layer thickness

without destructive test.

Part Design Compatibility Easily accommodates complex designs Simpler designs (due to line of sight process)

Lead times Lower than Plastics with Conductive Coating Higher than EMI Shielding Compounds.

Corrosion resistance Integral property Often requires protective topcoat.

Post-Mold Shielding Operations

Part shielded right out of the mold (Integral property).

y Additional shielding steps include masking and coating part with conductive

y Usually requires additional supplier.

Special Handling during molding

None Must be kept free of contaminants for coating to adhere properly.

Recyclability Reusable and recyclable Stripping process removes coating, but creates metallic “sludge” which must be disposed of.

Costs See detailed example below See detailed example below

Table 2


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The coating industry (where electrical conductivity is a surface property) utilizes surface resistivity as a mechanism to denote shielding capability; however, for absorption shielding (where electrical conductivity is mostly within part walls), there is little correlation between surface resistivity and shielding capability. In EMI Shielding Compounds, there is good correlation between volume resistivity (100 – 10-3 ohm-cm thought to provide effective shielding) and shielding effectiveness.

Laboratory evaluation of shielding material samples (via ASTM D4935) can provide a measurement of shielding effectiveness, but determining the actual shielding effectiveness of a product requires testing of the finished assembly.

During production, coaters test the surface resistivity of parts. While this step eliminates non-conductive parts, it does not identify other quality problems (scratched surfaces or poor coating adhesion and coating thickness variations).

Actual Cost Example of Conductive Coatings

Much has been publicly stated about the “high” costs of EMI Shielding Compounds. This myth may be attributed to trying

to compare $/pound compound costs with $/piece shielding costs, and unsubstantiated claims made by the Conductive Coatings industry. When $/piece (not $/pound) costs are considered, EMI Shielding Compounds are less costly than Conductive Coatings.

An actual cost example is highlighted in Exhibit A.

Method of Gathering Information

1. Coaters were advised that an OEM was looking to convert a metal part to plastic. The “revised” plastic part would need to incorporate EMI shielding, which might require a conductive coating.

2. Drawing 981221-AA (see Exhibit A) was submitted to two painters, two electroless platers, and two vacuum metallizers.

3. Quotes were received from each coater. Typically, the coater included a unit cost to shield, a tooling/fixturing/masking cost, a scrap rate, and the shielding material. Some coaters quoted both part P1 and P2, while others admitted that one or the other was not compatible with their process.

Exhibit A: Sample part drawing used to generate Conductive Coating costs.




Assumptions

1. Does not include any molding costs

y Molding time for EMI Shielding Compounds are the same or less than unfilled polymers due to better thermal conductivity

y Does not include any injection molding tool or fixture costs. (Same for both.)

2. Typical 3% coating scrap rate not included (supply 103 parts to coater to make 100 “good” parts).

3. Coating costs based on “best” market price of $0.80/pound for ABS.

4. No shipping costs to/from coating supplier.

5. Quantity noted is a lifetime quantity. Not unusual, as part designs continually change when electronics are involved.

6. Shielding effectiveness (and frequency range) is equivalent across all scenarios.

A few key insights related to the Conductive Coatings are:

y Coaters do not understand shielding. Rather, they just test ohms/square (surface resistivity) and declare the part good/bad.

y Part design and surface area to be coated are important, not plastic weight.

y Cost drivers include labor (cycle time), material usage, and batch quantity.

y No masking (coat entire part) appears cheaper for electroless plating and vacuum metallization (labor more costly than material). For painting, where material costs are significant, there is no clear cut “rule of thumb.”

y EMI Shielding Compounds appear less costly than painting under both scenarios.

This example was designed to offer Conductive Coatings the most favorable conditions possible. The following items would increase Coating costs (but not affect EMI Shielding Compound costs):

y Small run quantities at coaters

y Shipping costs to/from coaters

y Special packaging requirements (avoid scratching surfaces)

y Including cost of scrap. Critical for expensive molded parts.

y Higher than $0.80/pound ABS cost

y Increasing part design complexity with deep recesses, more

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surface area, etc. (leading to higher coater cycle times, more conductive coating usage, and/or higher coater masking costs)

y Higher molding costs (than EMI Shielding Compounds) due to longer cycle times.

Exact cost comparisons are almost impossible to make as there are many variables and assumptions that apply. Yet, even under the most favorable conditions for Conductive Coatings, Figures 1 and 2 highlights that EMI Shielding Compounds are less costly than Coatings under both low and high volume applications.

EMI PRIMER

What is EMI?

Electromagnetic radiation that adversely affects device performance is generally termed EMI (electromagnetic interference). Many electronic devices not only emit electromagnetic fields which might cause interference in other systems, but they are also susceptible to stray external fields which could affect its performance. As a result, they must be shielded to ensure proper performance.

An electronic device exhibits EMC (electromagnetic compatibility) if it operates effectively in its designated environment without unacceptable interference to other devices.

What does EMI consist of?

Electromagnetic waves consist of both an E (electric) field and an H (magnetic) field oscillating at right angles to each other. The ratio of E to H is called the wave impedance (measured in ohms). A device operating at high voltage, with only a small amount of current flow, generates waves with high impedance. These are considered E fields. Conversely, if

a device contains a large current flow compared to its voltage, it generates a low impedance, H field.

The importance of wave impedance is shown by an EMI wave encountering an obstacle such as a metal shield. If the impedance of the wave differs greatly from the natural impedance of the shield, much of the energy is reflected and the rest is transmitted across the surface boundary where absorption in the shield further attenuates it.

EMI emissions from most electronic devices are typically high frequency, high impedance. The major wave component is the E field. Metals are intrinsically low impedance because of their high conductivity. Thus, the high impedance E wave energy is mostly reflected from metal shields. Low impedance waves (H field dominant) are mostly absorbed in a metal shield because they are more closely matched to the metal’s inherent impedance. For maximum H-field absorption, shields need to have high magnetic permeability (ability of material to serve as path for magnetic energy).

In general, the intensity of the interference caused by the signal diminishes with increasing distance from its source.

What is EMI shielding?

Shielding is the use of conductive materials to reduce EMI by reflection and/or absorption. Shielding can be applied to different areas of the electronic system from equipment enclosures to individual devices (such as circuit boards).

Effective placement of shielding (barrier between a susceptible system and an external source of electromagnetic radiation) causes an abrupt discontinuity in the path of electromagnetic waves. At high frequencies, most of the wave energy is reflected from a shield’s surface, while a smaller portion is absorbed. At lower frequencies, absorption generally predominates.

Figure 1 Figure 2




Shielding performance is a function of the properties and configuration of the shielding material (conductivity, permeability and thickness), the frequency, and distance from the source to the shield.

What does Grounding have to do with EMI shielding?

Conductive components are grounded to protect equipment users from electric shock. If a system is properly grounded, all conductive elements are theoretically at zero potential.

Shielding against EMI emissions is commonly provided by a conductive enclosure. The separate parts of the enclosure must be electrically bonded together and grounded for the shielding to work. Ineffective grounding may actually increase EMI emission levels, with the ground itself becoming a major radiating source.

What is Shielding Effectiveness?

How well a shield reduces (attenuates) the energy of a radiated electromagnetic field is referred to as its shielding effectiveness (SE). The overall expression is:

shielding effectiveness =reflection loss + absorption loss + small correction factor for

back surface reflections

The standard unit of SE measurement is the decibel (dB). The decibel value is the ratio of two measurements of electromagnetic field strength taken before and after shielding is in place. Every 20 dB increase in SE represents a tenfold reduction in EMI leakage through a shield. A 60 dB shield reduces (attenuates) field strength by a factor of 1,000 times (e.g., from 5 volts per meter to 5 millivolts/meter or a 99.9% attenuation level).

Shielding requirements for commercial electronics generally range from 40 to 60 dB. Establishing a system’s shielding requirements involves determining the radiated frequencies and the government specifications the unit must meet.

Among the typical applications for EMI shielding are the following:

EMI should be considered at the design phase of any system so that potential interference problems can be minimized.

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Since interference problems can occur anywhere within a system, shielding consideration needs to be given to the whole assembly:

y Printed Circuit Boards (PCB) – Noise originates and ultimately may affect the board level (most basic) components.

y Cables – Signal-carrying cables can act as antennas to radiate EMI. A number of shielding products (not related to EMI Shielding Compounds) can reduce EMI cable problems.

y Apertures – The amount of EMI leakage through an opening is a function of the maximum dimension of the opening. A long, narrow slot will leak much more radiation than a round hole of the same area. A slot can act as an antenna if the length exceeds one half of a wavelength (problem becomes greater at higher frequencies). Conductive EMI gaskets inserted between mating surfaces preserve current continuity of the enclosure, thereby minimizing leakage.

y Enclosures – Typically made from metal, Conductive Coatings, or EMI Shielding Compounds. Enclosures must be penetrated at various points to allow entry of cables, provide access for repair/assembly, provide ventilation, and create windows. Without attention to the design and shielding of these features, the assembly will behave like a leaky bucket.

Where is EMI shielding needed?

Uses for EMI shielding abound in computers, medical devices, telecommunications, and other types of electronic equipment. This type of equipment contains micro-circuitry that switches at high speed. Each switching event results in a short duration electrical pulse, which has a characteristic frequency inversely proportional to its time length. The FCC regulations define specific field strength limits between 30 MHz and 2000 MHz (2 GHz).

A Word About EMI Regulations

FCC regulations classify devices by their intended market – Class A devices include products for industrial and business environments while Class B devices are primarily intended for use in homes. FCC emission standards are more stringent for the mass-market Class B equipment than the Class A equipment.

Manufacturers of electronic products contend with three EMI issues:

y Suppression of internally generated EMI to prevent excessive levels of radiated and/or conducted emissions. The FCC in the United States and European Community (EC) set standards for EMI emission levels that electronic devices must meet before being sold in those countries.

y External ambient interference with equipment operation. Many companies set their own specifications for immunity to EMI over a range of frequencies. This is not yet a FCC requirement, however EC regulations do include immunity requirements.

y Internally generated emissions interfering with equipment operation. EMI from one circuit can interfere with the function of another

in the same system or subsystem (cross-talk). This problem frequently occurs in equipment with high-density packaging of PCBs and is the most common source of system EMI susceptibility.

How are devices tested for EMI Compliance?

Compliance testing requires sophisticated equipment and must be performed by accredited labs. If emission problems are found, the device will require additional shielding or redesign. n

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Eliminating the Need for

Exclusion Zones in Nuclear Power Plants

Philip F. KeeblerElectric Power Research Institute


El iminat ing the Need for Exclus ion Zones in Nuclear Power Plants FEATURE

Utilities operating nuclear power plants have been dealing with electromagnetic interference (EMI) problems for over two decades. Many early problems

that affected the operation of instrumentation and control (I&C) equipment in plants stemmed from the use of wireless transmission devices (WTDs) (e.g., radio walkie-talkies, cellular phones, etc) inside the plant in the vicinity of system cabinets and cable trays carrying bundles of cables. A simple and partially effective method of reducing EMI events caused by WTDs has been to mark off exclusion zones around system cabinets and areas where I&C equipment is installed. The use of these zones has presented some problems for existing plants. For example, some plants have had to expand the area of some zones that became ineffective upon the use of new WTDs that evidently presented an increased risk to the operation and EMI protection of I&C equipment. The sizes of some expanded zones are larger than 2,000 square feet. In addition, some zones encroach upon human traffic areas used by plant personnel to move from area to area within a plant.

Exclusion zones have also been recognized as a problem in the design of new plants. Some plant planners and designers have elected not to use exclusion zones realizing that even a well-planned program designed to limit the use of WTDs in these zones simply presents too high of a risk in causing an EMI event. Success of the exclusion zone strategy depends upon limiting the use of WTDs in those zones. Plant engineers and technicians must be able to use their WTDs in areas close to I&C equipment during maintenance and troubleshooting and possibly even in situations where cabinet doors must be open. Moreover, controlling the inventory of WTDs, especially radio walkie-talkies, will also present problems for plant staff. If radios are categorized by power level, then a plant worker may need a low-power radio when none are available. In this situation, a high-power radio may be the only option available during an emergency situation in the plant.

This article is Part 1 of 2 addressing the issue of exclusion zones in existing plants. Past EPRI research has provided useful guidance in EMC helping to avoid EMI events given the state of plant EM environments in the last 17 years. However, with increasing use of digital I&C equipment in existing plants, the planned widespread use of this equipment in new plants, and the increasing demand to use WTDs in nuclear plants, changing EM environments requires the development of new and more effective approaches to manage EMC and the risks associated with EMI events in the plants of today and tomorrow.

BACKGROUND – HISTORY OF EXCLUSION ZONES IN PREVIOUS EPRI REPORTSNuclear power plants require a very high degree of protection from EMI. To achieve this, previous guidelines1 published in a series by the Electric Power Research Institute (EPRI) used a methodology of performing plant electromagnetic (EM) surveys and from that data establishing recommended emissions and immunity levels, tests and EM management strategies. EPRI TR-102323 Revision 1 states in its abstract:

Nuclear power plants undertaking digital upgrades have been required to conduct expensive, site-specific electromagnetic surveys to demonstrate that electromagnetic interference (EMI) will not affect the operation of sensitive electronic equipment. This study was prompted by utilities desiring a more complete understanding of the EMI problem and to provide technically sound alternatives. …. Based on the emissions levels and expected types and levels of interference in nuclear power plants, guidelines for equipment susceptibility tests were developed. … the levels are conservative based on the analyzed data. The working group defined specifications to obtain additional emissions data to validate these guidelines, develop a basis for equipment emissions testing, bound highest observed emissions from nuclear plants and eliminate the need for site surveys. ….. The report includes minimum EMI limiting practices and guidance on equipment and plant emission levels.

One of the major changes made from the original report by the first revision (Rev. 1) was “an increase of the margin between the allowable plant emissions limit and the susceptibility limit from 6 dB to 8 dB.” However, a technical basis is not given in the report for the change. A discussion of the 8 dB buffer is provided in Chapter 7 of that report stating:

The limit for plant emissions was chosen to be 8 dB below the recommended equipment susceptibility testing level …. This limit is selected only to provide a reference point by which the utility engineer may determine if the emissions data from his plant are adequately bounded by the recommended susceptibility testing levels, thus allowing application of the generic susceptibility limits in this report. The plant emissions limit was chosen to be 8 dB below the recommended susceptibility levels to provide additional conservatism in when determining if the recommendations in this report can be applied to a particular facility.

1 Guidelines for Electromagnetic Interference Testing in Power Plants: Revision 1 to TR-102323-R1, EPRI, Palo Alto, CA: January 1997.

Guidelines for Electromagnetic Interference Testing of Power Plant Equipment: Revision 2 to TR-102323, EPRI, Palo Alto, CA: November 2000. 1000603.

Guidelines for Electromagnetic Interference Testing of Power Plant Equipment: Revision 3 to TR-102323, EPRI, Palo Alto, CA, and the U.S. Department of Energy, Washington, D.C.: 2004. 1003697.


FEATURE El iminat ing the Need for Exclus ion Zones in Nuclear Power Plants

While the reports utilize a strategy of studying plant emissions, and from that and other information, developing an EM protection plan, even in the conclusions of Rev. 1 in that report, the danger of relying too heavily on plant EM survey data is noted.

Operating experience from group members has shown that the nuclear power industry EMI/RFI problems are primarily due to infrequent transient interference and not steady-state EMI. Transient interference is well understood and documented in various industry standards. The industry standards do not require site emissions testing (mapping), but instead define equipment susceptibility testing levels based upon expected maximum plant EMI/RFI levels. Steady-state emissions recorded over a short period of time are unlikely to capture a transient event. The only EMI/RFI emitters that could affect digital equipment operation are portable transceivers. It is reasonable to conclude that steady-state mapping is not useful for identifying threats to digital systems.

Based on an understanding of sources of EMI in nuclear power plants, generic emissions measurements were performed to characterize both steady-state and transient EMI. Procedures were developed to describe the highest observed environment for key safety systems.

What is evident is that while previous versions of the report gave a central role to data obtained in plant EM surveys, they also recognized the dangers of relying on that data exclusively. In particular, the fact that most interference events occur due to infrequent, transient events was recognized. Guidance solely centered around the statement, “The only EMI/RFI emitters that could affect digital equipment operation are portable transceivers.” must be revised to address the risks posed by the broader availability and use of intelligent WTDs that are appearing in existing

plants as well as the ones that will be used in new plants. While certainly portable transceivers are a well identified risk, EMI events caused by the use of today’s modern cellular telephones and other WTDs in the vicinity of I&C equipment present real risks that must be addressed in any plan defining the management of EMC for nuclear plants.

After surveying the data available on plant EM environment, both steady-state and transient, a strategy is recommended for assuring the required level of interference protection. Emissions and immunity levels and tests are recommended for equipment. In order to assure that the immunity levels are not exceeded, the previous versions of the EPRI TR-102323 report recommended the use of exclusion zones to keep electromagnetic and RF sources away from I&C systems. In Chapter 6 of Rev. 1, the following section discusses the method of providing protection from portable transceivers.

Controlling Emissions SourcesPortable Transceivers (Walkie -Talkies)

1. Proper administrative control of portable transceivers is necessary to protect EMI/RFI sensitive equipment. To provide at least 8 dB margin between the transceiver emissions limit (4 V/m) and the recommended equipment susceptibility limit (10 V/m), a minimum transmitter exclusion distance must be maintained. The transceiver field intensity can be estimated knowing the device power level and assuming the highest antenna gain factor of one according to the equation:Vd = (30 P) 0.5

d Eq. 4.1 from EPRI TR-102323 Revision 1

where P is the effective radiated power of the transceiver in watts; d is the distance in meters from the transceiver and Vd is the field strength in volts/meter.

A portable transceiver with an effective radiated power of 3 watts generates a field strength of 9.5 V/m at a distance of 1 meter; 4.75 V/m at 2 meters and 0.95 V/m at 10 meters. The field strength falls of linearly with distance. Alternatively, the transceiver field strength can be measured at 1 meter by testing in accordance with Electronic Industry Standard (EIA), EIA-329 , Part II for Mobile Radios (20).

To determine the minimum transceiver exclusion distance:

1. Calculate the transceiver field strength for a distance, d of 1 meter using Equation 6.1.

2. Referring to Figure 1 (Figure 6-1 in EPRI TR-102323 Rev. 1), determine the minimum transceiver exclusion distance corresponding to the calculated transceiver field strength at 1 meter.

Figure 1: Recommended Minimum Exclusion Distance (in meters) as a Function of Transceiver Field Strength (V/m)

at 1 Meter. (EPRI TR-102323 (1997) Revision 1)


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The minimum exclusion distance is required to ensure a margin of at least 8 dB between the transceiver emissions and sensitive equipment susceptibility testing levels. It is acceptable to increase the minimum transceiver distance or to even restrict their use in rooms where EMI/RFI sensitive equipment is located. The group recognizes the need to use these devices and has developed this guidance to support their use where transceivers and EMI/RFI sensitive equipment must operate in a shared environment.

As can be seen by the section title, Portable Transceivers (Walkie-Talkies), at the time the report was written the primary concern was walkie-talkies. The report next goes on to discuss arc welding and gives guidance on how to control emissions from that source. The report assumes that the types of portable wireless devices are limited, generally hardware based radios, serving primarily a single function, for practical purposes the only concern was walkie-talkies. For these transceivers, exclusion zones were an effective strategy. Since that time and increasingly, wireless is being utilized in a rapidly growing variety of ways.

Devices increasingly are using digital techniques, controlled by software, in contrast to the traditional hardware-based radios. The trend is more toward multi-function devices that are equipped to transmit on multiple bands using a variety of protocols. Witness the very popular eBook readers, which often are equipped with a cell phone interface, capable of operating on any of several frequency bands, using a variety of RF protocols and in addition have a WiFi radio.

Increasingly, these devices aggressively use power control to maximize battery life. This means that the very same device

may operate any of its several radios at different frequencies, using a different protocol and with a wide variation in its transmit power. MIMO (multiple-input, multiple-output) is widely used, allowing some devices to simultaneously transmit on multiple frequencies over any of several antennas. One highly successful smart phone has three different antennas built into its edge.

By the Rev. 2 of the EPRI TR-102323 report, the graph (shown in Figure 2) was modified to indicate a 4 V/m maximum emission limit, reduced from the 5 V/m defined in Rev. 1. In addition, a 1/3 meter absolute minimum protection distance was added. The total distance scale was reduced from 10 meters to 4 meters. In addition, a second scale was added to the vertical axis showing the effective radiated power as well as the field strength. While the guidance and verbiage remains relatively the same, these differences indicate a growing need for additional EMC protection while also the difficulty of enforcing an exclusion zone over larger areas.

The Rev. 3 version of EPRI TR-102323 (2004) keeps the graph unchanged but refines the equation by adding a gain factor:

Vd = (30 PG) 0.5

d Eq. 4.1 from EPRI TR-102323 Revision 3

While the changes in Rev. 2 and 3 of the EPRI TR-102323 report show a growing sophistication with both threat presented by portable transceivers and the difficulties of effectively implementing and enforcing an exclusion zone strategy, the view of portable transceivers remains relatively constant, with walkie-talkies remaining in the section title for all three revisions.

However, exclusion zones have in some cases failed to provide the required protection and are becoming increasingly burdensome to establish and enforce. This was the consensus, lead by one lead I&C engineer from a major US utility in the south who is currently designing advanced nuclear plants (with one under construction) at the December 2008 EPRI Nuclear EMI Working Group Meeting held in Washington, DC.

Interference incidents which have occurred give evidence to the failure of the exclusion zone strategy to provide the desired level of EMC protection for I&C systems in existing nuclear plants. There are many documented cases of malfunction and upset of I&C systems in existing plants caused by operation of a portable wireless transmission device (not always a walkie-talkie) too close to a standard system cabinet with its doors closed.

Figure 2 (Figure 6-1 in EPRI TR-102323 Rev. 2): Recommended Minimum Exclusion Distance (in meters) as a Function of Transceiver Field Strength

(V/m) at 1 Meter. (EPRI TR-102323 (2000) Revision 2)




At times, the failure is caused by a source of EM energy that was not recognized as such where an exclusion zone was not involved. One example occurred when the starter for a high intensity discharge (HID) lighting system (magnetically-ballasted) emitted an EM pulse when it attempted to strike a burned out lamp. Because the lamp was burned out, the starter repeatedly attempted to ignite it, emitting a continuing stream of EM pulses as a result. These emissions caused false detections to be registered in a radiation monitor located in another room in the plant. Radiated EM pulses from failed lamps were converted into a band of conducted emissions coupled into the signal loop of the radiation monitoring system. This caused frequent false alarms in the control room.

Another reason for the failure of exclusion zones is that with the increasing use of wireless technology, enforcement of exclusion zones is increasingly problematic. As wireless technologies are adopted and become a more significant part of the work equipment for various personnel, like maintenance workers and security personnel, conflicts are created when enforcement of the exclusion zone would deprive a worker of the tools they rely on to perform their job. This kind of conflict is likely to become increasingly prevalent as wireless technologies are used for an ever

increasing variety of functions. Moreover, in today’s culture of increased security required to protect nuclear plants and instantly respond to any potential threat, security and plant personnel, any restriction on the use of portable wireless devices will only limit the effectiveness of these personnel to protect the staff and the plant from a possible catastrophic situation. Security personnel must be focused on protecting the plant and staff without having to worry about tripping a critical safety-related I&C system.

The job of an I&C engineer and other plant personnel on the plant floor frequently involves the use of portable wireless devices when the doors of system cabinets are open. Communications are needed with other personnel out in the plant to maintain and troubleshoot I&C systems. Without these communications, standard procedures needed to bring I&C systems back up on line could not be performed.

Additionally, one concern of planners for advanced plants is that use of the exclusion zone strategy will lead to the ‘approved use’ and ‘not approved use’ of the inventory of portable wireless devices in the plant. If wireless devices were to begin being segregated based on approval from whether or not they are likely to cause an EMI problem, additional

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confusion will result when plant personnel strive to manage this divided inventory. One engineering planner was worried that all ‘approved’ wireless devices would be in use by plant personnel when one was needed. This would result in the selection of a ‘non-approved’ device for use on the plant floor even though it might be against a plant’s policy.

Today, plants are now approving the use of some cell phones and wireless telephones while not approving others. The decision to ‘approve’ or ‘not approve’ is sometimes based on misleading information, incorrect test results, incomplete test procedures, or data for the wireless device that may lead plant personnel to suspecting that a device may or may not cause an EMI problem.

Fortunately, exclusion zones are one of three methods for protecting equipment from electromagnetic interference (EMI). Those methods are:

1. Keep unwanted energy out of sensitive I&C equipment by separating the emitting equipment from sensitive equipment. This is the exclusion zone strategy.

2. Protect sensitive equipment from the unwanted energy by using additional shielding or filtering either at the system cabinet level or inside the cabinet but external to the sensitive equipment.

3. Design sensitive equipment to be inherently immune to the effects of unwanted energy.

In Rev. 3 and earlier versions of ERPI TR-102323, Guidelines for Electromagnetic Interference Testing of Power Plant Equipment, an exclusion zone strategy for dealing with portable transceivers, guided by a simple logic, implemented the first of these strategies.

ADVANTAGES & LIMITATIONS OF EXCLUSION ZONESExclusion zones have significant advantages in existing nuclear plants early on when there were fewer portable wireless devices. However, they have also presented a number of sound limitations, which will continue to be used with digital I&C upgrades in existing plants and rolled over to design advanced plants unless a different strategy is taken. Among the advantages of exclusion zones are:

y They are directly controlled by each individual plant.

y They can be customized to the specific needs and conditions in each plant or area of a plant.

y Exclusion zones do not require specialized training or equipment.

y They are not dependent on equipment vendors, outside labs or other external entities.

y They can focus on specific classes of equipment that are problematic.

y Exclusion zones do not increase the cost of equipment or require specialized equipment installation practices.

One of the very real advantages of exclusion zones is that they are directly under the control of each individual plant. A plant is not dependent on an outside entity, such an equipment vendor or test lab. If the exclusion zone fails, it is because the plant where the failure occurred did not enforce it adequately. An exclusion zone can also fail in a sense if its bounded area is too small or if its dimensions are not adequate to provide EMC protection for the expected inventory of portable wireless devices used in a specific plant. Thus, the responsibility to maintain quality control and enforce the exclusion zone rests with the plant, which will suffer the consequences if there is a failure.

A further advantage of exclusion zones is that they can be customized for each individual plant or for specific areas in a plant. For example, if a plant has one area in which the equipment is highly immune to interference, it may not need an exclusion zone in that area at all. However, another plant, using different equipment that is more interference susceptible may require a significant level of protection for a corresponding area. Also, a plant may adjust exclusion zones from time to time, such as relaxing them during maintenance activities, when an area is off-line, or when an I&C system is upgraded to a system thought to be more immune to electromagnetic energy. Exclusion zones offer a high degree of flexibility for local conditions.

Exclusion zones also do not require specialized training or equipment. RF testing is expensive and requires a high degree of expertise to do well. These factors increase the cost of testing and also increase the chance that testing may fall short of what is required. It is not uncommon for testing to be performed with inadequate equipment, by a non-accredited test lab or by personnel who are not appropriately trained and experienced. The use of exclusion zones avoids these issues.

Another advantage of exclusion zones is also an important weakness. If only portable transceivers, especially walkie-talkies are the problem, then an exclusion zone can keep those devices away from I&C systems. This avoids requiring I&C systems take on the cost and complexity of providing significantly higher levels of immunity. If walkie-talkies are the problem, then keeping them away is an effective and efficient solution. How this becomes a weakness will be discussed later, under the disadvantages.

Exclusion zones also have the advantage that they do not increase equipment or installation costs. Requiring levels of RF immunity beyond what vendors are accustomed to will inevitably raise the price of the equipment. The typical pattern is that when vendors are required to meet new requirements they apply quick but inefficient solutions like add-on filtering


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and shielding not specifically designed for that equipment. Typically, they resort to expensive shielding and filtering. One reason for this is that they seldom have the expertise on staff to develop alternative solutions. It also occurs because they want to avoid the cost of equipment redesign and find a solution that simply protects their existing and typically vulnerable circuitry or equipment.

Over time vendors usually learn how to design equipment that has inherent RF immunity. This kind of solution typically adds little or even no cost to the equipment, but requires considerably more design expertise. This approach is usually introduced as vendors acquire the requisite expertise on their staff and are driven to provide immunity and lower prices by competitive pressures. Design changes may also be introduced to enhance EMC protection after the vendor is made aware of an EMI problem, especially one that ended up costing them money back to the customer. The result is that in the long run requiring higher levels of RF immunity does not inherently raise the cost of the equipment much, but in the short term it typically does.

These advantages of exclusion zones are significant and explain why this strategy was adopted in earlier versions of EPRI TR-102323. It must also be noted that exclusion zones are very amenable to use in a hybrid strategy. Indeed, the EPRI TR-102323 report does not rely exclusively on exclusion zones, but recommends them as part of a EMI control strategy that includes testing for emissions and immunity. From this viewpoint, the question is not whether exclusion zones should be used or not, but rather is their use, coordinated with other components of a total control strategy optimal for the current and future EM environment that plants will operate in.

The disadvantages of exclusion zones are also significant and well understood by those who are responsible for implementing and enforcing them. These include:

y It can be difficult or even impossible to implement exclusion zones.

y Enforcement of exclusion zones is increasingly difficult and even impossible.

y They are the direct responsibility of each individual plant costing time and resources.

y Exclusion zones can take on different shapes and areas even across plants that use similar designs; there are enough differences in exclusion zones across these plants to create enough differences in the design and implementation of system-wide policies designed to limit the use of wireless transmission devices.

y Exclusion zones often come in conflict with the legitimate need to use wireless enabled technologies to perform necessary job functions.

y Exclusion zones are a product of oversimplifying the problem and as a result are a flawed solution.

y Exclusion zones must use general rules that are often overly conservative.

y Exclusion zones often cannot be fully implemented around I&C systems because of physical barriers (e.g., rails, steps, other equipment) in the way.

y Exclusion zones can extend into areas that must remain clear and walk way areas that must support the heavy traffic of plant personnel.

y Exclusion zones are designed to protect I&C equipment from EM energy emanating from a known inventory of wireless transmission devices (typically portable walkie-talkies). Plants strive to control the use of wireless transmission devices, especially cell phones, owned by contractors and visitors. If these devices are allowed in a plant, then specific exclusion zones may not adequately protect I&C equipment.

Exclusion zones can be difficult or even impossible to implement. They require control of a substantial area around sensitive equipment. However, at times the required protection area is difficult or impossible to control. An example is an I&C system installed near a wall adjacent to an area where it is permissible to use wireless transmission devices, or an external wall, adjoining a parking lot. What radios will be in vehicles entering the parking lot is difficult to control, if it is possible to control them at all with any certainty. Especially when the required protection distance grows to be 3 to 10 meters, it expands beyond the typical room and takes in a significant area. Some exclusion zones take up a very large area of plant floor.

The explosive growth in the use of wireless makes enforcement of exclusion zones increasingly problematic. Wireless devices are now incorporating intelligent decision-making technologies and code making more effective use of unused spectrum. The electronic book reader illustrated in

Figure 3: An Example of an Innovative Product (Electronic Book Reader) that has an Integrated Cell Phone Transmitter




Figure 3 is an example. Wireless is used in a wider and wider variety of products and applications. It is increasingly difficult to even identify what is a wireless device. Even medical implants are including wireless transceivers, albeit to date those are operating at lower power. How do you enforce an exclusion zone if the transceiver is in an implant inside the body of a plant worker?

When exclusion zones are used, every plant must assign personnel and expend time and effort to implement and enforce them. When a plant elects to use a new wireless technology capable of reaching power levels higher than technologies previously used, new calculations must be made to determine the layout of new exclusion zones. It is not one zone that must be revised but many. (Why should plant personnel strive to keep exclusion zones updated when other more effective strategies can be applied?) This is an ongoing cost, using resources that typically are needed elsewhere. Further, enforcement of exclusion zones is an ongoing responsibility that has potentially significant consequences if there is ever a failure. Enforcement must be ongoing and vigilant to assure that there is never a failure. Assuring such continued vigilance typically requires overly conservative and redundant monitoring to assure continual and effective compliance.

Another problem with exclusion zones is that they regularly create conflicts between the need to protect sensitive I&C systems and the need to use wireless services. The increasing use of wireless for an ever expanding variety of purposes promises to make this kind of problem increasingly common. A worker uses and comes to rely on wireless tools to perform their job but then is told he or she cannot use the tools that have become necessary for their job in the exclusion zone, where they may be required to go to perform maintenance, maintain security or some other job function. These kinds of conflicts occur and create what appear to many as rules without reason.

These kinds of conflicts are exacerbated because exclusion zones must be implemented as general rules, without regard for the differences in wireless services. If, for example cell phones are discovered to cause an EMI problem in a nuclear plant then all cell phones, in all frequency bands and at all power levels must be excluded. However, personnel will often discover that their cell phone creates no interference, making the exclusion zone seem arbitrary and needless. This may lead some plants to issue ‘blanket approval’ for the use of all cell phones—a strategy that presents undefined risks to the operation of I&C equipment.

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The fact is that originally cell phones operated in the 800 MHz band, using RF power of up to two (2) watts. Today, most cell phones still use the 800 MHz band but are also equipped to operate in the 1,900 MHz band, where the maximum power is one (1) watt. Further, the 700 MHz band frequencies have already been auctioned, although equipment has not been deployed there yet. The Advanced Wireless Services (AWS) band is scheduled to be auctioned, adding frequencies up to 2,100 MHz. Other mobile services are moving forward in the 2,300 MHz and 3,500 MHz bands. The future will see an increasing variety of mobile services, using different frequencies and power levels. Exclusion zones must treat

But are portable transceivers

the only problem? More

specifically are portable

transceivers a significantly

worse source of EM fields

than other sources? If they

are, then exclusion zones are

an effective remedy.

In General Plant Environments

Exclusion zones have been used as an EMC control measure in a variety of plant environments, even those outside of the nuclear power industry. It can be an effective method for controlling EMI. A critical element in the use of an exclusion zone is the degree to which the zone can be controlled. The more reliably an environment can be controlled, the higher the effectiveness of the exclusion zone strategy. As the ability to control the environment is compromised, the effectiveness of the exclusion zone strategy also degrades. So, a fundamental requirement for an exclusion zone strategy to be effective is the ability to control the environment around sensitive equipment. The exclusion zone strategy is not recommended when the area around sensitive equipment cannot be reliably controlled.

Two specific times of plant operation when exclusion zones collapse are when the plant is under unscheduled shutdown and when the plant is under scheduled shutdown. Under unscheduled shutdown, the number one goal of every single plant personnel is to work towards getting the problem resolved and the plant back online. When power is not being generated, money is lost and lots of it. Plant workers simply work without interruption and barriers to aid in getting the plant up and running again. During this time, extremely heavy radio usage takes place. However, not all systems are fully offline. This is absolutely the case in nuclear power plants. Thus, a good number of I&C systems will need to remain online to preserve certain safety functions. Some of these systems may employ the use of exclusion zones.

Under scheduled shutdown, the plant and its personnel are given a fixed number of days to perform the scheduled work (typically refueling). Plant personnel are rewarded for getting the work done and the plant back online early. During this time, certain I&C systems must be functional in order to get

them all equally, not only because most people cannot tell one device from another, but increasingly devices can operate on multiple bands and which band they use is determined dynamically by the network.

A further complication is that cell phones and many other wireless services use very aggressive power control. They only use as much RF power as is necessary to sustain their communications link. Cell phones will vary their RF power by up to 15 dB, a factor of more than 30. The same cell phone in one location, where it has good signal conditions to the network, will operate at 1/30th the power as the same cell phone in another location with poor signal conditions. Exclusion zones must assume the worst and control these devices as if they are operating at maximum power. Indeed, the plant has no control over how much RF power they will use, and it is changing dynamically. So, how is the plant supposed to know if a cell phone provider changes the operation of its network? This could result in changing how the RF power levels are managed. The only option with the exclusion zone strategy is then to be conservative in order to assure the required level of protection.

The use of exclusion zones in existing nuclear plants comes from an analysis that finds portable transceivers, particularly walkie-talkies, to be the only EM threat, so simply keeping them away from I&C systems is an effective and efficient solution. But are portable transceivers the only problem? More specifically are portable transceivers a significantly worse source of EM fields than other sources? If they are, then exclusion zones are an effective remedy.

However, there are many sources of EM fields, both natural and man-made. Can a relatively low level of immunity in I&C systems provide adequate protection against most sources and then by using exclusion zones the more powerful fields from portable transceivers are effectively dealt with? In fact,

exclusion zones only give the delusion of protection.

In particular, there are low-frequency, high-impact events that present a rare but important risk category. Two examples of low-frequency events that produce very high levels of EM are Electromagnetic Pulse (EMP) and terroristic use of EM fields. While these events are rare, they are real risks. If they do occur, should nuclear plants be protected against them? Having I&C systems with sufficient immunity to protect against portable transceivers also will increase their ability to withstand EM fields coming from other sources.




the work done correctly and on time. Some of these systems may employ the use of exclusion zones.

The exclusion zone strategy also comes under pressure when competing legitimate interests come into conflict. For the purposes of EMC, an exclusion zone might be desirable. However, there might be very legitimate reasons why wireless equipment should be brought into close proximity to equipment inside an exclusion zone. Maintenance personnel are more effective if they can use their cell phones or walkie-talkies to verify equipment functionality or get needed technical support from another plant engineer. Many exclusion zones are so large that troubleshooting some

The use of exclusion zones

is increasingly rejected.

Other methods of EMC

control are found more

effective. Shielding, filtering

or improved immunity, but

implemented at the right level,

are increasingly the preferred

methods for EMC control.

Philip F. Keebler, Sr. Research Engineer, EMC GroupElectric Power Research Institute, Knoxville, Tennessee

[email protected]

I&C systems requires the use of three personnel: one at the system cabinet to observe indicators and make measurements, one in the middle of the exclusion zone acting as a ‘repeater’ to deliver the message to personnel outside the exclusion zone so the information can be radioed to personnel in the control room or another area of the plant. Other examples are created when space is limited and different equipment must be put into close proximity, due to its functionality. There are a wide variety of reasons that can arise and put pressure on the use of exclusion zones.

A simple reason exclusion zones are problematic is that real estate inside a plant is in high demand and is generally expensive. Having a lot of unused space in any environment is generally inefficient. Spreading equipment out requires more building space, costing money. Often, the space simply is not available. However, even when space is available, it comes at a cost, usually a high cost. Mapping out an exclusion zone for a specific I&C system may permanently mark that area as unusable for any other function.

For these reasons, the use of exclusion zones is increasingly rejected. Planners engaging in digital upgrades in existing plants and in specifying digital equipment for advanced nuclear plants do not want to see exclusion zones in their plants. Other methods of EMC control are found more effective. Shielding, filtering or improved immunity, but implemented at the right level, are increasingly the preferred methods for EMC control.

In Advanced Nuclear Plant Environments

The disadvantages of exclusion zones become increasingly relevant when considering the environments of advanced nuclear power plants. Looking to the future, the use of wireless for communications, data transmission and sensor networks is a growing reality. The ability to exclude these services from areas were I&C systems operate is not only

increasingly problematic but also undesirable. Indeed, some I&C systems will greatly benefit from wireless connectivity, for example, to distributed sensor networks. The ability to enforce an exclusion zone will be a growing problem as wireless is integrated into an ever increasing variety of equipment types. Therefore, a different method for providing the required level of protection is required.

CONCLUSIONThis article, Part 1 of 2 on the topic of exclusion zones and their strategies in nuclear power plants, presented a history of the development and use of exclusion zones originally defined

by EPRI research in the area of EMC for nuclear power plants. Early strategies served their purpose in a time when wireless devices were few. Moving towards a more effective strategy for protecting digital I&C equipment from radiated threats in plant environments requires an understanding of the advantages and disadvantages of exclusion zones as presented in this article. Effective and dynamic protection of digital I&C equipment against radiated threats must be an inherent part of I&C systems allowing plant engineers to focus on plant safety, operation, maintenance, and upgrades without the challenges presented by the use of exclusion zones. Nuclear power plants are facing more challenges, and those that can be resolved providing a higher degree of safety and reduced risk will help utilities maintain safe plants that are profitable. Part 2 of this article will address Elements of the Exclusion Zone Strategy with a focus on peeling back the layers of immunity for I&C systems to establish whole-system immunity. n

REFERENCES y Guidelines for Electromagnetic Interference Testing in Power Plants, EPRI TR-102323, Rev 1, Electric Power Research Institute, Palo Alto, CA, 1996.

y Guidelines for Electromagnetic Interference Testing in Power Plants, Revision 2 to EPRI TR-102323, TR-1000603, Electric Power Research Institute, Palo Alto, CA, 2000.

y Guidelines for Electromagnetic Interference Testing in Power Plants, Revision 3 to EPRI TR-102323, TR-1003697, Electric Power Research Institute, Palo Alto, CA, 2004.

y Guidelines for Evaluating Electromagnetic and Radio-Frequency Interference in Safety-Related Instrumentation and Control Systems, Regulatory Guide (R.G.) 1.180, U. S. Nuclear Regulatory Commission, 1996.


Rethinking the Role of Power and Return Planes

by Glen Dash, Ampyx LLC

There may be a better use for PCB planes than to just distribute power, namely to provide shielding.


Rethinking the Role of Power and Return Planes FEATURE

To begin, we will test the circuit shown in Figure 1 for its EMI characteristics. A clock driver, running at 25 MHz and using HC technology, drives an HC load.

Techniques commonly thought of as good EMC practice are used throughout. A wafer-type low inductance capacitor is placed beneath each IC. The run connecting the clock to its load is straight and placed immediately adjacent to the return plane. A damping resistor is in use. Telescoping antenna elements are connected to the return plane and extend out 19 inches from either edge of the board simulating the use of I/O cables. The telescoping elements are set to produce a system resonance at 125 MHz, the 5th harmonic of the clock.

We also covered both the top and the bottom of our circuit with copper foil creating what are, in effect, shields on the top and bottom. Everything is covered, the batteries, the ICs and the connections between the clock driver and its load. The device is shown in Figure 2 (page 34). Solder was used to

ensure a good electrical connection where seams of the copper tape came together, which accounts for the rough appearance.

Emission results are shown in Figure 4 (page 34) and are unimpressive.

Why should this circuit radiate so much energy? Part of the reason is that a complete shield is not in use. The top shield is still separated from the bottom shield, the top shield being connected to V+ and the bottom shield to V-. There is a gap between V+ and V- represented by the dielectric between the PC board’s two planes and it is that gap that makes all the difference.

The source of the radiation can be traced to a phenomenon we have noted elsewhere. When a MOS driver switches, there is a moment during the transition when both the

Figure 1: The device we first tested had shields over the top and bottom of the PCB, the top shield connected to V+ and the bottom to V-. The shields were formed with copper tape soldered at the seams.


FEATURE Rethinking the Role of Power and Return Planes

P and N channel devices are both on. A brief burst of noise known as Idd Delta (or Idd Noise) is produced. This impulse is on the order of hundreds of picoseconds to a few nanoseconds in length and one to ten milliamps in amplitude per gate for most MOS based technologies. This impulse is impressed onto the power planes which can modeled as a kind of parallel plate transmission line. The impedance of a parallel plate transmission line is well known.

It is:

Where:

d = Distance between the planes

w = Width of the planes

εr = Relative permittivity

ε0 = Dielectric constant in free space= 8.85 x 10 -12

µ0 = free space permeability = 4π x 10 -7

The impedance of a transmission line is also a function of its capacitance and inductance per unit length and is equal to:

Where:

L = Inductance in Henries per unit length

C = Capacitance in Farads per unit length

As for the capacitance per meter of length, that too is well known. Ignoring fringing fields it is:

These three equations allows us to derive the approximate inductance per unit length of a parallel plate transmission line:

Figure 2: The top side of our experimental circuit carries V+ and the bottom, V-. Components and wires, top and

bottom, are covered with foil.

Figure 3: The test setup. Note the telescoping elements used to simulate I/O cables. Figure 4


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It is this inductance that gives rise to our problems, specifically the inductance of the return plane. Since the transmission line is symmetrical, we can assign half the total inductance to the return:

For our circuit, d=1.6mm and w=11.5cm, resulting in a return inductance of approximately .09 nh/cm.

We can use circuit models to describe the phenomenon. In Figure 5a a current source, which we model as impulsive with fundamental frequency of 25 MHz and of a peak amplitude of 1-10 milliamps, drives a nearby filter consisting of a bypass capacitor and an associated ferrite bead. That filter, in turn, is connected to the elemental inductances and capacitances which comprise the transmission line formed by the power planes.

The model helps explain why our shields do not work. Currents passing down the transmission line formed by the power planes result in a voltage drop across the return plane. The resulting voltage drop, Vr causes the attached telescopic antennas to radiate like a dipole.

Real world circuits are, of course, more complicated. They act like a transmission lines terminated here and there with bypass capacitors and, at their edges, not at all. That makes emissions difficult to predict. However we can say that the emissions are a function of at least three things: (1) the impedance of the return plane, (2) resonances caused by the combination of various inductances and capacitances, and (3) transmission line effects from the power planes acting as poorly terminated transmission lines.

Some authors have recommended controlling emissions by flattening the impedance presented by power planes. [1] Here we propose a different approach, the use of planes to provide shielding.

Figure 5: Transmission line characteristics of the power and return planes are modeled here. The model can be simplified as shown in (b).

Figure 6: Going somewhat against convention, we sought to lower emissions by hard wiring the ICs to the supply using ordinary wires, isolating the top shield

from V+ and then connecting both shields together. Emissions dropped significantly.




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Figure 7: Our comparative emissions results.

At first blush, Figure 6 does not look very much different than Figure 1, but there is a crucial difference. Here the top and bottom shields are connected together and the top shield isolated from the supply. We have routed separate wires from our power supply to the ICs to provide power. This time when emissions are measured, the fall is dramatic (Figure 7). Only one emission is found at all greater than 5 uV/m at 10m, it being at 125 MHz and about 20 dB down from the device of Figure 1.

The reason for the dramatic fall is quite simple, we now have a Faraday cage and it is working the way it should. Figure 7 is simply confirmation of what we already know, that if you put a complete shield around a circuit, it does not radiate very much.

Unfortunately, complete shielding is often not a practical option. In order to evaluate a more practical solution, we removed the shielding over the integrated circuits as shown in Figure 8 (page 38). While radiation did increase, the reduction in emissions was still dramatic (Figure 7).

We also experimented with a serrated connection between the top and bottom shields as shown in Figure 9 (page 38). It had no significant effect on emissions.

We are not contending that a well designed, low impedance power source is not important -- it is. Providing a low impedance, low Q power source is vital to preserving noise margin.

However, it may not be the key to reducing emissions.

In Figure 10 (page 38) we show some PCB stack ups where the outer layers are used for a shield. Figure 10(a), for example, shows a six-layer stack up. The top layer is used to support components.

The second and sixth layers comprise an internal shield. They carry no traces though they will be studded with holes to allow vias. No gaps or openings should be permitted in this shield layer, just holes. The inner layers contain power and circuit layers. These inner layers do not extend to the edge of the board. Instead, a small portion (a centimeter or so) is reserved for a shield ring. Vias connect layer 2 to layer 6.

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The six layer stack up does not allow for much circuitry so the eight layer stack of Figure 10(b) may be more practical. Again, the top layer is used for component support and layers 2 and 8 comprise the shield. The outer centimeter or so of layers 3, 5, 6 and 7 are reserved for the shield rings. Vias passing through these rings connect the layers together, completing the shield. We have also chosen to make layer 4 a shield layer, isolating the high speed layer 3 from power layer 5.

A 10-layer stack up is also shown in Figure 10(c).

There are as many variations as there are combinations of circuit, power and shield layers, but all share a common theme. A shield is formed consisting of two of the outer layers of the PCB connected together at their edges through the use of shield rings and vias on the intervening layers

Note, however, that any conductors that exit this shield will radiate unless they are filtered or shielded. Fortunately, the

Figure 11: Even two well designed PCBs may radiate if interconnected with multi-conductor cable carrying high frequency currents. The inductance of the cable causes a

voltage drop that drives the two PCBs and their attached I/O cables as if they were two halves of a dipole, even if they are

shielded. A return strap can be used to “short out” Vr as shown in (b). Other designs can exhibit similar problems, but similar

solutions can be employed as illustrated in (c) and (d).

Figure 8: We modified the device by removing the shields over the ICs. Emission rose, but were still significantly lower than those detected from the device of Figure 1.

Figure 9: We serrated the edge of the fully shielded device of Figure 8. Emissions were not noticeably affected.

Figure 10: Some suggested stack ups.




support layer 1 and the shield layer adjacent to it are available to facilitate filtering and shielding.

Among the most challenging designs are those involving two or more PC boards (Figure 11). Let us assume that all the boards shown in Figure 11 have been properly designed as called for in this article. When interconnected they may still radiate badly. The problem is that the connection between the boards is inductive.

One solution is to provide a shorting strap as shown in Figure 11(b). While the connection between the two boards is inductive, the shorting strap essentially shorts out this voltage and greatly lessens radiation. To minimize its inductance, however, it must be nearly as wide as it is long.

Figure 11(c) shows a display board interconnected with a main unit, an arrangement common in notebook computers. I/O cables attached to the computer may radiate badly even if both the computer and the display board are well designed. The inductance of the cabling between them may be the culprit. It can cause a voltage drop between the display board and the main unit. This in turn causes the main unit and its attached I/O to act as one side of an antenna system and the display unit to act as its counterpoise. One solution is to short out the voltage source, Vr, with a short, fat shorting bar or strap as shown. n

Glen Dash is the author of numerous papers on electromagnetics. He was educated at MIT and was the founder of several companies dedicated to helping companies achieve regulatory compliance. Currently he operates the Glen Dash Foundation which uses ground penetrating radar to map archaeological sites, principally in Egypt. [email protected]

REFERENCES1. J. Pattavina, “Bypassing PC Boards: Thumb Your Nose at

Rules of Thumb,” EDN, page 149, October 22, 1998.

Copyright Ampyx LLC

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Antenna characteristics, such as input impedance are considerably deviated from those in free space when another antenna is located in the vicinity of the antenna. This often causes system degradation problems. In this article, effects of a parasitic

wire located beneath the slotted ground plane are investigated on the coupling between monopole antennas above the ground plane. The method of moments is applied to the problem and a combined matrix formulation that includes mutual coupling effects between the elements located in both regions is newly introduced. It is shown that a wire beneath the ground plane

considerably affects coupling characteristics between two monopoles above the ground plane when the slot resonates.

© 2010 IEEE Reprinted, with permission, from 2010 IEEE International Symposium on Electromagnetic Compatibility Proceedings.

Effects of a Wire Beneath the Ground Plane on Antenna Coupling through a Slot

Takehiro Morioka and Kazuhiro Hirasawa


Effects of a Wire Beneath the Ground Plane on Antenna Coupl ing through a S lot FEATURE

With the development of wireless communications, antennas have been improved to meet the requirements of the system. A number of studies

have been published on the improvement method of the antenna characteristics by combining radiating elements. A common approach to improve radiation patterns and to enhance operating frequency band is to add a parasitic element. Especially for radiation pattern improvement, a combination of slot and wire antennas can often provide a suitable radiation pattern for the purpose [1] - [3]. When a slot antenna is made on the ground plane, it radiates electromagnetic fields into both sides of the ground plane. Since the backward radiation is not necessary for most of the communication antennas, the slot antennas are usually used with the cavity backed to radiate electromagnetic fields into one side of the ground plane.

On the other hand, when antennas for different purposes are required to operate in a limited area, some radiated power of an antenna is absorbed by the other antennas and this often causes system degradation problems. To reduce coupling between two closely located wire antennas, the load impedance at the port of the receiving antenna was adjusted and the coupling was reduced [4]. However, this method is generally not practical since the load impedance at the port of the receiving antenna is fixed at the characteristic impedance of the feeding system of the antenna. Another method to reduce coupling between two monopole antennas operating at different frequencies has been proposed. A center loaded slot was made on an infinite ground plane to reduce coupling at two frequencies [5].

A slot made on the ground plane couples two regions above and beneath the ground plane. Consequently, electromagnetic fields above the ground plane are affected by structures beneath the ground plane. However, most of the studies have not taken into account the effects of the structure in the region beneath the ground plane. In this article, coupling between two monopole antennas designed to operate at different frequencies is considered. A parasitic monopole is located beneath the ground plane and the effects of structures beneath the ground plane through the slot are investigated.

ANALYTICAL METHOD

Consider a simple model as shown in Figure 1a. A wire and a source are located above the ground plane. Beneath a ground plane another wire is located. A space is divided into two regions by an infinite ground plane. Regions above and beneath the ground plane are named region 1 and 2, respectively. An aperture is made on the ground plane. Incident electromagnetic fields radiated from the source are denoted E i , H i. The scattered fields by the ground plane with the aperture and by wire 1 are denoted E ss , H ss, and

, respectively. Penetrating fields through the

aperture from region 1 to 2 are denoted E p , H p and the scattered fields by wire 2 are . Accordingly, total electromagnetic fields in each region can be respectively written as follows:

At the surface of the aperture boundary conditions are given by:

where is is the current flowing across the aperture and i1 is the unit normal vector on the boundary of the regions pointing from region 2 to 1. By applying the equivalent theorem the aperture can be covered with a conductor and each region can be isolated by the infinite ground plane as shown in Figure 1b.

Figure 1: Analytical model of the problem


FEATURE Effects of a Wire Beneath the Ground Plane on Antenna Coupl ing through a S lot

Boundary conditions at the surface of the ground plane are given by:

Consequently, this model can be separated into two problems using the image theory. Finally, when the source is a transmitting antenna and the aperture is a narrow slot, we have the following equations:

where n and eφ are the unit vectors normal and tangential to the cylindrical elements. Note that the slot is replaced by a cylindrical magnetic current having an equivalent radius.

Electric currents and on wire 1 and 2 are expressed by the subsectional expansion and weight functions as follows:

By applying the method of moments (MoM) hybrid matrix equations for region 1 and 2 are obtained as:

In this expression of the matrix elements are the self-impedances of the electric current, self-admittances of the magnetic current, and mutual-impedances between magnetic and electric currents. Matrixes in equations (14) and (15) are (N1 + N3) × (N1 + N3) and (N2 + N3) × (N2 +N3), respectively. The following relationships are obtained by applying

[6]:

Using (16) – (18), (14) and (15) can be combined and a single matrix equation is obtained as follows:

This is a (N1 + N2 + N3) × (N1 + N2 + N3) matrix.

RESULTS AND DISCUSSIONTo investigate the effects of the boundary condition beneath the ground plane on the electromagnetic fields above the ground plane, a concrete model is considered. Two monopole antennas are closely located on the ground plane.

Figure 2 is a sketch of the analytical model of a typical problem. An infinite ground plane is in the x-y plane. It is assumed that the ground plane is an infinitely thin perfect conductor. Two regions separated by the infinite ground plane are named region 1: above the ground plane, and region 2: beneath the ground plane, respectively. n1 and n2 are the unit normal vector on the ground plane pointing out to each region. Although most of the ground plane has a finite size and the diffracted electromagnetic fields by the edges of the ground plane should be taken into account for the coupling evaluation, a simple model with an infinite ground plane is expected to show the interaction between region 1 and 2 through a slot clearly. Two monopole antennas are located vertically on the ground plane. Antennas #1 and #2 are separated by d centered at the origin. Heights of antennas #1

Figure 2: Antenna arrangement to evaluate the effect of a parasitic wire beneath the ground plane through a slot




and #2 are h1 and h2 , respectively. A slot of length l and width w, is made on the ground plane. The center of the y-directed slot is on the x-axis. A parasitic element beneath the ground plane (region 2) is connected to the ground plane. The height of the parasitic element is hp and the base is at (xp , yp).

Some useful coefficients are introduced to investigate effects of the parasitic element beneath the ground plane. As stated in Section I, when some antennas are located in the vicinity of the transmitting antenna, some radiated power is absorbed by them and this often causes system degradation problems. A coupling coefficient is introduced to evaluate the level of the coupling between antennas [4]. It is defined as a ratio of the received power at the load of the receiving antenna Pr to the input power to the transmitting antenna Pin as:

where the parameters are shown in Figure 3. The coupling coefficient can be easily measured by using a network analyzer as |S21|.

Most part of the power radiated by the transmitting antenna reaches to a far region above the ground plane. The radiation coefficient is defined as the ratio of the radiated power into region 1 Prad1 to Pin as:

Since the slot radiates electromagnetic fields from both sides of the ground plane, a part of the radiated power reaches to a far region beneath the ground plane. There is no consumed power by the structure in region 2 in our analytical model. Accordingly, the penetration coefficient can be defined as the ratio of the penetrated power into region 2 Prad2 to Pin as:

Coupling Coefficients

1) Single-band operation: Figure 4 shows the frequency characteristics of the coupling coefficient. To simplify the problem antennas #1 and #2 are designed to be the same height as h1 = h2 = 50 mm. This Figure contains calculated coupling coefficients by the MoM and measured ones. In the measurement, a square ground plane whose one side length was 1 m was used. Three conditions were considered. They are the cases when two antennas are on an infinite and a slotted ground plane. In addition to these, the other case when antennas are on a slotted ground plane with a

parasitic monopole beneath the ground plane is considered. The coupling coefficients on the ideal ground plane are about –13 dB in the entire frequency range from 1350 MHz to 1550 MHz. By making a narrow slot ( w = 1 mm and l = 97 mm), a reduction of coupling coefficient by 14 dB is obtained at 1460 MHz. By locating a parasitic monopole of hp = 50 mm at ( xp , yp) = (70 mm, 0 mm), a reduction of the coupling coefficient by 40 dB is obtained at 1480 MHz compared with the one with the ideal ground plane. Measured and calculated coupling coefficients are in good agreement for all the cases. Although the measured frequency for the maximum reduction is slightly different from the calculated one, the difference is less than 1%.

2) Dual-band Operation: A recent electrical device often contains systems operating at different frequencies. To analyze this kind of complex situation, the heights of antenna #1 and #2 should be different. In this article, antennas #1 and #2 are designed to operate around 1.5 GHz and 1.0 GHz, respectively. The heights of the antennas are h1 = 50 mm and h2 = 75 mm.

Figure 4: Measured and calculated frequency characteristics of the coupling coefficient

Figure 3: Radiated, penetrated and received power


FEATURE Effects of a Wire Beneath the Ground Plane on Antenna Coupl ing through a S lot

Since the slot is designed to be l = 100 mm, it resonates around 1.5 GHz. Penetrated electromagnetic fields strongly coupled with the parasitic element in region 2 and this affects the coupling coefficient in region 1. Accordingly, a strong effect on the coupling may be obtained by the parasitic element when the slot resonates. In Figure 4 a remarkable reduction of coupling between monopole antennas operating at the same frequency was obtained at the resonant frequency of the slot. The coupling coefficient remains almost the same at off-resonant frequencies of the slot. By loading an impedance element to the slot, the slot can be resonant at two different frequencies. By the same procedure shown in [5], a simple circuit shown in Figure 5 is loaded at the center of the slot to make the slot resonate at both 1.0 GHz and 1.5 GHz. Capacitors and an inductor are C0 (series) = 0.2 pF, C΄ (parallel) = 0.406 pF, and L = 0.0277 μ H.

The reduction of the coupling coefficient at 1GHz should be obtained by loading an impedance element at the center of the slot. Figure 5 shows the coupling coefficients at 1.0 GHz with respect to the parasitic element location on

the x-axis for various heights of the parasitic element when antenna #1 is fed. With a center loaded slot a reduction of the coupling coefficient by 19 dB is obtained. It is clear that coupling between antennas in region 1 is remarkably affected by the parasitic element in region 2. The most effective height of the parasitic element (hp = 65 mm) is 87% of the quarter wavelength of the operating frequency at 1.0 GHz. xp = 60 mm is a suitable location to reduce the coupling coefficient.

To obtain the maximum reduction of the coupling center of the slot. coefficient the parasitic element location is changed in the y-direction. Figure 6 shows the coupling coefficient with respect to the base location of the parasitic element when hp = 65 mm. Since the structure of the analytical model is symmetric with respect to the x-z plane, coupling coefficients in the region where yp < 0 are not shown. When the parasitic monopole is located in the vicinity of the slot little reduction of the coupling coefficient is obtained. The maximum reduction is obtained when the base of the parasitic monopole is located at (xp, yp) = (61 mm, 0 mm).

Figure 7 shows the frequency characteristics of the coupling coefficient. Since two antennas are operating at the same time, two cases should be studied. When antenna #1 is considered as a transmitting antenna, antenna #2 should be a receiving antenna and visa versa. The load impedance at the port of the receiving antenna is equal to the characteristic impedance of the feed system and it is 50 Ω for the ordinary system. Frequency characteristics of the coupling coefficient in Figure 7a are obtained when antenna #2 is fed. When antennas are located on the ideal ground plane, the maximum coupling is obtained around 1.5 GHz when antenna #1 resonates. By introducing a slot between the antennas, a reduction of the coupling coefficient by 10 dB is obtained at 1450 MHz. However, no reduction is obtained around 1.0 GHz since the unloaded slot does not resonate. By loading a simple circuit shown in Figure 5, the slot resonates at 1.0 GHz and a reduction of about 10 dB is obtained. On the other hand, the bandwidth where the reduction of the coupling coefficient is obtained around 1.5 GHz becomes narrower due to the high-Q characteristics of the loaded circuit. By locating a parasitic element beneath the ground plane at a proper location a remarkable reduction of the coupling coefficient by 21 dB is obtained.

As shown in Figure 7b, when antenna #1 is fed, the maximum coupling coefficient is obtained around 900 MHz when antenna #2 resonates. When antenna #2 is fed, a coupling coefficient reduction of 10 dB is obtained around 1.5 GHz due to the unloaded slot resonance. A remarkable reduction of the coupling coefficient is obtained at both of the frequency bands by loading an impedance element at the center of the slot.

Figure 5: Coupling coefficient at 1.0 GHz with respect to the height and location

Figure 6: Coupling coefficient with respect to the location of the parasitic element (hp = 50 mm) when the monopole antenna #1 (h1 = 50 mm) is fed.




It is apparent that the remarkable effects on the coupling between the antennas above the ground plane by adding a parasitic element at a proper location beneath the ground plane.

Radiation and Penetration Coefficients

Figure 8 shows the frequency characteristics of R and P when antenna #1 is fed. No penetration of power into region 2 is obtained without a slot on the ground plane. However, the radiated power from antenna #1 is received by antenna #2 and the minimum R is obtained around 900 MHz. By introducing an unloaded slot the power penetrates into region 2 around 1.5 GHz due to the resonance of the slot and P becomes 18%. In addition to this, the bandwidth of the penetration is wide. On the other hand, the bandwidth of penetration centered at 1.5 GHz becomes narrower by loading the impedance at the center of the slot. At 1.0 GHz a considerable penetration into region 2 is found. Consequently, R is reduced to 70%.

We are mainly interested in the near field coupling effects and the radiation patterns are not discussed here.

CONCLUSIONS Effects of a parasitic wire located beneath the ground plane were investigated on the electromagnetic characteristics above the ground plane through a slot. The method of moments was applied to the problem and a combined matrix formulation that contains mutual coupling between the elements located in both regions was newly introduced. The coupling between closely located monopoles was investigated to show the validity of the method and it became apparent that a wire beneath the ground plane considerably affects coupling characteristics above the ground plane when the slot resonates. n

REFERENCES 1. A. Clavin, D. A. Huebner, and F. J. Kilburg, “An improved

element for use in array antennas,” IEEE Trans. Antennas Propagat., vol. AP-20, pp. 521-526, July 1974.

2. A. B. Papierz, S. M. Sanzgiri, and S. R. Laxpati, “Analysis of antenna structure with equal E- and H-patterns,” in Proc. Inst. Elec. Eng., 124, pp. 25-30, January 1977.

3. M. Kominami, and K. Rokusima, “Analysis of an antenna composed of arbitrarily located slots and wires,” IEEE Trans. Antennas Propagat., vol. AP-32, pp.154-158, February 1984.

4. K. Hirasawa, “Bounds of uncertain interference between closely located antennas,” IEEE Trans. Electromaagn. Compat., vol. EMC-26, pp. 129-133, August 1984.

5. T. Morioka, and K. Hirasawa, “Reduction of coupling between two wire antennas using a slot,” IEICE Trans.Commun., vol. E80-B, pp. 699-705, May 1997.

6. R. F. Harrington, “Resonant behavior of a small aperture backed by a conducting body,” IEEE Trans. Antennas Propagat., vol. AP-30, pp. 205-212, March 1982.

Takehiro Morioka, National Institute of Advanced Industrial Science and Technology (AIST), [email protected]

Kazuhiro Hirasawa, University of Tsukuba

Figure 7: Frequency characteristics of the coupling coefficient

Figure 8: Relative radiation, penetration and received power when antenna #1 (h1 = 50 mm) is fed



The Future of EMC Engineeringby Mark I. Montrose, Montrose Compliance Services, Inc.

Most of the time we only think about our daily work, either research or applied engineering with a focus on immediate revenue generation or publishing the results of outstanding research. Insufficient time is given to thinking about the future, especially products and services that will make not only our lives richer, but that of humanity. Marketing seems to have all the fun in this department while engineers enjoy designing with advances in semiconductor technology.

Every few months a new item is released that allows us greater access to content, namely wireless technology. This includes numerous iProducts, 4G phones, advanced gaming consoles, and higher bandwidth computing devices and networks, to name a few. Notice that there is a pattern here-small, hand-held device. What about large systems of systems and the infrastructure to support our quality of life.

Engineers in the future must provide significant impact for society by minimizing worldwide energy consumption while developing new products and services that bring value to users As a result, some facets of engineering problems in the future will deal with not only electrical aspects of circuits and systems, but second order effects such as advances in semiconductor technology, reducing the cost of manufacturing, implementing lower power consuming devices, recycling, and ancillary legal requirements mandated internationally.

One of the most important engineering challenges in the future lies in energy creation, distribution and utilization. There is a voracious appetite for electricity required for survival in a complex, interdisciplinary, and multicultural world. Different cultures view advances in electrical engineering with either awe such as those in third world countries, or with a shrug as if, so what’s new, does it make my life easier and more fun, and can I afford it?

We must ensure that there is sufficient electrical power to sustain life on this planet, and the need to conserve

this precious resource through advances in system design using sound engineering principles. This is best achieved by designing circuits, systems, and power supplies that manage electrical networks in an efficient and cost effective manner on a large scale.

A country with a sophisticated infrastructure and high quality network of electrical power generation and distribution is a major contributor to the world’s economy. Countries with minimal availability of electric power generally have poor economies and quality of life.

If we do not perform due diligence as EMC engineers, we could be a contributor to a potential shortage of electrical power since we are able to produce only so much electricity at one time. Without new power plants coming online, where are we going to get the power to sustain our life style and the ability to recharge our hand-held products, not to mention the lights in our house, our entertainment systems and appliances, and everything else that uses electricity? Electrical supply and demand is a challenge for all engineers to think about not only today, but for our future. n

Mark I. Montrose is an EMC consultant with Montrose Compliance Services, Inc. having 30 years of applied EMC experience. He currently sits on the Board of Directors of the IEEE (Division VI Director) and is a long term past member of the IEEE EMC Society Board of Directors as well as Champion and first President of the IEEE Product Safety Engineering Society. He provides professional consulting and training seminars worldwide and can be reached at [email protected].

The Need for Energy Conservation




Low Compression Conductive Foam

A new EMI shielding material has been introduced by Leader Tech to significantly improve the quality and perfor-mance of die-cut enclosure gaskets. The new low compression CFS Conductive Foam Shielding material is manufactured in sheets that have a low-resistance polyester fabric surface and a resilient Nickel-Copper polyurethane foam center. These characteristics make CFS the ideal choice for intricate die-cut finishing operations found in many I/O panel, backplane and access panel applications. A standard conductive, pressure sensitive adhesive facilitates fast and easy installation.

Leader Tech’s CFS gaskets offer a typical Shielding Effectiveness of 60dB between 10MHz-3GHz. In addition, the conductive foam exhibits a compression load of 2.1 psi at 30% compression and has an operational temperature range from -40°F to +156°F. For more information, call (813) 855-6921or visit http://www.leadertechinc.com.

LCR Electronics Honored with Five Star Supplier Excellence Award

LCR Electronics, a manufacturer of EMI filters, backplanes and rugged system enclosures for military, telecom and commercial applications, was recognized for its quality and perfor-mance by Raytheon Integrated Defense Systems (IDS) at an award ceremony held at the Wyndham Hotel in Andover, Massachusetts on April 13, 2011.

LCR was one of only 14 companies to be presented with the coveted Five Star Supplier Excellence Award. This is the highest honor that can be achieved by a Raytheon IDS supplier. Suppliers must achieve 100% on-time delivery; provide product with a 100% quality record and

implement a continuous process and performance improvement program.

LCR’s role in the Patriot Air and Missile Defense System dates back over the last five years. LCR’s backplanes and enclosure systems are used in the Raytheon Patriot Radar and Fire Control System. LCR is currently under a five year Long Term Agreement (LTA) that includes in excess of 20 different backplane and enclosure system assemblies. For more information, visit http://www.lcr-inc.com.

Keystone Compliance Adds Environmental Laboratory Manager

Keystone Compliance, LLC, an EMI/EMC compliance test lab in New Castle, PA, has announced the appointment of Scott Maxwell to the position of Environmental Laboratory Manager. Maxwell will lead Keystone Compliance’s entry into environmental testing.

Maxwell has over 20 years of experience in the environmental testing industry. His experience includes direct exposure to various types of environmental testing including Dynamics (vibration, shock, shock response spectrum (SRS), and seismic), and Climatics (temperature, humidity, solar radiation, altitude, thermal vacuum). Maxwell also managed a fire resistance testing laboratory that included Telecom (NEBS) GR-63-CORE System Level Fire resistance testing and FAA Jet Engine Fire Simulation with FAA, DER, and government witness. Additionally, Maxwell has managed and performed nuclear qualification testing, pressure testing, air and fluid flow testing and vehicle crash testing. Maxwell has served on various boards and committees and possesses an intimate understanding of the various military, commercial, and industry specific test specifications used in today’s test protocols.

Keystone Compliance will begin providing environmental testing in June of 2011, initially focusing on the following standards: y Military Standards (including

MIL-STD-810, MIL-STD-202, MIL-STD-883, MIL-STD-167)

y Aerospace Standards (including RTCA/DO-160)

y Automotive Standards (including SAE/USCAR-28, AKLV 16, SAE J1113)

y Commercial Standards (including ISTA)

y Telecommunication Standards (including GR-63-CORE, ETSI)

For more information, visit http://www.keystonecompliance.com.

David D. Shipp Receives 2011 IEEE Richard Harold Kaufmann Award

David D. Shipp, an engineer whose many areas of expertise have improved electrical equipment and systems reliability as well as workplace safety in many industries, has been honored by IEEE with the 2011 IEEE Richard Harold Kaufmann Award.

The award, sponsored by IEEE Industry Applications Society, recognizes Shipp for contributions to the design, analysis and protection of electrical power systems and personnel in industrial and commercial applications. The award was presented May 4, 2011 at the Industrial and Commercial Power Systems Technical Conference in Los Angeles, California.

For 38 years Shipp has worked at the forefront of power technology, contributing important solutions in areas ranging from power systems analysis, failure investigations, design and protection to power quality to arc flash solutions and safety measures. Shipp’s arc flash studies have resulted in mitigation methods and solutions that have saved lives and reduced injury and risk to maintenance personnel. An arc flash is a short circuit through the air from one exposed conductor to another with excessive heat/energy being released. Arc flashes can damage equipment and cause injuries to nearby people. His patented Arc Flash Reduction Maintenance System has been incorporated into overcurrent protection devices, improving electrical workplace safety across many industries.

Shipp was instrumental in determining why massive internal ground fault damage was occurring in industrial generators and how to mitigate it. Shipp was a key participant in an IEEE team that determined the accepted generator ground fault current selection for design/standards at that time was too high. The Hybrid High Resistance Grounding system was developed to automatically switch the generator ground fault level to a lower level when an internal ground fault was detected, which greatly reduced

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damage to the generator for internal faults but permits higher levels required for the external power system. The work resulted in revisions to the American National Standards Institute (ANSI)/IEEE generator standards.

An IEEE Fellow, Shipp owns three patents and occasionally serves as a legal expert witness. He received Hart E&P magazine’s Meritorious Engineering Award for two different applications involving submersible pumps for the oil industry. He also received the Engineer of the Year Award from Eaton Electrical for his arc flash efforts. Shipp received a bachelor’s degree in electrical engineering (power option) from Oregon State University, Corvallis. He began his career in 1972 at Westinghouse Electric Corporation. Since 1998 he has worked for Eaton Electrical, Warrendale, Pennsylvania, where he is a principal engineer.

Reza Zoughi, Innovator Receives 2011 IEEE Joseph F. Keithley Award in Instrumentation and Measurement

Reza Zoughi, an engineer whose dedication to developing microwave and millimeter wave inspection techniques has improved Nondestructive Testing and Evaluation (NDT&E) of critical materials and infrastructure, was honored by IEEE with the 2011 IEEE Joseph F. Keithley Award in Instrumentation and Measurement.

The award, recognizing Zoughi for contributions to microwave and millimeter wave measurement techniques for nondestructive testing and evaluation, was presented May 11, 2011 at the IEEE International Instrumentation and Measurement Technology Conference in Hangzhou, China.

A proponent of microwave and millimeter wave NDT&E techniques for over two decades, Zoughi has focused on expanding the science, engineering, application and utility of these methods for use in many real-world problems. NDT&E involves examining critical characteristics of materials and structures without affecting their usefulness. Standard techniques such as radiography, ultrasonics, thermography, etc. are not always capable of evaluating today’s thick dielectric-based composite materials used in aerospace, space, civil structures

and transportation applications. Microwave and millimeter wave signals can easily penetrate inside of these materials and interact with their inner structures. Through Zoughi’s team discoveries and efforts at popularizing these unique techniques, they have gained significant acceptance and utility as effective NDT&E methods for many unique applications.

An IEEE Fellow, Zoughi is also a Fellow of the American Society for Nondestructive Testing (ASNT). He is named the co-inventor on ten US patents. His awards include the IEEE Instrumentation and Measurement Society Distinguished Service Award, the ASNT Research Award for Sustained Excellence and the Colorado State Board of Agriculture Excellence in Undergraduate Teaching Award. He received his bachelor’s, masters and doctorate degrees, all in electrical engineering, from the University of Kansas in Lawrence. Subsequently, in 1987 he joined the Electrical and Computer Engineering Department at Colorado State University, Ft. Collins, where he established the Applied Microwave Nondestructive Testing Laboratory (amntl). In 2001 he joined the Electrical and Computer Engineering Department at Missouri University of Science and Technology (formerly University of Missouri-Rolla), where he is currently the Schlumberger Distinguished Professor of Electrical and Computer Engineering.

MET Laboratories Offers ISO Certification of RFID Devices

MET Laboratories has announced that they are now offering ISO Certification of RFID devices based on several ISO-developed RFID-based standards and corresponding test methods including conformance, and interoperability where applicable. RFID products such as proximity and vicinity cards, and passive and active RFID will benefit from this testing. Many vendors pursue this recognition to gain a competitive advantage.

MET Labs has developed and managed certification programs for EPCglobal and DASH7, and manages an international network of independent Approved RFID Test Centers (ARTCs) that offer RFID testing and certification services. For more information about MET Laboratories, please visit http://www.METLabs.com.

Grounding Point Added to ESD Clip

Static Dynamics has taken the industry standard ESD Clip, added a Grounding Point for wrist straps and a snap for use as a cart ground or auxiliary ground cord, making it easy to ground yourself to the cart and the cart to a common ground. The new product, called the ESD Clip + GP, also electrically connects a wire shelf to a shelf post to reduce ESD risks caused by ungrounded shelving.

Install one ESD Clip + GP at each desired Grounding Point and then use standard ESD Clips to provide grounding for the remaining shelves. The entire unit should be grounded by using metal feet, a grounding chain or cable, conductive wheels, or other suitable method. The clips install without tools in about 5 seconds to fully assembled and loaded shelving and provide visual indication that the shelves are grounded. The ESD Clip + GP fits most Metro Super Erecta, Super Adjustable, and other compatible shelving. Visit http://www.Static-Dynamics.com or call (503) 646-2200 for more information.

TÜV SÜD America Adds ENERGY STAR® Certification

The U.S. Environmental Protection Agency (EPA) began the next phase in the life of the renowned ENERGY STAR Program, in January of this year - requiring ENERGY STAR-qualified products to be tested by laboratories that have been recognized by the EPA and certified by EPA-recognized Certification Bodies.

TÜV SÜD has been officially recognized by EPA to certify a wide range of products for the ENERGY STAR Program. Under this recognition, TÜV SÜD is able to qualify and verify that products meet ENERGY STAR requirements. For more information please visit http://tuvamerica.com/industry/consumer/energystar.cfm.


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June 21 – June 23Non-Destructive Testing: Visual TestingUL UniversityNorthbrook, ILwww.incompliancemag.com/events/110621_2

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June 24Electric Signs: Designing for Compliance to UL 48UL UniversityCincinnati, OHwww.incompliancemag.com/events/110624

June 28 – June 30Designing for Compliance to IEC 60601-1 3rd EditionUL UniversitySan Jose, CAwww.incompliancemag.com/events/110628

July 11 – July 15Photovoltaic (PV) System Installation TrainingUL UniversityResearch Triangle Park, NCwww.incompliancemag.com/events/110711

July 12Understanding Ground Resistance Testing A One Day Training SeminarAEMC InstrumentsRochester, NYwww.incompliancemag.com/events/110712

July 13 – July 14Plastics: Specifying and Evaluating Materials for Electrical, Electronic and Mechanical ApplicationsUL UniversityNorthbrook, ILwww.incompliancemag.com/events/110713

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www.ets-lindgren.com

Phone +1.512.531.6400 • [email protected] in the US, Finland, UK, France, India, Singapore, Japan, China, Taiwan

©2010 ETS-Lindgren

Whatever The Shielding Application...We’ve Got You Covered.For reliable EMI/RFI shielding performance, turn to the most experienced manufacturer in the shielding industry: ETS-Lindgren. No other shielding company provides the product development, design/consultation, engineering expertise, and quality testing that result in the industry’s most effective EMI/RFI protection from interference.

It doesn’t matter where on the RF Spectrum you test, we have the attenuation solution you need. Whether it is Cellular, Bluetooth, Wi-Fi, UWB, WiMAX, MIMO or the next standard on the horizon, ETS-Lindgren can provide unmatched shielding performance every step of the way.

Contact is at 630.307.7200, or visit our website at www.ets-lindgren.com.

http://www.ets-lindgren.com


EMC Chambers

Compact3,5 and 10 Meter

Near Field/ Far Field Chambers

ReverberationChambers

MIL-STD 461 Chambers

With more than 5,000 chambers worldwide, we have the experience, knowledge and capabilities to provide our customers with the finest shielded enclosures available.

We are commited to uncompromising quality control, quick and accurate response to client needs and reliable, competent, on-time service.

9260 Broken Arrow Expressway Tulsa, OK 74145 Phone 918 / 624 2888 Fax 918 / 624 2886Email: [email protected] Website: www.bradenshielding.com

A Partner You Can Count On


http://www.bradenshielding.com

In Compliance Mag May

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