New Ways to Tame and Test EMC

Higher-frequency operation, shrinking case size, and increased funtionality challenge the developers of today’s compact consumer electronics. Very small products such as cell phones and PDAs represent the complex systems for which effective EMC solutions are critical.

Especially for PDAs and notebook computers, Murata offers the BLA2A Series of four-circuit surface-mount ferrite bead arrays. These 1 × 2-mm components reduce EMI at the source, helping to ensure standards compliance. Similarly, the EMC10C Clock Oscillator from the EMC Components Group uses spread-spectrum techniques to reduce EMI by as much as 20 dB.

Of course, EMC is not confined to phones and computers. Brian Ward, a product manager at AVX, said, “Automotive circuitry has to withstand the large voltage spikes generated by motors, switches, and passengers. The growing reliance on electrical systems in automotive safety systems, power trains, and convenience items increases the requirements for circuit protection.”

More generally, filtering can be used to remove unwanted noise, for example, on input power lines. Several models are available, from Picor’s QPI-1 Active Filter for 48-V DC telecom equipment to Schurter’s 30-A, single-phase AC block filters with leakage specifications appropriate for either industrial or medical applications.

Noise containment and avoidance may be accomplished with the use of shielding and gaskets. Several products from these categories have been presented in this showcase.

Typical of the continuing innovation and performance improvement in gaskets are the GORE-SHIELD supersoft SMT EMI gasket segments. Either 3.4- or 8-mm long, separate pieces are placed on the PCB to form the required gasket pattern and reflowed at the same time as all the other SMT components.

Important as all these devices are, it is the test side of EMC that is particularly well represented. A number of amplifiers, flicker and harmonics test instruments, a portable EMI measurement system, and an antenna capable of handling a 15-kW input are included. Of special interest, the emSniffer from emv Benelux features a magnetic-field sensitivity of 0.1 × 10-12 Tesla to guarantee that you can find any significant leaks in an offending shield.

Many products from several categories are described. To learn more about their specifications and intended applications, read on.

On-Site Measurements

The TS-EMF System consists of a spectrum analyzer, an isotropic sensor sensitive in three axes, and measurement and analysis software. The small system fits in a knapsack and covers conventional radio services from 80 MHz to 2.5 GHz. The software is easy to operate so agencies and communities can determine the frequencies and strengths of their local electromagnetic fields.

Rohde & Schwarz,

Surface-Mount Gasket

The GORE-SHIELD® Supersoft SMT EMI Gaskets comprise a silver-coated hollow silicone extrusion and a solderable silver-plated copper support layer mechanically crimped together. As an example, part No. 25SMT-4442-2 measures 8 × 1.7 × 1.7 mm, requires 3.1 N force to compress to 1.35 mm, and exhibits 0.02-W resistance. Compression set for all supersoft SMT parts is 5% after 1,000 hours at 85°C.

W. L. Gore & Associates

Noncorrosive Caulking

ECCOSHIELD® VY-AL is a conductive caulking compound that uses silver-coated aluminum as a conductive filler material in place of silver-coated copper, the filler in ECCOSHIELD® VY. This change of material offers improved galvanic corrosion properties when used in conjunction with aluminum substrates.

Emerson & Cuming

Miniscule Ferrite Array

The BLA2A Series Surface-Mount Ferrite Bead Array measures 2.0 mm × 1.0 mm and filters four circuits in one package. The component is intended for use in small electronic products where it has been particularly difficult in these types of applications to meet FCC EMI emissions regulations within very limited board space.

Murata Electronics North America

Harmonics and Flicker Tester

The PC-based MXCTS Test System, based on the company’s MX AC Power System platform, supports single- and three-phase IEC 61000-3-11 flicker and IEC 61000-3-12 harmonics test standards for high-power AC products. The CTSMX Software residing on the PC platform handles test-stand-ard implementation details. Test reports, including tabular harmonics data and graphical displays, are generated using MS Word. The system also accommodates interharmonics, a requirement driven by IEC 61000-4-7.

California Instruments

Flexible Conductive Epoxy

The nickel-filled, two-part EP21TDCNFL Epoxy Adhesive features enhanced flexibility, a volume resistivity of <5 to 10 W/cm, and tensile lap shear strength of approximately 2,000 psi. A temperature range of 4°K to 250°F suits the cured epoxy to cryogenic applications. It also is recommended for difficult bonding applications that will involve thermal cycling, thermal shock, and vibration.

Master Bond

Reliable Power Filter

A line of single-phase block filters supplements the manufacturer’s range of power entry modules. With ratings up to 30 A at 250 V and >200 kh MTBF, the filters attenuate differential noise below 300 MHz and are available with leakage current from <0.25 mA to 5 mA to satisfy IEC 60950 information technology specifications or <5 µA to 80 µA for IEC 60601 electromedical devices.


Fabric-Over-Foam Gaskets

A range of fabric-over-foam gaskets is available in many sizes and shapes. All the gaskets are UL 94 V-0 rated and combine a bromine-free, resilient, soft foam core with abrasion-resistant Ni/Ag fabric covering. The E Series of fabric-over-foam continuous strip gaskets has a surface resistance <0.1 W/sq and comes in custom as well as standard D, R, P, and 
L profiles.

JEMIC Shielding Technology

Shield Leakage Tester

The emSniffer Leakage Tester injects a modulated 102-kHz RF current on the inside of a shield. On the outside of the shield, a receiver with a sensitivity of 0.1 × 10-12 Tesla allows the operator to pinpoint any imperfections in the shield seams, welds, entry panels, air filters, or doors. Red and green LEDs indicate an output current level, and receiver gain is selectable from 0 to 60 dB in 20-dB steps.

emv Benelux

Rugged Amplifier

The Model PT186-2KWR Military Rug-gedized Pulse Amplifier covers the 6.5- to 18.0-GHz frequency range for up to 6% duty-cycle pulses. The traveling wave-tube amplifier provides digital display of collector voltage and current, helix voltage and current, forward and reflected RF power, filament hours, beam hours, duty cycle, pulse width, and pulse repetition frequency. A choice of input power type including 400 Hz is available.

Instruments for Industry

Modular Simulator

Modula is an open-architecture system that simulates electromagnetic interference effects and performs immunity tests to international, national, and in-house standards. Interbus connections enable external system components to be included in the same manner as modules housed in the system casing itself, such as a pulse generator or a high-voltage source. Ethernet (TCP/IP protocol) is used to connect to a PC for networking purposes. The operating system software has been developed using the LabVIEW stand-ard running under Windows.

Schaffner EMC

Power Entry Module

The DC11 and DC12 Series Power Entry Modules combine an AC inlet, an optional filter, and a rocker switch in a small package. Lighted or unlighted one- or two-pole switches are used, rated for 100 A for 3 or 4 ms and 5 A continuously, with a 50,000-cycle lifetime at 10 A and 250 V. The low-pass filter attenuates common-mode and differential-mode noise below 1 MHz.


Low-Emission Oscillator

The Model EMC10C Clock Oscillator uses spread-spectrum techniques to reduce electromagnetic emissions and associated harmonics by as much as 20 dB. It directly replaces 3.3- or 5.0-V crystal oscillators and is plug compatible with 5 × 7 mm surface-mount packages. Selected frequencies between 6 and 120 MHz are available to meet the master clock requirements of major CISC, RISC, and DSP processors.

EMC Component Group

Solid-State RF Amplifier

The 200-W Model SMX200 RF/Microwave Amplifier provides 53-dBm minimum output from 10 kHz to 1,000 MHz. Features include type N input and output connectors; digital display of forward and reflected RF power; status indicators; indication of faults such as VSWR overload, thermal overload, overcurrent, and airflow; and a choice of input power type. The 125-lb amplifier input and output VSWR typically is 2.0:1.

Instruments for Industry

Conductive Silicones

BISCO® EC-2000 Series of Conductive Silicones is a conductive EMI/RFI shielding material available in wide, continuous rolls. The nickel-graphite-filled material is soft and easily compressible, provides high shielding performance, and resists flame and corrosion. EC-2000 products fall in the 30- to 40-Shore A durometer range and have a range of thicknesses from 0.020” to 0.125”. They can replace fabric-over foam in thin, intricately shaped applications.

Rogers Corporation

Microwave Amplifiers

The 5-W Model 5S4G11 Broadband Microwave Solid-State Amplifier has a bandwidth of 4.0 to 10.6 GHz. Air-cooled and self-contained, the amplifier features 7-W nominal output at 3-dB compression, 5.5 W minimum; 6 W nominal at 1-dB compression, 4.5 W minimum; ±2.0-dB typical flatness, ±3.0 dB maximum; 37-dB maximum gain; and -20 dBc maximum harmonic distortion at 5 W.

Amplifier Research

Nonsnag BeCu Gaskets

EMI/RFI gaskets in the low-profile SPIDER Series feature a continuous web of fingers on each side and are available in any full-finger length up to 16” in all finishes. They support bidirectional applications requiring a small closing force and come in stick-on 125LPS35 and hook and stick-on 125LPS45H060 models.


Radiated Reference Source

The battery-powered, self-contained CGO-5100 Comb Generator provides frequency harmonics at 100-MHz intervals from 1 GHz to 18 GHz. Its output is stable and uniformly radiated in the horizontal plane and can be used as a reference signal for validating open-air test sites and checking the shielding effectiveness of an enclosure.


Flicker/Harmonics Tester

The Model PHF-X Flicker and Harmonics Tester includes an integrated analyzer, a reference impedance, an AC source, and control software. These elements are combined to address IEC/EN/JEDEC test and analysis requirements. Additionally, the PHF-X is sufficiently flexible to accommodate the latest amendments to the stand-ards.

Haefely EMC Test Instruments

Harmonics and Flicker Tester

The PC-based MXCTS Test System, based on the company’s MX AC Power System platform, supports single- and three-phase IEC 61000-3-11 flicker and IEC 61000-3-12 harmonics test standards for high-power AC products. The CTSMX Software residing on the PC platform handles test-stand-ard implementation details. Test reports, including tabular harmonics data and graphical displays, are generated using MS Word. The system also accommodates interharmonics, a requirement driven by IEC 61000-4-7.

California Instruments

High-Speed Connectors

The Infinity Series of Connectors is available with mechanical latches to suit InfiniBand™ requirements or with thumbscrews for Fibre Channel applications. A full die-cast shell improves mechanical stability and contributes to EMI shielding effectiveness when compared to connectors with plastic housings. The connectors accept wire sizes from 24 to 30 AWG, and a variety of filtering and keying options are available.

Amphenol Canada

Reflective Coatings

A new range of spray-applied Electrodag® Coatings and screen-printed Electrodag® Inks is designed for antenna fabrication. The reflective materials are available with silver, silver-plated copper, nickel, or graphite conductive fillers and a selection of resins to suit process, VOC, or substrate requirements. High adhesion allows the inks to be printed in custom designs on both flexible and rigid plastic.

Acheson Colloids

Conductive Foam Gasket

The CF2 Series Conductive Foam provides high shielding effectiveness for gasketing purposes with conductivity in the X, Y, and Z axes. It requires a low compressive force, can be die cut for custom configurations, and is available in flame-retardant variations.

Insul-Fab of Texas

Active EMI Filter

The QPI-1 Active Filter provides more than 40 dB of common-mode and 80 dB of differential-mode attenuation at 500 kHz in 48-V DC-DC converter applications. It covers the 36- to 76-V international telecom bus specification including the 100-V, 100-ms surge rating; handles 12 A; and supports single or multiple DC converters up to 576 W at nominal line voltage.


AC Line Filter Capacitors

Type MEXY metallized polyester class X2 and Y2/X2 film capacitors have been added to the manufacturer’s product range. MEXY capacitors feature UL, CSA, and VDE approvals and a small plastic box size and are available with values from 0.001 to 2.2 µF. The voltage rating is 275 VAC/250 VAC, and the operating temperature ranges from -40°C to 100°C.

Cornell Dubilier

Portable EMI Absorber

The AEWM Series of Absorbing Wall Modules comprises 2’ × 8’ and 4’ × 8’ panels covered with 12”-, 18”-, 24”-, or 36”-deep absorbers. Mounted on casters, the modules can be moved within a test chamber to absorb interfering signals on a selective basis to reduce moding problems. Attenuation ranges from 9 dB at 100 MHz to 32 dB at 1 GHz for the 12” absorbers or 21 dB to 41 dB for 36” absorbers. The wall modules are available with or without 24-gauge sheet metal backing.

Advanced Electromagnetics

Broadband RF Amplifier

The Model 5156 500-W GaAsFET Amplifier covers the 0.8- to 2.5-GHz frequency range and provides a minimum linear P1dB power of 400 W, a small signal gain of +58 dB, ±2-dB gain flatness, and a +15-dB noise figure. These specifications are much better than those of an equivalent power traveling wave tube amplifier, and the 5156 adds solid-state reliability.


Gasket and Seal

The Flexi-Shield EMI Gasket comprises a conductive metal spiral wrapped around a soft silicone tube. Requiring only 2-lb closure force per linear inch, the low-force gasket combines a minimum 100-dB at 1 GHz shielding effectiveness with the wind/rain/dust sealing performance of an elastomer. Shielding effectiveness can be as high as 130-dB in moderate- and standard-force tin-plated gaskets. A range of materials and closure forces is available.


Vent Panels

MaxAir™ Vent Panels are constructed of nickel/copper-plated polymeric honeycomb with a compressible conductive foam band. Compared to traditional honeycomb vent panels, the frameless, dent-resistant vents permit 10% to 20% more useable airflow throughout the surface. The panels can be machined to accommodate special features such as recess and rabbit cuts and come standard in ¼” and 1/8” cell sizes and ¼” and ½” thicknesses. Other thicknesses are available on request.

Laird Technologies

Log-Periodic Antenna

The Radiant Arrow AT2526 Log-Periodic Antenna covers the 
26- to 250-MHz frequency band and accepts up to 15-kW input. The bent-element design achieves a 60% size reduction and minimizes field loss while maintaining gain and beam width. It comes with a wall bracket and two nonmetallic masts for vertical mounting. It also can be mounted in two perpendicular planes with an optional tripod.

Amplifier Research

Low-Loss Cables

The SAC-xxG Series of high-frequency, low-loss, flexible cables features improved power handling and low VSWR. Standard length cables are available with frequency operation from DC to 18 GHz, 26 GHz, and 40 GHz. Model SAC-18G supports operation up to 18 GHz and uses a Precision N connector. SAC-26G can be used up 26 GHz and has 3.5-mm connectors; SAC-40G is suited for work up to 40 GHz with 2.9-mm connectors.

A.H. Systems

Receiver and Analyzer

The ESPI Test Receiver features 3-dB and 6-dB EMI filters, quasipeak detection, and an available preselector. It also is a fully equipped spectrum analyzer with 10-Hz to 10-MHz resolution bandwidths, signal tracking, gated sweep, and test routines for TOI, ACP, and OBW.

Rohde & Schwarz

Surge Suppressors

Three PowerSure Surge II surge suppressors provide eight protected power outlets with spacing for three transformer blocks and two always-on outlets. The Professional Series handles surges to 30,000 A. The Network Series adds data-line protection and increased current capability to 60,000 A. The DSS Series includes phone-line and dual-input high-bandwidth coaxial surge suppression. Thermal fuses ensure fail-safe operation.


Revamped RF Amplifiers

Twenty of the company’s 1,000-MHz amplifiers have been re-engineered to improve performance and value. Representative of the new products is Model 5125 (70 W), which replaces Model 5027 (40 W). In addition to a 75% power increase, Model 5125 offers a lower price than Model 5027. Similarly, Model 5126 (120 W) has taken the place of Model 5040 (70 W) for the same price.


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Published by EE-Evaluation Engineering
All contents © 2003 Nelson Publishing Inc.
No reprint, distribution, or reuse in any medium is permitted
without the express written consent of the publisher.

October 2003

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