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EMC engineering--A constant challenge: Here are three basic suggestions that can make EMC engineering more effective. (Dealing with EMC).

It isn't easy to be an EMC engineer in 2002. The unwanted RF generation and susceptibility of newly developed products, the life-blood of a modern electronics company, present constant challenges.

"Semiconductor speeds are getting faster every day," said Ron Demcko, applications engineering manager at AVX. "Chip and product sizes are smaller, and there is the constant drive for lighter weights. Voltages are lower, which increases the operating current. Circuits are more sensitive, so EMI becomes more critical."

As logical steps to fight the problem, manufacturers recommend three procedures. First, put EMC tools in the hands of the designer. Then, simplify the EMC testing. Finally, get flexible test equipment so you can adapt to specification changes quickly and inexpensively.

Put EMC Tools in the Hands of the Designer

With the increasing challenges of EMI control, manufacturers are recognizing that a product designer needs EMC tools. You can't afford to wait for a trip to the EMC testing lab, the most expensive place to find RF leakage or undue susceptibility. Problems must be discovered and corrected at the designer's workstation.

"The industry is driven by the need to make EMC more straightforward," Robert Bathiany, vice president of Bantam Instruments, said. "Assurance of satisfactory performance must come early in the design cycle. This forces designers to use better components to reduce emissions and encourages them to get low-cost, easy-to-use personalized test equipment for upfront evaluation of a new product."

GTEMs and other anechoic chambers are popular because they simulate the open area test site (OATS) and enable a design engineer to get an early indication of the EMI characteristics of a new design. As Mark Lapchak, senior engineer at Sypris Test and Measurement (formerly Bell Technologies), has found, "Designers are looking for more sophisticated methods for modeling RF emissions at the PC level. This enables them to optimize the EMC characteristics as the product develops."

Simplify EMC Testing

Turnkey systems are becoming popular for automated EMC testing. Since the life cycle for the typical product is decreasing rapidly, it is very important to get new designs to the market as soon as possible. "A uniform EMC test method will help to accomplish this," Travise Miranda, manager at Coin-Power, observed. "This means that processes must be automated using optimum hardware and software."

Get Flexible Test Equipment

Since changing standards are inevitable in the world of EMC, choosing a test system with flexible hardware and software architecture can be very important in the long run to keep the cost of ownership under control. "Our CTS system is built around the PC platform," said Herman van Eijkelenburg, vice president of product development at California Instruments, "so we have flexibility to accommodate changing requirements."

Several companies have developed new products to help control unwanted RF. You'll find an interesting range of components and test equipment available.

EMC Products

Card-Cage Gaskets

The SPRING-LINE[TM] Card-Cage Gaskets provide EMI shielding to PCI/EISA configurations of 1 to 10 expansion slots of a PC or server chassis. The basic contact fingers are constructed of stainless steel, but tin-plated stainless steel parts can be provided if needed for galvanic conformity. Custom gaskets are offered for unique configurations.

Chomerics, Division of Parker Hannifin, 781-935-4350 www.rsleads.com/203ee-179

Dipole Antenna

The DP-Series Antennas are half-wave, fixed-length precision dipoles for generating traceable calibrated fields or measurement of electrical fields at a given frequency. Several models cover the GSM, TDMA, PCS, and Bluetooth communications systems used in Europe, North America, and Asia. Custom frequencies also are available. Each antenna has a female SMA connector and a nominal impedance of 50 [OMEGA] TDK RF Solutions, 512-258-9478, www.rsleads.com/203ee-200

GPS Gasket Pads

The GORE-SHIELD[R] SMT EMI Gasket Pad can be used to connect a GPS patch antenna to a PCB in a wireless handset. It reduces signal reflections as compared to a BeCu spring contact and helps contain the EMI emissions generated by the interconnect. The pads are offered in several sizes and provided on an EIA-standard tape-and-reel for pick-and-place mounting. W. L. Gore & Associates, 800-445-4673, www.rsleads.com/203ee-202

Foam Gaskets

New Conductive Foam meets UL 94 HB requirements and is used for EMI protection on connector shields, input/output (I/O) gaskets, and other nondynamic applications. The foam provides X-, Y-, and Z-axis conductivity similar to that of metal gaskets yet has the compression characteristics of fabric-over-foam. Shielding effectiveness is >90 dB across a wide band of operating frequencies. The uncompressed thickness is 0.060" or 0.125", and the foam can be compressed to 10% to 50% of its original thickness. Laird Technologies, 800-843-4556, www.rsleads.com/203ee-189

Choke Coils

The DLW21S (0805 size) and DLP31D (1206 size) Common-Mode Choke Coils provide EMI filtering for high-speed interfaces such as the USB, IEEE 1394, and low-voltage differential signaling (LVDS). The DLW21S features a two-line choke coil with up to 370-[OMEGA] common-mode impedance at 100 MHz. The DLP31D is a two-pair common-mode choke coil array with up to 470-[OMEGA] impedance at 100 MHz and appropriate for the IEEE 1394 interface. Murata Electronics North America, 770-436-1300, www.rsleads.com/203ee-195

Power-Line Filter

The FN3100 Three-Phase Power-Line Filter works with the newest-technology AC motor drives and frequency inverters. Handling power in both directions, the FN3100 accepts inputs up to 520 VAC with current ratings of 35 A, 50 A, 80 A, 110 A, 150 A, 200 A, or 300 A. It can smooth the returned power waveform in power regeneration applications. Each filter mounts in a slimline housing. Schaffner EMC, 732-225-9533, www.rsleads.com/203ee-197

Filtered Connectors

A series of D-subminiature connectors features a planar filter technology where the filter is embedded inside the connector body. It comes in a 0.318" right-angle footprint with ground straps and PCB locking clips. Typical insertion loss at 100 MHz is 25 dB. The dielectric-withstand voltage is 300 VDC. Pin configurations range from nine to 37 position in plug-in and socket styles. Conec, 905-790-2200, www.rsleads.com/203ee-234

Clip-On Gaskets

Clip-On Shielding Gaskets are appropriate where a small dynamic range and clip-on mounting are required. The gaskets come in 112 basic configurations to mount on substrates from 0.035" to 0.120" thick. The 99-485-06, for example, is used for sliding movements in the longitudinal direction while the 99-490-06 accepts perpendicular compression. Attenuation is >100 dB at frequencies <1 GHz.

Shielded Enclosures

Eclipse Shielding, 949-458-8336, www.rsleads.com/203ee-183

The Series 71 and Series 81 Shielded Enclosures are designed for EMC testing in medical, industrial, and governmental applications. The Series 81 room is a solid cell; the Series 71 enclosure uses a partial copper screen for RF suppression for see-through and hear-through convenience for applications below 3 GHz. Both types of rooms are modular and constructed of galvanized steel lining and come in several sizes. Options include door types, line filters, waveguide air vents or feedthroughs, and RF-proof floors.

Lindgren RF Enclosures, 630-307-7200, www.rsleads.com/203ee-192

Connectors

In the Series 100 Chip-Cap Filtered Connector, chip capacitors surface-mount on an integrated PCB. Since the footprint is 0.318" or 0.590", the Series 100 Connector occupies the same space as an unfiltered type. The current rating is 5 A, and capacitor values range from 50 pF to 47,000 pF. The connectors are available in 9-pin, 15-pin, 25-pin, and 37-pin male or female configurations.

Immunity Analysis Software

Spectrum Control, 814-474-1571, www.rsleads.com/203ee-199

Version 4 of the Radiated Immunity[TM] Software for product analysis runs on any PC with Windows 98 or later. A designer can experiment with different design parameters, and the software will enable determination of the optimum noise-mitigation techniques. Calculations account for the electromagnetic field characteristics, cable layout, shielding, and grounding. Circuit impedances, circuit balance, and filtering also enter into the analysis loop. A given design can be analyzed or several layouts compared simultaneously.

Wire Wound Chip Inductors

SpectraSoft, 310-371-3903, www.rsleads.com/203ee-198

The LQ-LBH Series Wire Wound Chip Inductors include 20 models in the EIA 0603 case size. The series is designed to reduce EMI in cell-phone antenna unit matching circuits, VCC circuits, and high-frequency wireless LAN devices and modules. The series provides inductance ranges of 2.7 to 100 nH and maximum current ratings of 200 mA to 1 A. The inductors also have DC resistance values typically of 0.03 to 1.0 [omega] and self-resonant frequency characteristics of 2 to 10 GHz minimum.

Elastomer Gaskets

Taiyo Yuden, 847-925-0888, www.rsleads.com/203ee-237

The Metallized Fabric Over Elastomer Gaskets offer >100-dB shielding effectiveness from 30 MHz to 10 GHz. They come in square, rectangular, flat, D, C-Fold, and knife-edge profiles, each with stick-on mounting. Shielding is accomplished by nickel-plating a highly conductive copper substrate. The metallized soft nylon fabric bonds to an open-celled polyurethane foam that has a low compression force. The gaskets can be used in operating environments from -40[degrees]F to 158[degrees]F. Surface resistivity is <0.02 [omega].

Measurement Control Software

Tech-Etch, 508-747-0300, www.rsleads.com/203ee-201

EMITest [TM] 4.0 EMC Measurement Control Software offers automated, semiautomated, and manual measurement modes. The new features include table and antenna mast control, harmonics calculations, interactive scan control, comparison of ambient sweep data with current measurement, and recording multiple markers on a screen capture.

ESD Simulators

CKC Laboratories, 800-500-4362, www.rsleads.com/203ee-233

The PESD 3010 and the PESO 1610 ESD Simulators include JEC 61000-4-2 R-C values. The PESD 3010 provides 30-kV direct and air discharges, and optional R-C values for other ESD test standards are available. The PESD 1610 supplies 16-kV air and 9-kV direct discharges and is battery or wall powered via a pistol-integrated charger unit. Both models feature 20% lighter pistols, redesigned grips, large ergonomic trigger switches, and large LCDs to assist in programming the automated testers.

GaAsFET Amplifiers

Haefely Test, 703-904-5725, www.rsleads.com/203ee-235

A family of amplifiers covers the frequency range from 0.7 to 3.0 GHz, exceeding the requirement of the C63-42000 immunity standard. The small, lightweight, solid-state amplifiers are available with outputs of 10, 30, 50, 100, and 200 W. The usable linear power typically is only 0.75 dB below the saturated output power level. The high power versions are suited for replacement of 1- to 2.5-GHzTWTAs.

Conductive Polymer

OPHIRRF, 310-306-5556, www.rsleads.com/203ee-236

The EP51N Polymer System is an electrically conductive epoxy resin for producing adhesives, sealants, or potting. The two-component compound uses nickel powder to establish the degree of conductivity without compromising its strength. It has a working life of 5 to 10 mm and cures fully in <3 h at ambient temperatures. Volume resistivity is 5 to 10 [ohm]/cm. Tensile lap shear strength exceeds 1,200 psi.

Power-Line CDN

Master Bond, 20 1-3438983. www.rsleads.com/203ee-194

The M Series Power-Line Coupling! Decoupling Network (CON) is used in testing for immunity to conducted disturbances in the range of 150 kHz to 80 MHz as specified by EN 61000-46. It injects common-mode disturbances to equipment under test while blocking them from other equipment on the line. The network is rated at 25 A, 480 VAC or 600 VOC and provided with one to five lines to handle different versions of single-phase or three-phase power.

Com-Power, 949-587-9800, www.rsleads.com/203ee-181

Test Software

The CTS Version 3.0 Harmonics and Flicker Test Software for the company's Compliance Test System supports Amendment 14 of the EN 61000-3-2 Harmonics Test Standard, It also will handle the next version of the EN 61000-4-7 Testing and Measurement Techniques Standard as referenced in EN 61000-3-2. Existing systems can be upgraded with this package, and it is standard with new systems.

Balun Transformer

California Instruments, 858-677-9040, www.rsleads.com/203ee-178

The SMD Balun Transformer for RF applications has dual winding for noise suppression, such as in a twisted-pair cable interface for IEEE 1394 applications. The transformer heights range from 2.3 mm to 4.8 mm. Various winding arrangements, impedance ratios, and header configurations are available.

Motor Controllers

Inter-Technical, 914-347-2474, www.rsleads.com/203ee-188

EMC-friendly electronic controllers provide motor control, power distribution, and interface to electronic wiring assemblies. EMI is suppressed by capacitors, inductors, and chokes. Suitable motor types include brush or brushless, shaded-pole, switched-reluctance, wound field, and universal. Speed and torque functions can be manipulated with the controllers.

EMI Filters

LCR Electronics, 610-278-0840, www.rsleads.com/203ee-191

The W2H and W3H Feedthrough Capacitors provide decoupling in high di/dt environments while reducing noise at frequencies to 5 GHz. They come in 0612 and 0805 case sizes and operate at 25 VDC, 50 VDC, or 100 VDC. Available capacitances range from 22 pF to 100,000 pF. The current ratings are from 0.5 A to 5 A, and DC resistance is <0.15 [omega] for all models. With NPO or X7R dielectrics, the components operate at -55[degrees]C to 125[degrees]C. The capacitors are available in standard tape-and-reel packaging.

Test Chamber

AVX, 843-448-9411, www.rsleads.com/203ee-176

The EMC Precompliance Test System for frequencies from 30 MHz to 3 GHz is self-contained and includes a LoPro[TM] Turntable with a controller. It comes with a receiver and measurement software and resolves measurements with <6-dB uncertainty. The system has a hybrid broadband antenna, tripod, and cables plus a line impedance stabilization network (LISN) and E and H near-field probes.

Power Input Filter

ETS-Lindgren, 512-531-6400, www.rsleads.com/203ee-185

The high-performance version of the P Series EMI-RFI Power Input Filter is used to provide compliance with EN 60950, UL 1950, and CSA 22.2. It attenuates noise on a power line at frequencies above 150 kHz. Each filter is in a shielding can and has a standard IEC 320 connector. The current rating is 6 A or 10 A. A switch and mounting ears can be included if desired. Single or dual voltages are accepted as well as single or dual fuses.

Spectrum Analyzer

CII Technologies, 847-680-7400, www.rsleads.com/203ee-180

The 401A Personal Spectrum Analyzer handles EMC precompliance measurements from 1 MHz to 1.024 GHz. The E-field probe is calibrated in dBm or dB[micro]V/m, and sensitivity is -95 dBm. For a measurement, the operator enters only the distance of the probe from the test device. Limit lines for FCC part 15A/B and CISPR 22A/B are stored and either can be displayed on the 128-pixel x 128-pixel LCD. The 1.2-lb battery-operated instrument has an RS-232 interface to an external computer.

SM Ceramic Filters

Bantam Instruments, 408-736-3030, www.rsleads.com/203ee-177

The company's line of surface-mountable multilayer ceramic EMI filters is now available in three sizes. The terminal C section devices are rated from 300-mA to 2-A DC current. Capacitance ranges from 22 pF to 200 nF in dielectric types COG and Z7R. The filters are rated at 50 or 100 V over the temperature range of -55[degrees]C to 125[degrees]C. Insertion loss is 3 dB at 0.1 MHz to >60 dB through 1 GHz. The filters are packaged in bulk or tape-and-reel configurations.

Syfer/ Synergistic Technology Group, 520-760-0291, www.rsleads.com/203ee-238
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Author:Strock, Jud
Publication:EE-Evaluation Engineering
Geographic Code:4EUUK
Date:Mar 1, 2002
Words:2508
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