Controlling interference in an increasingly harsh environment challenges manufacturers of electronic products for every new design. And to make matters worse, manufacturers also must meet a growing number of EMI/RFI requirements as new regulations are adopted by a variety of governing committees.
Exports to Europe must meet the new immunity and susceptibility standards by January 1996, and the FCC now requires intentional radiators to be tested to the tenth harmonic of the fundamental frequency. The FCC also is considering more regulations for medical devices.
To help resolve these issues, companies offer materials that provide shielding effectiveness in the microwave region, where gaps or slots act as radiating apertures. Manufacturers also are providing enclosures that capture any EMI/RFI generated from boards, assemblies and subracks.
Equipment to verify compliance of new products before they make their way to market includes GTEM cells, antennas and test instruments such as signal generators. To meet current and evolving standards, you must consider frequency ranges to 26.5 GHz and beyond.
Software also is important in the quest to meet EMI/RFI requirements. Compliance design engineers use the software to correctly evaluate the effects of enclosures, vent holes and ground structures.
The most recent advances in EMI/RFI test instruments, software and shielding materials are outlined here–in EE‘s 9th annual EMI/RFI Product Showcase. This information can help you quiet the interference problem in your product.
EMI/RFI Products
EMI/RFI Shields Compatible
With No-Clean Fluxes
Custom-made EMI/RFI shields are suitable for surface-mount and through-hole processes and are compatible with no-clean fluxes. The shields are stamped from copper-based or low-expansion alloys and plated with copper or nickel and coated with tin or tin/lead. They are provided in thicknesses from 0.005″ to 0.015″ and lengths from 1/4″ to 3″. A.J. Knott Tool & Manufacturing Corp., (508) 473-1234.
H- and E-Field Probes
Extend RF Field Monitoring
Four isotropic field probes extend the capability of Amplifier Research’s ultrabroadband field monitor system to include low- and high-intensity magnetic (H) and electric (E) fields. The Model FP2103 helps monitor low-intensity H-fields and the Model FP2130 senses high intensity H-fields. The Model FP2031 is for low-intensity E-fields while the FP2033 is the high-intensity E-field probe. Each unit has an integral battery-powered transceiver. Amplifier Research, (215) 723-8181.
Software Characterizes
EM Effects in 2-D and 3-D
The MaxwellR SI Eminence software suite includes an adaptive spectral domain technique that characterizes DC through full-wave electromagnetic effects in 2-D and 3-D structures. With the software, designers can solve the complete set of Maxwell’s equations. Far-field radiation patterns are computed at user-specified viewing angles. Radiation parameters including input impedance, efficiency and beam area can be obtained. Ansoft Corp., (412) 261-3200.
Broadband Antenna Aids in
Emission/Susceptibility Tests
The Model LPB-2513 Broadband Antenna is used for emissions and susceptibility testing from 30 MHz to 1 GHz and requires no antenna changes during EMC measurements. The antenna combines the electrical properties of log-periodic and biconical designs. It measures 36″ x 51″ x 28″ when horizontally polarized. The rear elements can be removed for storage. Antenna Research Associates, Inc., (301) 937-8888.
Spring Gaskets
Deflect Independently
The 102-Series Canted-Coil EMI Spring Gaskets deflect independently when compressed. The patented spring resists compression-set and fatigue and adjusts to dimensional variations. Standard spring materials are beryllium copper and stainless steel. The gaskets are available with gold, silver nickel and tin plating. The gasket height is 0.015″ and diameters start at 0.025″. Bal Seal Engineering Co., Inc., (800) 366-1006.
Field-Sensing Probe System
Reads Levels to 300 V/m
The EM-4420 Isotropic Probe E-Field Sensing System provides the sensitivity and dynamic range for automated radiated immunity testing. The system consists of four isotropic field probes and a remote fiber-optic transmitting unit. It provides 0.5-V/m field sensitivity and is capable of reading levels of 300 V/m. A rechargeable battery pack provides power for approximately 16 h. Electro-Metrics, Inc., (518) 843-2600.
Shielded Cabinet Meets
Shock and Vibration Needs
A line of shielded racks designed for severe shock and vibration applications meets criteria of MIL-STD-810D and MIL-STD-901. The racks are constructed of stainless steel, beryllium copper finger stock and silver-coated compression gasketing. Vertical racks and sloped front consoles are available. Equipto Electronics Corp., (708) 897-4691.
Broadband Amplifier Provides
75 W at 1,000 MHz
The SMX100 is a broadband amplifier providing 75 W of linear RF power from 0.01 MHz to 1,000 MHz in two bands. The minimum saturated output power is more than 100 W. The unit offers 40 dB of gain control and a built-in capability of leveling on an externally derived signal. It helps meet requirements of IEC 801-3, including Draft 7, and IEC 801-6. Instruments For Industry, Inc., (800) 467-7705.
Woven Gaskets Provide
130-dB Shielding at 1 GHz
The ElectroShield line of plated woven EMI gaskets provides shielding effectiveness of 130 dB at 1 GHz. The gaskets are made from nylon woven over a foam core and plated for maximum conductivity. A coating passivates the surface for galvanic compatibility and corrosion resistance. The gaskets exhibit low closure force and compression set. They are available in a variety of plated nylons, profiles and core materials. Instrument Specialties Co., Inc., (717) 424-8510.
Modular Jack Connectors Have
Built-In Surge Absorption
The CUJ 8-Pin Series of modular jack connectors has built-in filters for both high-voltage surges and electromagnetic noise. A varistor helps protect equipment against high-voltage surges from communication lines and power cables. An L-type noise filter provides high-frequency noise suppression. Applications include connections for ISDN, LAN and telecommunications equipment. Murata Electronics North America, Inc., (404) 436-1300.
Instrument Case Offers
EMI Protection and Modularity
The Vario-Module PC iS Instrument Case allows industrial personal computer users and OEMs to combine different backplanes, power supplies and disk drives in one EMI-protected cabinet. The case has a 4U height and is 420-mm deep. It provides vibration damping for three 5 1/4″ or 3 1/2″ disk drives. The module has room for eight PCBs and accommodates AT or PS/2 power supplies. Rittal Corp., (800) 477-4000.
Transparent Shield Offers
80-dB Attenuation at 1 GHz
SURFSHIELD is a transparent shield product based on a microfine mesh bonded to an acrylic film. It is available in thicknesses as small as 0.25 mm and a maximum size of 1,000 mm x 1,000 mm. Surface finishes include diffuse etch and antireflection coatings. Terminations are completed via a flying mesh of lead or silver conductive paint. Applications include shielding in mobile phones, paging equipment, switch panels, lighting and industrial measuring and control equipment. Romag Inc., (305) 484-5750.
EMI Filters Help Meet
EN-55011 Requirements
A family of power line filters helps manufacturers of electronic motors meet the requirements of EN-55011. The FN-350 Series is for single-phase power lines and the FN-351 Series is for three-phase lines. The single-phase models are rated at 250 VAC with current ratings from 8 A to 100 A. The three-phase series has a 440 VAC rating with current ratings from 8 A to 600 A. Typical attenuation exceeds 50 dB common mode and 60 dB differential mode at 1 MHz. All models meet the IEC-950 requirements and have safety approvals from UL, CSA and VDE. Schaffner EMC, Inc., (800) 367-5566.
Thermoformed Shielding Offers
60-dB Shielding Effectiveness
A Conductive Thermoformed Shielding Component offers structural support, and acoustical and EMI shielding. It provides shielding effectiveness of 60 dB in the 10-MHz to 1-GHz range. The material uses a process that joins conductive material to rigid thermoplastic. It conforms to complex geometrical shapes or PCB landscapes in products including computers, cellular phones, telecommunications equipment and medical devices. Schlegel Corp., (800) 204-0863.
Shielded VME System Rack
Offers 12 or 21 Slots
A family of EMC-shielded VME system subracks is available in 12- and 21-slot configurations and provides mounting provisions for two 5 1/4″ drives. The system features an automatic daisy-chaining capability. Integral cooling is provided via three fans. Power-supply options of 750 W are available. Provisions are included for mounting I/O cards and I/O cabling on the rear of the unit. Schroff, Inc. (800) 451-8755.
BeCu Shielding Strips
Require Low Closure Force
SOFTSTOCK is a beryllium copper shielding fingerstock that provides high shielding effectiveness and requires low closure force. It is available for large and small enclosures and supplies a shielding effectiveness of 100 dB at 10 MHz and >90 dB at 1 GHz. Tecknit, (908) 272-5500.
Signal Generator Covers
5-kHz to 3-GHz Range
The Signal Generator SMT frequency range extends from 5 kHz to 3 GHz, covering conventional analog receiver measurements and those required by IEC 801. It features programmable RF, LF and level sweeps as well as the correction of external frequency response. The unit has a digital sweep function with a selectable start and stop frequency, span, step width and step time. The generator offers broadband FM modulation from DC to 8 MHz with deviation to 20 MHz, phase modulation from DC to 2 MHz, and amplitude modulation. Rohde and Schwarz, distributed by Tektronix, Inc., (800) 426-2200.
Thermoformable Material
Provides EMI Shielding
The 3M 6100 Thermoformable Material provides EMI shielding for plastic parts during the thermoforming cycle. It is thin, porous laminate of two nonwoven layers. The top layer is a uniform web of metal fibers. The bottom layer is a polymer that acts as a hot-melt adhesive that bonds to the host plastic. It is used on heavy- or light-gauge plastics. 3M Electrical Specialties Division, (800) 328-0016.
Elastomer Gaskets Offered
In O-Ring Configuration
ULTRA-VANSHIELD Dual Elastomer EMI/RFI gaskets now are offered in O-Ring configurations. Molded, cut or spliced versions are supplied with an inside diameter as small as 0.020″. The gasket is constructed of an elastomer inner core with a conductive metallic component on the outer surface. Applications include I/O panels, bezels, connectors, knobs, shafts and RFI environmental sealing. Vanguard Products Corp., (203) 744-7265.
Plastic Enclosures Have
Internal EMI/RFI Coatings
VERONEX Plastic Enclosures are available in a variety of internal coatings for applications requiring EMI/RFI shielding. The enclosures are provided in five plan sizes and nine heights. They have a nonscratch finish and are made from a high-impact polystyrene that has a UL94-VO fire rating. Versions offering protection against ingress of water and dust are available. VERO Electronics, Inc., (800) 242-2863.
Shielding Gaskets Offered
In Dispenser Roll
Custom-designed GORE-SHIELD Gaskets are available in dispenser rolls to minimize operator handling of cut gaskets. The gaskets are suitable for D-subminiature interconnections, flange connectors and waveguide covers. The gaskets are made from expanded polytetrafluoroethylene and provide 100 dB of shielding per MIL-G-83528 standards. Gore-Shield is chemically inert and resistant to corrosion. The operating temperature range is -200°C to +200°C. W.L. Gore & Associates, Inc., (800) 231-4EMI.
Two Series of Enclosures Meet
Military or Commercial Needs
The FCC Level Series meets commercial and industrial requirements and the Tempest Series of Modular Enclosures accommodates higher attenuation levels. The enclosures feature heavy-gauge steel frames and components which are plated, masked in contact areas and painted. Gasketing materials are applied on the plated contact surfaces. Design engineering is offered for custom requirements. Emcor Products, (507) 289-3371.
High-Current EMI Filters
Offered in Single-/Three-Phase
The 640, 650 and 660 EMI Filter Series are available in single- and three-phase versions. The lines have current ratings of 20 A, 30 A, 40 A and 60 A, and voltage ratings of 250 V rms or 440 V rms. The filters meet IEC 950 requirements. Potter Production Corp., (612) 831-9222.
Conductive Coating Meets
EPA VOC Regulations
The Isolex(R) WB-120 Coating is a conductive, waterborne spray that provides shielding attenuation to 50 dB across the FCC-mandated frequency range from 30 MHz to 1 GHz. It meets EPA regulations for volatile organic compounds (VOCs). The gray-color coating contains 1.8 lb/gal VOC and offers a 1-mil-thick coverage rate from 600 sq. ft. to 615 sq. ft. Morton Industrial Coatings, Morton International, Inc. (800) 255-3294.
Grounding Sleeve and Grommet
Eliminate Interference
The SHV-ERKO strain-relief connector is equipped with a circular grounding sleeve under a cable braid to eliminate the EMI gap often found in connector designs. The nickel-plated brass panel-mount connector assembly has a perbunan O-ring, making the assembly liquid-tight up to grade IP 68. A tapered neoprene bushing prevents penetration of dust, moisture or oil into the cable’s outer jacket. Olflex Wire & Cable, Inc., (800) 353-3539.
50-Watt RF Amplifier
Immune to Load Mismatch
The 50W1000A RF Power Amplifier delivers a minimum of 50-W CW power from 1 MHz to 1 GHz. No tuning or switching is required to access the full bandwidth. A front-panel analog gain control with a 20-dB minimum range facilitates manual adjustment of output power and radiated field strength during shielded-room testing. The amplifier operates without damage, fold-back or oscillation at full rated power under worst-case VSWR or shorted- or open-cable conditions. Amplifier Research, (215) 723-8181.
Clip-On Gasket Designed for
Thinner, Lighter Materials
A miniature clip-on EMI shielding gasket can be used on thin, lightweight materials where high temperatures or design factors prevent adhesive mounting. The gaskets are made of beryllium copper and recover 100% of their original height at up to 75% compression. They are available with a D Lance for added holding power, and in standard lengths of 24(“) or cut to specification. Instrument Specialties Co., Inc., (717) 424-8510.
Software Automates, Controls
EMC Testing Environment
The System 55(TM) EMC Testing Software for Windows(TM) is designed to perform automated EMC radiated and conducted susceptibility testing, including test facility calibration and device testing per IEC 801-3 and 6 (IEC 1000-4-3 & 6). Test plans can be defined, saved, recalled and executed with minimal operator intervention. The calibration mode assists in gathering data regarding antenna, amplifier, sensors and test-room performance. The software also can control the testing environment, such as changing the physical orientation of equipment. IFI, Inc., (516) 467-8400.
Common-Mode Choke Coil
Is SMT-Compatible
The PLM250 Series of high-performance DC common-mode choke coils is compatible with surface-mount technology. The coils have an impedance of >10 k(ohm) to eliminate or reduce noise in electronic circuits. Murata Electronics, (404) 436-1300.
Foil-Over-Foam Gasket Designed
For Permanent Installations
The ElectroFoil EMI Gasket is made of aluminum foil over a polyethylene foam gasket for applications where high shielding performance, light weight, galvanic compatibility with aluminum, and conventional weather-sealing characteristics are required. It is supplied with pressure-sensitive adhesive for easy installation. The gasket can be used at temperatures from -10oC to +120oC. An internal stiffener makes the gasket more damage-resistant during shipping and keeps it from being stretched or distorted. Instrument Specialties Co., Inc., (717) 424-8510.
Fast-Transient Generator
Meets EN50082-1 Requirements
The NSG 2025 Family of fast transient and burst interference generators meets the EMC requirements of the EN 50082-1 and -2, IEC 1000-4-4 and the IEEE C.62.41 standards. The modular configuration of the hardware lets you select the appropriate pulse generator, coupling network, control elements and UUT connections. Pulse generators are available with a maximum burst amplitude of 4.4 kV or 8 kV, and a network current of 16 A or 30 A. A Windows(TM)-based software package controls the instruments. Schaffner EMC Inc., (800) 367-5566.
Pliable, Conductive Gaskets
Shield Small Gaps
MicroGaskets are pliable, conductive gaskets for shielding small gaps in electronic enclosures. They are made from silver-metallized nylon over an elastomeric core and sealed with an acrylic coating. The outside layer, available in sizes of 1 mm, 2 mm and 3 mm, does not abrade or rub off. The gaskets provide a conductivity range of 10-1(ohm)/sq to 10-2(ohm)/sq. Applications include portable telephones, hand-held equipment and cable grounding. Schlegel Corp., (800) 204-0863.
EMC Subrack Provides
High-Frequency Shielding
The HF Line of shielded 19(“) subracks minimizes high-frequency EMI and protects against noise and RFI. Stainless steel contact strips provide shielding for the aluminum subrack. PCBs and plug-in units mount from the front and rear. Side panels offer universal mounting positions to accommodate boards of different depths and heights. Schroff, Inc., (800) 451-8755.
BeCu Gasket Offers
Enhanced Gripping Power
The D Lance EMI gasket, made from beryllium copper, snaps into mounting holes to enhance gripping power and provide improved conductivity. To mount clip-on gaskets on aluminum or other soft metals, an alternate T Lance design provides appropriate grip and conductivity. Typical shielding effectiveness with 25% deflection is 110 dB @ 100 kHz, 100 dB @ 10 MHz and 90 dB @ 1 GHz. Tecknit, (908) 272-5500.
Suppressor Offered In
Seven Voltage Ranges
The 0603 TransGuard Transient Voltage Suppressor is offered in seven voltage ranges. The devices, rated at 0.1 J transient energy, are available in 3.6, 5.6, 9.0, 14.0, 18.0, 26.0 and 30 VDC. Energy is dissipated between the multiple electrodes for repeated surge-strike capability. It withstands multiple ESD strikes with no degradation in performance, as required by IEC 801-2. Response time is <1 ns. The suppressor can be used with cellular phones, pagers, portable computers and hand-held instruments. AVX Corp., (803) 946-0244.Modular Jack
Filters EMI
The RJ-45 Modular Jack filters EMI on signal lines. Filtering is achieved with a high-impedance, high-resistivity ferrite block. The jack is available in shielded and nonshielded versions. Amphenol Canada Corp., (416) 291-4401.
Copyright 1995 Nelson Publishing Inc.
March 1995