Emc Design Fundamentals

March 25, 2018 | Author: Vinod Kumar | Category: Electromagnetic Compatibility, Electromagnetic Interference, Power Supply, Hertz, Alloy
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EMC DesignFundamentals EMC Design Fundamentals James Colotti EMC Certified by NARTE Staff Analog Design Engineer Telephonics - Command Systems Division Revision 3 1 Copyright Telephonics 2003-2005 Outline Outline ♦ Introduction - Importance of EMC - Problems with non-compliance ♦ Concepts & Definitions ♦ Standards - FCC, US Military, EU, RTCA ♦ Design Guidelines and Methodology - EM Waves, Shielding - Layout and Partitioning - Power Distribution - Power Conversion - Signal Distribution ♦ Design Process ♦ References and Vendors Revision 3 2 Copyright Telephonics 2003-2005 Introduction Introduction Revision 3 3 Copyright Telephonics 2003-2005 Importance of EMC Importance of EMC ♦ Electromagnetic Compatibility (EMC) requires that systems/equipment be able to tolerate a specified degree of interference and not generate more than a specified amount of interference ♦ EMC is becoming more important because there are so many more opportunities today for EMC issues ♦ Increase use of electronic devices - Automotive applications - Personal computing/entertainment/communication ♦ Increased potential for susceptibility/emissions - Lower supply voltages - Increasing clock frequencies, faster slew rates - Increasing packaging density - Demand for smaller, lighter, cheaper, lower-power devices Revision 3 4 Copyright Telephonics 2003-2005 Problems with Non-Compliance Problems with Non-Compliance ♦ Product may be blocked from market ♦ Practical impact can be minor annoyance to lethal …and everything in between Significant Property Loss Lost Revenue, Minor Property Loss Death or Serious Injury Annoyance, Delays •RADAR, Landing System Interruption •Erroneous Ordnance Firing •Improper Deployment of Airbags •Critical communications Interference/Interruption •Automated Monetary Transactions •AM/FM/XM/TV Interference •Cell Phone Interference Revision 3 5 Copyright Telephonics 2003-2005 Non-Compliance (continued) Non-Compliance (continued) ♦ Fortunately, industry is well regulated and standards are comprehensive ♦ Major EMC issues are relatively rare ♦ For cost-effective compliance - EMC considered throughout product/system development Revision 3 6 Copyright Telephonics 2003-2005 Concepts & Definitions Concepts & Definitions Revision 3 7 Copyright Telephonics 2003-2005 Concepts & Definitions Concepts & Definitions ♦ Electromagnetic Interference (EMI) - Electromagnetic emissions from a device or system that interfere with the normal operation of another device or system - Also referred to as Radio Frequency Interference (RFI) ♦ Electromagnetic Compatibility (EMC) - The ability of equipment or system to function satisfactorily in its Electromagnetic Environment (EME) without introducing intolerable electromagnetic disturbance to anything in that environment - In other words: Tolerate a specified degree of interference, Not generate more than a specified amount of interference, Be self-compatible Revision 3 8 Copyright Telephonics 2003-2005 Concepts & Definitions, Continued Concepts & Definitions, Continued ♦ For an EMC problem to exist: - System/Device that generates interference - System/Device that is susceptible to the interference - Coupling path ♦ Mitigation of EMC Issues - Reduce interference levels generated by culprit - Increase the susceptibility (immunity) threshold of the victim - Reduce the effectiveness of the coupling path - Combination of the above System/Device that generates interference (Culprit) System/Device that is susceptible to Interference (Victim) Coupling Path Conducted • Power Lines • Signal Lines Radiated • Magnetic • Electric • Plane Wave Operating Freq Selection Reduce # of Interconnections Operating Freq Selection Reduce Signal Level Filter Interconnections Freq Dithering Add Local Filtering Shielding Add Local Filtering Modify Signal Routing Increase Separation Modify Signal Routing Receiver (Victim) Coupling Path Source (Culprit) Revision 3 9 Copyright Telephonics 2003-2005 Standards Standards Revision 3 10 Copyright Telephonics 2003-2005 Some of the Institutes that Establish EMC Standards Some of the Institutes that Establish EMC Standards ♦ Federal Communication Commission (FCC) ♦ US Military ♦ European Union (EU) ♦ Radio Technical Commission for Aeronautics (RTCA) ♦ This lecture’s main focus is on EMC Fundamentals, not - Electro Static Discharge (ESD) - Direct Lightning Effects - Antenna Lead Conducted Emissions/Susceptibility - RF Radiation Safety Revision 3 11 Copyright Telephonics 2003-2005 FCC Part 15 FCC Part 15 66 to 56 * 56 60 79 73 Quasi-Peak Limit (dBuV) Average Limit (dBuV) Frequency (MHz) 56 to 46 * 46 50 0.15 – 0.5 0.5 – 5 5 - 30 Class B 66 60 0.15 – 0.5 0.5 - 30.0 Class A Conducted Emissions *Decrease as logarithm of frequency Revision 3 12 Copyright Telephonics 2003-2005 FCC Part 15 FCC Part 15 Field Strength Limit (uV/m) Frequency (MHz) 100 150 200 500 30 – 88 88 – 216 216 – 960 above 960 Class B (3 meters) 90 150 210 300 30 – 88 88 – 216 216 – 960 above 960 Class A (10 meters) General Radiated Emission Revision 3 13 Copyright Telephonics 2003-2005 MIL-STD-461E MIL-STD-461E ♦ Requirements for the Control of EMI Characteristics of Subsystems & Equipment Conducted Susceptibility, Dampened Sinusoidal Transients, Cables & Power Leads, 10 kHz to 100 MHz CS116 Radiated Susceptibility, Transient Electromagnetic Field RS105 Radiated Susceptibility, Electric Field, 10 kHz to 40 GHz RS103 Radiated Susceptibility, Magnetic Field, 30 Hz to 100 kHz RS101 Radiated Emissions, Antenna Spurious and Harmonic Outputs, 10 kHz to 40 GHz RE103 Radiated Emissions, Electric Field, 10 kHz to 18 GHz RE102 Radiated Emissions, Magnetic Field, 30 Hz to 100 kHz RE101 Conducted Susceptibility, Bulk Cable Injection, Impulse Excitation CS115 Conducted Susceptibility, Bulk Cable Injection, 10 kHz to 200 MHz CS114 Conducted Susceptibility, Structure Current, 60 Hz to 100 kHz CS109 Conducted Susceptibility, Antenna Port, Cross Modulation, 30 Hz to 20 GHz CS105 Conducted Susceptibility, Antenna Port, Rejection of Undesired Signals, 30 Hz to 20 GHz CS104 Conducted Susceptibility, Antenna Port, Intermodulation, 15 kHz to 10 GHz CS103 Conducted Susceptibility, Power Leads, 30 Hz to 50 kHz CS101 Conducted Emissions, Antenna Terminal, 10 kHz to 40 GHz CE106 Conducted Emissions, Power Leads, 10 kHz to 10 MHz CE102 Conducted Emissions, Power Leads, 30 Hz to 10 kHz CE101 Description Req’t Revision 3 14 Copyright Telephonics 2003-2005 EU Standard Examples (Emissions) EU Standard Examples (Emissions) Limitation of voltage changes, voltage fluctuations and flicker in public low-voltage supply systems EN61000-3-3 Limits for harmonic current emissions (equipment input current up to and including 16 A per phase) EN61000-3-2 Limits and methods of measurement of radio disturbance characteristics of electrical lighting and similar equipment EN55015 Emission requirements for household appliances, electric tools and similar apparatus EN55014-1 Limits and methods of measurement of radio disturbance characteristics of broadcast receivers and associated equipment EN55013 Industrial, scientific and medical (ISM) radio frequency equipment - Radio disturbance characteristics - Limits and methods of measurement (Also known as CISPR-11) EN55011 Limits and methods of measurement of radio disturbance characteristics of information technology equipment (Also known as CISPR-22) EN55022 Generic emissions standard for industrial environment EN50081-2 Generic emissions standard for residential, commercial and light industrial environments. EN50081-1 Description Standard Revision 3 15 Copyright Telephonics 2003-2005 EU Standard Examples (Immunity) EU Standard Examples (Immunity) Equipment for general lighting purposes — EMC immunity requirements EN61547 Voltage Dips and Interruptions Test EN61000-4-11 Immunity for residential, commercial and light-industrial environments EN61000-6-1 Immunity for industrial environments EN61000-6-2 Electrostatic Discharge EN61000-4-2 Electromagnetic compatibility — Product family standard for lifts, escalators and passenger conveyors — Immunity EN12016 Power Frequency Magnetic Test EN61000-4-8 Conducted Immunity Test EN61000-4-6 Surge Test EN61000-4-5 Electrical Fast Transient/Burst Test EN61000-4-4 Radiated Susceptibility Test EN61000-4-3 Description Standard Revision 3 16 Copyright Telephonics 2003-2005 Standard Example - RTCA Standard Example - RTCA ♦ DO-160, Environmental Conditions & Test Procedures for Airborne Equipment Power Lines: 0.15-30 MHz Interconnecting Cables: 0.15-100 MHz Radiated: 2-6,000 MHz Emission of Radio Frequency 21 Conducted: 0.01-400 MHz Radiated: 0.1-2, 8 or 18 GHz Radio Frequency Susceptibility (Radiated and Conducted) 20 0.01 - 150 kHz or 0.2 - 15 kHz Audio Frequency Conducted Susceptibility – Power Inputs 18 Interconnection Cabling E field and H Field 400 Hz – 15 kHz and spikes Induced Signal Susceptibility 19 Pin & Bulk injection, Pulse & Dampened Sine Lightning Induced Transient Susceptibility 22 Power Leads Up to 600 V or 2x Line Voltage Voltage Spike 17 115 VAC, 28 VDC and 14 VDC Power Voltage/frequency range, interruptions, surges Power Input 16 Notes Title Section Revision 3 17 Copyright Telephonics 2003-2005 Standard Summary Standard Summary ♦ Numerous EMC standards exists ♦ Common Fundamental Theme - Conducted Emission Limits - Radiated Emission Limits - Conducted Susceptibility (Immunity) Limits - Radiated Susceptibility (Immunity) Limits Revision 3 18 Copyright Telephonics 2003-2005 Design Guidelines and Methodology Design Guidelines and Methodology Revision 3 19 Copyright Telephonics 2003-2005 Electromagnetic Waves Electromagnetic Waves ♦ Electromagnetic waves consist of two orthogonal fields - Electric, E-Field (V/m) - Magnetic, H-Field (A/m) ♦ Wave Impedance, Z W =E/H Ω Revision 3 20 Copyright Telephonics 2003-2005 Electromagnetic Waves Electromagnetic Waves ♦ E-Fields, high impedance, wire (dipole) ♦ H-Fields, low impedance, current loops (xformer) ♦ In far field, all waves become plane waves d/λ π λ 2 > d Far Field for a Point Source Ω = = • • = = − − m F m H Z W 377 120 10 36 1 10 4 9 7 0 0 π π π ε µ Impedance of Plain Wave Revision 3 21 Copyright Telephonics 2003-2005 Shielding Shielding ♦ Enclosure/Chassis - Mechanical Structure - Thermal Path - Can form an overall shield (important EMC component) - Can be used as “first” line of defense for Radiated emission/susceptibility ♦ Some Applications Cannot Afford Overall Shield - Rely of other means of controlling EMC ♦ Enclosure material - Metal - Plastic with conductive coating (Conductive paint or vacuum deposition) Revision 3 22 Copyright Telephonics 2003-2005 Shielding Illustration Shielding Illustration Revision 3 23 Copyright Telephonics 2003-2005 Shielding Effectiveness Shielding Effectiveness ♦ Shielding effectiveness (SE) is a measure of how well an enclosure attenuates electromagnetic fields ♦ Theoretical SE of homogeneous material - Reflective losses, R - Absorption losses, A and - Secondary reflective losses, B (ignore if A>8 dB) Outside Inside E E Log SEdB 10 20 = A R SE B A R SE + = ⇒ + + = Revision 3 24 Copyright Telephonics 2003-2005 SE Equations SE Equations R = 20Log h 10 0 462 0136 0354 . . . r f r f r r r r | \ | . | + + ¸ ( ¸ ( ( ( ( µ σ µ σ | | . | \ | r 2 r 3 10 e r f Log 10 - 354 = R σ µ R = 168 + 10 Log p 10 f σ µ r r | \ | . | | Magnetic Field Reflective Loss Electric Field Reflective Loss Plane Wave Reflective Loss A t f r r = 0 003338 . µ σ Absorptive Loss where: t = Material thickness (mils) µ r = Material permeability relative to air σ r = Material conductivity relative to copper f = Frequency (Hz) r = Source to shield distance (inches) Revision 3 25 Copyright Telephonics 2003-2005 SE Theoretical Examples SE Theoretical Examples >200 >200 >200 >200 >200 125 Magnetic (dB) Cold Rolled Steel (60 mils) >200 >200 >200 >200 >200 >200 Electric (dB) >200 >200 >200 >200 >200 >200 Plane (dB) >200 >200 >200 >200 165 141 Plane (dB) >200 184 106 74 57 45 Magnetic (dB) Copper (3 mils) >200 193 154 162 186 >200 Electric (dB) >200 >200 >200 1G 188 >200 >200 100M 130 >200 >200 10M 118 >200 >200 1M 121 >200 101 100k 129 >200 58 10k Plane (dB) Electric (dB) Magnetic (dB) Aluminum (60 mils) Freq (Hz) ♦ r=12” ♦ µ r = 1 (Aluminum), 180 (Cold Rolled Steel), 1 (Copper) ♦ σ r = 0.6 (Aluminum), 0.17 (Cold Rolled Steel), 1 (Copper) Revision 3 26 Copyright Telephonics 2003-2005 SE Practical Considerations SE Practical Considerations ♦ SE is typically limited by apertures & seams - Removable Covers - Holes for control/display components - Holes for ventilation - Holes for connectors ♦ Mitigation of apertures and seams - Minimize size and number of apertures and seams - Use gaskets/spring-fingers to seal metal-to-metal interface - Interfaces free of paint and debris - Adequate mating surface area - Avoid Galvanic Corrosion - Use of EMI/conductive control/display components Revision 3 27 Copyright Telephonics 2003-2005 Holes/Apertures d>t Holes/Apertures d>t 0dB SE ≈ t d d Log SE 2 20 10 λ ≈ d 2 If < λ d 2 If > λ ♦ Single Hole t d s ♦ Multiple Holes n Log d 20Log SE 10 10 10 2 − ≈ λ 1 < > < d s and d 2 s If λ where: t = Material thickness n = Number of Holes s = edge to edge hole spacing Notes: 1. d is the longest dimension of the hole. 2. Maximum SE is that of a solid barrier without aperture. Revision 3 28 Copyright Telephonics 2003-2005 Holes/Apertures d<t (w<t) Holes/Apertures d<t (w<t) ♦ Behaves like a waveguide below cutoff t w w c 2 = λ Cutoff wavelength Absorption factor of WG below cutoff For frequencies well below cutoff Absorption loss 2 1 2 | | . | \ | − = c c f f λ π α w c π λ π α = = 2 55 2 109 4 164 6 >200 8 Loss t/w w t t A 3 . 27 686 . 8 = = α Revision 3 29 Copyright Telephonics 2003-2005 Enclosure Seams Enclosure Seams ♦ SE can be limited by the failure of seams to make adequate contact - Contact area must be conductive - Adequate cross-section of overlap - Adequate number of contact points ♦ Gasketing helps ensure electrical contact between fasteners Revision 3 30 Copyright Telephonics 2003-2005 Gasketing Examples Gasketing Examples ♦ Fingerstock (≈100 dB @ 2GHz) - Large Selection (shape, size, plating) - Wide mechanical compression range - High shielding effectiveness - Good for frequent access applications - No environmental seal ♦ Oriented Wire (≈80 dB @ 2GHz) - Provides both EMI and Moisture Seal - Lower SE than all-metal gaskets - Sponge or Solid Silicone, Aluminum or Monel - Mechanically versatile – die cut ♦ Conductive Elastomers (≈80 dB @ 2GHz) - Provides both EMI and Moisture Seal - Lower SE than all-metal gaskets - Mechanically versatile – die cut or molded Courtesy of Tecknit Revision 3 31 Copyright Telephonics 2003-2005 Panel Components Panel Components Air Ventilation Panels EMC Switch Shield Shielded Windows Courtesy of Tecknit Revision 3 32 Copyright Telephonics 2003-2005 Galvanic Series Galvanic Series ♦ Galvanic Corrosion -Two dissimilar metals in electrical contact in presence of an electrolyte Revision 3 33 Copyright Telephonics 2003-2005 Galvanic Series Table Galvanic Series Table 0.35 Beryllium Copper, Low Brasses or Bronzes, Silver Solder, Copper, Ni-Cr Alloys, Austenitic Corrosion-Resistant Steels, Most Chrome- Moly Steels, Specialty High-Temp Stainless Steels 0.40 Commercial Yellow Brasses and Bronzes 0.15 Silver, High-Silver Alloys 0.30 Nickel, Nickel-Copper Alloys, Titanium, Titanium Alloys, Monel 0.10 Rhodium Plating 0.00 Gold, Wrought Platinum, Graphite Carbon 1.85 Beryllium 1.75 Wrought and Cast Magnesium Alloys 1.25 Wrought Zinc, Zinc Die Casting Alloys 1.20 Hot-Dip Galvanized or Electro-Galvanized Steel 0.95 Cast aluminum Alloys (other than Al-Si), Cadmium Plating 0.90 Wrought Aluminum Alloys (except 2000 series cast Al-Si alloys), 6000 Series Aluminum 0.85 Wrought Gray or Malleable Iron, Plain Carbon and Low-Alloy Steels, Armco Iron, Cold-Rolled Steel 0.75 Wrought 2000 Series Aluminum Alloys 0.70 Lead, High-Lead Alloys 0.65 Tin-Lead Solder, Terneplate 0.60 Chromium or Tin Plating, 12% Cr type Corrosion Resistant Steels, Most 400 Series Stainless Steels 0.50 18% Cr-type Corrosion Resistant Steels, Common 300 Series Stainless Steels 0.45 High Brasses and Bronzes, Naval Brass, Muntz Metal Anodic Index (V) Metallurgical Category Revision 3 34 Copyright Telephonics 2003-2005 Galvanic Series Notes Galvanic Series Notes ♦ For harsh environments - Outdoors, high humidity/salt - Typically design for < 0.15 V difference ♦ For normal environments - Storage in warehouses, no-temperature/humidity control - Typically < 0.25 V difference ♦ For controlled environments - Temperature/humidity controlled - Typically design for < 0.50 V difference ♦ Mitigation of Galvanic Corrosion - Choosing metals with the least potential difference - Finishes, such as MIL-C-5541, Class 3 using minimal dip immersion - Plating - Insulators, as electrically/thermally appropriate Revision 3 35 Copyright Telephonics 2003-2005 System Partitioning/Guidelines System Partitioning/Guidelines ♦ Minimize interconnections between WRAs/LRUs ♦ Minimize the distribution of analog signals ♦ Control interference at the source Power Bus Signals Culprit Potential Victim Potential Victim Potential Victim Revision 3 36 Copyright Telephonics 2003-2005 Control Interference at the Source Control Interference at the Source ♦ Preferred Approach – Shield/Filter the Source (Culprit) Power Bus Signals Culprit Potential Victim Potential Victim Potential Victim ♦ Alternate Approach – Shield/Filter Potential Receivers (Victims) Power Bus Signals Culprit Potential Victim Potential Victim Potential Victim Revision 3 37 Copyright Telephonics 2003-2005 CCA Layout and Partitioning CCA Layout and Partitioning ♦ Layout is 3 Dimensional - Component placement (X & Y) - Signal and Power Routing (X & Y) - PWB Stack Up (Z) ♦ Dedicate layer(s) to ground - Forms reference planes for signals - EMI Control (high speed, fast slew rate, critical analog/RF) - Simpler impedance control ♦ Dedicate layer(s) to Supply Voltages - In addition to dedicated ground layers - Low ESL/ESR power distribution Revision 3 38 Copyright Telephonics 2003-2005 One and Two Layer One and Two Layer One Sided Signals, Grounds, Supplies • Inexpensive • Difficult to control EMI without external shield • Difficult to control impedance Dielectric Two Sided Signals, Ground, Supplies • Inexpensive (slightly more than 1 sided) • EMI mitigation with ground plane • Impedance control simplified with ground plane Dielectric Ground Plane Revision 3 39 Copyright Telephonics 2003-2005 Radiation Example, 50 MHz Clock Radiation Example, 50 MHz Clock E-Field Probe ♦ Adding ground plane reduces emission of fundamental ≈40 dB E-Field Probe PWB: 2” x 6” x 0.060” (FR4) Trace: 5” x 0.050” E-Field Probe Spacing: 2” (Emco 7405-004) Source: 50 MHz, 4 ns rise/fall, 3 Vp With Ground Plane (Micro-Strip) No Ground Plane Revision 3 40 Copyright Telephonics 2003-2005 Multi-Layer Stack Up Examples Multi-Layer Stack Up Examples Signal Ground Plane Signal Signal Supply Plane Signal Ground Plane Signal Ground Plane Signal High Speed Digital PWB • High Density • Ten Layers • Two Micro-Strip Routing Layers • Four Asymmetrical Strip-Line Routing Layers • Single Supply Plane • Two Sided 1 1 Signal Signal Supply Plane Ground Plane Signal Signal High Speed Digital PWB • Moderate Density • Six Layers • Two Micro-Strip Routing Layers • Two Buried Micro-Strip Routing Layers • Single Supply Plane • Two Sided 2 2 Analog Signal/Power Ground Plane Analog Signal/Power Digital Signal Digital Supply Plane Signal Ground Plane Signal Ground Plane Digital Signal Mixed Analog/RF/Digital PWB • Moderate Density • Ten Layers • Two Micro-Strip Routing Layers • Four Asymmetrical Strip-Line Routing Layers • Single Digital Supply Plane • Analog supplies on inner layers - Routing Clearance Considerations - Improved isolation • Two Sided 3 3 Revision 3 41 Copyright Telephonics 2003-2005 PWB Example PWB Example FPGA & Support Logic High Speed Digital I/O VME I/O Digital & Power ♦ Three Channel, L-Band VME Receiver - Shield removed for clarity IF Processing RF Sections Video ADCs Revision 3 42 Copyright Telephonics 2003-2005 CCA Level Shielding CCA Level Shielding ♦ Used in conjunction with PWB ground plane(s) ♦ Supplement shielding of overall enclosure or instead of overall enclosure ♦ Isolate sections of CCA - Local Oscillators, Front Ends, High Speed Digital, Low Level Analog (audio, video) Courtesy of Mueller Metal CCA Shield Examples Metalized Plastic Shield Examples Courtesy of Leader Tech Revision 3 43 Copyright Telephonics 2003-2005 COTS Power Supply Selection COTS Power Supply Selection (AC/DC Power Converters) (AC/DC Power Converters) ♦ EMC Selection Considerations - AC Input EMC Specification Compliance - Radiated emission/immunity compliance - Open frame, enclosed, stand-alone - Hold-Up Time - DC to AC Noise Isolation - DC to DC Noise Isolation (Multi-output) - DC to DC Galvanic Isolation (Multi-output) ♦ Non-EMC Selection Considerations - Safety compliance - Size & weight - Efficiency - Line/Load/Temperature Regulation - Operating/Storage Temperature Ranges Revision 3 44 Copyright Telephonics 2003-2005 DC/DC Converter Design/Selection DC/DC Converter Design/Selection ♦ Small Converters at CCA Level - Local regulation in critical applications - Generate unavailable voltages (3.3 to 1.25 VDC for FPGA core) - Many complete COTs solutions available (Vicor, Interpoint, etc.) - Many discrete solutions available (Linear Tech, National, etc.) ♦ Linear - Inherently Quiet - Provide noise isolation, input to output - Typically much less efficient (depends on V In -V Out difference) - Three terminal devices provide no Galvanic isolation ♦ Switching - Can be configured for Galvanic isolation - Typically noisier than Linear (however mitigation options exist) - Pulse Width Modulation, Controlled di/dt and dV/dt - Pulse Width Modulation, Spread Spectrum - Resonant mode (zero current switching) Revision 3 45 Copyright Telephonics 2003-2005 PWM, Controlled Transition, Spread Spectrum PWM, Controlled Transition, Spread Spectrum ♦ Linear Technology LT1777 (Controlled di/dt & dV/dt) Controlled Transition Time PWM Standard PWM ♦ Linear Technology LTC3252 (Spread spectrum 1.0-1.6 MHz) Spread Spectrum PWM Fixed Frequency PWM Revision 3 46 Copyright Telephonics 2003-2005 PWM, Resonant Mode Comparison PWM, Resonant Mode Comparison ♦ Resonant Mode Vs PWM - 48 VDC Input, 5 VDC Output - 100 kHz to 30 MHz, Input Noise Courtesy of Vicor PWM Topology Resonant Mode Topology Revision 3 47 Copyright Telephonics 2003-2005 Power Distribution – System Level Power Distribution – System Level DC Power Bus (Single Voltage) System AC Power DC/DC Converter Load AC/DC Power Converter DC/DC Converter Load DC/DC Converter Load DC/DC Converter Load DC Power Supply (Multiple Voltages) System AC Power Load AC/DC Power Converter Load Load Load DC Power (Multiple Voltages) System AC Power Load(s) AC/DC Power Converter DC Power (Multiple Voltages) System AC Power Load(s) AC/DC Power Converter DC Power (Multiple Voltages) System AC Power Load(s) AC/DC Power Converter ♦ Distributed DC - One Primary Converter - Multiple Secondary Converters at each load - Typical Application: Large ground based system ♦ Direct DC - One Primary Converter for all loads - Typical Application: Home Computer ♦ Separate Primary - One AC/DC Converter per unit - Typical Application: RADAR System housed in multiple units Revision 3 48 Copyright Telephonics 2003-2005 Power Distribution Examples Power Distribution Examples AN/APS-147 LAMPS RADAR (Separate Primary Distribution) Multiple Access Beamforming Equipment (Distributed DC) Personal Computer (Direct DC Distribution) Courtesy of Dell Revision 3 49 Copyright Telephonics 2003-2005 Power Distribution Comparison Power Distribution Comparison x - + Load Iso + + - Power Effic x - + Load Reg x - + Load Ground Loops May not be practical on large systems with heavy current demands and/or tight regulation requirements Only one Converter is directly exposed to input. Notes Separate Primary Direct DC Distributed DC Architecture ♦ Legend: “+” Advantage “-” Disadvantage “x” Neutral Revision 3 50 Copyright Telephonics 2003-2005 Signal Distribution Signal Distribution ♦ Avoid routing analog signals over long distances in harsh environments, but if unavoidable: - Differential - Amplify at source and attenuate/filter at destination ♦ Inter-Unit (LRU or WRA) - Digital preferred over analog - Differential preferred over single ended - Minimize number of interconnects Revision 3 51 Copyright Telephonics 2003-2005 Cable Shields Cable Shields ♦ Shields of external interconnecting cables - Essentially extensions of the chassis enclosure ♦ Shielding Effectiveness and Transfer Impedance - Properties of material - Degree of coverage - Geometry ♦ Shields are an important part of EMC design, especially in systems that require compliance to EMP and/or Indirect Lightning Effects Revision 3 52 Copyright Telephonics 2003-2005 Cable Shield Termination Cable Shield Termination ♦ Maintaining quality SE and Transfer Impedance depends on effective termination of shields at both ends - 360 Degree Backshells - If high frequency isolation is needed, avoid using long leads to terminate shields Coax Shield Terminated with Excessive Lead Length Unassembled 360 Degree Backshell for D Connector Circular D38999 Mil Connector with 360 Degree Backshel Exploded View of 360 Degree Backshell for D38999 Connector l Revision 3 53 Copyright Telephonics 2003-2005 Shield Example Shield Example 95% Coverage Double Copper Shield Shielding Effectiveness 60 80 90 90 100 100 100 100 Plane Wave (dB) 60 60 10 G 80 80 1 G 0.0060 90 90 100 M 0.0011 90 90 10 M 0.0014 100 70 1 M 0.0080 100 36 100 k 0.0080 100 16 10 k 100 0 1 k Xer Z (Ω/m) Electric (dB) Magnetic (dB) Frequency (Hz) Revision 3 54 Copyright Telephonics 2003-2005 Transfer Impedance Example Transfer Impedance Example s i T I V Z = (Ω per meter) CS116 of MIL-STD-461E Example 10 A at 10 MHz I S V i Transfer Impedance ( ) ( ) mV m m A l Z I V T s i 22 2 0011 . 0 10 = | . | \ | Ω = = Induced Voltage of 22 mV is well below damage/upset threshold of most logic families. Revision 3 55 Copyright Telephonics 2003-2005 Coupling Example #1, 0.3-200 MHz Coupling Example #1, 0.3-200 MHz ♦ Two Parallel Lines, One shielded, One unshielded - 0.5” Over Ground Plane, 10” Long, Separated by 2” - Shielded Line has 0.5” exposed Both shielded ends grounded with 1” loop (19 nH) Both ends of shield ungrounded Both ends of shield grounded with 3” loop (60 nH) Continuous shield with both ends of grounded directly Both ends of shield directly grounded Revision 3 56 Copyright Telephonics 2003-2005 Coupling Example #2, 0.3-200 MHz Coupling Example #2, 0.3-200 MHz ♦ Two Parallel Lines, One shielded, One unshielded - 0.5” Over Ground Plane, 10” Long, Separated by 0.5” - Shielded Line has 0.5” exposed Both ends of shield ungrounded Both shielded ends grounded with 1” loop (19 nH) Both ends of shield grounded with 3” loop (60 nH) Continuous shield with both ends of grounded directly Both ends of shield directly grounded Revision 3 57 Copyright Telephonics 2003-2005 Filter Connectors Filter Connectors ♦ Applications for connectors with integral filtering and/or transient suppressors - Shields not permitted on interconnection cables - Isolation needed between assemblies (WRAs, LRUs) ♦ Filtering effectiveness is typically much better than discrete filters - Parasitics - Interconnection Coupling (between filter & connector) Courtesy of G&H Technology Revision 3 58 Copyright Telephonics 2003-2005 Discrete Filter vs. Filter Connector Discrete Filter vs. Filter Connector ♦ Portable RADAR System, I/O Cables Unshielded ♦ RADAR Headset cable interferes with 100 - 200 MHz Communication band Filter Connector (1nH, 8000 pF) Discrete LC Filter at Connector (1nH, 8200p) Baseline Revision 3 59 Copyright Telephonics 2003-2005 Signal Spectra & Filter Connectors Signal Spectra & Filter Connectors 20 dB/Decade 40 dB/Decade f 1 f 2 Frequency (Hz) A(f) ( ) MHz ns t f W 9 . 15 20 1 1 1 = = = π π ( ) MHz ns ns t t f f r 159 2 2 1 2 1 2 2 = | | . | \ | + = | | . | \ | + = π π Frequency Domain Typical 50 MHz Clock Example ♦ Come in many types and filter capabilities - Filter Topologies: Pi, C, LC - Various cutoff frequencies - In some cases, not larger than standard non-filtered version ♦ Selection Considerations - Spectrum of Signals - Source/Sink Capability of Driver - Source/Load Impedances - Cable effects t r Time A(t) t w t f Time Domain Revision 3 60 Copyright Telephonics 2003-2005 EMC Design Process EMC Design Process Revision 3 61 Copyright Telephonics 2003-2005 Design Process Design Process ♦ Starts with a System/Device Specification - Describes the applicable EMC Requirement(s) ♦ Develop and Implement an EMC Control Plan - Details EMC Requirements and clarifies interpretation - Lists applicable documents - Defines management approach - Defines the design procedures/techniques - EMC design is most efficiently accomplished when considered early in the program ♦ Process Example - Intended for large system - Can easily be tailored for smaller system or a single device. Revision 3 62 Copyright Telephonics 2003-2005 EMC Design Flow Diagram EMC Design Flow Diagram System/Device Specification Generate EMC/EMI Control Plan • Cull EMC Requirements from System/Device Specification and clarifies interpretation • Summarize applicable documents, specifications and standards • EMC Program Organization and Responsibilities • Defines design procedures and techniques Chassis/ Enclosure Bonding and Grounding PWB Layout and Construction • Shielding • Material Selection • Gasketing • Covers Mechanical Design Electrical Design System Design Hardware Partitioning and Location Power Conversion and Distribution Signal Distribution • Conversion Topology Linear, Resonant, PWM • Connector Selection Filter/Non-Filter • Filter location/type • Single Ended, Differential • Logic Family • Connector Selection Filter/Non-Filter • Filter location/type • Cable harnessing and shielding • Signal Spectrum • Micro-strip, stripline • Number of layers • Ground layers • Separation of analog, RF, digital and power • System functional allocation • Separation of analog, RF, digital and power • Single vs. Multi Point Ground • Chassis component bonding • EMC Engineer may need to be involved with SOW and/or specification prior to contract award. Revision 3 63 Copyright Telephonics 2003-2005 Typical EMC Engineer’s Involvement Typical EMC Engineer’s Involvement ♦ Prepare EMC Section of Proposal ♦ Contract/SOW Review and Recommendations ♦ Interference Prediction ♦ Design Testing ♦ Interference Control Design ♦ Preparation of EMC Control Plan ♦ Subcontractor and Vendor EMC Control ♦ Internal Electrical and Mechanical Design Reviews ♦ EMC Design Reviews with the Customer ♦ Interference Testing of Critical Items ♦ Amend the EMC Control Plan, as Necessary ♦ Liaison with Manufacturing ♦ In-Process Inspection During Manufacturing ♦ Preparation of EMC Test Plan/Procedure ♦ Performance of EMC Qualification Tests ♦ Redesign and Retest where Necessary ♦ Preparation and Submittal of EMC Test Report or Declaration Design Manufacture Test Pre-Award Revision 3 64 Copyright Telephonics 2003-2005 References References Revision 3 65 Copyright Telephonics 2003-2005 References References ♦ “New Dimensions in Shielding”, Robert B. Cowdell, IEEE Transactions on Electromagnetic Compatibility, 1968 March ♦ “Alleviating Noise Concerns in Handheld Wireless Products”, Tony Armstrong, Power Electronics Technology, 2003 October ♦ “Electromagnetic Compatibility Design Guide”, Tecknit ♦ “Metals Galvanic Compatibility Chart”, Instrument Specialties ♦ “EMI Shielding Theory”, Chomerics ♦ “Shield that Cable!”, Bruce Morgen, Electronic Products, 1983 August 15 ♦ “Interference Coupling - Attack it Early”, Richard J Mohr, Electronic Design News, 1969 July ♦ “Simplified Method of Analyzing Transients in Interference Prediction” H.L. Rehkopf, Presented at the Eighth IEEE Symposium of EMC, San Francisco, CA, 1966 ♦ “Electronic Systems Failures & Anomalies Attributed to EMI” NASA Reference Publication 1374 Revision 3 66 Copyright Telephonics 2003-2005 Committees and Organizations Committees and Organizations ♦ Comité Internationale Spécial des Perturbations Radioelectrotechnique (CISPR) ♦ Federal Communication Commission (FCC), www.FCC.gov ♦ European Union, www.Europa.eu.int ♦ Radio Technical Commission for Aeronautics (RTCA) www.RTCA.org ♦ National Association of Radio & Telecommunications Engineers (NARTE), www.NARTE.org Revision 3 67 Copyright Telephonics 2003-2005 Gasket and Shielding Vendors Gasket and Shielding Vendors ♦ www.Chomerics.com ♦ www.LairdTech.com ♦ www.Tecknit.com ♦ www.Spira-EMI.com ♦ www.WaveZero.com ♦ www.LeaderTechInc.com Revision 3 68 Copyright Telephonics 2003-2005 Backshell Vendors Backshell Vendors ♦ www.SunBankCorp.com ♦ www.TycoElectronics.com Revision 3 69 Copyright Telephonics 2003-2005 Filter Connector Vendors Filter Connector Vendors ♦ www.GHtech.com ♦ www.SpectrumControl.com ♦ www.Amphenol-Aerospace.com ♦ www.EMPconnectors.com ♦ www.Sabritec.com Outline ♦ Introduction - Importance of EMC - Problems with non-compliance ♦ ♦ ♦ Concepts & Definitions Standards - FCC, US Military, EU, RTCA EM Waves, Shielding Layout and Partitioning Power Distribution Power Conversion Signal Distribution Design Guidelines and Methodology ♦ ♦ Revision 3 Design Process References and Vendors Copyright Telephonics 2003-2005 1 Introduction Revision 3 Copyright Telephonics 2003-2005 2 faster slew rates Increasing packaging density Demand for smaller. cheaper.Automotive applications .Personal computing/entertainment/communication - ♦ Increased potential for susceptibility/emissions Lower supply voltages Increasing clock frequencies. lower-power devices Revision 3 Copyright Telephonics 2003-2005 3 .Importance of EMC ♦ Electromagnetic Compatibility (EMC) requires that systems/equipment be able to tolerate a specified degree of interference and not generate more than a specified amount of interference ♦ EMC is becoming more important because there are so many more opportunities today for EMC issues ♦ Increase use of electronic devices . lighter. Landing System Interruption •Erroneous Ordnance Firing •Improper Deployment of Airbags •Critical communications Interference/Interruption •Automated Monetary Transactions Revision 3 Copyright Telephonics 2003-2005 4 . Minor Property Loss Significant Property Loss Death or Serious Injury •RADAR.Problems with Non-Compliance ♦ ♦ Product may be blocked from market Practical impact can be minor annoyance to lethal …and everything in between Annoyance. Delays •AM/FM/XM/TV Interference •Cell Phone Interference Lost Revenue. Non-Compliance (continued) ♦ Fortunately.EMC considered throughout product/system development ♦ ♦ Revision 3 Copyright Telephonics 2003-2005 5 . industry is well regulated and standards are comprehensive Major EMC issues are relatively rare For cost-effective compliance . Concepts & Definitions Revision 3 Copyright Telephonics 2003-2005 6 . Also referred to as Radio Frequency Interference (RFI) ♦ Electromagnetic Compatibility (EMC) . Not generate more than a specified amount of interference.Concepts & Definitions ♦ Electromagnetic Interference (EMI) .The ability of equipment or system to function satisfactorily in its Electromagnetic Environment (EME) without introducing intolerable electromagnetic disturbance to anything in that environment .Electromagnetic emissions from a device or system that interfere with the normal operation of another device or system . Be self-compatible Revision 3 Copyright Telephonics 2003-2005 7 .In other words: Tolerate a specified degree of interference. Coupling path System/Device that generates interference (Culprit) Coupling Path Conducted • Power Lines • Signal Lines Radiated • Magnetic • Electric • Plane Wave System/Device that is susceptible to Interference (Victim) ♦ Mitigation of EMC Issues - Reduce interference levels generated by culprit Increase the susceptibility (immunity) threshold of the victim Reduce the effectiveness of the coupling path Combination of the above Source (Culprit) Modify Signal Routing Add Local Filtering Operating Freq Selection Freq Dithering Reduce Signal Level Coupling Path Increase Separation Shielding Reduce # of Interconnections Filter Interconnections Receiver (Victim) Modify Signal Routing Add Local Filtering Operating Freq Selection Revision 3 Copyright Telephonics 2003-2005 8 . Continued .System/Device that is susceptible to the interference .System/Device that generates interference .♦ For an EMC problem to exist: Concepts & Definitions. Standards Revision 3 Copyright Telephonics 2003-2005 9 . not Electro Static Discharge (ESD) Direct Lightning Effects Antenna Lead Conducted Emissions/Susceptibility RF Radiation Safety Revision 3 Copyright Telephonics 2003-2005 10 .Some of the Institutes that Establish EMC Standards ♦ ♦ ♦ ♦ ♦ Federal Communication Commission (FCC) US Military European Union (EU) Radio Technical Commission for Aeronautics (RTCA) This lecture’s main focus is on EMC Fundamentals. 0 0.5 .5 – 5 5 .FCC Part 15 Conducted Emissions Frequency (MHz) Class A Class B 0.5 0.15 – 0.30 Quasi-Peak Limit (dBuV) 79 73 66 to 56 * 56 60 Average Limit (dBuV) 66 60 56 to 46 * 46 50 *Decrease as logarithm of frequency Revision 3 Copyright Telephonics 2003-2005 11 .30.5 0.15 – 0. FCC Part 15 General Radiated Emission Frequency (MHz) Class A (10 meters) 30 – 88 88 – 216 216 – 960 above 960 30 – 88 88 – 216 216 – 960 above 960 Field Strength Limit (uV/m) 90 150 210 300 100 150 200 500 Class B (3 meters) Revision 3 Copyright Telephonics 2003-2005 12 . Cross Modulation. Cables & Power Leads. Dampened Sinusoidal Transients. Intermodulation. 15 kHz to 10 GHz Conducted Susceptibility. Power Leads. 30 Hz to 20 GHz Conducted Susceptibility. Magnetic Field. Antenna Port. Bulk Cable Injection. Electric Field. 10 kHz to 40 GHz Radiated Susceptibility. 30 Hz to 10 kHz Conducted Emissions. Bulk Cable Injection. Transient Electromagnetic Field Revision 3 Copyright Telephonics 2003-2005 13 . 10 kHz to 40 GHz Radiated Susceptibility. 30 Hz to 50 kHz Conducted Susceptibility. 60 Hz to 100 kHz Conducted Susceptibility. Impulse Excitation Conducted Susceptibility. Antenna Port. Structure Current. Power Leads. Antenna Spurious and Harmonic Outputs.MIL-STD-461E ♦ Requirements for the Control of EMI Characteristics of Subsystems & Equipment Req’t CE101 CE102 CE106 CS101 CS103 CS104 CS105 CS109 CS114 CS115 CS116 RE101 RE102 RE103 RS101 RS103 RS105 Description Conducted Emissions. Antenna Port. Rejection of Undesired Signals. 10 kHz to 40 GHz Conducted Susceptibility. 10 kHz to 10 MHz Conducted Emissions. 10 kHz to 18 GHz Radiated Emissions. 30 Hz to 100 kHz Radiated Susceptibility. 10 kHz to 200 MHz Conducted Susceptibility. Antenna Terminal. Magnetic Field. 10 kHz to 100 MHz Radiated Emissions. 30 Hz to 20 GHz Conducted Susceptibility. 30 Hz to 100 kHz Radiated Emissions. Power Leads. Electric Field. Limits and methods of measurement (Also known as CISPR-11) EN55013 EN55014-1 EN55015 EN61000-3-2 EN61000-3-3 Limits and methods of measurement of radio disturbance characteristics of broadcast receivers and associated equipment Emission requirements for household appliances. scientific and medical (ISM) radio frequency equipment Radio disturbance characteristics . Generic emissions standard for industrial environment Limits and methods of measurement of radio disturbance characteristics of information technology equipment (Also known as CISPR-22) EN55011 Industrial. commercial and light industrial environments.EU Standard Examples (Emissions) Standard EN50081-1 EN50081-2 EN55022 Description Generic emissions standard for residential. voltage fluctuations and flicker in public low-voltage supply systems Copyright Telephonics 2003-2005 14 Revision 3 . electric tools and similar apparatus Limits and methods of measurement of radio disturbance characteristics of electrical lighting and similar equipment Limits for harmonic current emissions (equipment input current up to and including 16 A per phase) Limitation of voltage changes. EU Standard Examples (Immunity) Standard EN61000-4-2 EN61000-4-3 EN61000-4-4 EN61000-4-5 EN61000-4-6 EN61000-4-8 EN61000-4-11 EN61000-6-1 EN61000-6-2 EN61547 EN12016 Electrostatic Discharge Radiated Susceptibility Test Electrical Fast Transient/Burst Test Surge Test Conducted Immunity Test Power Frequency Magnetic Test Voltage Dips and Interruptions Test Immunity for residential. escalators and passenger conveyors — Immunity Description Revision 3 Copyright Telephonics 2003-2005 15 . commercial and light-industrial environments Immunity for industrial environments Equipment for general lighting purposes — EMC immunity requirements Electromagnetic compatibility — Product family standard for lifts. interruptions.15-100 MHz Radiated: 2-6.150 kHz or 0.01 .000 MHz Pin & Bulk injection.1-2. 8 or 18 GHz Power Lines: 0.Standard Example . Pulse & Dampened Sine 17 18 19 Voltage Spike Audio Frequency Conducted Susceptibility – Power Inputs Induced Signal Susceptibility 20 21 Radio Frequency Susceptibility (Radiated and Conducted) Emission of Radio Frequency 22 Lightning Induced Transient Susceptibility Revision 3 Copyright Telephonics 2003-2005 16 . Environmental Conditions & Test Procedures for Airborne Equipment Section 16 Power Input Title Notes 115 VAC. 28 VDC and 14 VDC Power Voltage/frequency range.15 kHz Interconnection Cabling E field and H Field 400 Hz – 15 kHz and spikes Conducted: 0.01-400 MHz Radiated: 0.RTCA ♦ DO-160. surges Power Leads Up to 600 V or 2x Line Voltage 0.15-30 MHz Interconnecting Cables: 0.2 . Standard Summary ♦ ♦ Numerous EMC standards exists Common Fundamental Theme Conducted Emission Limits Radiated Emission Limits Conducted Susceptibility (Immunity) Limits Radiated Susceptibility (Immunity) Limits Revision 3 Copyright Telephonics 2003-2005 17 Design Guidelines and Methodology Revision 3 Copyright Telephonics 2003-2005 18 Electromagnetic Waves ♦ Electromagnetic waves consist of two orthogonal fields - Electric, E-Field (V/m) - Magnetic, H-Field (A/m) ♦ Wave Impedance, ZW=E/H Ω Revision 3 Copyright Telephonics 2003-2005 19 all waves become plane waves d> λ 2π Far Field for a Point Source ZW = µ0 = ε0 H m = 120π = 377 Ω 1 F • 10 −9 36π m 4π • 10 −7 Impedance of Plain Wave d/λ Revision 3 Copyright Telephonics 2003-2005 20 . low impedance.Electromagnetic Waves ♦ ♦ ♦ E-Fields. current loops (xformer) In far field. high impedance. wire (dipole) H-Fields. Plastic with conductive coating (Conductive paint or vacuum deposition) Revision 3 Copyright Telephonics 2003-2005 21 .Metal .Shielding ♦ Enclosure/Chassis - Mechanical Structure Thermal Path Can form an overall shield (important EMC component) Can be used as “first” line of defense for Radiated emission/susceptibility ♦ ♦ Some Applications Cannot Afford Overall Shield .Rely of other means of controlling EMC Enclosure material . Shielding Illustration Revision 3 Copyright Telephonics 2003-2005 22 . Shielding Effectiveness ♦ Shielding effectiveness (SE) is a measure of how well an enclosure attenuates electromagnetic fields EInside SEdB = 20 Log10 EOutside ♦ Theoretical SE of homogeneous material . A and . R .Reflective losses.Secondary reflective losses. B (ignore if A>8 dB) SE = R + A + B ⇒ SE = R + A Revision 3 Copyright Telephonics 2003-2005 23 .Absorption losses. 10 Log10    σ r   Electric Field Reflective Loss where: t = Material thickness (mils) µr = Material permeability relative to air σr = Material conductivity relative to copper f = Frequency (Hz) r = Source to shield distance (inches) Rp = 168 + 10 Log σ   r  10  µ f   r  Plane Wave Reflective Loss Revision 3 Copyright Telephonics 2003-2005 24 . 003338t µrσrf Absorptive Loss Magnetic Field Reflective Loss  f 3µr r 2   Re = 354 . + + 0.354  fσ r µr  fσ r  A = 0.SE Equations    0.462  R h = 20Log10    r      µr 0136r . 180 (Cold Rolled Steel). 1 (Copper) σr = 0. 0.SE Theoretical Examples Freq (Hz) 10k 100k 1M 10M 100M 1G Aluminum (60 mils) Magnetic (dB) Electric (dB) Plane (dB) Cold Rolled Steel (60 mils) Magnetic (dB) Electric (dB) Plane (dB) Copper (3 mils) Magnetic (dB) Electric (dB) Plane (dB) 58 101 >200 >200 >200 >200 >200 >200 >200 >200 >200 >200 141 165 >200 >200 >200 >200 125 >200 >200 >200 >200 >200 >200 >200 >200 >200 >200 >200 >200 >200 >200 >200 >200 >200 45 57 74 106 184 >200 >200 186 162 154 193 >200 129 121 118 130 188 >200 ♦ ♦ ♦ r=12” µr = 1 (Aluminum).17 (Cold Rolled Steel).6 (Aluminum). 1 (Copper) Revision 3 Copyright Telephonics 2003-2005 25 . SE Practical Considerations ♦ SE is typically limited by apertures & seams Removable Covers Holes for control/display components Holes for ventilation Holes for connectors ♦ Mitigation of apertures and seams - Minimize size and number of apertures and seams Use gaskets/spring-fingers to seal metal-to-metal interface Interfaces free of paint and debris Adequate mating surface area Avoid Galvanic Corrosion Use of EMI/conductive control/display components Revision 3 Copyright Telephonics 2003-2005 26 . Holes/Apertures d>t ♦ d Single Hole If If ♦ s d Multiple Holes If s < λ 2 <d >d SE ≈ 0dB SE ≈ 20 Log10 λ 2 > d and s <1 d λ 2 λ 2d SE ≈ 20Log10 λ 2d − 10 Log10 n t t where: t = Material thickness n = Number of Holes s = edge to edge hole spacing Notes: 1. d is the longest dimension of the hole. 2. Revision 3 Copyright Telephonics 2003-2005 27 . Maximum SE is that of a solid barrier without aperture. 3 w Absorption loss 8 6 4 2 Revision 3 Copyright Telephonics 2003-2005 .686αt = 27.Holes/Apertures d<t (w<t) ♦ Behaves like a waveguide below cutoff λc = 2w α= 2π Cutoff wavelength w λc  f  1−   f   c 2 Absorption factor of WG below cutoff α= t 2π λc = π w For frequencies well below cutoff t/w Loss >200 164 109 55 28 t A = 8. Enclosure Seams ♦ SE can be limited by the failure of seams to make adequate contact .Contact area must be conductive .Adequate cross-section of overlap .Adequate number of contact points ♦ Gasketing helps ensure electrical contact between fasteners Revision 3 Copyright Telephonics 2003-2005 29 . Aluminum or Monel Mechanically versatile – die cut ♦ .Mechanically versatile – die cut or molded Conductive Elastomers (≈80 dB @ 2GHz) Courtesy of Tecknit Revision 3 Copyright Telephonics 2003-2005 30 .Lower SE than all-metal gaskets . size. plating) Wide mechanical compression range High shielding effectiveness Good for frequent access applications No environmental seal ♦ - Oriented Wire (≈80 dB @ 2GHz) Provides both EMI and Moisture Seal Lower SE than all-metal gaskets Sponge or Solid Silicone.Gasketing Examples ♦ - Fingerstock (≈100 dB @ 2GHz) Large Selection (shape.Provides both EMI and Moisture Seal . Panel Components Air Ventilation Panels EMC Switch Shield Shielded Windows Courtesy of Tecknit Revision 3 Copyright Telephonics 2003-2005 31 . Galvanic Series ♦ Galvanic Corrosion -Two dissimilar metals in electrical contact in presence of an electrolyte Revision 3 Copyright Telephonics 2003-2005 32 . 85 Commercial Yellow Brasses and Bronzes High Brasses and Bronzes. Plain Carbon and Low-Alloy Steels.10 0. Copper.00 0. Titanium. Monel Beryllium Copper.65 0. Cadmium Plating Hot-Dip Galvanized or Electro-Galvanized Steel Wrought Zinc. High-Silver Alloys Nickel.75 0. Common 300 Series Stainless Steels Chromium or Tin Plating. Muntz Metal 18% Cr-type Corrosion Resistant Steels. Most ChromeMoly Steels. Titanium Alloys. Cold-Rolled Steel Wrought Aluminum Alloys (except 2000 series cast Al-Si alloys). Wrought Platinum.60 0. Low Brasses or Bronzes.75 1. Nickel-Copper Alloys.Galvanic Series Table Metallurgical Category Gold. Armco Iron.45 0. Austenitic Corrosion-Resistant Steels. Terneplate Lead. Naval Brass.40 0.20 1.95 1.50 0.25 1.70 0. High-Lead Alloys Wrought 2000 Series Aluminum Alloys Wrought Gray or Malleable Iron.30 0.15 0. 6000 Series Aluminum Cast aluminum Alloys (other than Al-Si). Ni-Cr Alloys.85 0. Specialty High-Temp Stainless Steels Anodic Index (V) 0. Silver Solder.90 0. 12% Cr type Corrosion Resistant Steels. Most 400 Series Stainless Steels Tin-Lead Solder. Graphite Carbon Rhodium Plating Silver.35 0. Zinc Die Casting Alloys Wrought and Cast Magnesium Alloys Beryllium Revision 3 Copyright Telephonics 2003-2005 33 . high humidity/salt .Temperature/humidity controlled .Typically design for < 0.Typically design for < 0. as electrically/thermally appropriate Revision 3 Copyright Telephonics 2003-2005 34 . Class 3 using minimal dip immersion Plating Insulators. no-temperature/humidity control .Typically < 0.Outdoors.15 V difference ♦ For normal environments . such as MIL-C-5541.Galvanic Series Notes ♦ For harsh environments .50 V difference ♦ Mitigation of Galvanic Corrosion - Choosing metals with the least potential difference Finishes.Storage in warehouses.25 V difference ♦ For controlled environments . System Partitioning/Guidelines ♦ ♦ ♦ Minimize interconnections between WRAs/LRUs Minimize the distribution of analog signals Control interference at the source Culprit Potential Victim Potential Victim Potential Victim Power Bus Signals Revision 3 Copyright Telephonics 2003-2005 35 . Control Interference at the Source ♦ Preferred Approach – Shield/Filter the Source (Culprit) Potential Victim Potential Victim Potential Victim Culprit Power Bus Signals ♦ Alternate Approach – Shield/Filter Potential Receivers (Victims) Potential Victim Potential Victim Potential Victim Culprit Power Bus Signals Revision 3 Copyright Telephonics 2003-2005 36 . fast slew rate.Simpler impedance control ♦ Dedicate layer(s) to Supply Voltages . critical analog/RF) .PWB Stack Up (Z) ♦ Dedicate layer(s) to ground .EMI Control (high speed.Component placement (X & Y) .In addition to dedicated ground layers .CCA Layout and Partitioning ♦ Layout is 3 Dimensional .Low ESL/ESR power distribution Revision 3 Copyright Telephonics 2003-2005 37 .Signal and Power Routing (X & Y) .Forms reference planes for signals . One and Two Layer Signals. Grounds. Supplies Dielectric Two Sided Ground Plane • Inexpensive (slightly more than 1 sided) • EMI mitigation with ground plane • Impedance control simplified with ground plane Revision 3 Copyright Telephonics 2003-2005 38 . Ground. Supplies Dielectric One Sided • Inexpensive • Difficult to control EMI without external shield • Difficult to control impedance Signals. 3 Vp No Ground Plane With Ground Plane (Micro-Strip) Revision 3 Copyright Telephonics 2003-2005 39 .050” E-Field Probe Spacing: 2” (Emco 7405-004) Source: 50 MHz.060” (FR4) Trace: 5” x 0. 4 ns rise/fall.Radiation Example. 50 MHz Clock E-Field Probe E-Field Probe ♦ Adding ground plane reduces emission of fundamental ≈40 dB PWB: 2” x 6” x 0. Routing Clearance Considerations .Multi-Layer Stack Up Examples 1 Signal Ground Plane Signal Signal Ground Plane Supply Plane Signal Signal Ground Plane Signal 3 2 Signal Ground Plane Analog Signal/Power Analog Signal/Power Signal Signal Ground Plane Supply Plane Signal Signal Ground Plane Digital Supply Plane Digital Signal Digital Signal Ground Plane Signal High Speed Digital PWB • High Density • Ten Layers • Two Micro-Strip Routing Layers • Four Asymmetrical Strip-Line Routing Layers • Single Supply Plane • Two Sided High Speed Digital PWB • Moderate Density • Six Layers • Two Micro-Strip Routing Layers • Two Buried Micro-Strip Routing Layers • Single Supply Plane • Two Sided Mixed Analog/RF/Digital PWB • Moderate Density • Ten Layers • Two Micro-Strip Routing Layers • Four Asymmetrical Strip-Line Routing Layers • Single Digital Supply Plane • Analog supplies on inner layers .Improved isolation • Two Sided Revision 3 Copyright Telephonics 2003-2005 40 . Shield removed for clarity VME I/O Digital & Power IF Processing RF Sections Video ADCs FPGA & Support Logic High Speed Digital I/O Revision 3 Copyright Telephonics 2003-2005 41 .PWB Example ♦ Three Channel. L-Band VME Receiver . video) Metal CCA Shield Examples ♦ Courtesy of Leader Tech Metalized Plastic Shield Examples Courtesy of Mueller Revision 3 Copyright Telephonics 2003-2005 42 .Local Oscillators. High Speed Digital.CCA Level Shielding ♦ ♦ Used in conjunction with PWB ground plane(s) Supplement shielding of overall enclosure or instead of overall enclosure Isolate sections of CCA . Low Level Analog (audio. Front Ends. stand-alone Hold-Up Time DC to AC Noise Isolation DC to DC Noise Isolation (Multi-output) DC to DC Galvanic Isolation (Multi-output) Safety compliance Size & weight Efficiency Line/Load/Temperature Regulation Operating/Storage Temperature Ranges ♦ Non-EMC Selection Considerations Revision 3 Copyright Telephonics 2003-2005 43 .COTS Power Supply Selection (AC/DC Power Converters) ♦ EMC Selection Considerations - AC Input EMC Specification Compliance Radiated emission/immunity compliance Open frame. enclosed. National. Spread Spectrum Resonant mode (zero current switching) Revision 3 Copyright Telephonics 2003-2005 44 .3 to 1. etc. input to output Typically much less efficient (depends on VIn-VOut difference) Three terminal devices provide no Galvanic isolation ♦ Linear - ♦ Switching Can be configured for Galvanic isolation Typically noisier than Linear (however mitigation options exist) Pulse Width Modulation. etc. Controlled di/dt and dV/dt Pulse Width Modulation. Interpoint.) Inherently Quiet Provide noise isolation.DC/DC Converter Design/Selection ♦ Small Converters at CCA Level - Local regulation in critical applications Generate unavailable voltages (3.) Many discrete solutions available (Linear Tech.25 VDC for FPGA core) Many complete COTs solutions available (Vicor. 6 MHz) Fixed Frequency PWM Spread Spectrum PWM Revision 3 Copyright Telephonics 2003-2005 45 . Controlled Transition.0-1.PWM. Spread Spectrum ♦ Linear Technology LT1777 (Controlled di/dt & dV/dt) Standard PWM Controlled Transition Time PWM ♦ Linear Technology LTC3252 (Spread spectrum 1. Input Noise Courtesy of Vicor PWM Topology Resonant Mode Topology Revision 3 Copyright Telephonics 2003-2005 46 . Resonant Mode Comparison ♦ Resonant Mode Vs PWM . 5 VDC Output .PWM.48 VDC Input.100 kHz to 30 MHz. Typical Application: RADAR System housed in multiple units 47 DC Power (Multiple Voltages) Revision 3 Copyright Telephonics 2003-2005 .Power Distribution – System Level System AC Power AC/DC Power Converter DC Power Bus (Single Voltage) ♦ DC/DC Converter Distributed DC DC/DC Converter DC/DC Converter DC/DC Converter Load Load Load Load .One AC/DC Converter per unit .Multiple Secondary Converters at each load .Typical Application: Large ground based system System AC Power AC/DC Power Converter DC Power Supply (Multiple Voltages) ♦ Load Direct DC Load Load Load .Typical Application: Home Computer System AC Power AC/DC Power Converter Load(s) DC Power (Multiple Voltages) ♦ Load(s) System AC Power AC/DC Power Converter Separate Primary DC Power (Multiple Voltages) System AC Power AC/DC Power Converter Load(s) .One Primary Converter .One Primary Converter for all loads . Power Distribution Examples AN/APS-147 LAMPS RADAR (Separate Primary Distribution) Multiple Access Beamforming Equipment (Distributed DC) Courtesy of Dell Personal Computer (Direct DC Distribution) Revision 3 Copyright Telephonics 2003-2005 48 . Power Distribution Comparison Architecture Load Ground Loops + Load Reg Power Effic Load Iso Notes Distributed DC + - + Only one Converter is directly exposed to input. May not be practical on large systems with heavy current demands and/or tight regulation requirements Direct DC - - + - Separate Primary x x + x ♦ Legend: “+” Advantage “-” Disadvantage “x” Neutral Revision 3 Copyright Telephonics 2003-2005 49 . Amplify at source and attenuate/filter at destination ♦ Inter-Unit (LRU or WRA) .Differential preferred over single ended . but if unavoidable: .Minimize number of interconnects Revision 3 Copyright Telephonics 2003-2005 50 .Signal Distribution ♦ Avoid routing analog signals over long distances in harsh environments.Digital preferred over analog .Differential . Geometry ♦ Shields are an important part of EMC design.Cable Shields ♦ ♦ Shields of external interconnecting cables .Essentially extensions of the chassis enclosure Shielding Effectiveness and Transfer Impedance .Properties of material .Degree of coverage . especially in systems that require compliance to EMP and/or Indirect Lightning Effects Revision 3 Copyright Telephonics 2003-2005 51 . If high frequency isolation is needed.360 Degree Backshells .Cable Shield Termination ♦ Maintaining quality SE and Transfer Impedance depends on effective termination of shields at both ends . avoid using long leads to terminate shields Coax Shield Terminated with Excessive Lead Length Unassembled 360 Degree Backshell for D Connector Revision 3 Circular D38999 Mil Connector with 360 Degree Backshell Copyright Telephonics 2003-2005 Exploded View of 360 Degree Backshell for D38999 Connector 52 . 0011 0.0080 0.Shield Example 95% Coverage Double Copper Shield Shielding Effectiveness Frequency (Hz) 1k 10 k 100 k 1M 10 M 100 M 1G 10 G Magnetic (dB) 0 16 36 70 90 90 80 60 Electric (dB) 100 100 100 100 90 90 80 60 Plane Wave (dB) 100 100 100 100 90 90 80 60 0.0060 Xer Z (Ω/m) Revision 3 Copyright Telephonics 2003-2005 53 .0014 0.0080 0. 0011 (2m ) = 22mV m  Induced Voltage of 22 mV is well below damage/upset threshold of most logic families. Revision 3 Copyright Telephonics 2003-2005 54 .Transfer Impedance Example ZT = CS116 of MIL-STD-461E Example 10 A at 10 MHz IS Vi Is (Ω per meter) Vi Transfer Impedance Ω  Vi = I s Z T l = (10 A) 0. 5” Over Ground Plane.3-200 MHz ♦ Two Parallel Lines.Coupling Example #1. 0. 10” Long. Separated by 2” .5” exposed Both ends of shield ungrounded Both ends of shield grounded with 3” loop (60 nH) Both shielded ends grounded with 1” loop (19 nH) Both ends of shield directly grounded Continuous shield with both ends of grounded directly Copyright Telephonics 2003-2005 55 Revision 3 . One shielded.Shielded Line has 0.0. One unshielded . 0.3-200 MHz ♦ Two Parallel Lines. 0. One unshielded .5” .5” exposed Both ends of shield ungrounded Both ends of shield grounded with 3” loop (60 nH) Both shielded ends grounded with 1” loop (19 nH) Both ends of shield directly grounded Continuous shield with both ends of grounded directly Copyright Telephonics 2003-2005 56 Revision 3 .Shielded Line has 0. Separated by 0.Coupling Example #2.5” Over Ground Plane. One shielded. 10” Long. Parasitics .Filter Connectors ♦ Applications for connectors with integral filtering and/or transient suppressors .Interconnection Coupling (between filter & connector) ♦ Courtesy of G&H Technology Revision 3 Copyright Telephonics 2003-2005 57 . LRUs) Filtering effectiveness is typically much better than discrete filters .Shields not permitted on interconnection cables .Isolation needed between assemblies (WRAs. 8000 pF) Revision 3 Copyright Telephonics 2003-2005 58 . Filter Connector ♦ ♦ Portable RADAR System.200 MHz Communication band Baseline Discrete LC Filter at Connector (1nH. 8200p) Filter Connector (1nH. I/O Cables Unshielded RADAR Headset cable interferes with 100 .Discrete Filter vs. Various cutoff frequencies .Signal Spectra & Filter Connectors ♦ Come in many types and filter capabilities . not larger than standard non-filtered version ♦ Selection Considerations - Spectrum of Signals Source/Sink Capability of Driver Source/Load Impedances Cable effects Time Domain A(t) tw Frequency Domain A(f) 20 dB/Decade 40 dB/Decade f1 f2 Frequency (Hz) Typical 50 MHz Clock Example f1 = Time 1 1 = = 15.9MHz πtW π (20ns ) f2 = tr tf  2 1  2 1 =     (2ns + 2ns )  = 159 MHz π  tr + t f  π     Revision 3 Copyright Telephonics 2003-2005 59 .Filter Topologies: Pi. LC .In some cases. C. EMC Design Process Revision 3 Copyright Telephonics 2003-2005 60 . Can easily be tailored for smaller system or a single device. Revision 3 Copyright Telephonics 2003-2005 61 .Describes the applicable EMC Requirement(s) ♦ Develop and Implement an EMC Control Plan - Details EMC Requirements and clarifies interpretation Lists applicable documents Defines management approach Defines the design procedures/techniques EMC design is most efficiently accomplished when considered early in the program ♦ Process Example .Intended for large system .Design Process ♦ Starts with a System/Device Specification . specifications and standards • EMC Program Organization and Responsibilities • Defines design procedures and techniques Mechanical Design Electrical Design System Design Chassis/ Enclosure • • • • Shielding Material Selection Gasketing Covers Bonding and Grounding • Single vs. digital and power Power Conversion and Distribution • Conversion Topology Linear.EMC Design Flow Diagram System/Device Specification • EMC Engineer may need to be involved with SOW and/or specification prior to contract award. Differential • Logic Family • Connector Selection Filter/Non-Filter • Filter location/type • Cable harnessing and shielding • Signal Spectrum 62 Revision 3 Copyright Telephonics 2003-2005 . PWM • Connector Selection Filter/Non-Filter • Filter location/type Signal Distribution • Single Ended. Generate EMC/EMI Control Plan • Cull EMC Requirements from System/Device Specification and clarifies interpretation • Summarize applicable documents. Multi Point Ground • Chassis component bonding Hardware Partitioning and Location • System functional allocation • Separation of analog. stripline Number of layers Ground layers Separation of analog. digital and power • • • • PWB Layout and Construction Micro-strip. Resonant. RF. RF. as Necessary Liaison with Manufacturing Manufacture In-Process Inspection During Manufacturing Preparation of EMC Test Plan/Procedure Test Performance of EMC Qualification Tests Redesign and Retest where Necessary Preparation and Submittal of EMC Test Report or Declaration Copyright Telephonics 2003-2005 63 Revision 3 .Typical EMC Engineer’s Involvement ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ Prepare EMC Section of Proposal Pre-Award Contract/SOW Review and Recommendations Interference Prediction Design Design Testing Interference Control Design Preparation of EMC Control Plan Subcontractor and Vendor EMC Control Internal Electrical and Mechanical Design Reviews EMC Design Reviews with the Customer Interference Testing of Critical Items Amend the EMC Control Plan. References Revision 3 Copyright Telephonics 2003-2005 64 . Rehkopf. Electronic Design News.References ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ “New Dimensions in Shielding”. IEEE Transactions on Electromagnetic Compatibility. Bruce Morgen. CA.Attack it Early”. Cowdell. 1966 “Electronic Systems Failures & Anomalies Attributed to EMI” NASA Reference Publication 1374 Copyright Telephonics 2003-2005 65 ♦ Revision 3 . Electronic Products. 1983 August 15 “Interference Coupling . San Francisco. 1969 July “Simplified Method of Analyzing Transients in Interference Prediction” H. Instrument Specialties “EMI Shielding Theory”. Tecknit “Metals Galvanic Compatibility Chart”. 2003 October “Electromagnetic Compatibility Design Guide”. Robert B. Richard J Mohr. Chomerics “Shield that Cable!”.L. Presented at the Eighth IEEE Symposium of EMC. 1968 March “Alleviating Noise Concerns in Handheld Wireless Products”. Tony Armstrong. Power Electronics Technology. org ♦ ♦ ♦ ♦ Revision 3 Copyright Telephonics 2003-2005 66 .eu.FCC. www.Committees and Organizations ♦ Comité Internationale Spécial des Perturbations Radioelectrotechnique (CISPR) Federal Communication Commission (FCC). www.org National Association of Radio & Telecommunications Engineers (NARTE).Europa.int Radio Technical Commission for Aeronautics (RTCA) www.RTCA. www.gov European Union.NARTE. Spira-EMI.Chomerics.Tecknit.LeaderTechInc.com www.LairdTech.Gasket and Shielding Vendors ♦ ♦ ♦ ♦ ♦ ♦ www.com www.com Revision 3 Copyright Telephonics 2003-2005 67 .com www.com www.WaveZero.com www. SunBankCorp.Backshell Vendors ♦ ♦ www.TycoElectronics.com www.com Revision 3 Copyright Telephonics 2003-2005 68 . com Revision 3 Copyright Telephonics 2003-2005 69 .com www.SpectrumControl.Filter Connector Vendors ♦ ♦ ♦ ♦ ♦ www.Amphenol-Aerospace.com www.com www.Sabritec.com www.EMPconnectors.GHtech.
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