Henry Ott Consultants

Electromagnetic Compatibility Consulting and Training


Electromagnetic Compatibility Engineering

by

Henry W. Ott


Detail Table of Contents


Preface


Part 1, EMC Theory


1. Electromagnetic Compatibility


1.1 Introduction
1.2 Noise and Interference   
1.3 Designing for Electromagnetic Compatibility
1.4 Engineering Documentation and EMC
1.5 United States’ EMC Regulations
    1.5.1 FCC Regulations
    1.5.2 FCC Part 15, Subpart B
    1.5.3 Emissions
    1.5.4 Administrative Procedures
    1.5.5 Susceptibility
    1.5.6 Medical Equipment
    1.5.7 Telecom
    1.5.8 Automotive   
1.6 Canadian EMC Requirements
1.7 European Union’s EMC Requirements
    1.7.1 Emission Requirements
    1.7.2 Harmonics and Flicker
    1.7.3 Immunity Requirements
    1.7.4 Directives and Standards
1.8 International Harmonization
1.9 Military Standards
1.10 Avionics
1.11 The Regulatory Process
1.12 Typical Noise Path
1.13 Methods of Noise Coupling
    1.13.1 Conductively Coupled Noise   
    1.13.2 Common Impedance Coupling
    1.13.3 Electric and Magnetic Field Coupling
1.14 Miscellaneous Noise Sources
    1.14.1 Galvanic Action
    1.14.2 Electrolytic Action   
    1.14.3 Triboelectric Effect   
    1.14.4 Conductor Motion
1.15 Use of Network Theory
Summary
Problems
References
Further Reading


2. Cabling

2.1 Capacitive Coupling
2.2 Effect of Shield on Capacitive Coupling
2.3 Inductive Coupling
2.4 Mutual Inductance Calculations   
2.5 Effect of Shield on Magnetic Coupling
    2.5.1 Magnetic Coupling Between Shield and Inner Conductor
    2.5.2 Magnetic Coupling–Open Wire to Shielded Conductor
2.6 Shielding to Prevent Magnetic Radiation   
2.7 Shielding a Receptor Against Magnetic Fields
2.8 Common Impedance Shield Coupling
2.9 Experimental Data
2.10 Example of Selective Shielding
2.11 Shield Transfer Impedance
2.12 Coaxial Cable Versus Twisted Pair
2.13 Braided Shield
2.14 Spiral Shields
2.15 Shield Terminations
    2.15.1 Pigtails
    2.15.2 Grounding of Cable Shields
2.16 Ribbon Cables
2.17 Electrically Long Cables
Summary
Problems
References
Further Reading


3. Grounding

3.1 AC Power Distribution and Safety Grounds
    3.1.1 Service Entrance
    3.1.2 Branch Circuits
    3.1.3 Noise Control
    3.1.4 Earth Grounds
    3.1.5 Isolated Grounds
    3.1.6 Separately Derived Systems
    3.1.7 Grounding Myths
3.2 Signal Grounds
    3.2.1 Single-Point Ground Systems   
    3.2.2 Multipoint Ground Systems
    3.2.3 Common Impedance Coupling
    3.2.4 Hybrid Grounds
    3.2.5 Chassis Grounds
3.3 Equipment/System Grounding
    3.3.1 Isolated Systems
    3.3.2 Clustered Systems
    3.3.3 Distributed Systems
3.4 Ground Loops
3.5 Low-Frequency Analysis of Common-Mode Choke
3.6 High-Frequency Analysis of Common-Mode Choke
3.7 Single Ground Reference For a Circuit
Summary
Problems
References
Further Reading


4. Balancing and Filtering

4.1 Balancing
    4.1.1 Common-Mode Rejection Ratio
    4.1.2 Cable Balance
    4.1.3 System Balance
    4.1.4 Balanced Loads
4.2 Filtering
4.2.1 Common-Mode Filters
4.2.2 Parasitic Effects in Filters
4.3 Power Supply Decoupling
    4.3.1 Low-Frequency Analog Circuit Decoupling
    4.3.2 Amplifier Decoupling
4.4 Driving Capacitive Loads
4.5 System Bandwidth
4.6 Modulation and Coding
Summary
Problems
References
Further Reading


5. Passive Components

5.1 Capacitors
    5.1.1 Electrolytic Capacitors
    5.1.2 Film Capacitors
    5.1.3 Mica and Ceramic Capacitors
    5.1.4 Feed-Through Capacitors
    5.1.5 Paralleling Capacitors
5.2 Inductors
5.3 Transformers
5.4 Resistors
    5.4.1 Noise in Resistors
5.5 Conductors
    5.5.1 Inductance of  Round Conductors
    5.5.2 Inductance of  Rectangular Conductors
    5.5.3 Resistance of Round Conductors
    5.5.4 Resistance of Rectangular Conductors
5.6 Transmission Lines
    5.6.1 Characteristic Impedance
    5.6.2 Propagation Constant
    5.6.3 High-Frequency Loss
    5.6.4 Relationship Among C, L, and εr
    5.6.5 Final Thoughts
5.7 Ferrites
Summary
Problems
References
Further Reading


6. Shielding

6.1 Near Fields and Far Fields
6.2 Characteristic and Wave Impedances
6.3 Shielding Effectiveness
6.4 Absorption Loss
6.5 Reflection Loss
    6.5.1 Reflection Loss to Plane Waves
    6.5.2 Reflection Loss in the Near Field
    6.5.3 Electric Field Reflection Loss   
    6.5.4 Magnetic Field Reflection Loss
    6.5.5 General Equation for Reflection Loss
    6.5.6 Multiple Reflections in Thin Shields
6.6 Composite Absorption and Reflection Loss
    6.6.1 Plane Waves
    6.6.2 Electric Fields
    6.6.3 Magnetic Fields
6.7 Summary of Shielding Equations
6.8 Shielding With Magnetic Materials
6.9 Experimental Data
6.10 Apertures
    6.10.1 Multiple Apertures
    6.10.2 Seams
    6.10.3 Transfer Impedance   
6.11 Waveguide Below Cutoff
6.12 Conductive Gaskets
    6.12.1 Joints of Dissimilar Metals
    6.12.2 Mounting of Conductive Gaskets
6.13 The “Ideal” Shield
6.14 Conductive Windows   
    6.14.1 Transparent Conductive Coatings
    6.14.2 Wire Mesh Screens
    6.14.3 Mounting of Windows
6.15 Conductive Coatings
    6.15.1 Conductive Paints
    6.15.2 Flame/Arc Spray
    6.15.3 Vacuum Metalizing   
    6.15.4 Electroless Plating
    6.15.5 Metal Foil Linings
    6.15.6 Filled Plastics
6.16 Internal Shields
6.17 Cavity Resonance
6.18 Grounding of Shields
Summary
Problems
References
Further Reading


7. Contact Protection

7.1 Glow Discharges
7.2 Metal-Vapor or Arc Discharges   
7.3 AC Versus DC Circuits
7.4 Contact Material
7.5 Contact Rating
7.6 Loads With High Inrush Currents
7.7 Inductive Loads
7.8 Contact Protection Fundamentals
7.9 Transient Suppression for Inductive Loads
7.10 Contact Protection Networks for Inductive Loads
    7.10.1 C Network   
    7.10.2 R-C Network
    7.10.3 R-C-D Network
7.11 Inductive Loads Controlled by a Transistor Switch
7.12 Resistive Load Contact Protection
7.13 Contact Protection Selection Guide
7.14 Examples
Summary
Problems
References
Further Reading


8. Intrinsic Noise Sources

8.1 Thermal Noise
8.2 Characteristics of Thermal Noise
8.3 Equivalent Noise Bandwidth
8.4 Shot Noise
8.5 Contact Noise   
8.6 Popcorn Noise
8.7 Addition of Noise Voltages
8.8 Measuring Random Noise
Summary
Problems
References
Further Reading


9. Active Device Noise

9.1 Noise Factor
9.2 Measurement of Noise Factor
    9.2.1 Single-Frequency Method
    9.2.2 Noise Diode Method   
9.3 Calculating S/N Ratio and Input Noise Voltage From
       Noise Factor
9.4 Noise Voltage and Current Model
9.5 Measurement of Vn and In
9.6 Calculating Noise Factor and S/N Ratio From Vn--In
9.7 Optimum Source Resistance
9.8 Noise Factor of Cascaded Stages
9.9 Noise Temperature
9.10 Bipolar Transistor Noise
    9.10.1 Transistor Noise Factor
    9.10.2 Vn-In for Transistors   
9.11 Field-Effect Transistor Noise
    9.11.1 FET Noise Factor
    9.11.2 Vn-In Representation of FET Noise  
9.12 Noise in Operational Amplifiers
    9.12.1 Methods of Specifying Op-Amp Noise
    9.12.2 Op-Amp Noise Factor
Summary
Problems
References
Further Reading


10. Digital Circuit Grounding

10.1 Frequency Versus Time Domain
10.2 Analog Versus Digital Circuits
10.3 Digital Logic Noise
10.4 Internal Noise Sources
10.5 Digital Circuit Ground Noise
    10.5.1 Minimizing Inductance
    10.5.2 Mutual Inductance
    10.5.3 Practical Digital Circuit Ground Systems
    10.5.4 Loop Area   
10.6 Ground Plane Current Distribution and Impedance
    10.6.1 Reference Plane Current Distribution
    10.6.2 Ground Plane Impedance
    10.6.3 Ground Plane Voltage
    10.6.4 End Effects
10.7 Digital Logic Current Flow
    10.7.1 Microstrip Line
    10.7.2 Stripline
    10.7.3 Digital Circuit Current Flow Summary
Summary
Problems
References
Further Reading


Part 2, EMC Applications



11. Digital Circuit Power Distribution

11.1 Power Supply Decoupling
11.2 Transient Power Supply Currents
    11.2.1 Transient Load Current
    11.2.2 Dynamic Internal Current
    11.2.3 Fourier Spectrum of the Transient Current
    11.2.4 Total Transient Current
11.3 Decoupling Capacitors
11.4 Effective Decoupling Strategies
11.4.1 Multiple Decoupling Capacitors
11.4.2 Multiple Capacitors of the Same Value
    11.4.3 Multiple Capacitors of Two Different Values
    11.4.4 Multiple Capacitors of Many Different Values
    11.4.5 Target Impedance
    11.4.6 Embedded PCB Capacitance   
    11.4.7 Power Supply Isolation
11.5 The Effect on Decoupling on Radiated Emissions
11.6 Decoupling Capacitor Type and Value
11.7 Decoupling Capacitor Placement and Mounting
11.8 Bulk Decoupling Capacitors
11.9 Power Entry Filters
Summary
Problems
References
Further Reading


12. Digital Circuit Radiation

12.1 Differential-Mode Radiation
    12.1.1 Loop Area   
    12.1.2 Loop Current
    12.1.3 Fourier Series
    12.1.4 Radiated Emission Envelope   
12.2 Controlling Differential-Mode Radiation
    12.2.1 Board Layout
    12.2.2 Canceling Loops
    12.2.3 Dithered Clocks
12.3 Common-Mode Radiation
12.4 Controlling Common-Mode Radiation
    12.4.1 Common-Mode Voltage
    12.4.2 Cable Filtering and Shielding
    12.4.3 Separate I/O Grounds
    12.4.4 Dealing With Common-Mode Radiation Issues
Summary
Problems
References
Further Reading


13. Conducted Emissions

13.1 Power Line Impedance
    13.1.1 Line Impedance Stabilization Network
13.2 Switched-Mode Power Supplies
    13.2.1 Common-Mode Emissions
    13.2.2 Differential-Mode Emissions
    13.2.3 DC-To-DC Converters
    13.2.4 Rectifier Diode Noise
13.3 Power-Line Filters
    13.3.1 Common-Mode Filtering
    13.3.2 Differential-Mode Filtering
    13.3.3 Leakage Inductance   
    13.3.4 Filter Mounting
    13.3.5 Power Supplies With Integral Power-Line Filters
    13.3.6 High-Frequency Noise
13.4 Primary-to-Secondary Common-Mode Coupling   
13.5 Frequency Dithering
13.6 Power Supply Instability
13.7 Magnetic Field Emissions
13.8 Variable Speed Motor Drives
13.9 Harmonic Suppression
    13.9.1 Inductive Input Filters
    13.9.2 Active Power Factor Correction
    13.9.3 AC Line Reactors
Summary
Problems
References
Further Reading


14. RF and Transient Immunity

14.1 Performance Criteria
14.2 RF Immunity
    14.2.1 The RF Environment
    14.2.2 Audio Rectification   
    14.2.3 RFI Mitigation Techniques
14.3 Transient Immunity
    14.3.1 Electrostatic Discharge
    14.3.2 Electrical Fast Transient
    14.3.3 Lightning Surge
    14.3.4 Transient Suppression Networks
    14.3.5 Signal Line Suppression
    14.3.6 Protection of High-Speed Signal Lines
    14.3.7 Power Line Transient Suppression
    14.3.8 Hybrid Protection Network
14.4 Power Line Disturbances
    14.4.1 Power Line Immunity Curve   
Summary
Problems
References
Further Reading


15 Electrostatic Discharge   

15.1 Static Generation
    15.1.1 Inductive Charging
    15.1.2 Energy Storage
15.2 Human Body Model
15.3 Static Discharge
    15.3.1 Decay Time
15.4 ESD Protection in Equipment Design
15.5 Preventing ESD Entry
    15.5.1 Metallic Enclosures   
    15.5.2 Input/Output Cable Treatment
    15.5.3 Insulated Enclosures
    15.5.4 Keyboards and Control Panels
15.6 Hardening Sensitive Circuits
15.7 ESD Grounding
15.8 Nongrounded Products
15.9 Field-Induced Upset
    15.9.1 Inductive Coupling
    15.9.2 Capacitive Coupling
15.10 Transient Hardened Software Design
    15.10.1 Detecting Errors in Program Flow
    15.10.2 Detecting Errors in Input/Output
    15.10.3 Detecting Errors in Memory
15.11 Time Windows
Summary
Problems
References
Further Reading


16. PCB Layout and Stack-Up

16.1 General PCB Layout Considerations
    16.1.1 Partitioning
    16.1.2 Keep Out Zones
    16.1.3 Critical Signals
    16.1.4 System Clocks
16.2 PCB-to-Chassis Ground Connection
16.3 Return Path Discontinuities
    16.3.1 Slots in Ground/Power Planes
    16.3.2 Split Ground/Power Planes
    16.3.3 Changing Reference Planes
    16.3.4 Referencing the Top and Bottom of the Same Plane
    16.3.5 Connectors
    16.3.6 Ground Fill
16.4 PCB Layer Stackup
16.4.1 One- and Two-Layer Boards   
16.4.2 Multilayer Boards
16.4.3 General PCB Design Procedure
Summary
Problems
References
Further Reading


17. Mixed-Signal PCB Layout

17.1 Split Ground Planes
17.2 Microstrip Ground Plane Current Distribution
17.3 Analog and Digital Ground Pins
17.4 When Should Split Ground Planes be Used?
17.5 Mixed Signal ICs
    17.5.1 Multi-Board Systems
17.6 High-Resolution A/D and D/A Converters
    17.6.1 Stripline
    17.6.2 Asymmetric Stripline
    17.6.3 Isolated Analog and Digital Ground Planes
17.7 A/D and D/A Converts Support Circuitry
    17.7.1 Sampling Clocks
    17.7.2 Mixed-Signal Support Circuitry
17.8 Vertical Isolation
17.9 Mixed-Signal Power Distribution
    17.9.1 Power Distribution
    17.9.2 Decoupling
17.10 The IPC Problem
Summary
Problems
References
Further Reading


18. Precompliance EMC Measurements

18.1 Test Environment
18.2 Antennas Versus Probes
18.3 Common-Mode Currents on Cables
    18.3.1 Test Procedure
    18.3.2 Cautions
18.4 Near Field Measurements
    18.4.1 Test Procedure
    18.4.2 Cautions
18.4.3 Seams and Apertures in Enclosures
18.5 Noise Voltage Measurements
    18.5.1 Balanced Differential Probe
    18.5.2 DC to 1-GHz Probe
    18.5.3 Cautions
18.6 Conducted Emission Testing
    18.6.1 Test Procedure
    18.6.2 Cautions
    18.6.3 Separating C-M From D-M Noise
18.7 Spectrum Analyzers
    18.7.1 Detector Functions
    18.7.2 General Test Procedure
18.8 EMC Crash Cart
    18.8.1 Mitigation Parts List
18.9 One-Meter Radiated Emission Measurements
    18.9.1 Test Environment
    18.9.2 Limits For 1-m Testing
    18.9.3 Antennas For 1-m Testing
18.10 Precompliance Immunity Testing
    18.10.1 Radiated Immunity
    18.10.2 Conducted Immunity
    18.10.3 Transient Immunity
18.11 Precompliance Power Quality Tests
    18.11.1 Harmonics
    18.11.2 Flicker
18.12 Margin
    18.12.1 Radiated Emission Margin
    18.12.2 Electrostatic Discharge Margin
Summary
Problems
References
Further Reading


Appendix

A. The Decibel


A.1 Properties of Logarithms
A.2 Using the Decibel for Other Than Power Measurements
A.3 Power Loss or Negative Power Gain
A.4 Absolute Power Level
A.5 Summing Powers Expressed in Decibels   


B. The Ten Best Ways to Maximize the Emission
         from Your Product


C. Multiple Reflections of Magnetic Fields in
              Thin Shields


D. Dipoles for Dummies

D.1 Basic Dipoles for Dummies
D.2 Intermediate Dipoles for Dummies
D.3 Advanced Dipoles for Dummies
    D.3.1 Impedance of a Dipole
    D.3.2 Dipole Resonance
    D.3.3 Receiving Dipole
    D.3.4 Theory of Images
    D.3.5 Dipole Arrays
    D.3.6 Very High-Frequency Antennas
Summary
Further Reading


E. Partial Inductance

E.1 Inductance
E.2 Loop Inductance
    E.2.1 Inductance of a Rectangular Loop
E.3 Partial Inductance
    E.3.1 Partial Self-Inductance
    E.3.2 Partial Mutual-Inductance
    E.3.3 Net Partial Inductance
    E.3.4 Partial Inductance Applications
        E.3.4.1 Rectangular Loop
        E.3.4.2 Two Unequal Diameter Parallel Conductors
    E.3.5 Transmission Line Example
E.4 Ground Plane Inductance Measurement Test Setup
E.5 Inductance Notation
Summary
References
Further Reading


F. Answers to Problems


Index




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Henry Ott Consultants
48 Baker Road Livingston, NJ 07039
Phone: 973-992-1793,   FAX: 973-533-1442

  July 17, 2009