Introduction to Electromagnetic Compatibility

Transcription

1 Introduction to Electromagnetic Compatibility Second Edition CLAYTON R. PAUL Department of Electrical and Computer Engineering, School of Engineering, Mercer University, Macon, Georgia and Emeritus Professor of Electrical Engineering, University of Kentucky, Lexington, Kentucky

2 Contents Preface xvi i 1 Introduction to Electromagnetic Compatibility (EMC) Aspects of EMC History of EMC Examples Electrical Dimensions and Waves Decibels and Common EMC Units Power Loss in Cables Signal Source Specification 37 Problems 43 References 48 2 EMC Requirements for Electronic Systems Governmental Requirements Requirements for Commercial Products Marketed in the United States Requirements for Commercial Products Marketed outside the United States Requirements for Military Products Marketed in the United States Measurement of Emissions for Verification of Compliance Radiated Emissions Conducted Emissions Typical Product Emissions A Simple Example to Illustrate the Difficulty in Meeting the Regulatory Limits 78

3 viii CONTENTS 2.2 Additional Product Requirements Radiated Susceptibility (Immunity) Conducted Susceptibility (Immunity) Electrostatic Discharge (ESD) Requirements for Commercial Aircraft Requirements for Commercial Vehicles 2.3 Design Constraints for Products 2.4 Advantages of EMC Design Problems References Signal Spectra-the Relationship between the Time Domain and the Frequency Domain Periodic Signals The Fourier Series Representation of Periodic Signals Response of Linear Systems to Periodic Input Signals Important Computational Techniques Spectra of Digital Waveforms The Spectrum of Trapezoidal (Clock) Waveforms Spectral Bounds for Trapezoidal Waveforms Effect of Rise/Falltime on Spectral Content Bandwidth of Digital Waveforms Effect of Repetition Rate and Duty Cycle Effect of Ringing (Undershoot/Overshoot) Use of Spectral Bounds in Computing Bounds on the Output Spectrum of a Linear System Spectrum Analyzers Basic Principles Peak versus Quasi-Peak versus Average Representation of Nonperiodic Waveforms The Fourier Transform Response of Linear Systems to Nonperiodic Inputs Representation of Random (Data) Signals Use of SPICE (PSPICE) In Fourier Analysis 155 Problems References 4 Transmission Lines and Signal Integrity The Transmission-Line Equations The Per-Unit-Length Parameters Wire-Type Structures 186

4 CONTENTS ix Printed Circuit Board (PCB) Structures The Time-Domain Solution Graphical Solutions The SPICE Model High-Speed Digital Interconnects and Signal Integrity Effect of Terminations on the Line Waveforms Effect of Capacitive Terminations Effect of Inductive Terminations Matching Schemes for Signal Integrity When Does the Line Not Matter, i.e., When is Matching Not Required? Effects of Line Discontinuities Sinusoidal Excitation of the Line and the Phasor Solution Voltage and Current as Functions of Position Power Flow Inclusion of Losses Effect of Losses on Signal Integrity Lumped-Circuit Approximate Models 283 Problems 287 References 297 Nonideal Behavior of Components Wires Resistance and Internal Inductance of Wires External Inductance and Capacitance of Parallel Wires Lumped Equivalent Circuits of Parallel Wires Printed Circuit Board (PCB) Lands Effect of Component Leads Resistors Capacitors Inductors Ferromagnetic Materials-Saturation and Frequency Response Ferrite Beads Common-Mode Chokes Electromechanical Devices DC Motors Stepper Motors AC Motors Solenoids Digital Circuit Devices Effect of Component Variability Mechanical Switches Arcing at Switch Contacts 360

5 x CONTENTS The Showering Arc Arc Suppression 364 Problems 369 References Conducted Emissions and Susceptibility Measurement of Conducted Emissions The Line Impedance Stabilization Network (LISN) Common- and Differential-Mode Currents Again Power Supply Filters Basic Properties of Filters A Generic Power Supply Filter Topology Effect of Filter Elements on Common- and Differential-Mode Currents Separation of Conducted Emissions into Commonand Differential-Mode Components for Diagnostic Purposes Power Supplies Linear Power Supplies Switched-Mode Power Supplies (SMPS) Effect of Power Supply Components on Conducted Emissions Power Supply and Filter Placement Conducted Susceptibility 416 Problems References 7 Antennas 7.1 Elemental Dipole Antennas The Electric (Hertzian) Dipole The Magnetic Dipole (Loop) The Half-Wave Dipole and Quarter-Wave Monopole 7 Antennas Antenna Arrays Characterization of Antennas Directivity and Gain Effective Aperture Antenna Factor Effects of Balancing and Baluns Impedance Matching and the Use of Pads The Friis Transmission Equation Effects of Reflections The Method of Images

6 CONTENTS xi Normal Incidence of Uniform Plane Waves on Plane, Material Boundaries Multipath Effects Broadband Measurement Antennas The Biconical Antenna The Log-Periodic Antenna 490 Problems 494 References Radiated Emissions and Susceptibility Simple Emission Models for Wires and PCB Lands Differential-Mode versus Common-Mode Currents Differential-Mode Current Emission Model Common-Mode Current Emission Model Current Probes Experimental Results Simple Susceptibility Models for Wires and PCB Lands Experimental Results Shielded Cables and Surface Transfer Impedance 546 Problems 550 References Crosstalk Three-Conductor Transmission Lines and Crosstalk The Transmission-Line Equations for Lossless Lines The Per-Unit-Length Parameters Homogeneous versus Inhomogeneous Media Wide-Separation Approximations for Wires Numerical Methods for Other Structures Wires with Dielectric Insulations (Ribbon Cables) Rectangular Cross-Section Conductors (PCB Lands) The Inductive -Capacitive Coupling Approximate Model Frequency-Domain Inductive-Capacitive Coupling Model Inclusion of Losses : Common-Impedance Coupling Experimental Results Time-Domain Inductive -Capacitive Coupling Model Inclusion of Losses : Common-Impedance Coupling Experimental Results 617

7 xii CONTENTS 9.5 Lumped-Circuit Approximate Models An Exact SPICE (PSPICE) Model for Lossless, Coupled Lines Computed versus Experimental Results for Wires Computed versus Experimental Results for PCBs Shielded Wires Per-Unit-Length Parameters Inductive and Capacitive Coupling Effect of Shield Grounding Effect of Pigtails Effects of Multiple Shields MTL Model Predictions Twisted Wires Per-Unit-Length Parameters Inductive and Capacitive Coupling Effects of Twist Effects of Balancing 698 Problems 701 References Shielding Shielding Effectiveness Shielding Effectiveness : Far-Field Sources Exact Solution Approximate Solution Reflection Loss Absorption Loss Multiple-Reflection Loss Total Loss Shielding Effectiveness : Near-Field Sources Near Field versus Far Field Electric Sources Magnetic Sources Low-Frequency, Magnetic Field Shielding Effect of Apertures 745 Problems 750 References System Design for EMC Changing the Way We Think about Electrical Phenomena Nonideal Behavior of Components and the Hidden Schematic "Electrons Do Not Read Schematics" 763

8 CONTENTS xiii What Do We Mean by the Term "Shielding"? What Do We Mean by the Term "Ground"? Safety Ground Signal Ground Ground Bounce and Partial Inductance Partial Inductance of Wires Partial Inductance ofpcb Lands Currents Return to Their Source on the Paths of Lowest Impedance Utilizing Mutual Inductance and Image Planes to Force Currents to Return on a Desired Path Single-Point Grounding, Multipoint Grounding, and Hybrid Grounding Ground Loops and Subsystem Decoupling Printed Circuit Board (PCB) Design Component Selection Component Speed and Placement Cable I/O Placement and Filtering The Important Ground Grid Power Distribution and Decoupling Capacitors Reduction of Loop Areas Mixed-Signal PCB Partitioning System Configuration and Design System Enclosures Power Line Filter Placement Interconnection and Number of Printed Circuit Boards Internal Cable Routing and Connector Placement PCB and Subsystem Placement PCB and Subsystem Decoupling Motor Noise Suppression Electrostatic Discharge (ESD) Diagnostic Tools The Concept of Dominant Effect in the Diagnosis of EMC Problems 850 Problem 856 References 857 Appendix A The Phasor Solution Method 859 A.1 Solving Differential Equations for Their Sinusoidal, Steady-State Solution 859

9 AV CONTENTS A.2 Solving Electric Circuits for Their Sinusoidal, Steady-State Response 863 Problems 867 References 869 Appendix B The Electromagnetic Field Equations and Waves 871 B.1 Vector Analysis 872 B.2 Maxwell's Equations 881 B.2.1 Faraday's Law 881 B.2.2 Ampere's Law 892 B.2.3 Gauss' Laws 898 B.2.4 Conservation of Charge 900 B.2.5 Constitutive Parameters of the Medium 900 B.3 Boundary Conditions 902 B.4 Sinusoidal Steady State 907 B.5 Power Flow 909 B.6 Uniform Plane Waves 909 B.6.1 Lossless Media 912 B.6.2 Lossy Media 918 B.6.3 Power Flow 922 B.6.4 Conductors versus Dielectrics 923 B.6.5 Skin Depth 925 B.7 Static (DC) Electromagnetic Field Relationsa Special Case 927 B.7.1 Maxwell's Equations for Static (DC) Fields 927 B Range ofapplicability for Low-Frequency Fields 928 B.7.2 Two-Dimensional Fields and Laplace's Equation 928 Problems References Appendix C Computer Codes for Calculating the Per-Unit-Length (PUL) Parameters and Crosstalk of Multiconductor Transmission Lines C.1 WIDESEPYOR for Computing the PUL 941 C.2 C.3 Parameter Matrices of Widely Spaced Wires 942 RIBBONYOR for Computing the PUL Parameter Matrices of Ribbon Cables PCB.FOR 947 for Computing the PUL Parameter Matrices of Printed Circuit Boards 949

10 CONTENTS xv C.4 C.5 C.6 C.7 MSTRP.FOR for Computing the PUL Parameter Matrices of Coupled Microstrip Lines 951 STRPLINEYOR for Computing the PUL Parameter Matrices of Coupled Striplines 952 SPICEMTL.FOR for Computing a SPICE (PSPICE) Subcircuit Model of a Lossless, Multiconductor Transmission Line 954 SPICELPI.FOR For Computing a SPICE (PSPICE) Subcircuit of a Lumped-Pi Model of a Lossless, Multiconductor Transmission Line 956 Appendix D A SPICE (PSPICE) Tutorial 959 D.1 Creating the SPICE or PSPICE Program 960 D.2 Circuit Description 961 D.3 Execution Statements 966 D.4 Output Statements 968 D.5 Examples 970 References 974 Index 975