Electronic Systems Design for EMC Compliance


circuit boards and schematic

Well-designed electronic systems operate reliably in their intended electromagnetic environment. These systems are not affected by voltage spikes on their power or signal lines; they function normally in the presence of strong electric or magnetic fields; and the systems’ own fields do not interfere with other systems nearby. In a well-designed system, the cost of grounding, shielding and filtering is usually a negligible percentage of the overall system component costs. Unfortunately, many electronic systems are not well designed. It is not unusual for a company to spend millions of dollars and thousands of man-hours attempting to track down and correct system malfunctions that are the direct result of improper grounding and shielding. This course reviews the fundamental grounding, filtering and shielding concepts that all engineers can utilize to ensure the safety and reliability of their products at the lowest possible cost.

Today's rapid development cycles require products to meet their EMC requirements the first time they come into the lab for testing. Board layout changes and other EMC "fixes" can significantly add to the cost of a product and/or delay its development schedule. First-pass compliance with EMC requirements starts with the circuit board layout. Printed circuit board layout is often the single most important factor affecting the electromagnetic compatibility of electronic systems. Boards that are auto-routed or laid out according to a list of “design rules” do not usually meet electromagnetic compatibility requirements on the first pass; and the products using these boards are more likely to require expensive fixes such as ferrites on cables or shielded enclosures. Taking the time to ensure that components are properly placed, transition times are not left to chance, and traces are optimally routed will generally result in products that meet all electromagnetic compatibility and signal integrity requirements on time and on budget.

Many electronic systems employ mixed-signal boards (boards with both analog and digital circuits). Mixed-signal boards require that special attention be paid to the routing of the low-frequency currents. Minor mistakes in the layout of these boards can mean the difference between a reliable product and a product with severe EMC problems.

The cables that carry power and signals to and from the system, or between boards in a system, are another key design consideration. Shielded cables are not always better than unshielded cables, and choosing the right cable for the right application can be as important as circuit board design and layout for ensuring that a product will be cost effective and meet all EMC requirements.

This course stresses the fundamental concepts and tools that electronics engineers can employ to avoid electromagnetic compatibility and signal integrity problems. Students completing the course will be able to make good decisions regarding board layout and system design for EMC. They will also be introduced to tools and techniques for quickly reviewing designs in order to flag potential problems well before the first hardware is built and tested.

Continuing Education Credit: 1.5 CEUs, 15 PDHs

Course Outline

Elements of an EMC Problem
Heat pipes on a circuit board
EMC Design Considerations Circuit Board Filter Magnetic Field Shielding
Part 1 - Important Fundamental Concepts
  1. Introduction
    • Overview of Electromagnetic Compatibility
    • Coupling Mechanisms
  2. Signal Routing and Termination
    • Tracing Current Paths / Concept of Least Impedance
    • Transition Time Control
    • RLC Circuits
    • Transmission Lines
  3. Identifying the Unintentional Antennas on a Board
    • Essential Elements of an Antenna
    • What Makes a Good Antenna
    • What Makes a Poor Antenna
  4. Noise Sources and Coupling Mechanisms
    • Integrated Circuits as Sources of EMI
    • Parasitic Oscillations and Unexpected Noise Sources
    • Coupling Between Noise Sources and Antennas
    • Differential Mode to Common Mode Conversion
  5. Grounding
    • Ground vs. Current Return
    • Ground Structures and Grounding Conductors
  6. Strategies for Mixed-Signal PCB Layout
    • Managing Current Return Paths
    • Managing Ground
    • Design Examples
  7. Filtering
    • Insertion Loss
    • First-Order Low-Pass Filters
    • Second-Order Low-Pass Filters
    • Component Parasitics
  8. Shielding
    • Electric Field Shielding
    • Magnetic Field Shielding
    • Shielding to Reduce Radiated Emissions
    • Cable Shielding
Part 2 - Advanced Design and Modeling Techniques
  1. DC Power Distribution and Decoupling
    • Effective Power Distribution Strategies
    • Choosing and Locating Decoupling Capacitors
    • Low-Inductance Capacitor Connections
    • Isolating PLLs and Other Sensitive Devices
  2. Key System-Level Design Considerations
    • For Radiated Emissions Tests
    • For Conducted Emissions Tests
    • For Radiated Susceptibility
    • For ESD and Transient Tests
  3. An EMC Compliance Strategy
    • Which Circuits or Nets Deserve Attention?
    • Which Transition Times Require Control?
    • Which Current Paths need to be Traced?
    • Which Nets Have a Balance Mismatch (and does it matter)?
    • Where are the Antennas?
    • Where will ESD and Transient Currents Flow?
    • What's the Worst That Could Happen?
  4. Computer Modeling Tools
    • Schematic and Board Layout Tools
    • Circuit Solvers
    • Field Solvers
    • Full-Wave Modeling Tools
    • Design Rule Checkers
    • Maximum Emissions/Coupling Calculators
    • Modeling Examples
  5. Specific Design Examples
    • Printer Control Circuit
    • Wireless Router
    • Power Inverter / Motor Driver
    • Others Provided by the Class
  6. Course Summary
    • Review of Key Concepts
    • Resources for EMC and Signal Integrity Engineers

Course Instructor

Professor Todd Hubing

Dr. Todd H. Hubing is a Professor Emeritus of Electrical and Computer Engineering at Clemson University and former Director of the Clemson Vehicular Electronics Laboratory. He and his students at Clemson have worked on the development and analysis of a wide variety of electronic products. EMC design rules can vary greatly depending on whether you are designing high-speed computing equipment, low-cost mixed-signal consumer products or high-power industrial controls; but the basic EMC principles are the same in all industries. By applying these principles in an organized manner, it is possible to review a design circuit-by-circuit to guarantee that any particular EMC requirement will be met. This approach is more effective than the blind application of design guidelines and is the primary emphasis of every EMC design class taught by Dr. Hubing.