Recent Open-Enrollment Courses

The Physics of Electromagnetic Compatibility Measurements


In a radiated electromagnetic emissions measurement, does it make a difference whether the excess cable is bundled neatly or coiled on the floor? Does it matter where an ESD simulator is grounded? Why do products that fail to meet EMC requirements in Laboratory A tend to do much better in Laboratory B? This course reviews the equipment, test set-ups and primary coupling mechanisms associated with each of the major electromagnetic compatibility tests. The goal of the course is to provide a basic understanding of the physics involved in order to make better, more meaningful and more repeatable measurements.

The primary EMC tests covered by this course are Conducted and Radiated Emissions, Radiated Immunity, Bulk Current Injection, Electrical Fast Transient testing and Electrostatic Discharge testing. Other EMC tests such as Lightning Immunity, Magnetic Field Emissions and Power Disturbance tests will also be discussed. Commercial, automotive and military EMC test procedures in each of these categories will be reviewed. While the course will refer to industry standard tests, the focus is on the general physics, not the specific requirements of any given standard.

For each EMC test, the course reviews the test equipment, test settings and set-up parameters that affect the measurement results. Basic models of the measurements are presented that help test engineers and technicians to understand exactly what is being measured. These models illustrate and how sometimes seemingly minor decisions related to the test set-up can significantly affect the results of a measurement.

People who might benefit from taking this course include engineers and technicians that are new to field of EMC and want to become familiar with EMC test procedures; as well people who have been conducting EMC tests for many years that want to develop a better understanding of the physics involved. The course can also benefit product engineers who are responsible for negotiating EMC test plans and/or ultimately ensuring that their designs will comply with EMC requirements.
Course Outline

Electronic Systems Design for EMC Compliance

circuit board

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 learn techniques for quickly reviewing designs in order to flag potential problems well before the first hardware is built and tested.
Course Outline