Design for Electromagnetic Compatibility--In a Nutshell

Frontmatter

PDF

Open Access

Chapter 1. Introduction

Abstract

This chapter introduces electromagnetic compatibility (EMC), its most essential terms and definitions, and why it is wise to consider EMC early during product development.

Reto B. Keller

PDF View full text

Open Access

Chapter 2. Regulations and Standards

Abstract

This chapter presents the principles of EMC regulations and standards and their implications on the launch of an EMC compliant product. In addition, a way is presented on how to test EMC for global market access. The landscape of regulations, directives, and standards is constantly changing. Therefore, please check if the references made in this chapter are still valid before applying the information presented here.

Reto B. Keller

PDF View full text

Open Access

Chapter 3. Decibel

Abstract

This chapter introduces the topic decibel in a compact form. Decibel is defined as the ratio of two quantities, typically power, voltage, or current. In the field of EMC, the decibel must be understood. One advantage of decibels is that a gain of 10 dB means a gain of 10 dB for current, voltage, and power likewise. This fact helps to prevent misinterpretations and helps to simplify things. This is the main reason why EMC and high-frequency system engineers like to work with decibels.

This chapter assumes that values of voltages V [V], currents I [A], power P [W], electric field strengths E [V/m], and magnetic field strength H [A/m] are given as root-mean-square (RMS) values.

Reto B. Keller

PDF View full text

Open Access

Chapter 4. Frequency and Wavelength

Abstract

Understanding the relationship between frequency f [Hz] and wavelength λ [m] is fundamental for a professional EMC design engineer. This chapter introduces the term wavelength λ and explains how the wavelength of an electromagnetic wave depends on the cable insulation or PCB material.

Reto B. Keller

PDF View full text

Open Access

Chapter 5. Time-Domain and Frequency-Domain

Abstract

This chapter introduces the transformation from time-domain to frequency-domain and vice versa. Electrical signals—periodic or nonperiodic—can be measured in the time-domain (e.g., with an oscilloscope) or in the frequency-domain (e.g., with a spectrum analyzer). This means that an electrical signal can be described either in the time- or frequency-domain. The time-domain representation helps you to determine the signal integrity (ringing, reflection). In contrast, the frequency-domain representation helps you to determine at which frequencies a signal potentially leads to radiated emissions.

As an EMC design engineer and troubleshooter, it is crucial to understand the dependencies and relationship between the time-domain and the frequency-domain.

Reto B. Keller

PDF View full text

Open Access

Chapter 6. RF Parameters

Abstract

This section introduces some of the most common radio-frequency (RF) parameters used in the field of EMC and high-frequency circuit design and measurement. A particular emphasis lays on the term impedance matching and distinguishing between good and poor impedance matching.

Reto B. Keller

PDF View full text

Open Access

Chapter 7. Transmission Lines

Abstract

In EMC, it is essential to understand the concept of transmission lines and when to apply it. Because once a signal interconnection line exceeds a critical length l _critical [m], impedance matching (\( \underline {Z}_{source}\), \( \underline {Z}_{line}\), \( \underline {Z}_{load}\)) must be considered to prevent reflections and ringing, thus preventing unwanted radiated emissions and bad signal quality—a signal integrity topic.

This chapter introduces transmission lines and their most important properties.

Reto B. Keller

PDF View full text

Open Access

Chapter 8. Electromagnetic Fields

Abstract

Abstract

Reto B. Keller

PDF View full text

Open Access

Chapter 9. Antennas

Abstract

This chapter is a brief introduction to antennas and electromagnetic radiation, focusing on antennas for EMC tests. We skip the math intense part around Maxwell’s Equations.

The formulas and statements in this chapter apply to the far-field (not the near-field), free-space, matched impedances (of antennas and receiver/transmitter equipment), and matched polarization (of the electromagnetic waves and the antenna polarization).

Reto B. Keller

PDF View full text

Open Access

Chapter 10. Skin Effect

Reto B. Keller

PDF View full text

Open Access

Chapter 11. Components

Abstract

In order to choose the right components for EMI filters, it is essential to understand the properties and nonideal behavior of passive filter components. Therefore, in this chapter, the high-frequency behavior and other undesirable effects of conductors (wires, cables, PCB traces), resistors, capacitors, inductors, ferrite beads, common-mode chokes, baluns, varistors, and TVS diodes are presented.

Reto B. Keller

PDF View full text

Open Access

Chapter 12. Noise Coupling

Abstract

Noise coupling is one of the essential and constantly recurring topics in EMC. An EMC design engineer must consider any noise coupling paths constantly during the design and when troubleshooting.

First of all, this chapter discusses coupling paths. Then it is shown which coupling leads typically to differential-mode noise and which coupling does typically lead to common-mode noise.

Reto B. Keller

PDF View full text

Open Access

Chapter 13. Shielding

Abstract

In the field of EMC, shields are used to:

1.

Reduce electromagnetic emissions from a product.

 

2.

Increase immunity against electric, magnetic, and/or electromagnetic radiation.

 

The shielding theory presented in this book is based on the accepted shielding theory for electromagnetic waves, initially proposed by Schelkunoff ((1943) Electromagnetic waves. D. van Nostrand Company Inc, New York, pp 303–312) in 1943. The formulas in this chapter are approximations for shields with high electrical conductivity. Before we jump into the theory of shielding, here are two practical pieces of advice:

1.

Cables and wires. Every single signal which enters and/or leaves a shielded enclosure must be filtered or shielded. In case the cable is shielded, contact the cable shield 360^∘ with the shielded enclosure.

 

2.

Slots and apertures. Slots and apertures reduce the shielding effectiveness SE or even lead to higher emissions than without the shield in case of resonances inside a shielding enclosure Hubing ((2021) EMC Question of the Week: 2017–2020. LearnEMC, LLC, Stoughton). If the linear dimension l [m] of a slot or aperture is larger than λ∕2, the shield is assumed to be useless Ott ((2009) Electromagnetic compatibility engineering. Wiley, New York).

 

Reto B. Keller

PDF View full text

Open Access

Chapter 14. Grounding

Abstract

Considering grounding in EMC is fundamental. Grounding has to be considered from the very beginning of a hardware development project. This chapter presents the basic grounding concepts and how to apply them.

Reto B. Keller

PDF View full text

Open Access

Chapter 15. Filtering

Abstract

In EMC, filtering helps to minimize emissions of a product and increase the product’s immunity against electromagnetic interference. This chapter presents the concepts of determining the right filter type and ensuring the proper components are chosen regarding power dissipation, noise current type, and high-frequency behavior.

Filters can be classified according to their attenuation in the frequency-domain:

• Low-pass filters
• High-pass filters
• Band-pass filters
• Band-stop filters

or according to active components involved or not:

• Passive filters
• Active filters

or according to the noise current type:

• Differential-mode noise filters
• Common-mode noise filters

or according to the suppression of transients:

• ESD filters
• Burst filters
• Surge filters

or according to the implementation in hardware or software:

• Analog filters (hardware)
• Digital filters (software)

In this chapter, all the filter types listed above are explained in further detail.

Reto B. Keller

PDF View full text

Open Access

Chapter 16. EMC Design Guidelines

Abstract

These EMC design guidelines are here to help you understand the basics of a good design of PCBs and cabling. Good in this context means with low electromagnetic interference (EMI). The guidelines presented in this chapter are the personal guidelines of the author and helped him to pass EMC testing of several products. However, be aware that guidelines alone cannot do magical things to your design and they cannot be universally applied. Be wary! However, getting the basics right will reduce the pain of EMC testing and increase the chances of right-first-time. And that is all that we want, right?

Reto B. Keller

PDF View full text

Backmatter

PDF