EMI Suppression Filters (EMC and Noise Suppression)Noise Suppression Products/EMI Suppression Filters

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Chapter 2

Mechanism of Causing Electromagnetic Noise

2-5. Summary of Chapter 2

Chapter 2 has described the overview of the noise source origin of electronic devices and in particular, has further described the mechanism of noise being caused by digital circuits, which often poses a problem. The relationship of topics described in this section is as follows:

Relationship of topics

Fig. 2-5-1 Relationship of topics

There are three cases for the noise sources of electronic devices as shown in Fig. 2-5-2.

  1. (i) Signal
  2. (ii) Power supply
  3. (iii) Surge

Digital circuit is a typical circuit that can emit the nose of (i) and (ii).
A digital circuit operates with various frequency components called harmonics. This current flows not only in the signal line but also in the power supply and ground. However, if any leaks to the outside, it becomes noise as shown in Fig. 2-5-3.
To make full use of digital circuits, the EMC design is required for the signal and power supply as shown in Fig. 2-5-3. This chapter describes the basic theory that is required for this EMC design.

Summary of Chapter 2
Fig. 2-5-2 Summary of Chapter 2
EMC design of digital circuit
Fig. 2-5-3 EMC design of digital circuit
[Japanese] EMC設計技術 -基礎編-
(社)エレクトロニクス実装学会, 電磁特性技術委員会編 2004
Introduction to Electromagnetic Compatibility
Clayton R. Paul
John Wiley & Sons Inc. 1992
Noise Reduction Techniques in Electronic Systems Second Edition
Henry W. Ott
John Wiley & Sons Inc. 1988

Murata Manufacturing Co., Ltd. Catalog C39, 2010
High-Speed Digital Design: a Handbook of Black Magic
Howard Johnson, Martin Graham
Prentice Hall PTR. 1993
High-Speed Signal Propagation: Advanced Black Magic
Howard Johnson, Martin Graham
Pearson Education Inc. 2003
[Japanese] よくわかるプリント板実装の高速・高周波対策
日刊工業新聞社 2009

Next: Chapter 3 Factors of making noise problems complex