EMI Filter Design: 3rd Edition (Paperback) book cover

EMI Filter Design

3rd Edition

By Richard Lee Ozenbaugh, Timothy M. Pullen

CRC Press

272 pages | 148 B/W Illus.

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With today’s electrical and electronics systems requiring increased levels of performance and reliability, the design of robust EMI filters plays a critical role in EMC compliance. Using a mix of practical methods and theoretical analysis, EMI Filter Design, Third Edition presents both a hands-on and academic approach to the design of EMI filters and the selection of components values. The design approaches covered include matrix methods using table data and the use of Fourier analysis, Laplace transforms, and transfer function realization of LC structures. This edition has been fully revised and updated with additional topics and more streamlined content.

New to the Third Edition

  • Analysis techniques necessary for passive filter realization
  • Matrix method and transfer function analysis approaches for LC filter structure design
  • A more hands-on look at EMI filters and the overall design process

Through this bestselling book’s proven design methodology and practical application of formal techniques, readers learn how to develop simple filter solutions. The authors examine the causes of common- and differential-mode noise and methods of elimination, the source and load impedances for various types of input power interfaces, and the load impedance aspect of EMI filter design. After covering EMI filter structures, topologies, and components, they provide insight into the sizing of components and protection from voltage transients, discuss issues that compromise filter performance, and present a goal for a filter design objective. The text also includes a matrix method for filter design, explains the transfer function method of LC structures and their equivalent polynomials, and gives a circuit design example and analysis techniques. The final chapter presents packaging solutions of EMI filters.


"This 3rd edition book is an excellent resource for solving EMI problems. It provides a systematic procedure for identifying noise sources and provides the design tools needed to solve problems. It will be an invaluable reference book for working electrical engineers as well as students who want to learn about EMI filtering and EMI noise problems. … The book is filled with design equations that can be immediately put to use by the reader. This book can be a guidebook for diagnosing troublesome EMI issues in existing designs, and it can also be used to prevent EMI issues from occurring in the first place because of the information in this book. … This is a book that should be used by every electrical engineer involved with EMI issues. It is filled with design equations, but more importantly it will provide you with an understanding of EMI issues, thus, making you a better design engineer."

—John J. Shea, IEEE Electrical Insulation Magazine, March/April, Vol. 29, No.2, 2013

Table of Contents

EMI Filters


Technical Challenges

Types of EMI Filters

No Such Thing as Black Magic

It Is All in the Mathematics

Why Call EMI Filters Black Magic?

What Is EMI?

Regular Filters versus EMI Filters

Specifications: Real or Imagined

The Inductive Input for the 220-A Test Method

The 400-Hz Filter Compared with the 50- or 60-Hz Filter

Common Mode and Differential Mode: Definition, Cause, and Elimination

Definition of Common and Differential Modes

The Origin of Common-Mode Noise

Generation of Common-Mode Noise—Load

Elimination of Common-Mode Noise—Line and Load

Generation of Differential-Mode Noise?

Three-Phase Virtual Ground

EMI Filter Source Impedance of Various Power Lines

Skin Effect

Applying Transmission Line Concepts and Impedances

Applying Transmission Line Impedances to Differential and Common Mode

Differences among Power Line Measurements

Simple Methods of Measuring AC and DC Power Lines

Other Source Impedances

The Various AC Load Impedances

The Resistive Load

Off-Line Regulator with Capacitive Load

Off-Line Regulator with an Inductor ahead of the Storage Capacitor

The Power Factor Correction Circuit

Transformer Load

The UPS Load

DC Circuit—Load and Source

Various Source Impedance

Switcher Load

DC Circuit for EMI Solutions or Recommendations

Some Ideas for the Initial Power Supply

Other Parts of the System

Lossy Components

Radiated Emissions

Typical EMI Filters—Pros and Cons

The π Filter

The T Filter

The L Filter

The Typical Commercial Filter

The Cauer Filter

The RC Shunt

The Conventional Filters

Filter Components—the Capacitor

Capacitor Specifications

Capacitor Construction and Self-Resonant Frequency

Veeing the Capacitor

Margins, Creepage, and Corona—Split Foil for High Voltage

Capacitor Design—Wrap-and-Fill Type

Filter Components—the Inductor

Inductor Styles and Specifications

Core Types

High-Current Inductors

Inductor Design

Converting from Unbalanced to Balanced

Common-Mode Components

The Capacitor to Ground

Virtual Ground

Z for Zorro

Common-Mode Inductor

Common-Mode Calculation

Differential Inductance from a Common-Mode Inductor

Common-Mode Currents—Do They All Balance?

The Transformer’s Addition to the EMI Filter

Transformer Advantages


Leakage Current

Common Mode

Voltage Translation—Step Up or Down

The Transformer as a Key Component of the EMI Package

Skin Effect


Electromagnetic Pulse and Voltage Transients

Unidirectional versus Bidirectional

The Three Theories

Initial High-Voltage Inductor

The Arrester Location

How to Calculate the Arrester

The Gas Tube

What Will Compromise the Filter?


Power Supplies—Either as Source or Load

9- and 15-Phase Autotransformers

Neutral Wire Not Part of the Common-Mode Inductor

Two or More Filters in Cascade—the Unknown Capacitor

Poor Filter Grounding

The "Floating" Filter

The Unknown Capacitor in the Following Equipment

Filter Input and Output Too Close Together


Waves as Noise Sources

The Spike

The Pulse

The Power Spectrum—dB μA/MHz

MIL-STD-461 Curve

Initial Filter Design Requirements

Differential-Mode Design Goals

The Differential-Mode Filter Input Impedance

The Differential-Mode Filter Output Impedance

The Input and Output Impedance for a DC Filter

Common-Mode Design Goals

Estimation of the Common-Mode Source Impedance

Methods of Reducing the Inductor Value due to High Current

Matrices, Transfer Functions, and Insertion Loss

Synthesis, Modeling, and Analysis

Review of the A Matrix

Transfer Functions

Review of Matrix Topologies

The π Filter

The L Matrix

The T Filter

The Cauer or Elliptic Matrix

The RC Shunt

Filter Applications and Thoughts

Single-Phase AC Filter

Three-Phase Filters

Low-Current Wye

High-Current Wye

The Single Insert

The Low-Current Delta

High-Current Delta

Telephone and Data Filters

Pulse Requirements—How to Pass the Pulse

The DC-DC Filter

Low-Current Filters

Matrix Applications: A Continuation of Chapter 16

The Impedance of the Source and Load

dB Loss Calculations of a Single π Filter

Example of the Calculations for a Single π Filter

Double π Filter: Equations and dB Loss

Triple π Filter: Equations and dB Loss

Network Analysis of Passive LC Structures

Lossless Networks

Network Impedances Using Z Parameters

Network Admittances Using Y Parameters

Transfer Function Analysis—H(jω)

Transfer Function Analysis—H(s)

Coefficient-Matching Technique

EMI Filter Stability

Filter Design Techniques and Design Examples

Filter Design Requirements

Design Techniques

Filter Design Summary

EMI Filter Design Example

Four-Pole LC Structure

Packaging Information

The Layout

Estimated Volume

Volume-to-Weight Ratio

Potting Compounds

Appendix A: K Values of Different Topologies

Appendix B: LC Passive Filter Design

Appendix C: Conversion Factors


About the Authors

Richard Lee Ozenbaugh is a consultant of EMI filter design and magnetics engineering for such companies as Hughes Aircraft Corporation, Parker Hannifin Aerospace, Franklin Electric, McDonnell Douglas, and Cirrus Logic. Involved in the electrical and electronics industries since the early 1950s, he has worked as a radar specialist for the U.S. Navy as well as an engineer for Hopkins Engineering and RFI Corporation.

Timothy M. Pullen is a principal electrical engineer at Rockwell Collins. He has over 25 years of experience in the research, design, and development of electronic systems for commercial and military applications, including power electronics, motor control, and full authority digital engine control technology. His areas of expertise include model-based design and control, analog circuit design, and filter design.

Subject Categories

BISAC Subject Codes/Headings:
TECHNOLOGY & ENGINEERING / Electronics / General
TECHNOLOGY & ENGINEERING / Power Resources / Electrical