Electromagnetic Bandgap (EBG) Structures E-Book

Antonio Orlandi

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 332

Veröffentlichungsjahr: 2017

Beschreibung

An essential guide to the background, design, and application of common-mode filtering structures in modern high-speed differential communication links Written by a team of experts in the field, Electromagnetic Bandgap (EBG) Structures explores the practical electromagnetic bandgap based common mode filters for power integrity applications and covers the theoretical and practical design approaches for common mode filtering in high-speed printed circuit boards, especially for boards in high data-rate systems. The authors describe the classic applications of electromagnetic bandgap (EBG) structures and the phenomena of common mode generation in high speed digital boards. The text also explores the fundamental electromagnetic mechanisms of the functioning of planar EBGs and considers the impact of planar EBGs on the digital signal propagation of single ended and differential interconnects routed on top or between EBGs. The authors examine the concept, design, and modeling of EBG common mode filters in their two forms: on-board and removable. They also provide several comparisons between measurement and electromagnetic simulations that validate the proposed EBG filters' design approach. This important resource: * Presents information on planar EBG based common mode filters for high speed differential digital systems * Provides systematic analysis of the fundamental mechanisms of planar EBG structures * Offers detailed design methodology to create EBG filters without the need for repeated full-wave electromagnetic analysis * Demonstrates techniques for use in practical real-world designs Electromagnetic Bandgap (EBG) Structures: Common Mode Filters for High Speed Digital Systems offers an introduction to the background, design, and application of common-mode filtering structures in modern high-speed differential communication links, a critical issue in high-speed and high-performance systems.

Leseprobe

CONTENTS

Cover

Series Page

Title Page

Copyright

About the Authors

Preface

Acknowledgments

Chapter 1: Introduction

1.1 Motivations

1.2 Scope of the Book

References

Chapter 2: Planar EBGs: Fundamentals and Design

2.1 Fundamental Behavior of Planar EBG

2.2 Identification of the Bandgap Limits: fHigh

2.3 Identification of the Bandgap Limits: fLow

2.4 Characterization of fLow for Different Patch Matrix Configurations

2.5 Experimental Validation

2.6 Embedded Planar EBG

2.7 Application Examples

2.8 Conclusions

References

Chapter 3: Impact of Planar EBGs on Signal Integrity in High-Speed Digital Boards

3.1 Coupling Mechanisms Between Microstrip Lines and Planar EBGs

3.2 Impact of EBG Reference to Striplines

3.3 Conclusions

References

Chapter 4: Planar Onboard EBG Filters for Common Mode Current Reduction

4.1 EBG Structures as Common Mode Filters: Overview and Operating Principles

4.2 Resonant Patch-Based Common Mode Filters: Basic Behavior and Features

4.3 Resonant Patch-Based Filters: Experimental Validation

4.4 EBG-Based CM Filters: Design Approach

4.5 Onboard EBG-Based Common Mode Filters: Typical Structures

4.6 Additional Design Considerations

4.7 EBG-Based CM Filters: Hardware Measurements

4.8 Conclusions

References

Chapter 5: Special Topics for EBG Filters

5.1 Introduction

5.2 Increased Bandwidth Filter: Multiple Size Patches

5.3 Increased Bandwidth Filter: Multiple Size Bridge Width

5.4 Conclusions

References

Chapter 6: Removable EBG Common Mode Filters

6.1 Design Concept of Removable EBG Filter

6.2 Categorization of Filters and Structures

6.3 Removable EBG Common Mode Filters Design Approach

6.4 Design Examples and Typical Results

6.5 Summary of Advantages and Drawbacks

References

Chapter 7: EBG Common Mode Filters: Modeling and Measurements

7.1 Design Considerations for the EBG Filter Test Fixture

7.2 Experimental Design Considerations When Trying to Quantify the Cross Talk Performance of an EBG Filter

7.3 Experimental Design Considerations When Trying to Quantify the Total Radiated Power from an EBG Filter

7.4 Conclusions

References

Index

End User License Agreement

List of Tables

Table 2.1

Table 2.2

Table 3.1

Table 4.1

Table 4.2

Table 4.3

Table 4.4

Table 4.5

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Table 7.1

List of Illustrations

Figure 1.1

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Figure 5.1

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Figure 6.1

Figure 6.2

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Figure 6.21

Figure 6.22

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Figure 6.27

Figure 6.28

Figure 6.29

Figure 6.30

Figure 7.1

Figure 7.2

Figure 7.3

Figure 7.4

Figure 7.5

Figure 7.6

Figure 7.7

Figure 7.8

Guide

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Table of Contents

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IEEE Press445 Hoes LanePiscataway, NJ 08854

IEEE Press Editorial BoardTariq Samad, Editor in Chief

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Saeid Nahavandi

Mohammad Shahidehpour

Ekram Hossain

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Zidong Wang

Electromagnetic Bandgap (EBG) Structures

Common Mode Filters for High-Speed Digital Systems

Antonio Orlandi, Bruce Archambeault,

Francesco de Paulis, and Samuel Connor

Copyright © 2017 by The Institute of Electrical and Electronics Engineers, Inc. All rights reserved.

Published by John Wiley & Sons, Inc., Hoboken, New Jersey.

Published simultaneously in Canada.

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ISBN: 978-1-119-28152-8

About the Authors

Antonio Orlandi (M'90–SM'97–F'07) was born in Milan, Italy in 1963. He received the Laurea degree in Electrical Engineering from the University of Rome “La Sapienza,” Italy, in 1988 and the Ph.D. degree in Biomedical Engineering from the University “Campus Biomedico,” Italy, in 2012. He was with the Department of Electrical Engineering, University of Rome “La Sapienza” from 1988 to 1990. Since 1990, he has been associated with the Department of Electrical Engineering of the University of L'Aquila where he is currently Full Professor and Chair of the UAq EMC Laboratory. Author of more than 320 technical papers, he has published in the field of electromagnetic compatibility in lightning protection systems and power drive systems. Current research interests are in the field of numerical methods and modeling techniques to approach signal/power integrity, EMC/EMI issues in high-speed digital systems. Dr. Orlandi received the IEEE Transactions on Electromagnetic Compatibility Best Paper Award in 1997, IEEE Transactions on Advanced Packaging Best Paper Award in 2011, the IEEE EMC Society Technical Achievement Award in 2003 and 2012, the IBM Shared University Research Award in 2004, 2005, 2006 and 2012, the CST University Award in 2004, the IEEE International Symposium on EMC Best Paper Award in 2009, 2010, 2013, the IEEE International Conference on SI/PI Best Paper Award in 2016, the DesignCon Best Paper Award in 2011 and 2012, and the IEEE Transactions on Electromagnetic Compatibility Best Paper Award Honorable Mention in 2015. He is co-recipient of the 2015 CISCO University Program Fund Award on “TSV modeling and measurement.” From 1996 to 2000, and from 2010 up to December 2015, he has been Associate Editor of the IEEE Transactions on Electromagnetic Compatibility. Since January 2016, he is the Editor-in-Chief of the IEEE Transactions on Electromagnetic Compatibility. Dr. Orlandi is member of the “Education,” TC-9 “Computational Electromagnetics,” and Past Chairman of the TC-10 “Signal Integrity” Committees and Vice-Chair of TC-12 “EMC for Emerging Wireless Technologies” of the IEEE EMC Society. He is General Co-Chair of the 2017 IEEE SIPI Conference. From 2001 to 2006, he served as Associate Editor of the IEEE Transactions on Mobile Computing and from 1999 to the end of the Symposium was Chairman of the TC-5 “Signal Integrity” Technical Committee of the International Zurich Symposium and Technical Exhibition on EMC.

Bruce Archambeault is an IEEE Fellow, an IBM Distinguished Engineer Emeritus, and an Adjunct Professor at Missouri University of Science and Technology. He received his B.S.E.E degree from the University of New Hampshire in 1977 and M.S.E.E degree from Northeastern University in 1981. He received his Ph.D. from the University of New Hampshire in 1997. His doctoral research was in the area of computational electromagnetics applied to real-world EMC problems. He has taught numerous seminars on EMC and Signal Integrity across the United States and the world, including the past 15 years at Oxford University.

Dr. Archambeault has authored or coauthored a number of papers in computational electromagnetics, mostly applied to real-world EMC applications. He is a member of the Board of Directors for the IEEE EMC Society and a past Board of Directors member for the Applied Computational Electromagnetics Society (ACES). He currently serves as the President-Elect for Conferences of the EMC Society. He has served as a past IEEE/EMCS Distinguished Lecturer, EMCS TAC Chair, and Associate Editor for the IEEE Transactions on Electromagnetic Compatibility. He is the author of the book PCB Design for Real-World EMI Control and the lead author of the book titled EMI/EMC Computational Modeling Handbook.

Francesco de Paulis (S'08, M'13) was born in L'Aquila, Italy in 1981. He received the Specialist degree (summa cum laude) in Electronic Engineering from University of L'Aquila, L'Aquila, Italy, in 2006. In August 2006, he joined the EMC Laboratory at the Missouri University of Science and Technology (formerly University of Missouri-Rolla), USA, where he received the M.S. degree in Electrical Engineering in May 2008. He received the Ph.D. degree in Electrical and Information Engineering in 2012 from the University of L'Aquila, L'Aquila, Italy.

He was involved in the research activities at the UAq EMC Laboratory, L'Aquila, Italy, from August 2004 to August 2006 and at the MST EMC Laboratory, Rolla, MO, from August 2006 to May 2008. From June 2004 to June 2005, he had an internship at Selex Communications, L'Aquila, within the layout/SI/PI design group. He is currently a Research Assistant at the UAq EMC Laboratory, University of L'Aquila, Italy. His main research interests are in developing fast and efficient analysis techniques for SI/PI and design of high-speed signals on PCB and packages, analysis and characterization of composite materials for shielding, RF interference in mixed-signal system, TSVs in silicon chips and interposers, EMI problem investigation, TDR techniques, and fault and degraded joint remote detection in power transmission lines.

Dr. de Paulis received from the IEEE EMC Society the Past President's Memorial Award in 2010. He was the recipient of the Best Paper Award in 2010, 2013, and 2016, and the Best Student Paper Award in 2009 and in 2011 at the IEEE International Symposium on EMC. He received the Paper Award in the power and RF design category in 2010, 2011, and 2012 at the IEC DesignCon. He was selected as Distinguished Reviewer of the Transaction on EMC for the year 2014.

Samuel Connor (M'04–SM'07) received his Bachelor's Degree in Electrical Engineering from the University of Notre Dame in 1994. Sam is currently a Senior Technical Staff Member in the IBM Systems Group, where he leads the EMC Design Center of Competency. Sam is a past-chair for both TC-9 and the Eastern North Carolina Chapter of the IEEE EMC Society, has served on numerous EMC Symposium Committees, and was a Distinguished Lecturer during 2012–2013.

Preface

As differential digital signal data rates increased to many Gb/s range, it became apparent that small amounts of mismatch within a differential pair of traces could create common mode signals that could adversely affect the electromagnetic compatibility (EMC) performance of systems. Therefore, it became important to find a way to filter the unwanted common mode signals while not affecting the signal integrity of the differential signals. Unfortunately, discrete common mode filter components can be used to only a few Gb/s data rate without too much impact on the intentional differential signal, so an alternative was needed.

Electromagnetic bandgap (EBG) filters appeared like a perfect solution, since no discrete components are required. However, at the time this research effort began, the previous work on EBGs was more of a “try it and see what we get” approach rather than a straightforward design that could be used in the real world of high-speed data communications product development. The planar EBG technology, deeply studied by the same authors and initially conceived for noise mitigation in power distribution networks, was found appropriate to develop resonance-based common mode filters.

This research to develop straightforward design equations to predict the required size of the EBG elements and to validate these equations with simulations and measurements has taken a number of years and a team approach. The primary researchers on the team are from the University of L'Aquila, but team members from IBM and the Missouri University of Science and Technology also contributed throughout the effort. This team approach of university and industry has worked well to create a design approach that is useful in the real world, while still being interesting and worthy of academia! The result is a set of filter designs that maintain reasonable insertion loss and cross talk performance of the intentional differential signal, strike a good balance between miniaturization and design complexity, and provide alternatives for mitigating the direct radiation from the filter structure.

The authors want to acknowledge the contributions of Dr. Carlo Olivieri at University of L'Aquila as well as Dr. Michael Cracraft of IBM. Their contributions to this work have been significant!

Acknowledgments

To my wife Antonia and my “kids” Michele, Anna, and Cecilia.

—Antonio Orlandi

Dedicated to my wife of 45 years for her constant support and love.

—Bruce Archambeault

I would like to express my gratitude to all researchers and engineers who contributed, throughout the last decade, to the development of the EBG project, and who do not appear explicitly in this book. In particular, Leo Raimondo and Danilo Di Febo of the UAq EMC Laboratory (University of L'Aquila), Muhammet Hilmi Nisanci of the UAq EMC Laboratory, and now of Sakarya University (Turkey), Eng. Riccardo Cecchetti of Technolabs/Intecs (L'Aquila plant), Dr. Jun Fan of the MS&T EMC Laboratory (Missouri University of Science and Technology), and Dr. Xiaoxiong Gu of IBM.

—Francesco de Paulis

Many thanks to my IBM colleagues who contributed to the design, fabrication, and testing of the EBG test boards over the course of our research. And most of all, I would like to thank my wife, Caroline, for her love and support throughout this project.

—Samuel Connor

1Introduction

1.1 Motivations

This book is focused on a specific use of electromagnetic bandgap (EBG) structures: their function as common-mode (CM) filter in high-speed differential digital systems and/or hybrid mixed-signal circuits.

In order to appreciate the potential of these structures as signal filter, it is instructive to give a look to the historical development of the EBG structures at least since 1999 when they were proposed as high-impedance electromagnetic surfaces for band-stop filter [1,2].

The first application was related to flat metal sheets used in many antennas as reflectors or ground planes. These sheets support surface waves [3,4], that is, propagating electromagnetic waves that are bound to the interface between metal and free space. If the metal surface is smooth and flat, the surface wave will not couple to external propagating plane waves. However, they will radiate vertically if scattered by bends, discontinuities, or surface texture and this can generate, in case of multiple antenna placement, unwanted mutual coupling and interference.

By applying a special texture on a conducting surface, it is possible to alter its electromagnetic properties [5,6]. In the limit where the period of the surface texture is much smaller than the wavelength, the structure can be described using an effective medium model, and its qualities can be described by the surface impedance. A smooth conducting sheet has a low surface impedance; however, with a specially designed textured surface, the sheet can have a high surface impedance, thus inhibiting the flow of the currents over a selected frequency range.

The first example of EBG as high-impedance surface consisted in an array of metal protrusions on a flat metal sheet. They are arranged in a two-dimensional lattice and can be visualized as mushrooms protruding from the surface [7–11]. The surface can be easily fabricated using standard printed circuit boards (PCB) technology. The protrusion are formed as metal patches connected to the lower continuous conducting surfaces by plated through-hole vias.

If the protrusions are small compared to the operating wavelength, their electromagnetic behavior can be described by using the lumped circuit theory. The EBG structure behaves like a network of parallel resonant LC circuits, which act as a two-dimensional electric filter to block the flow of currents along the sheet. In the frequency range where the surface impedance is high, the tangential magnetic field is small, even with a large electric field along the surface.

The mushroom-type EBG configuration has inspired the PCB designers to use this structure for suppressing noise in power planes [12]. An ideal power delivery network (PDN) is assumed to supply clean power to integrated circuits. However, electromagnetic noise in power/ground-reference planes can cause fluctuation or disturbance in the power supply voltage, which, in turn, leads to false switching, jitter, and malfunctioning in analog or digital circuits. Modern digital electronic circuits have increased the clock frequency and pulse edge rate, and has contributed to the decreased of the power supply voltage and noise margin. This power/ground-reference noise creates significant challenges for electromagnetic compatibility and signal/power integrity engineers. Simultaneous switching noise has become one of the major concerns [13,14] in high-speed PCB design.

This type of disturbance has been discussed extensively over the last decade [15–21] and different approaches have been proposed. Most prominent of these involve the use of discrete decoupling capacitors and embedded capacitances [22,23]. However, this approach fails when operated at high frequencies due to the inherent inductance of discrete capacitors and especially the inductance associated with connecting the capacitors to the power/ground-reference planes. Embedded capacitance is usually two very closely spaced planes (often with a higher than normal dielectric constant); it is an expensive solution and reliability considerations limit its practical use. Mushroom EBGs have proven effective for noise suppression at frequencies above 1 GHz and can be effective when discrete capacitors and/or embedded capacitance cannot be effective. When the mushroom-type configuration is implemented in PCB, it uses three layers where the EBG pattern layer with specially designed vias is inserted between the power plane and a ground-reference plane, as shown in Figure 1.1. This configuration makes the fabrication more expensive since extra PCB layers are used for the filter.

Figure 1.1 Mushroom EBG configuration. (a) Top view. (b) Cross-sectional view. (c) Perspective view.

The natural evolution of the mushroom-type EBG applied to PDN in printed circuit boards have been the planar EBG structures used either for switching noise mitigation or in mixed-signal boards [24–33]. These structures consist of a power distribution system of only two layers, instead of three of the mushroom type, with one of the layers patterned in a periodic fashion, effectively creating a frequency band-stop filter. These structures, in contrast to the previously described mushroom filters, do not have vias or require the third layer. These features make such structures very attractive for PCB applications from the manufacturing and cost perspectives.

Their basic structure is illustrated in Figure 1.2.

Figure 1.2 Planar EBG configuration. (a) Top view. (b) Cross-sectional view. (c) Perspective view.

In this basic structure, the solid layer can be used for one voltage level and the EBG patterned one for a second voltage level (often ground-reference). Between these two layers, there is a uniform substrate material whose nature (organic, ceramic, lossy, etc.) depends on the application of the board and the performances of the filter. For one-dimensional wave propagation, the unit cell of this planar EBG structure can be modeled with the basic equivalent circuit shown in Figure 1.3 [34–38].

Figure 1.3 Qualitative equivalent circuit of a unit cell of a planar EBG structure.

The left part of the figure describes the propagation characteristics between the EBG patch and the continuous power plane represented by the equivalent patch inductance Lp and capacitance Cp. The second part of the figure characterizes the bridge effects between two adjacent unit cells. The gap between two patches generates a fringing electric filed associated with the equivalent capacitance Cb and the bridge's inductance Lbridge. A repetition of these cells can be conceptually viewed as an electric filter of parallel LC resonators.

The basic structure of the mushroom-like EBG structure has evolved to the concept of the ground-reference surface perturbation lattice (GSPL) geometry [39–44]. This structure is similar to the EBG filter but with multiple vias, and its design or use is typically appropriate when there is a need to enhance the bandwidth of the bandgap for power delivery noise suppression [45–49]. By using multiple shorting vias and optimizing their arrangement, the GSPL structure presents a wider bandwidth bandgap than that of the mushroom-like structure. In the GSPL, the mechanism of the bandwidth enhancement is based on the optimization of the vias locations. A one-dimensional equivalent circuit model, conceptually similar to that illustrated in Figure 1.3, can be used to predict the stopband. Test structures are manufactured on FR4 substrate to compare the measured results and the numerical ones. Figure 1.4 shows a GSPL with four vias.

Figure 1.4 GSPL with four vias. MB = mother board.

After the previous brief review of the main frequency-selective structures similar to or derived from the EBGs, it is possible to move toward the description of a more specific application: their use as signals filter in digital systems.

Where data rates get into the high hundreds of megabits (Mb/s) or gigabits (Gb/s), signal integrity (SI) concerns will usually require that differential signaling is used in order to ensure the required signal quality. Dielectric loss for long traces, reflections from connectors and vias, and even surface roughness will reduce signal quality at the end of long traces at very high data rates.

Differential signaling is also more immune to external noise corrupting the intentional signals. The basic intention for differential signals is for two equal and opposite currents (and voltages) to exist on the pair of traces, and the ground-reference plane plays no role in the intentional signal current. In reality, this is true only when there are only two signal conductors in free space, with no other metal nearby. This perfect condition never occurs in typical printed circuit boards [50]; therefore, there is always some RF currents on the ground-reference plane in real-world PCBs.

The presence of common-mode noise in the differential signal is one of the main causes of electromagnetic interference (EMI) problems in chip packages and printed circuit boards, especially in the gigahertz range of state-of-the-art high-speed digital systems. The common-mode signal can propagate outside the shielded enclosure through connectors and cables and cause unwanted external radiation.

The previously introduced EBG structures are primarily used for noise mitigation in PCBs and packages, thus enhancing the power integrity performance of the power delivery network [51,52]. The regular planar EBG is investigated in Ref. [53], studying the effects of the patterned plane on both common-mode and differential-mode signal propagation along a differential microstrip line. These principles are applied for filtering the common-mode noise (due to some imbalance) in a differential signal [54–65].

The electromagnetic properties and the layout technique regulating the EBG common-mode filter behavior will be discussed in several parts and under different perspectives across the book. These EBG filters can be placed near I/O connectors on PCBs to reduce the amount of common-mode current that is coupled onto the cables or near ICs to suppress the common-mode noise near its source.

The most simple EBG-based CM filter is laid out on the PCB outermost stack-up layer (the so-called top and bottom layers) as in Figure 1.5 and is sometime referenced as an onboard EBG CM filter. The figure shows the real layout of a manufactured board that was employed for investigating the cross talk among adjacent differential pairs routed on the same EBG filter [66,67].

Figure 1.5 Basic onboard EBG CM filter structure for common-mode filtering: external layers layout.

These onboard EBG CM filters can also be laid out on the internal layers of the stack-up, as shown in Figure 1.6. The stripline filter consists of two patterned layers above and below the differential traces: In this way the return current flows on both the planes above and underneath the traces.A possible variation to the classic EBG structure is the removing of the bridges connecting the patches. This new configuration (Figure 1.7) in general provides deeper notches (but less bandwidth of the bandgap filter) than the regular EBG structure for filtering the common-mode signal.

Figure 1.6 Basic onboard EBG CM filter structure for common-mode filtering: internal layers layout.

Figure 1.7 Modified onboard EBG CM filter structure for common-mode filtering.

These EBG filter configurations are designed to attenuate the common-mode component of the signal, as shown by the common-mode mixed-mode scattering parameter Scc21 in Figure 1.8a, without affecting the transmission of the differential mode and thus without spoiling signal integrity of the output eye diagram as shown in Figure 1.8b.

Figure 1.8 Mixed-mode scattering parameters for EBG CM filters. (a) Scc21. (b) Sdd21.

A different layout strategy was adopted in Refs [68–73] to provide more flexibility in the filter design. The EBG filter is eliminated from the PCB stack-up, and it is modified to be a surface-mount component installed on top of a PCB. In the literature, this configuration is referred to as a removable EBG CM filter. Also, with this configuration, the key design concepts such as the use of standard multilayer laminate technology, the straightforward design procedure, and the reduced costs that make the EBG filter attractive are still valid. Moreover, the electromagnetic behavior of the filter remains unchanged, with the common-mode return currents of the differential pair being responsible for the common mode to EBG cavity mode coupling. The PCB area used by the removable EBG CM filter can be minimized by employing techniques for its miniaturization; the simplest strategy is to utilize a high-permittivity material whose larger costs, with respect to the standard laminates (i.e., FR-4), remains limited to a millimeter-size multilayer PCB rather than the main PCB.

A qualitative example of removable EBG CM filter is given in Figure 1.9.

Figure 1.9 Basic removable EBG CM filter structure for common-mode filtering.

The filter is attached to the PCB by means of four corner pads for the current return corresponding to pads on the PCB.

The performances of such removable configuration are as good as the onboard counterpart. Figure 1.10 shows a Scc21 for this filter, very well centered on the design frequency (i.e., 8 GHz) and its sensitivity due to the variation of geometrical parameters, as will be discussed in this book.

Figure 1.10 Mixed-mode scattering parameters Scc21 for a removable EBG CM filter.

In conclusion of this brief introduction to the topic of the implementation of the electromagnetic bandgap structures as CM filters for high-speed differential signals, it should be mentioned that the actual research trend is toward the miniaturization of these structures in order to minimize their dimensions without affecting the filtering performances [74].

The more recent scientific literature shows two different approaches to reach this goal: the use of material with high dielectric permittivity and the design of patterned structures using novel resonators with limited dimensions to excite the filter resonances.

The former approach has explored the use of ceramic dielectric such as the low-temperature co-fired ceramic (LTCC) [75,76] and it is suitable for the use of the removable filters because they allow a decoupling between the dielectric material of the main board and that of the component itself.

The latter is showing very promising miniaturization factors of around 10 times the standard EBG CM filters [77–79]. These resonators can be easily implemented on PCB or even on package substrate by designing an open stub with shorting via connecting to the reference plane. This configuration provides the shorting path of the common-mode return currents at gigahertz range and still maintains the isolation at DC level.

Finally, particularly significant to have a complete outlook of the EBG field of applications are Refs [80–83].

All the three-dimensional full-wave simulations have been performed by using the CST Studio Suite 2015 by Computer Simulation Technology (CST) [84] and the Advanced Design System (ADS) environment by Keysight Technology [85] for the transient and frequency analysis of the equivalent circuit models.

1.2 Scope of the Book

The book aims at providing the basic principles of operation of the planar EBG structures as common-mode filters for high data rate digital systems. The following is a brief description of the chapterwise coverage of different topics.

This chapter introduces the topic of the book, offering a brief historical perspective of the introduction and use of the EBGs in the printed circuit board world and their evolution into CM filters.

Chapter 2 describes the fundamental mechanisms of planar EBGs looking into details of the mechanisms of resonances and the definition of the lower and higher boundaries of the bandgap as well as proposes the design criteria for these structures with particular emphasis on their impact on power integrity.

Chapter 3 is devoted to the study of the structures described in Chapter 2, but also looking at their impact on the integrity of signals flowing on single-ended and/or differential traces routed above or between EBG filters. This chapter shows the common-mode filter on a differential trace referenced to a patterned plane is equivalent to the response of a single-ended trace reference to the same plane. This finding will be the basis for the use of the EBGs as filters.

Chapter 4 introduces the concept of onboard EBG CM filter based on a simple patch resonant cavity. This approach permits a simple and detailed theoretical treatment that allows the reader to easily design their own EBG CM filter for their specific application. Some full-wave examples and simulation results are presented and compared to validate the design approach.

Chapter 5 contains few specific topics concerning the design and implementation of EBG CM filters:

Techniques to enhance the bandwidth of the bandgap associated with the EBG such as multiple size of patches and bridges.

Approaches to reduce the overall size of the EBG on the printed circuit board.

Chapter 6 is similar in structure to Chapter 4: It discusses the evolution of the onboard EBG CM filters in removable EBG CM filters. These removable filters allow designers to replace EBG filters on the board according to their needs without redesigning the overall board. This chapter presents different topologies of removable EBG CM filters, from the one with the traces kept on the main PCB to the second configuration with the differential pair routed on (or inside) the removable part. This chapter also contains details of the miniaturization techniques for the EBG CM filters and their external electromagnetic radiation.

Chapter 7 describes a number of measurements made to validate the operations of CM EBG filters as designed in previous chapters. The main content of this chapter is to provide information and details of the measurement setup and procedures to measure the signal integrity and EMC performances of these EBG structures. A detailed description of the measurement techniques and of the calibration and de-embedding strategies are included.

References

1

D. Sievenpiper, High-impedance electromagnetic surfaces. Ph.D. dissertation, Department of Electrical Engineering, University of California at Los Angeles, CA, 1999.

2

D. Sievenpiper, L. Zhang, R.F.J. Broas, N.G. Alexopulos, and E. Yablonovitch, High-impedance electromagnetic surfaces with a forbidden frequency band.

IEEE Trans. Microw. Theory Tech.

, Vol. 47, No. 11, 1999, pp. 2059–2073.

3

C. Balanis,

Antenna Theory: Analysis and Design

, 2nd ed., John Wiley & Sons, Inc., New York, 1997.

4

A.S. Ramo, J. Whinnery, and T. Van Duzer,

Fields and Waves in Communications Electronics

, 2nd ed., John Wiley & Sons, Inc., New York, 1984.

5

D. Sievenpiper and E. Yablonovitch, Circuit and method for eliminating surface currents in metal. US Patent 60/079953, March 30, 1998.

6

L. Brillouin, Wave guides for slow waves.

J. Appl. Phys.

, Vol. 19, 1948, pp. 1023–1041.

7

M.N.M. Tan, M.T. Ali, S. Subahir, T.A. Rahman, and S.K.A. Rahim, Backlobe reduction using mushroom-like EBG structure, in Proc. of the IEEE Symposium on Wireless Technology and Applications (ISWTA), September 23–26, 2012, pp. 206–209.

8

X. Chen, Z.J. Su, L. Li, and C.H. Liang, Radiation pattern improvement in closely-packed array antenna by using mushroom-like EBG structure, in IET International Radar Conference 2013, April 14–16, 2013, pp. 1–3.

9

C. Neo and Y. H. Lee, Patch antenna enhancement using a mushroom-like EBG structures, in 2013 IEEE Antennas and Propagation Society International Symposium (APSURSI), July 7–13, 2013, pp. 614–615.

10

M. Coulombe, S.F. Koodiani, and C. Caloz, Compact elongated mushroom (EM)-EBG structure for enhancement of patch antenna array performances.

IEEE Trans. Antennas Propag.

Vol. 58, No. 4, 2010, pp. 1076–1086.

11

M.Z. Azad and M. Ali, Novel wideband directional dipole antenna on a mushroom like EBG Structure.

IEEE Trans. Antennas Propag.

, Vol. 56, No. 5, 2008, pp. 1242–1250.

12

B. Archambeault,

PCB Design for Real-World EMI Control

, Kluwer Academic Publishers, Norwell, MA, 2002.

13

R. Senthinathan and J. Price,

Simultaneous Switching Noise of CMOS Device and Circuits

, Kluwer Academic Publishers, Norwell, MA, 1994.

14

V. Ricchiuti, Power supply decoupling on fully populated high-speed digital PCBs.

IEEE Trans. Electromagn. Compat.

, Vol. 43, No. 4, 2001, pp. 671–676.

15

W. Cui, J. Fan, Y. Ren, H. Shi, J.L. Drewniak, and R.E. DuBroff, DC power-bus noise isolation with power-plane segmentation.

IEEE Trans. Electromagn. Compat.

, Vol. 45, No. 2, 2003, pp. 436–443.

16

G.-T. Lei, R.W. Techentin, and B.K. Gilbert, High frequency characterization of power/ground-plane structures.

IEEE Trans. Microw. Theory Tech.

, Vol. 47, 1999, pp. 562–569.

17

S.V. Berghe, F. Olyslager, D. de Zutter, J.D. Moerloose, and W. Temmerman, Study of the ground bounce caused by power plane resonances.

IEEE Trans. Electromagn. Compat.

, Vol. 40, No. 2, 1998, pp. 111–119.

18

J.L. Knighten, B. Archambeault, J. Fan, G. Selli, A. Rajagopal, S. Connor, and J.L. Drewniak, PDN design strategies: IV. Sources of PDN noise, in IEEE EMC Society Newsletter, No. 212, 2007, pp. 54–64.

19

J.L. Knighten, B. Archambeault, J. Fan, G. Selli, L. Xue, S. Connor, and J.L. Drewniak, PDN design strategies: III. Planes and materials – are they important factors in power bus design? in IEEE EMC Society Newsletter, No. 210, 2006, pp. 58–69.

20

J.L. Knighten, B. Archambeault, J. Fan, G. Selli, L. Xue, S. Connor, and J.L. Drewniak, PDN design strategies: II. Ceramic SMT decoupling capacitors – does location matter? in IEEE EMC Society Newsletter, No. 208, 2006, pp. 56–67.

21

J.L. Knighten, B. Archambeault, J. Fan, G. Selli, S. Connor, and J.L. Drewniak, PDN design strategies: I. Ceramic SMT decoupling capacitors – what values should I choose? in IEEE EMC Society Newsletter, No. 207, 2005, pp. 46–53.

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