Microwave Bandpass Filters for Wideband Communications

A Much–Needed Systematic Guide to the Design of (Ultra–)WidebandBandpass Filters

Ultra–wideband (UWB) technology has attracted a lot of attentionin recent years, owing to its numerous applications in high–speedand high–capacity wireless communications. At the same time,conventional synthesis methodologies were shown to be inadequatefor bandpass filtering design covering a wide or ultra–widebandpass. This book responds to the need for a practical guide toemerging design techniques for advanced (ultra–)wideband bandpassfilters.

The authors introduce microwave wideband bandpass filter designtheory using the multiple–mode resonator (MMR) along with thealternative synthesis design method for wideband bandpass filters,particularly for filters with FCC–defined UWB frequencies from 3.1to 10.6 GHz. They demonstrate the application of both methods inthe design of (ultra–)wideband bandpass filters, showing how to usethese methods to implement filters in different frequencies andmaterials, calculate initial dimensions for various filterconfigurations, and more.

Special features of this book include:

Complete design procedures and tabulated design parameters forboth MMR and the synthesis design method

A large number of easy–to–follow design examples, which can bemodified by readers to achieve their own design specifications

Coverage of the basics, including transmission line theories andcomparison with the design of conventional narrow–band bandpassfilters

Microwave Bandpass Filters for Wideband Communications isan invaluable guide for researchers and engineers wishing toimprove their design cycle and filter performance. It is also auseful reference for newcomers to the field, who wish to gain abetter understanding of (ultra–)wideband bandpass designtheory.

PREFACE ix

1 INTRODUCTION 1

1.1 Background on UWB Technology 2

1.2 UWB Regulations 3

1.3 UWB Bandpass Filters 8

1.4 Organization of the Book 11

2 TRANSMISSION LINE CONCEPTS AND NETWORKS 18

2.1 Introduction 18

2.2 Transmission Line Theory 19

2.3 Microwave Network Parameters 26

2.4 Relative Theories of Network Analysis 42

2.5 Summary 52

3 CONVENTIONAL PARALLEL–COUPLED LINE FILTER 53

3.1 Introduction 53

3.2 Lumped–Element Lowpass Filter Prototype 54

3.3 Impedance and Frequency Transformation 65

3.4 Immittance Inverters 70

3.5 Lowpass Prototype Filter with Immittance Inverter 71

3.6 Parallel–Coupled Line Bandpass Filter 76

3.7 Summary 84

4 PLANAR TRANSMISSION LINE RESONATORS 85

4.1 Introduction 85

4.2 Uniform Impedance Resonator 87

4.3 Stepped Impedance Resonators 94

4.4 Multiple–Mode Resonator 104

4.5 Summary 113

5 MMR–BASED UWB BANDPASS FILTERS 116

5.1 Introduction 116

5.2 An Initial MMR–Based UWB Bandpass Filter 118

5.3 UWB Bandpass Filters with Varied Geometries 121

5.4 UWB Filters with Improved Out–of–Band Performance 130

5.5 UWB Bandpass Filter with a Notch Band 142

5.6 Summary 146

6 SYNTHESIS APPROACH FOR UWB FILTERS 149

6.1 Introduction 149

6.2 Transfer Function 150

6.3 Transmission Line Network with Pure Shunt/Series Stubs152

6.4 Transmission Line Network with Hybrid Series and Shunt Stubs163

6.5 MMR–Based UWB Filter with Parallel–Coupled Lines 178

6.6 Summary 187

7 OTHER TYPES OF UWB FILTERS 188

7.1 Introduction 188

7.2 UWB Filters with Highpass and Lowpass Filters 188

7.3 UWB Filters with Optimum Shunt Short–Circuited Stubs 191

7.4 UWB Filters with Quasi–Lumped Elements 195

7.5 UWB Filters with Composite CPW and Microstrip Structure197

7.6 UWB Filter with Microstrip Ring Resonator 199

7.7 UWB Filter using Multilayer Structures 203

7.8 UWB Filter with Substrate Integrated Waveguide (SIW) 205

7.9 UWB Filter with Notch Band 207

7.10 Summary 210

References 210

INDEX 214

LEI ZHU, PhD, is Associate Professor at the School ofElectrical and Electronic Engineering, Nanyang TechnologicalUniversity, Singapore. Dr. Zhu was the first to introduce anMMR–based filter in 2000, which has since spurred the successfuldevelopment of a new class of wideband filters with fractionalbandwidths larger than 60 percent.

SHENG SUN, PhD, is Research Assistant Professor in theDepartment of Electrical and Electronic Engineering at TheUniversity of Hong Kong.

RUI LI, PhD, is a Research Fellow in the Interconnectionand Advanced Packaging Program at Singapore′s Institute ofMicroelectronics. She was the recipient of both the NTU Researchand the Ministry of Education Scholarships in Singapore.