Tunable Evanescent-Mode Filters

About the Authors xiii Preface xiv Acknowledgments xvi List of Abbreviations xviii About the Companion Website xx Part I Principles 1 1 Background 3 1.1 Introduction 3 1.1.1 Filters Necessity 3 1.1.2 Alternative Filtering Methods 4 1.2 Filter Anatomy and Representation 5 1.2.1 The Basic Coupling Matrix (M Matrix) 5 1.2.2 Coupling-Routing Diagrams 8 1.2.3 Additions to the Coupling Matrix for Synthesis of Advanced and Practical Filter Responses 10 1.2.3.1 Positive and Negative Coupling Values 10 1.2.3.2 Finite Resonator Quality Factors 11 1.2.3.3 Resonator Frequency Tuning 13 1.2.3.4 Non-Resonating Nodes 13 1.2.3.5 Complex Impedance Loads 16 1.3 Tunable Resonators in Filters 20 1.3.1 Planar Tunable Resonators 21 1.3.2 Ferrimagnetic Tunable Resonators 22 1.3.3 Evanescent-Mode 3-D Tunable Resonators 22 2 Evanescent-Mode Resonators 25 2.1 Physical Structure 25 2.2 Analysis 26 2.2.1 Coaxial Cable Approximation 26 2.2.1.1 Unloaded Quality Factor 28 2.2.2 Tapered Resonator Model 30 2.2.2.1 Frequency Tuning Ratio 34 2.2.3 Tuning Range and Quality Factor Co-optimization 37 2.3 Coupling Techniques 38 2.3.1 External Coupling 38 2.3.2 Inter-Resonator Coupling 43 2.4 Coupling Values Polarity 44 2.4.1 External Coupling Polarity 44 2.4.2 Inter-Resonator Coupling Polarity 45 2.5 Advanced Evanescent-Mode Structures 48 2.5.1 Dual-Mode Resonators 48 2.5.2 Fractional Mode Resonators 49 2.6 Filter Examples 51 2.6.1 Chebyshev Bandpass Filter 51 2.6.2 Butterworth Bandstop Filter 53 Part II Implementation 55 3 Printed Circuit Board Technology 57 3.1 Evanescent-Mode Resonator Structure 57 3.1.1 Practical Considerations 58 3.2 Tunable Membrane 60 3.2.1 Piezoelectric Disk Tuners 60 3.2.2 Contactless Mechanical Actuators 61 4 Silicon Microfabrication 65 4.1 Generic Structure 65 4.2 MEMS Tuner Design 66 4.3 Microfabrication Process 68 4.3.1 MEMS Tuner Microfabrication 68 4.3.2 Evanescent-Mode Resonator Microfabrication 69 4.3.3 Bias Electrode Microfabrication 69 4.3.4 Filter Assembly 70 4.4 Mechanical Model and Power Handling 72 5 Injection Molding 77 5.1 Manufacturing Technology 77 5.1.1 Device Concept 77 5.1.2 Injection Molding Technology 78 5.1.3 Material Selection 80 5.1.4 Design for Moldability 81 5.2 Resonator and Filter RF Design 82 5.2.1 Resonator 82 5.2.2 Filter 83 5.3 Fabrication and Measurements 85 5.3.1 Resonator 85 5.3.2 Filter Performance Measurements 87 5.3.3 Power Handling 90 5.4 Discussion 93 5.5 Conclusion 95 5.6 How to Choose the Right Manufacturing Technology 95 5.7 How to Choose the Right Actuator for the Filter 96 Part III Applications 99 6 Absorptive Bandstop Filters 101 6.1 Design Principles of Absorptive Filters 101 6.1.1 Analysis of a Two-Pole Absorptive Bandstop Filter 101 6.1.2 W-Band Absorptive Bandstop Filter 104 6.1.2.1 Filter Design 104 6.1.2.2 Fabrication and Measurements 107 6.2 Triplet Quasi-absorptive Topology 109 6.2.1 Quasi-absorptive Filter Design and Implementation 111 6.2.1.1 Measured Results 114 7 Bandwidth and Passband Control 115 7.1 Bandwidth Control for Bandpass Filters 115 7.1.1 Filter Design 116 7.1.1.1 Bandwidth Variation 116 7.1.1.2 Quality Factor Impact 118 7.1.1.3 Impedance Matching 119 7.1.1.4 Simulated Results 120 7.1.2 Filter Implementation 122 7.2 BSF Bandwidth Control 126 7.2.1 Constant Bandwidth Coupling Concept 128 7.2.1.1 BWVariation Versus T-Line Length and Tuning Range 131 7.2.1.2 Phase Variation 134 7.2.2 Constant Bandwidth Filter Design 136 7.2.2.1 External Coupling 136 7.2.2.2 External Coupling Structures: Polarity Design 138 7.2.2.3 Inter-Resonator Coupling 140 7.2.3 Fabrication and Measurements 141 7.2.3.1 Constant FBW Filter 142 7.2.3.2 Constant ABW Filter 143 7.2.3.3 Four-Pole Filter 144 8 High-Order and Fractional-Order Evanescent-Mode Filters 147 8.1 High-Order Evanescent-Mode Filters 147 8.1.1 Independently Tunable Dual-Mode Evanescent-Mode Filter 147 8.1.1.1 Resonator Design 148 8.1.1.2 Filter Design 150 8.1.1.3 Experimental Validation 151 8.1.2 High Selectivity Dual-Mode Filters 152 8.1.2.1 Resonator Design 154 8.1.2.2 Constant Absolute Bandwidth BPF Filter 157 8.1.2.3 Filter A: Implementation and Validation 160 8.1.2.4 Filter B: Implementation and Validation 161 8.1.2.5 Filter C: Implementation and Validation 162 8.1.2.6 Filter D: Implementation and Validation 162 8.1.3 Four-Wedge Evanescent-Mode Resonator 165 8.1.3.1 Bandpass Filter Design 165 8.1.3.2 Design Example 167 8.2 Tunable Half-Mode SIW Filter 170 9 Advanced Evanescent-Mode Filter Structures 175 9.1 Bandpass-to-bandstop Reconfigurable Filter 175 9.1.1 Bandpass-to-bandstop Filter Theory 176 9.1.1.1 Coupling Structure to Switch M01 and M03 Simultaneously 177 9.1.2 Bandpass-to-bandstop Reconfigurable Filter Design 179 9.1.3 Measured Results 180 9.2 Field-programmable Filter Array 184 9.2.1 Positive-to-negative Coupling Structure 184 9.2.2 Response Enhancements Enabled By Positive-to-negative Inter-Resonator Coupling 185 9.2.2.1 Zero Net Coupling State Enhancement Using Destructive Interference 185 9.2.2.2 Local Stopband Attenuation Enhancement Technique 187 9.2.3 Resonator Array Design and Fabrication 188 9.2.4 Measured Results 189 10 Passive Applications 195 10.1 Impedance Tuner 195 10.1.1 Design and Fabrication 195 10.1.2 Measured Results 197 10.2 Single-ended (SE) and Balanced (BAL) Diplexers 198 10.2.1 Dual-Mode Diplexing Concept 198 10.2.1.1 Diplexing Architecture 198 10.2.1.2 Resonant Frequency Misalignment 199 10.2.1.3 Inter-Resonator Coupling 201 10.2.2 SE–SE Diplexer Implementation and Measurements 201 10.2.2.1 External Coupling 201 10.2.2.2 Measured Results 201 10.2.3 SE–BAL Diplexer Implementation and Measurements 202 10.2.3.1 External Coupling 202 10.2.3.2 Measured Results 203 10.2.4 BAL–BAL Diplexer Implementation and Measurements 205 10.2.4.1 External Coupling 205 10.2.4.2 Measured Results 205 10.3 Tunable Filtering Rat-race Couplers Based on Half- and Full-mode Evanescent-mode Resonators 207 10.3.1 Design 207 10.3.2 Full-mode Rat-race Coupler 209 10.3.2.1 Experimental Validation 209 10.3.3 Half-mode Rat-race Coupler 210 10.3.3.1 Half-mode Structure 210 10.3.3.2 Experimental Validation 211 11 Active Applications 215 11.1 Co-Design of Power Amplifiers and High-Q Filters 215 11.1.1 Filter Design 216 11.1.2 Transistor Characterization 217 11.1.3 Matching Filter Design 217 11.1.3.1 Fundamental and Harmonic Matchings 219 11.1.4 PA Design 220 11.1.5 Experimental Results 220 11.1.6 Co-Design of PA and Three-Pole High-Q Tunable Filter 222 11.2 Phase-Locked Loop 224 11.2.1 Frequency Synthesizer Architecture and Phase Noise Model 224 11.2.2 Circuit Design and Optimizations 226 11.2.2.1 Evanescent-Mode Cavity Resonator 226 11.2.2.2 Voltage-Controlled Oscillator Design 226 11.2.2.3 Phase-Locked Loop Design 227 11.2.2.4 Measured Results 229 11.3 Balanced–Balanced Tunable Filtering LNA 231 11.3.1 Cavity Resonator-LNA Co-Design 231 11.3.1.1 Evanescent-Mode Resonators 232 11.3.1.2 LNA 232 11.3.2 Implementation and Measured Results 233 12 Monitoring and Control 235 12.1 Monitoring and Control of PCB-based Resonators: Diplexer Example 235 12.1.1 System Architecture 235 12.1.1.1 Diplexer 236 12.1.1.2 Resonators Monitoring and Control 237 12.1.1.3 Spectrum Sensing 240 12.1.2 Control Loop Analysis 242 12.1.3 Design Details 242 12.1.3.1 Diplexer Structure 242 12.1.3.2 Oscillator and Frequency Counter 243 12.1.3.3 Control Unit and Charge Pump 246 12.1.4 Implementation and Measurements 247 12.1.4.1 Implementation 247 12.1.4.2 Monitoring Performance 248 12.1.4.3 RF Performance 250 12.1.4.4 Spectrum-aware Measurements 254 12.2 Monitoring and Control of Silicon-based Filters 254 12.2.1 Monitoring Concepts and Optimizations 255 12.2.1.1 Inductive Proximity Sensing 255 12.2.1.2 Circuit Optimization 257 12.2.1.3 Spiral Inductor 261 12.2.2 Control System Design 261 12.2.3 Testbed Filter Design 263 12.2.4 Implementation and Measurements 263 12.2.4.1 Fabrication 263 12.2.4.2 Sensing Feedback 265 12.2.4.3 Filter Monitoring and Control 266 12.3 Monitoring and Control Applications: Temperature Compensation 267 12.3.1 Temperature Control 268 12.3.1.1 Temperature Compensation System Implementation 268 12.3.1.2 Room Temperature Filter Performance 268 12.3.1.3 Temperature Compensation Performance 268 References 275 Index 289