Foreword xv Acknowledgments xix 1 Introduction to Communications Circuits 1 1.1 Introduction 1 1.2 Lower Frequency Analog Design and Microwave Design Versus Radio Frequency Integrated Circuit Design 2 1.2.1 Impedance Levels for Microwave and Low- Frequency Analog Design 2 1.2.2 Units for Microwave and Low-Frequency Analog Design 3 1.3 Radio Frequency Integrated Circuits Used in a Communications Transceiver 4 1.4 Overview 6 References 6 2 Issues in RFIC Design, Noise, Linearity, and Filtering 9 2.1 Introduction 9 v vi Radio Frequency Integrated Circuit Design 2.2 Noise 9 2.2.1 Thermal Noise 10 2.2.2 Available Noise Power 11 2.2.3 Available Power from Antenna 11 2.2.4 The Concept of Noise Figure 13 2.2.5 The Noise Figure of an Amplifier Circuit 14 2.2.6 The Noise Figure of Components in Series 16 2.3 Linearity and Distortion in RF Circuits 23 2.3.1 Power Series Expansion 23 2.3.2 Third-Order Intercept Point 27 2.3.3 Second-Order Intercept Point 29 2.3.4 The 1-dB Compression Point 30 2.3.5 Relationships Between 1-dB Compression and IP3 Points 31 2.3.6 Broadband Measures of Linearity 32 2.4 Dynamic Range 35 2.5 Filtering Issues 37 2.5.1 Image Signals and Image Reject Filtering 37 2.5.2 Blockers and Blocker Filtering 39 References 41 Selected Bibliography 42 3 A Brief Review of Technology 43 3.1 Introduction 43 3.2 Bipolar Transistor Description 43 3.3 b Current Dependence 46 3.4 Small-Signal Model 47 3.5 Small-Signal Parameters 48 3.6 High-Frequency Effects 49 3.6.1 fT as a Function of Current 51 3.7 Noise in Bipolar Transistors 53 3.7.1 Thermal Noise in Transistor Components 53 3.7.2 Shot Noise 53 3.7.3 1/f Noise 54 Contents vii 3.8 Base Shot Noise Discussion 55 3.9 Noise Sources in the Transistor Model 55 3.10 Bipolar Transistor Design Considerations 56 3.11 CMOS Transistors 57 3.11.1 NMOS 58 3.11.2 PMOS 58 3.11.3 CMOS Small-Signal Model Including Noise 58 3.11.4 CMOS Square Law Equations 60 References 61 4 Impedance Matching 63 4.1 Introduction 63 4.2 Review of the Smith Chart 66 4.3 Impedance Matching 69 4.4 Conversions Between Series and Parallel Resistor- Inductor and Resistor-Capacitor Circuits 74 4.5 Tapped Capacitors and Inductors 76 4.6 The Concept of Mutual Inductance 78 4.7 Matching Using Transformers 81 4.8 Tuning a Transformer 82 4.9 The Bandwidth of an Impedance Transformation Network 83 4.10 Quality Factor of an LC Resonator 85 4.11 Transmission Lines 88 4.12 S, Y, and Z Parameters 89 References 93 5 The Use and Design of Passive Circuit Elements in IC Technologies 95 5.1 Introduction 95 5.2 The Technology Back End and Metallization in IC Technologies 95 viii Radio Frequency Integrated Circuit Design 5.3 Sheet Resistance and the Skin Effect 97 5.4 Parasitic Capacitance 100 5.5 Parasitic Inductance 101 5.6 Current Handling in Metal Lines 102 5.7 Poly Resistors and Diffusion Resistors 103 5.8 Metal-Insulator-Metal Capacitors and Poly Capacitors 103 5.9 Applications of On-Chip Spiral Inductors and Transformers 104 5.10 Design of Inductors and Transformers 106 5.11 Some Basic Lumped Models for Inductors 108 5.12 Calculating the Inductance of Spirals 110 5.13 Self-Resonance of Inductors 110 5.14 The Quality Factor of an Inductor 111 5.15 Characterization of an Inductor 115 5.16 Some Notes About the Proper Use of Inductors 117 5.17 Layout of Spiral Inductors 119 5.18 Isolating the Inductor 121 5.19 The Use of Slotted Ground Shields and Inductors 122 5.20 Basic Transformer Layouts in IC Technologies 122 5.21 Multilevel Inductors 124 5.22 Characterizing Transformers for Use in ICs 127 5.23 On-Chip Transmission Lines 129 5.23.1 Effect of Transmission Line 130 5.23.2 Transmission Line Examples 131 5.24 High-Frequency Measurement of On-Chip Passives and Some Common De-Embedding Techniques 134 Contents ix 5.25 Packaging 135 5.25.1 Other Packaging Techniques 138 References 139 6 LNA Design 141 6.1 Introduction and Basic Amplifiers 141 6.1.1 Common-Emitter Amplifier (Driver) 141 6.1.2 Simplified Expressions for Widely Separated Poles 146 6.1.3 The Common-Base Amplifier (Cascode) 146 6.1.4 The Common-Collector Amplifier (Emitter Follower) 148 6.2 Amplifiers with Feedback 152 6.2.1 Common-Emitter with Series Feedback (Emitter Degeneration) 152 6.2.2 The Common-Emitter with Shunt Feedback 154 6.3 Noise in Amplifiers 158 6.3.1 Input-Referred Noise Model of the Bipolar Transistor 159 6.3.2 Noise Figure of the Common-Emitter Amplifier 161 6.3.3 Input Matching of LNAs for Low Noise 163 6.3.4 Relationship Between Noise Figure and Bias Current 169 6.3.5 Effect of the Cascode on Noise Figure 170 6.3.6 Noise in the Common-Collector Amplifier 171 6.4 Linearity in Amplifiers 172 6.4.1 Exponential Nonlinearity in the Bipolar Transistor 172 6.4.2 Nonlinearity in the Output Impedance of the Bipolar Transistor 180 6.4.3 High-Frequency Nonlinearity in the Bipolar Transistor 182 6.4.4 Linearity in Common-Collector Configuration 182 6.5 Differential Pair (Emitter-Coupled Pair) and Other Differential Amplifiers 183 6.6 Low-Voltage Topologies for LNAs and the Use of On-Chip Transformers 184 x Radio Frequency Integrated Circuit Design 6.7 DC Bias Networks 187 6.7.1 Temperature Effects 189 6.8 Broadband LNA Design Example 189 References 194 Selected Bibliography 195 7 Mixers 197 7.1 Introduction 197 7.2 Mixing with Nonlinearity 197 7.3 Basic Mixer Operation 198 7.4 Controlled Transconductance Mixer 198 7.5 Double-Balanced Mixer 200 7.6 Mixer with Switching of Upper Quad 202 7.6.1 Why LO Switching? 203 7.6.2 Picking the LO Level 204 7.6.3 Analysis of Switching Modulator 205 7.7 Mixer Noise 206 7.8 Linearity 215 7.8.1 Desired Nonlinearity 215 7.8.2 Undesired Nonlinearity 215 7.9 Improving Isolation 217 7.10 Image Reject and Single-Sideband Mixer 217 7.10.1 Alternative Single-Sideband Mixers 219 7.10.2 Generating 90° Phase Shift 220 7.10.3 Image Rejection with Amplitude and Phase Mismatch 224 7.11 Alternative Mixer Designs 227 7.11.1 The Moore Mixer 228 7.11.2 Mixers with Transformer Input 228 7.11.3 Mixer with Simultaneous Noise and Power Match 229 7.11.4 Mixers with Coupling Capacitors 230 Contents xi 7.12 General Design Comments 231 7.12.1 Sizing Transistors 232 7.12.2 Increasing Gain 232 7.12.3 Increasing IP3 232 7.12.4 Improving Noise Figure 233 7.12.5 Effect of Bond pads and the Package 233 7.12.6 Matching, Bias Resistors, and Gain 234 7.13 CMOS Mixers 242 References 244 Selected Bibliography 244 8 Voltage-Controlled Oscillators 245 8.1 Introduction 245 8.2 Specification of Oscillator Properties 245 8.3 The LC Resonator 247 8.4 Adding Negative Resistance Through Feedback to the Resonator 248 8.5 Popular Implementations of Feedback to the Resonator 250 8.6 Configuration of the Amplifier (Colpitts or -Gm ) 251 8.7 Analysis of an Oscillator as a Feedback System 252 8.7.1 Oscillator Closed-Loop Analysis 252 8.7.2 Capacitor Ratios with Colpitts Oscillators 255 8.7.3 Oscillator Open-Loop Analysis 258 8.7.4 Simplified Loop Gain Estimates 260 8.8 Negative Resistance Generated by the Amplifier 262 8.8.1 Negative Resistance of Colpitts Oscillator 262 8.8.2 Negative Resistance for Series and Parallel Circuits 263 8.8.3 Negative Resistance Analysis of -Gm Oscillator 265 8.9 Comments on Oscillator Analysis 268 8.10 Basic Differential Oscillator Topologies 270 xii Radio Frequency Integrated Circuit Design 8.11 A Modified Common-Collector Colpitts Oscillator with Buffering 270 8.12 Several Refinements to the -Gm Topology 270 8.13 The Effect of Parasitics on the Frequency of Oscillation 274 8.14 Large-Signal Nonlinearity in the Transistor 275 8.15 Bias Shifting During Startup 277 8.16 Oscillator Amplitude 277 8.17 Phase Noise 283 8.17.1 Linear or Additive Phase Noise and Leeson’s Formula 283 8.17.2 Some Additional Notes About Low-Frequency Noise 291 8.17.3 Nonlinear Noise 292 8.18 Making the Oscillator Tunable 295 8.19 VCO Automatic-Amplitude Control Circuits 302 8.20 Other Oscillators 313 References 316 Selected Bibliography 317 9 High-Frequency Filter Circuits 319 9.1 Introduction 319 9.2 Second-Order Filters 320 9.3 Integrated RF Filters 321 9.3.1 A Simple Bandpass LC Filter 321 9.3.2 A Simple Bandstop Filter 322 9.3.3 An Alternative Bandstop Filter 323 9.4 Achieving Filters with Higher Q 327 9.4.1 Differential Bandpass LNA with Q-Tuned Load Resonator 327 9.4.2 A Bandstop Filter with Colpitts-Style Negative Resistance 329 9.4.3 Bandstop Filter with Transformer-Coupled -Gm Negative Resistance 331 Contents xiii 9.5 Some Simple Image Rejection Formulas 333 9.6 Linearity of the Negative Resistance Circuits 336 9.7 Noise Added Due to the Filter Circuitry 337 9.8 Automatic Q Tuning 339 9.9 Frequency Tuning 342 9.10 Higher-Order Filters 343 References 346 Selected Bibliography 347 10 Power Amplifiers 349 10.1 Introduction 349 10.2 Power Capability 350 10.3 Efficiency Calculations 350 10.4 Matching Considerations 351 10.4.1 Matching to S22 * Versus Matching to Gopt 352 10.5 Class A, B, and C Amplifiers 353 10.5.1 Class A, B, and C Analysis 356 10.5.2 Class B Push-Pull Arrangements 362 10.5.3 Models for Transconductance 363 10.6 Class D Amplifiers 367 10.7 Class E Amplifiers 368 10.7.1 Analysis of Class E Amplifier 370 10.7.2 Class E Equations 371 10.7.3 Class E Equations for Finite Output Q 372 10.7.4 Saturation Voltage and Resistance 373 10.7.5 Transition Time 373 10.8 Class F Amplifiers 375 10.8.1 Variation on Class F: Second-Harmonic Peaking 379 10.8.2 Variation on Class F: Quarter-Wave Transmission Line 379 10.9 Class G and H Amplifiers 381 10.10 Class S Amplifiers 383 xiv Radio Frequency Integrated Circuit Design 10.11 Summary of Amplifier Classes for RF Integrated Circuits 384 10.12 AC Load Line 385 10.13 Matching to Achieve Desired Power 385 10.14 Transistor Saturation 388 10.15 Current Limits 388 10.16 Current Limits in Integrated Inductors 390 10.17 Power Combining 390 10.18 Thermal Runaway—Ballasting 392 10.19 Breakdown Voltage 393 10.20 Packaging 394 10.21 Effects and Implications of Nonlinearity 394 10.21.1 Cross Modulation 395 10.21.2 AM-to-PM Conversion 395 10.21.3 Spectral Regrowth 395 10.21.4 Linearization Techniques 396 10.21.5 Feedforward 396 10.21.6 Feedback 397 10.22 CMOS Power Amplifier Example 398 References 399 About the Authors 401 Index 403