Linear CMOS RF Power Amplifiers for Wireless Applications

Transcription

1 Linear CMOS RF Power Amplifiers for Wireless Applications

2 ANALOG CIRCUITS AND SIGNAL PROCESSING SERIES Consulting Editor: Mohammed Ismail. Ohio State University For other titles published in this series, go to

3 Paulo Augusto Dal Fabbro Maher Kayal Linear CMOS RF Power Amplifiers for Wireless Applications Efficiency Enhancement and Frequency-Tunable Capability

4 Dr. Paulo Augusto Dal Fabbro École Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland Prof. Maher Kayal École Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland Series Editors: Mohammed Ismail 205 Dreese Laboratory Department of Electrical Engineering The Ohio State University 2015 Neil Avenue Columbus, OH 43210, USA Mohamad Sawan Electrical Engineering Department École Polytechnique de Montréal Montréal, QC, Canada ISBN e-isbn DOI / Springer Dordrecht Heidelberg London New York Library of Congress Control Number: Springer Science+Business Media B.V No part of this work may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission from the Publisher, with the exception of any material supplied specifically for the purpose of being entered and executed on a computer system, for exclusive use by the purchaser of the work. Cover design: estudio Calamar S.L. Printed on acid-free paper Springer is part of Springer Science+Business Media (

5 Preface Advances in electronics have pushed mankind to create devices, ranging from incredible gadgets to medical equipment to spacecraft instruments. More than that, modern society is getting used to if not dependent on the comfort, solutions, and astonishing amount of information brought by these devices. One field that has continuously benefitted from those advances is the radio frequency integrated circuit (RFIC) design, which in its turn has promoted countless benefits to the mankind as a payback. Wireless communications is one prominent example of what the advances in electronics have enabled and their consequences to our daily life. How could anyone back in the eighties think of the possibilities opened by the wireless local area networks (WLANs) that can be found today in a host of places, such as public libraries, coffee shops, trains, to name just a few? How can a youngster, who lives this true WLAN experience nowadays, imagine a world without it? This book deals with the design of linear CMOS RF Power Amplifiers (PAs). The RF PA is a very important part of the RF transceiver, the device that enables wireless communications. Two important aspects that are key to keep the advances in RF PA design at an accelerate pace are treated: efficiency enhancement and frequencytunable capability. For this purpose, the design of two different integrated circuits realized in a 0.11 µm technology is presented, each one addressing a different aspect. With respect to efficiency enhancement, the design of a dynamic supply RF power amplifier is treated, making up the material of Chaps. 2 to 4. The frequencytunable capability is addressed in Chaps. 5 to 7, presenting the design of a tunable impedance matching network for use in multiband RF power amplifiers. This novel network is based on coupled inductors. The reader can jump directly to Chap. 5 if the interest is for the frequency-tunable PA. When background information is important to the understanding of the material being presented, the reader will be guided to the page of concern. In Chap. 1, a detailed outline of the book can be found. Chapter 8 summarizes the results obtained and conclusions that could be drawn from the work underlying this book. Additional information, regarding the measurement setups and the implementation of the impedance matching networks used in the characterization of the power amplifiers, can be found in the two appendices that close the book. v

6 vi Preface The material presented in this book is the offspring of a collaborative research between the Electronics Laboratory of the École polytechnique fédérale de Lausanne (EPFL) in Lausanne, Switzerland, and the Fujitsu Laboratories Ltd. in Yokohama, Japan. Acknowledgments Thanks to Yuu Watanabe and Kazuhiko Kobayashi, from Fujitsu Labs, for the support during all the collaboration project. Thanks also to Cédric Meinen, from EPFL, for his invaluable contributions to the design of the dynamic supply system. Lausanne, Switzerland Paulo Augusto Dal Fabbro Maher Kayal

7 Contents 1 Introduction Context Objectives Efficiency Enhancement Frequency-Tunable Capability Book Outline... 3 References Efficiency Enhancement Introduction BasicPrinciples Linearity Efficiency Overview of the Main Efficiency-Enhancement Techniques EnvelopeEliminationandRestoration Dynamic Supply RF Power Amplifier Conclusion References Design of the Dynamic Supply CMOS RF Power Amplifier Introduction High-Efficiency, Fast Modulator High-Speed Comparator Synchronous Switch LC Filter RFPowerAmplifier Design Procedure Stability Dynamic Supply RF Power Amplifier Conclusion References vii

8 viii Contents 4 Measurement Results for the Dynamic Supply CMOS RF Power Amplifier Introduction MainEvaluationBoard Modulator Characterization EnvelopeDetectionandProcessing RFPowerAmplifierCharacterization S-ParametersMeasurement Single-ToneMeasurements Dynamic Supply RF PA Characterization Two-ToneMeasurements OFDMMeasurements Conclusion References Frequency-Tunable Capability Introduction Scenario Definitions Tuning Range Overview of the Existing Frequency-Tunable Techniques Broadband Techniques Narrowband Techniques Conclusion References Design of the Frequency-Tunable CMOS RF Power Amplifier Introduction Output Impedance Matching The π-matchingnetwork Tunable Output Impedance Matching Input Impedance Matching Frequency-Tunable RF Power Amplifier RFPowerAmplifier Coupled Inductors ControlCircuit CompleteSystem Conclusion References Measurement Results for the Frequency-Tunable CMOS RF Power Amplifier Introduction Stand-Alone RF Power Amplifier Characterization Coupled Inductors Characterization Frequency-Tunable RF PA Measurement...108

9 Contents ix 7.5 HybridImplementation MeasurementResultsfortheHybridPA AnalysisandDiscussionoftheResults Conclusion References Conclusion Highlights MainContributions Efficiency Enhancement Frequency-Tunable Capability Impedance Matching FutureWork Efficiency Enhancement Frequency-Tunable Capability References Appendix A: Measurement Setups and Additional Screenshots SetupsUsedfortheS-ParameterMeasurements SetupUsedforthe2-ToneMeasurements SetupUsedfortheOFDMMeasurements Additional Screenshots References Appendix B: Procedure for Impedance Matching of Printed-Circuit RF Amplifiers Introduction Procedure for Impedance Matching PCB Access Lines Design and Fabrication SOLTCalibrationandMeasurement TRLCalibrationandMeasurement Access Line Modeling and De-Embedding MatchingNetworkImplementation SummarizedGuidelines ApplicationExample FirstStep Second Step ThirdStep FourthStep FifthStep AnalysisoftheResults References Index...157

10 Notation Abbreviations and Acronyms acc. to according to ACLR Adjacent Channel Leakage Ratio [dbc] ACPR Adjacent Channel Power Ratio [dbc] Bip. Bipolar bps bits per second BST Barium-Strontium-Titanate (ferroelectric material) CMFB Common-Mode FeedBack Const. Constant Supply Conv. Conventional CW Constant Wave DAC Digital-to-Analog Converter Discr. Discrete DPD Digital PreDistortion DPI Driving-Point Impedance DSP Digital Signal Processor Dyn. Dynamic Supply EDGE Enhanced Data rates for GSM Evolution EER Envelope Elimination and Restoration Eff. Efficiency FET Field Effect Transistor FM FerroMagnetic FR-4 Flame Retardant type 4 (base material for PCBs) GIC Generalized Impedance Converter GSG Ground-Signal-Ground GSM Global System for Mobile communications HBT Hetero-junction Bipolar Transistor HF High Frequency HFET Heterojunction FET LF Low Frequency LNA Low-Noise Amplifier xi

11 xii Notation LO Local Oscillator MEMS Micro-Electro-Mechanical System MESFET MEtal Semiconductor FET MIM Metal-Insulator-Metal (capacitor) Mod. Modulator MOS Metal-Oxide-Semiconductor NADC North American Digital Cellular PAE Power-Added Efficiency [%] PAPR Peak-to-Average Power Ratio PCB Printed-Circuit Board PDA Personal Digital Assistant PGS Patterned Ground Shield PIN p + intrinsic n + (diode) PWM Pulse-Width Modulation QAM Quadrature Amplitude Modulation RFC RF Choke rms Root Mean Square SFG Signal-Flow Graph SMA SubMiniature version A connector SMB SubMiniature version B connector SOLT Short-Open-Load-Thru SP Scattering Parameters SRF Self-Resonant Frequency TCM Trellis Coded Modulation TR Tuning Range [%] TRL Thru-Reflect-Line Tun. Tunable VCO Voltage-Controlled Oscillator VSWR Voltage Standing Wave Ratio

12 Notation xiii Greek Symbols α real part of the ratio between I ctrl and I RF β imaginary part of the ratio between I ctrl and I RF ε dielectric constant (or permittivity) [F/m] ε r relative dielectric constant (or relative permittivity) η d drain efficiency [%] Γ IN input reflection coefficient Γ L load reflection coefficient Γ ML load reflection coefficient for simultaneous conjugate match Γ MS source reflection coefficient for simultaneous conjugate match Γ opt optimum reflection coefficient Γ OUT output reflection coefficient Γ S source reflection coefficient λ wavelength [m] μ electron or hole effective mobility [m 2 /(V s)] ω angular frequency [rad/s] ω n undamped natural frequency [rad/s] φ phase of the ratio between I ctrl and I RF [ or rad] φ LC phase shift introduced by the LC filter [ or rad] φ td phase shift corresponding to t d [ or rad] φ total total modulator phase shift (φ LC + φ td ) [ or rad] ξ damping ratio

13 xiv Notation Roman Symbols b ratio between the electron and hole effective mobilities C ox MOS transistor s gate oxide capacitance per unit area [F/m 2 ] d in inner diameter of an inductor or transformer [m] d out outer diameter of an inductor or transformer [m] f c center frequency [Hz] f s modulator s switching frequency [Hz] G power gain [db or W/W] g m transconductance of a MOS transistor [A/V] I ctrl current that controls the tunable inductor [A] I d drain current of a MOS transistor [A] I RF current flowing through the tunable inductor [A] K Rollett stability factor k coupling factor between two magnetically coupled inductors L self inductance or MOS transistor channel length [H or m] M mutual inductance between two coupled inductors [H] m transformation factor of a matching network n number of turns of an inductor winding P DC DC power consumption [W] P in input power [dbm or W] P out output power [dbm or W] Q quality factor Q 0 loaded quality factor of a matching network Q u unloaded quality factor of an inductor r magnitude of the ratio between I clrl and I RF R Ls parasitic series resistance of an inductor [ ] r on on resistance of a MOS transistor [ ] R opt optimum resistance presented at the PA output [ ] s track spacing for a planar inductor or transformer [m] T dielectric thickness [m] t d modulator delay [s] t ed electrical delay of a transmission line [s] V knee turn-on drain voltage of a MOS transistor [V] V T threshold voltage of a MOS transistor [V] W MOS transistor s channel width [m] w track width for a planar inductor or transformer [m] Z 0 characteristic impedance of a system or transmission line [ ] Z opt optimum impedance [ ] impedance seen by the supply when looking to the PA [ ] Z PA