Feb 8, 2007 - The millimeter wave frequency doubler is designed for 5 V supply voltage and has the Gilbert cell-based differential architecture where both RF ...
Design of Millimeter-wave SiGe Frequency Doubler and Output Buffer for Automotive Radar Applications
Master thesis performed at Acreo AB in collaboration with Division of Electronic Devices, Dept. of Electrical Engineering, Linköping University by
Amjad Altaf
Report number: LiTH-ISY-EX--07/3978--SE February 2007
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Title Design of Millimeter-wave SiGe Frequency Doubler and Output Buffer for Automotive Radar Applications Master thesis in Division of Devices Department of Electrical Engineering Linköping University, Sweden by Amjad Altaf LiTH-ISY-EX--07/3978--SE
Supervisor: Darius Jakonis (Acreo AB, Norrköping) Examiner: Jerzy Dabrowski (ISY) Linköping: February 2007
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Presentation Date 2007-02-08 Publishing Date (Electronic version) 2007-02-15 Language
English
Division of Electronics Systems Department of Electrical Engineering
Type of Publication Licentiate thesis
ISRN: LiTH-ISY-EX--07/3978—SE
Thesis C-level Thesis D-level Report Other (specify below)
Title of series (Licentiate thesis)
Degree thesis
Number of Pages
88
ISBN (Licentiate thesis)
Series number/ISSN (Licentiate thesis)
URL, Electronic Version http://www.ep.liu.se
Publication Title Design of millimeter-wave SiGe frequency doubler and output buffer for automotive radar applications Author Amjad Altaf Abstract Automotive Radars have introduced various functions on automobiles for driver’s safety and comfort, as part of the Intelligent Transportation System (ITS) including Adaptive Cruise Control (ACC), collision warning or avoidance, blind spot surveillance and parking assistance. Although such radar systems with 24 GHz carrier frequency are already in use but due to some regulatory issues, recently a permanent band has been allocated at 77-81 GHz, allowing for long-term development of the radar service. In fact, switchover to the new band is mandatory by 2014. A frequency multiplier will be one of the key components for such a millimeter wave automotive radar system because there are limitations in direct implementation of low phase noise oscillators at high frequencies. A practical way to build a cost-effective and stable source at higher frequency is to use an active multiplier preceded by a high spectral purity VCO operating at a lower frequency. Recent improvements in the performance of SiGe technology allow the silicon microelectronics to advance into areas previously restricted to compound semiconductor devices and make it a strong competitor for automotive radar applications at 79 GHz. This thesis presents the design of active frequency doubler circuits at 20 GHz in a commercially available SiGe BiCMOS technology and at 40GHz in SiGe bipolar technology (Infineon-B7h200 design). Buffer/amplifier circuits are included at output VWDJHVWRGULYH ORDG7KHIUHTXHQF\GRXEOHUDW*+]LVEDVHGon an emitter-coupled pair operating in class-B configuration at 1.8 V supply voltage. Pre-layout simulations show its conversion gain of 10 dB at -5 dBm input, fundamental suppression of G%DQG1)RIG%,QSXWDQGRXWSXWLPSHGDQFHPDWFKLQJQHWZRUNVDUHGHVLJQHGWRPDWFK
DWERWKVLGHV
The millimeter wave frequency doubler is designed for 5 V supply voltage and has the Gilbert cell-based differential architecture where both RF and LO ports are tied together to act as a frequency doubler. Both pre-layout and post-layout simulation results are presented and compared together. The extracted circuit has a conversion gain of 8 dB at -8 dB input, fundamental suppression of 20 dB, NF of 12 dB and it consumes 42 mA current from supply. The layout occupies an area of 0.12 mm2 without pads and baluns at both input and output ports. The frequency multiplier circuits have been designed using Cadence Design Tool.
Number of pages: 88 Keywords Automotive Radar, VCO, Frequency Multiplier, SiGE, ACC, Millimeter-wave
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Abstract Automotive Radars have introduced various functions on automobiles for driver’s safety and comfort, as part of the Intelligent Transportation System (ITS) including Adaptive Cruise Control (ACC), collision warning or avoidance, blind spot surveillance and parking assistance. Although such radar systems with 24 GHz carrier frequency are already in use but due to some regulatory issues, recently a permanent band has been allocated at 77-81 GHz, allowing for long-term development of the radar service. In fact, switchover to the new band is mandatory by 2014. A frequency multiplier will be one of the key components for such a millimeter wave automotive radar system because there are limitations in direct implementation of low phase noise oscillators at high frequencies. A practical way to build a cost-effective and stable source at higher frequency is to use an active multiplier preceded by a high spectral purity VCO operating at a lower frequency. Recent improvements in the performance of SiGe technology allow the silicon microelectronics to advance into areas previously restricted to compound semiconductor devices and make it a strong competitor for automotive radar applications at 79 GHz. This thesis presents the design of active frequency doubler circuits at 20 GHz in a commercially available SiGe BiCMOS technology and at 40GHz in SiGe bipolar technology (Infineon-B7h200 design). Buffer/amplLILHUFLUFXLWVDUHLQFOXGHGDWRXWSXWVWDJHVWRGULYH ORDG The frequency doubler at 20 GHz is based on an emitter-coupled pair operating in class-B configuration at 1.8 V supply voltage. Pre-layout simulations show its conversion gain of 10 dB at -5 dBm input, fundamental suppression of 25dB and NF of 12dB. Input and output LPSHGDQFHPDWFKLQJQHWZRUNVDUHGHVLJQHGWRPDWFK DWERWKVLGHV The millimeter wave frequency doubler is designed for 5 V supply voltage and has the Gilbert cell-based differential architecture where both RF and LO ports are tied together to act as a frequency doubler. Both pre-layout and post-layout simulation results are presented and compared together. The extracted circuit has a conversion gain of 8 dB at -8 dB input, fundamental suppression of 20 dB, NF of 12 dB and it consumes 42 mA current from supply. The layout occupies an area of 0.12 mm2 vii
without pads and baluns at both input and output ports. The frequency multiplier circuits have been designed using Cadence Design Tool.
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Acknowledgments I am thankful to my God for providing me health and energy for this thesis work and other uncountable blessings throughout my life. I would like to express my gratitude to all those who helped me in completing this thesis work. I am deeply indebted to my academic supervisor Prof. Jerzy from Electronic Devices division of Linköping University whose technical help, valuable suggestions and encouragement assisted me through out the entire thesis work and writing this report. I am obliged to Acreo AB, Norrköping for giving me chance to use their technical resources required for this thesis work. I am deeply grateful to Dr. Darius Jakonis, my supervisor at Acreo, for his detailed and constructive comments, and for his important support throughout this work at Acreo. I warmly thank Joacim Olsson and Berthold Panznerthe for their valuable advices and friendly assistance. I wish to thank Patrick Blomqvist for his administrative help in keeping my stay at Acreo more comfortable. I am grateful to my parents for their constant encouragement and prays on which I have relied throughout my life. I have been much supported by my wife Beenish and daughter Maham for accommodating my busy schedule in my study program. My parents and my family, it is to them that I dedicate this work.
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Preface This master thesis work describes the design of frequency doubler circuits at 20 GHz and 40 GHz for automotive radar application. Frequency multiplier circuits facilitate building a cost-effective and stable source at higher frequency. Low-frequency, high spectral purity VCO’s are followed by frequency multiplier circuits because there are limitations to achieve low phase noise oscillator directly at high frequencies. SiGe BiCMOS technology is used for design of the frequency doubler at 20 GHz and SiGe bipolar technology for the frequency doubler at 40 GHz. Chapter-1 starts with an introduction to automotive radar systems, their working principle and current development status. Low-cost stable signal source for automotive radars at 77 GHz can be built using VCO at low frequency followed by some frequency multiplier circuit. This architecture has a few attractions over direct implementation of VCO at higher frequency and is the motivation to this thesis work. Chapter-2 is an introduction to frequency multipliers, their types and working principle. Theory of some basic cells used in common frequency multiplier circuits have been discussed followed by an overview of research work carried on frequency multiplier circuits. Chapter-3 describes design of frequency doubler circuits at 20 GHz in the commercially avaialable SiGe BiCMOS technology. Schematic design of single-ended and differential circuit is provided followed by simulation results of both architectures. Chapter-4 represents design of frequency doubler at 40 GHz in Infineon’s B7HF200 SiGe bipolar technology (fT=200GHz). Gilbert mixer is used for frequency doubling by feeding same signal to LO and RF ports. Schematic and layout design describing each step of balanced circuit architecture is provided. Chapter-5 is dedicated to the performance evaluation of 40 GHz frequency doubler circuit designed in Chapter-4. Simulations are carried out using Cadence Spectra RF environment tool. Circuit’s basic parameters like conversion gain, fundamental suppression, dc power consumption and NF for both schematic and layout are evaluated and compared together. xi
Chapter-6 concludes the work presented in this thesis report. The chapter also summarizes the key-points learned during the whole process followed by some recommendations for the future work.
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List of Abbreviations Balun BiCMOS BJT dB dBm DRC ETSI FDD FCC FET FM FMCW FSK CG HBT HEMT IF IIP3
Balanced Unbalanced Bipolar and CMOS technology on one chip Bipolar Junction Transistor Decibels Power level in dB (decibels) with respect to 1 mW Design Check Rules European Telecommunication Standards Institute Frequency Division Duplex Federal Communications Commission Field Effect transistor Frequency Modulation Frequency Modulated Continuous Wave Frequency Shift Keying Power / Voltage Conversion Gain Hetero Junction Bipolar Transistor High Electron-Mobility Transistors Intermediate Frequency Input Referred 3rd Order Intercept Point
I/O ITS LO LRR MMIC MOS PA PAC PLL PNoise PSK PSP PSS
Input/Output Intelligent Transport System Local Oscillator Long Range Radar Monolithic Microwave Integrated Circuits Metal Oxide Semiconductor Power Amplifier Periodic Phase Lock Loop Periodic Noise Phase Shift Keying Periodic Scattering Parameters Periodic Steady State xiii
QPAC QPSS RF RFIC Rx SRR SSB NF Tx VCO
Quasi Periodic Quasi Periodic Steady State Radio Frequency Radio Frequency Integrated Circuit Receiver Short Range Radar Single Side Band Noise Figure Transmitter Voltage control Oscillator
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Table of Contents ABSTRACT................................................................................................................ VII ACKNOWLEDGMENTS ...........................................................................................IX PREFACE.....................................................................................................................XI LIST OF ABBREVIATIONS...................................................................................XIII TABLE OF CONTENTS........................................................................................... XV LIST OF FIGURES ................................................................................................ XVII LIST OF TABLES ....................................................................................................XIX CHAPTER-1 OVERVIEW OF AUTOMOTIVE RADAR SYSTEMS............................................. 1 1.1. INTRODUCTION .............................................................................................. 3 1.2. NEED FOR AUTOMOTIVE RADAR ................................................................... 3 1.3. CURRENT STATUS OF AUTOMOTIVE RADARS ................................................ 5 1.3.1. Regulatory Aspects in US ......................................................................... 5 1.3.2. Regulatory Aspects in Europe .................................................................. 5 1.4. FUTURE CHALLENGES ................................................................................... 8 1.5. SIGE: COMPETITOR TECHNOLOGY FOR AUTOMOTIVE RADAR APPLICATIONS . 9 1.6. AUTOMOTIVE RADAR TYPES AND MODULATION SCHEMES......................... 10 1.6.1. FM-CW................................................................................................... 10 1.6.2. FSK......................................................................................................... 12 1.6.3. Pulse Doppler Radar.............................................................................. 13 1.7. FREQUENCY SOURCE FOR MILLIMETER-WAVE AUTOMOTIVE RADAR ......... 14 CHAPTER-2 FREQUENCY MULTIPLIER ARCHITECTURES ................................................ 17 2.1. INTRODUCTION ............................................................................................ 19 2.2. PASSIVE MULTIPLIERS .................................................................................. 19 2.3. ACTIVE MULTIPLIERS ................................................................................... 20 2.3.1. Emitter Coupled Pair as Simple BJT multiplier..................................... 21 2.3.2. Gilbert Multiplier Cell ........................................................................... 24 2.3.3. Common Frequency Doubler Circuits ................................................... 27 CHAPTER-3 THE DESIGN OF 20-GHZ FREQUENCY DOUBLER AND OUTPUT AMPLIFIER CIRCUIT............................................................................................... 29 3.1. INTRODUCTION ............................................................................................ 31 3.2. CIRCUIT SPECIFICATIONS ............................................................................. 31 3.3. PROPOSED SINGLE-ENDED CIRCUIT ............................................................. 32 3.3.1. Design Methodology .............................................................................. 33 3.3.2. Improvement by Second Harmonic Reflector......................................... 34
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3.3.3. Simulation Results .................................................................................. 35 3.4. PROPOSED DIFFERENTIAL CIRCUIT .............................................................. 38 3.4.1. Circuit Description................................................................................. 39 3.4.2. Optimum value of size ratio K................................................................ 41 3.4.3. Simulation Results .................................................................................. 42 CHAPTER-4 THE DESIGN OF 40-GHZ FREQUENCY DOUBLER AND OUTPUT AMPLIFIER CIRCUIT............................................................................................... 45 4.1. INTRODUCTION ............................................................................................ 47 4.2. TECHNOLOGY DETAILS ................................................................................ 47 4.3. CIRCUIT SPECIFICATIONS ............................................................................. 48 4.4. DESIGN CONSIDERATIONS ........................................................................... 48 4.5. PROPOSED ARCHITECTURE .......................................................................... 50 4.6. DESIGN DESCRIPTION .................................................................................. 50 4.6.1. Input Buffer Stage................................................................................... 50 4.6.2. Gilbert Cell............................................................................................. 52 4.6.3. Filter....................................................................................................... 55 4.6.4. Differential Amplifier ............................................................................. 56 4.6.5. Integrated Circuit................................................................................... 58 4.7. LAYOUT OF THE FREQUENCY DOUBLER CIRCUIT ........................................ 60 4.7.1. Layout Design Considerations ............................................................... 60 4.7.2. Pad Frame.............................................................................................. 61 4.7.3. Emitter-Follower Layout........................................................................ 62 4.7.4. Gilbert Cell and Filter Layout................................................................ 63 4.7.5. Frequency Doubler Core Layout............................................................ 64 4.7.6. Complete Layout .................................................................................... 65 4.7.7. Layout Verification................................................................................. 65 CHAPTER-5 SCHEMATIC AND LAYOUT SIMULATION RESULTS OF 40-GHZ FREQUENCY DOUBLER CIRCUIT ....................................................................... 67 5.1. 5.2. 5.3. 5.4. 5.5.
INTRODUCTION ............................................................................................ 69 CONVERSION GAIN AND NF......................................................................... 69 OUTPUT SPECTRUM AND FUNDAMENTAL SUPPRESSION .............................. 71 S11 AND S22................................................................................................ 72 CORNER ANALYSIS ...................................................................................... 74
CHAPTER-6 CONCLUSION AND FUTURE WORK.................................................................... 77 6.1. 6.2. 6.3.
INTRODUCTION ............................................................................................ 79 KEY POINTS LEARNED ................................................................................. 79 FUTURE WORK ............................................................................................ 80
REFERENCES............................................................................................................. 83
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List of Figures Figure 1: Installation of Automotive Radar and its different kind of applications [9] .......................................................................................... 4 Figure 2: The ‘Package Solution’ [9] ........................................................ 7 Figure 3: Time schedule for the development and rollout of 79 GHz SRR sensors [9].................................................................................................. 7 Figure 4: Prediction of the evaluation of automotive radar application [11] ............................................................................................................ 8 Figure 5: Typical FMCW Radar [17]...................................................... 11 Figure 6: Typical FSK Radar [17]........................................................... 12 Figure 7: Typical Pulse Radar [17] ......................................................... 13 Figure 8: RF-front end of FMCW automotive radar............................... 15 Figure 9: Emitter-Coupled pair [26]........................................................ 21 Figure 10 : The dc transfer characteristics of emitter-coupled pair [26]. 22 Figure 11: Two quadrant analog multiplier [26] ..................................... 23 Figure 12: Gilbert multiplier circuit ........................................................ 25 Figure 13: Frequency doubler based on class-B configuration and output amplifier [37]........................................................................................... 32 Figure 14: Collector current modelled as a train of rectified cosine pulses [38] .......................................................................................................... 33 Figure 15: Plot of Conversion Gain and NF versus input power ........... 36 Figure 16: Plot of Conversion Gain and NF versus frequency .............. 36 Figure 17: Output frequency spectrum for input signal of -8dBm at 20 GHz ......................................................................................................... 37 Figure 18: Input impedance matching.................................................... 37 Figure 19: Output impedance matching ................................................. 38 Figure 20: Frequency doubler consists of two identical unbalanced emitter-coupled pairs with emitter area ratio K and differential amplifier ................................................................................................................. 39 Figure 21: DC transfer curves of frequency doubler [43] ....................... 41 Figure 22: Relative size ratio K versus gain............................................ 41 Figure 23: Plot of Conversion Gain and NF versus input power ........... 42 Figure 24: Output frequency spectrum for input power -8dBm at 20 GHz ................................................................................................................. 43 Figure 25: Pseudo-differential output signals ........................................ 43 Figure 26: Use of active mixer as frequency doubler ............................ 49 Figure 27: Proposed architecture for frequency doubler at 40 GHz ...... 50 Figure 28: Emitter-follower circuit (common-collector configuration) [26] .......................................................................................................... 51 xvii
Figure 29: Small-signal equivalent circuit of emitter-follower circuit [26] ................................................................................................................. 51 Figure 30 Gilbert mixer.......................................................................... 53 Figure 31: Variable gain of Gilbert mixer in frequency doubler circuit 54 Figure 32: Effective inductance of a lossless transmission line for l
