Low Phase Noise, High Bandwidth Frequency Synthesis Techniques by Scott Edward Meninger Bachelor of Science in Electrical Engineering and Computer Science Boston University, June 1996 Master of Science in Electrical Engineering and Computer Science Massachusetts Institute of Technology, June 1999 Submitted to the Department of Electrical Engineering and Computer Science in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY May 2005 c Massachusetts Institute of Technology 2005. All rights reserved. Author.............................................................. Department of Electrical Engineering and Computer Science May 12, 2005 Certified by. Michael H. Perrott Assistant Professor Thesis Supervisor Accepted by . Arthur C. Smith Chairman, Department Committee on Graduate Students 2 Low Phase Noise, High Bandwidth Frequency Synthesis Techniques by Scott Edward Meninger Submitted to the Department of Electrical Engineering and Computer Science on May 12, 2005, in partial fulfillment of the requirements for the degree of Doctor of Philosophy Abstract A quantization noise reduction technique is proposed that allows fractional-N fre- quency synthesizers to achieve high closed loop bandwidth and low output phase noise simultaneously. Quantization induced phase noise is the bottleneck in state-of- the-art synthesizer design, and results in a noise-bandwidth tradeoff that typically limits closed loop synthesizer bandwidths to be <100kHz for adequate phase noise performance to be achieved. Using the proposed technique, quantization noise is re- duced to the point where intrinsic noise sources (VCO, charge-pump, reference and PFD noise) ultimately limit noise performance. An analytical model that draws an analogy between fractional-N frequency syn- thesizers and MASH Σ∆ digital-to-analog converters is proposed. Calculated per- formance of a synthesizer implementing the proposed quantization noise reduction techniques shows excellent agreement with simulation results of a behavioral model. Behavioral modeling techniques that progressively incorporate non-ideal circuit be- havior based on SPICE level simulations are proposed. The critical circuits used to build the proposed synthesizer are presented. These include a divider retiming circuit that avoids meta-stability related to synchronizing an asynchronous signal, a timing mismatch compensation block used by a dual divider path PFD, and a unit element current source design for reduced output phase noise. Measurement results of a prototype 0.18µm CMOS synthesizer show that quan- tization noise is suppressed by 29dB when the proposed synthesizer architecture is compared to 2nd order Σ∆ frequency synthesizer. The 1MHz closed loop bandwidth allows the synthesizer to be modulated by up to 1Mb/s GMSK data for use as a transmitter with 1.8GHz and 900MHz outputs. The analytical model is used to back extract on-chip mismatch parameters that are not directly measurable. This repre- sents a new analysis technique that is useful in the characterization of fractional-N frequency synthesizers. Thesis Supervisor: Michael H. Perrott Title: Assistant Professor 3 4 This thesis is dedicated to the example and inspiration of my parents, Donald T. and Mary J. Meninger. Dad, I miss you every day. You will always be my best man. 5 6 “While I’m still confused and uncertain, it’s on a much higher plane, d’you see, and at least I know I’m bewildered about the really fundamental and important facts of the universe.” Treatle nodded. ”I hadn’t looked at it like that,” he said, ”But you’re absolutely right. He’s really pushed back the boundaries of ignorance”. They both savored the strange warm glow of being much more ignorant than ordinary people, who were only ignorant of ordinary things. – Terry Pratchett, Equal Rites 7 8 Acknowledgments “Give a man a fire and he’s warm for a day, but set fire to him and he’s warm for the rest of his life.” – Terry Pratchett, Jingo In many ways, the grad school experience is like being set on fire. There’s an initial burst of enthusiasm after which you feel like you’re running around desperately asking people to put you out. After various periods of flaming up, someone dumps a bucket of water on you, and you wind up feeling a bit burnt out, but happy that the pain has stopped. And along the way you’ve learned a few valuable lessons.... ....Of course, another way of looking at it is that grad school is in no way like being lit on fire. In fact, one could argue that grad school is the exact opposite of being lit on fire. And one thing you definitely learn in grad school is to be very, very careful about general statements and assumptions, so I’ll just say that grad school is very much like being lit on fire, while in no way like being lit on fire. So, on to more important matters ... There are countless numbers of people to thank for the help, influence, and in- spiration they have given me over the course of my PhD experience. In advance, I apologize if anyone is not included in this acknowledgment section who should be. I’d like to start by thanking my thesis advisor Professor Mike Perrott. Mike has been a constant motivating force and positive influence on the work that is presented in this thesis. I have learned a phenomenal amount over the last four years, and owe much of my education to Mike’s personal tutelage. I owe my committee, Professors Anantha Chandrakasan and Jacob White a debt of gratitude for taking the time to meet with me during the course of this work, and for reading this thesis. 9 I would not have made it through the PhD experience without the help and support of numerous grad students working in MTL. They have aided me technically, as well as in the more important aspect of having some fun. Anh Pham, John Fiorenza, Nisha Checka, Albert Jerng, Andrew Chen, Mark Spaeth, and Tod Sepke all were sources of good technical discussions as well as good guys to grab a beer or go ski with. Tod also was very helpful (and patient) in helping me get a handle on noise processes and simulation. The members of the High Speed Circuits and Systems Group have coped with my .... personality over the last four years, and so I owe them a huge debt of gratitude. Ethan Crain has been a great lab-mate to design with and work out with. Assuming I’m not trying to keep up with him running, that is. I’m not sure who owes who a beer at this point, but I look forward to being able to enjoy one with him in a more relaxed setting soon. Charlotte Lau has borne the brunt of what will be referred to as my “humor”. Her patience and help (and lack of litigation to this point), are much appreciated. I’ll miss our trips to ABP for lunch, and the recognition that comes with walking around with the queen of MIT. Belal Helal and I have had far too many late night discussions that have increased our graduation dates as well as our understanding. Belal’s thoroughness has been an example. Matt Park is responsible for the excellent work on the data-weighted averager circuit used by my test chip. There are not many undergrads who I would trust with my something going into my thesis chip, but Matt was a clear exception. I’m looking forward to seeing the work he’ll produce in the future. I also owe thanks to Min Park, Chun-Ming Hsu, Shawn Kuo, and Muyi Ogunnika, who have helped me out in numerous ways over the last four years. Our group administrators, Rosa Fuentes and Valerie DiNardo, have been a great help getting the lab set up and putting through my very disorganized reimbursements. The MTL staff has done a great job helping the students make our way through the grad school experience. Debb Hodges Pabon, in particular, has always made herself 10 available to us and done a fantastic job coordinating the numerous MTL gatherings. I’d like to thank Marilyn Pierce in the EECS grad office for her help, guidance, and patience over the years that have comprised my eclectic grad school schedule. The folks at National Semiconductor helped make my tapeout process as easy as it could be. In particular, Sangamesh Buddhiraju’s CAD help was critical in getting the National setup working at MIT, and his excellent front-end work saved us countless hours of frustration. The National-MIT program wouldn’t even exist if it wasn’t for the work of Peter Holloway, who I’ve been lucky enough to work for and with over the years. Pete is truly one of the great guys I’ve met in the course of my travels, and I look forward to our paths crossing again. I’d like to thank MTL CICS and MARCO for funding my research. I’d also like to thank the folks at Teradyne, especially Kurt Ware and Ron Sartchev, for funding me as a Teradyne fellow for a year. It was encouraging along the way to see that my research was sparking real-world interest. I’d also like to thank Duke Xanthopoulos for helping me out with the initial CAD setup, and setting up a great situation for me at Cavium. I’m really looking forward to getting started. My friends have been very supportive, in what can only be called their unique and “special” way. The boys of DOAIHPS have helped me enjoy what little free time I’ve had over the last four years, and I’m looking forward to finally having some time to waste with them now. Ken, Chris, Rufus, and Rob, the first $1.35 (or, $1.85 now...) at York is on me.