LO Generation and Distribution for 60GHz Phased Array Transceivers

201 Pages·2011·17.45 MB·English

LO Generation and Distribution for 60GHz Phased
Array Transceivers
Cristian Marcu
Electrical Engineering and Computer Sciences
University of California at Berkeley
Technical Report No. UCB/EECS-2011-132
http://www.eecs.berkeley.edu/Pubs/TechRpts/2011/EECS-2011-132.html
December 14, 2011
Copyright © 2011, by the author(s).
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LO Generation and Distribution for 60GHz Phased Array Transceivers
by
Cristian Marcu
A dissertation submitted in partial satisfaction of the
requirements for the degree of
Doctor of Philosophy
in
Electrical Engineering
in the
Graduate Division
of the
University of California, Berkeley
Committee in charge:
Professor Ali M. Niknejad, Chair
Professor Elad Alon
Professor Paul K. Wright
Fall 2011
LO Generation and Distribution for 60GHz Phased Array Transceivers
Copyright 2011
by
Cristian Marcu
1
Abstract
LO Generation and Distribution for 60GHz Phased Array Transceivers
by
Cristian Marcu
Doctor of Philosophy in Electrical Engineering
University of California, Berkeley
Professor Ali M. Niknejad, Chair
Increased memory capacity and processing power in mobile devices has created a need for
radios that can transmit data at multi-Gb/s rates over a short range. However, battery
capacity has not kept pace with these advances so power consumption must be kept to a
minimumtomaintainlongbatterylife. Furthermore, consumerdevicesrequirelowcostcom-
ponents due to the strong market pressures continuously driving down Average Selling Prices
(ASP) leading to diminishing margins. This means a fully integrated solution including RF
and baseband components is more attractive than a modular solution.
The allocation of 7GHz of unlicensed bandwidth in the 60GHz band and the increasing
speed of CMOS technology provides an excellent opportunity for low cost, high data rate,
fully integrated radios to fulfill the unique requirements of modern mobile devices. Phased
array transceivers using simple modulation schemes should be used due to their high energy
efficiency. Phased arrays use spatial power combining to help overcome the high path loss at
60GHz and also provide beam-steering capabilities which can help to overcome fading issues
and create a secure means of communication.
Significant progress has been been made recently in the design of mm-wave CMOS building
blocks and transceivers, including some phased array transceivers. However, very little
attention has been paid to systematic optimization and design of the LO generation and
distribution subsystem. In this thesis we use the baseband phase shifting architecture as
a vehicle for optimizing LO generation and distribution in phased array transceivers. We
propose strategies for optimal low power design with a focus on holistic optimization from
architectural choices down to block level design resulting in an optimal and scalable LO
distribution methodology. Finally, we present sample designs of building blocks such as
oscillators and phase locked loops as well as a full LO generation and distribution subsystem
fora4-elementbasebandphased-arraytransceiverinastandarddigital65nmCMOSprocess.
i
To my wife Alex, my mom and dad, and my sister Gabi.
I couldn’t have done it without your love and support.
ii
Contents
List of Figures v
List of Tables x
1 Introduction 1
1.1 The 60GHz Band . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 CMOS for 60GHz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3 60GHz Transceivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.3.1 Link Budget Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.3.2 Phased Arrays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.4 Related Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
1.5 Thesis Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
1.5.1 Design Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2 Passive Design 14
2.1 Lumped Resonant Tanks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.2 Distributed Resonant Tanks . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.3 Tapered Transmission Line Resonators . . . . . . . . . . . . . . . . . . . . . 22
2.4 MEMS Resonators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.5 Passive Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
2.5.1 Inductors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
2.5.2 Capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
2.5.3 Varactors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
2.5.4 Transmission Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
iii
2.A Derivation of Lumped Resonant Tank Bandwidth . . . . . . . . . . . . . . . 44
2.B Derivation of Distributed Resonant Tank Bandwidth . . . . . . . . . . . . . 45
2.C Series-to-Parallel Transformation . . . . . . . . . . . . . . . . . . . . . . . . 47
3 Voltage Controlled Oscillator 49
3.1 A Short Introduction to Oscillators . . . . . . . . . . . . . . . . . . . . . . . 49
3.2 Design of a Cross-Coupled Oscillator . . . . . . . . . . . . . . . . . . . . . . 50
3.2.1 Startup Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
3.2.2 Tuning the Tank . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
3.2.3 Phase Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
3.2.4 Design Optimization . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
3.3 Other Fundamental Mode Oscillator Topologies . . . . . . . . . . . . . . . . 67
3.3.1 Colpitts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
3.3.2 Common-Drain Colpitts . . . . . . . . . . . . . . . . . . . . . . . . . 73
3.3.3 Differential Versions . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
3.4 Cross-Over Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
3.5 The Push-Push Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
3.6 Design Case Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
3.6.1 Push-push Oscillator Prototype . . . . . . . . . . . . . . . . . . . . . 90
3.6.2 Fundamental Oscillator Prototype . . . . . . . . . . . . . . . . . . . . 92
3.6.3 Performance Summary and Comparison . . . . . . . . . . . . . . . . 96
4 Low Power Phase Locked Loop Design 99
4.1 Phase Locked Loop Dynamics . . . . . . . . . . . . . . . . . . . . . . . . . . 101
4.1.1 The Linear Phase Domain Model . . . . . . . . . . . . . . . . . . . . 101
4.1.2 First Order PLL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
4.1.3 Second Order PLL . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
4.1.4 The Charge Pump and Phase Frequency Detector . . . . . . . . . . . 107
4.1.5 The Charge Pump PLL . . . . . . . . . . . . . . . . . . . . . . . . . 111
4.2 Noise in Charge Pump Phase Locked Loops . . . . . . . . . . . . . . . . . . 114
4.2.1 Noise Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
iv
4.2.2 Design Optimization . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
4.3 Frequency Dividers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
4.3.1 Flip-Flop Dividers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
4.3.2 Injection Locked Dividers . . . . . . . . . . . . . . . . . . . . . . . . 124
4.3.3 Regenerative Dividers . . . . . . . . . . . . . . . . . . . . . . . . . . 126
4.3.4 Prescalers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
4.4 Sample Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
4.A Spectral Purity Metrics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
5 LO Distribution 140
5.1 Mixer LO Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
5.2 LO Generation Strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
5.3 Mixer LO Buffer Design Methodology . . . . . . . . . . . . . . . . . . . . . . 148
5.3.1 Scalable Amplifier Model . . . . . . . . . . . . . . . . . . . . . . . . . 149
5.3.2 Scalable Transformer Model . . . . . . . . . . . . . . . . . . . . . . . 150
5.3.3 Equation Based Buffer Design . . . . . . . . . . . . . . . . . . . . . . 151
5.3.4 Optimization Based Buffer Design . . . . . . . . . . . . . . . . . . . . 156
5.3.5 Comparision Between Buffer Design Methods . . . . . . . . . . . . . 158
5.3.6 Injection Locked Oscillator As an LO Buffer . . . . . . . . . . . . . . 160
5.4 LO Distribution Strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163
5.5 Design Case Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169
6 Conclusion 173
Bibliography 174
v
List of Figures
1.1 Attenuation due to molecular resonances in the atmosphere (sea-level, 25◦C,
7.5g/m3 water vapor density). . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2 Constellations of simple modulation schemes. . . . . . . . . . . . . . . . . . . 2
1.3 Evolution of WLAN data rates. . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.4 ITRS Roadmap for RF CMOS Technology. . . . . . . . . . . . . . . . . . . . 4
1.5 Direct conversion transceiver block diagram. . . . . . . . . . . . . . . . . . . 6
1.6 QPSK constellation with noisy carrier. . . . . . . . . . . . . . . . . . . . . . 7
1.7 BER as a function of SNR for different modulation schemes. . . . . . . . . . 8
1.8 Uniform linear 8-element phased array transceiver block diagram. . . . . . . 9
1.9 Phased array architectures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.1 Lumped resonant tanks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.2 Transmission line with arbitrary load. . . . . . . . . . . . . . . . . . . . . . . 17
2.3 RLGC ladder representation of transmisison line. . . . . . . . . . . . . . . . 18
2.4 Ideal transmission line input impedance. . . . . . . . . . . . . . . . . . . . . 19
2.5 Lossy transmission line input impedance (plotted for Q=10). . . . . . . . . . 21
2.6 Current and voltage standing waves for a quarter-wavelength transmission line. 22
2.7 A tapered quarter wave transmission line utilizes wide width and large gap
spacing when the current is high (voltage is low) and narrow width and small
gap when the voltage is high (current is low). . . . . . . . . . . . . . . . . . 23
2.8 The layout of the optimized quarter wave line. The characteristic impedance,
Z , is non-constant. Slotting is introduced to satisfy design rules. . . . . . . 24
o
2.9 The optimum characteristic impedance profile. . . . . . . . . . . . . . . . . . 25
2.10 MEMS resonator model. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26