Analysis and Design of Monolithic Radio Frequency Linear Power Amplifiers by Burcin Baytekin BS

152 Pages·2004·0.71 MB·English

Analysis and Design of Monolithic Radio Frequency Linear Power
Amplifiers
by
Burcin Baytekin
B.S. (University of Southern California) 1997
M.S. (University of California, Berkeley) 1999
A dissertation submitted in partial satisfaction of the
requirements for the degree of
Doctor of Philosophy
in
Engineering - Electrical Engineering and Computer Science
in the
GRADUATE DIVISION
of the
UNIVERSITY of CALIFORNIA at BERKELEY
Committee in charge:
Professor Robert G. Meyer, Chair
Professor Ali M. Niknejad
Professor John A. Strain
Spring 2004
The dissertation of Burcin Baytekin is approved:
Chair Date
Date
Date
University of California at Berkeley
Spring 2004
Analysis and Design of Monolithic Radio Frequency Linear Power
Amplifiers
Copyright Spring 2004
by
Burcin Baytekin
1
Abstract
Analysis and Design of Monolithic Radio Frequency Linear Power Amplifiers
by
Burcin Baytekin
Doctor of Philosophy in Engineering - Electrical Engineering and Computer Science
University of California at Berkeley
Professor Robert G. Meyer, Chair
Linear power amplifiers (PAs) are becoming widely used in modern wireless com-
munication systems. The envelope of the signals in these systems is typically not constant,
so that the PA design must address the issue of device nonlinearity in order to limit the
amount of spectral regrowth, which can cause unacceptable levels of interference in the
adjacent channels.
Thisresearch focuses on a new computational methodfor efficiently analyzing the
relationship between spectral regrowth and physical distortion mechanisms in radio fre-
quencypower amplifiers. Itutilizes aVolterra series model whosecoefficients arecomputed
from basic SPICE parameters. The analysis uses a decomposition of the Volterra kernels
into simpler subsystems in order to greatly reduce the computation time.
The new computational approach was applied to the design of PAs using bipolar
transistors as the active element. A series-based model was developed for representing the
2
increase in active-device forward transit time at high collector current densities.
The design of a number of single-stage SiGe power amplifiers is also described.
Bias techniques are describedwhich allow theaverage PA current to increase at high signal
levels and thus reduce distortion-inducing gain compression. The amplifiers were tested
using the IEEE802.11b and IS-95 modulation schemes at different carrier frequencies and
these results are compared with the theoretical analysis.
Professor Robert G. Meyer
Dissertation Committee Chair
iii
To my parents,
Sevim and Ali Baytekin,
without their support I could not be where I am today
iv
Contents
List of Figures vi
List of Tables viii
I Power Amplifier Fundamentals 1
1 Introduction 2
1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2 Previous Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3 Research Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.4 Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2 Power Amplifier Design 11
2.1 Important PA Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.2 Classes of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.2.1 Class A Amplification . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.2.2 Class B Amplification . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.2.3 Class AB and C Modes . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.3 Supply Voltage, Breakdown and Efficiency . . . . . . . . . . . . . . . . . . . 23
2.4 Output Matching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.5 Input and Interstage Matching . . . . . . . . . . . . . . . . . . . . . . . . . 28
2.6 Thermal management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
2.7 Packaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2.8 Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
2.9 Electrostatic Discharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
3 Bipolar Transistor Technologies 43
3.1 Gallium-Arsenide Heterojunction Bipolar Transistors . . . . . . . . . . . . . 43
3.2 Silicon-Germanium Bipolar Transistors . . . . . . . . . . . . . . . . . . . . . 45
3.3 Thermal Runaway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
v
II Analysis 49
4 Volterra Series 50
4.1 Calculating the Volterra Kernels of a Circuit . . . . . . . . . . . . . . . . . 51
5 Computational Approach 56
5.1 Time and Frequency-Domain Calculations . . . . . . . . . . . . . . . . . . . 56
5.2 Decomposition of the Volterra Kernels . . . . . . . . . . . . . . . . . . . . . 58
5.3 Third-Order Volterra Subsystems . . . . . . . . . . . . . . . . . . . . . . . . 60
5.3.1 Second-Order Interaction Subsystem . . . . . . . . . . . . . . . . . . 60
5.3.2 Pure Third-Order Subsystem . . . . . . . . . . . . . . . . . . . . . . 62
5.4 Neglecting Even-Order Terms in Volterra Series . . . . . . . . . . . . . . . . 63
6 Device Modeling 66
6.1 Modeling the Variations in Forward Transit Time . . . . . . . . . . . . . . 70
III Application 75
7 Implementation 76
7.1 Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
7.2 Details of the Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
7.3 Kernel Calculations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
7.4 Simulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
8 Results 89
8.1 Analysis versus Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . 89
8.2 Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
9 Conclusion 96
9.1 Future Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
Bibliography 100
A Programs for Implementing the Computational Approach 107
A.1 Generating the Input Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
A.2 Spectral Regrowth Calculations . . . . . . . . . . . . . . . . . . . . . . . . . 112
A.2.1 Entering the Design and Model Parameters . . . . . . . . . . . . . . 117
A.2.2 Scaling the Input Signal Waveform . . . . . . . . . . . . . . . . . . . 122
A.2.3 Calculating the Input and Output Loss . . . . . . . . . . . . . . . . 123
A.2.4 Calculating the Third-Order Response . . . . . . . . . . . . . . . . . 125
A.2.5 First-Order Response Functions . . . . . . . . . . . . . . . . . . . . . 128
A.2.6 Second-Order Transfer Functions . . . . . . . . . . . . . . . . . . . . 133
A.2.7 Third-Order Transfer Functions . . . . . . . . . . . . . . . . . . . . . 137
vi
List of Figures
1.1 A typical wireless transmitter.. . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2 Intermodulation distortion. . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1 Simplified power amplifier schematic . . . . . . . . . . . . . . . . . . . . . . 14
2.2 Current and voltage waveforms for Class A amplifier . . . . . . . . . . . . . 16
2.3 The maximum collector efficiency of an ideal Class A amplifier versus the
load resistance R normalized to the optimum load resistance R . . . . 18
L Lopt
2.4 Current and voltage waveforms for Class B amplifier . . . . . . . . . . . . . 19
2.5 The efficiency of ideal Class A and Class B amplifiers versus output power
level normalized to the maximum available power. . . . . . . . . . . . . . . 21
2.6 The maximum efficiency of an ideal power amplifier versus the conduction
angle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.7 L-section output matching networks (a)Low-pass (b)High-pass . . . . . . . 27
2.8 L-section input or interstage matching networks (a)Low-pass (b)High-pass . 29
2.9 Band-pass matching network . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.10 Heat Dissipation Paths for IC Packages . . . . . . . . . . . . . . . . . . . . 31
2.11 Thermal Resistance Equivalent Circuit . . . . . . . . . . . . . . . . . . . . . 32
2.12 A flip-chip package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
2.13 Cross section of a flip-chip package with active and inactive solder bumps . 36
2.14 General two-port amplifier model . . . . . . . . . . . . . . . . . . . . . . . . 38
2.15 Simplified human body model for electrostatic discharge . . . . . . . . . . . 39
2.16 Grounded-base-npn clamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
2.17 ESD current paths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
4.1 (a)Nonlineartransconductormodelbasedonpowerseries(b)Theequivalent
model of the same transconductor for calculating Volterra kernels . . . . . . 52
5.1 Third-orderVolterra subsystems(a) Purethird-ordersubsystem(b) Second-
order interaction subsystems. . . . . . . . . . . . . . . . . . . . . . . . . . . 59
5.2 Compressed spectrum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
6.1 Nonlinear bipolar transistor model . . . . . . . . . . . . . . . . . . . . . . . 67
vii
6.2 (a) Electric field and (b) space-charge density in the the collector-base junc-
tion including the effects of mobile electrons due to collector current . . . . 71
7.1 IEEE802.11b transmit spectrum mask . . . . . . . . . . . . . . . . . . . . . 77
7.2 Die photo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
7.3 Simplified schematic of the power amplifier . . . . . . . . . . . . . . . . . . 79
7.4 Conventional local-bias circuit . . . . . . . . . . . . . . . . . . . . . . . . . . 81
7.5 Local-bias circuit without base resistor . . . . . . . . . . . . . . . . . . . . . 81
7.6 Norton equivalent of the schematic of the power amplifier in figure 7.3 . . . 83
7.7 The schematic for calculating the first-order response of the power amplifier
presented in figure 7.6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
7.8 The schematic for calculating the second and third-order responses of the
power amplifier in figure 7.6 . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
7.9 Simulation method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
7.10 Input and output power spectral density calculated by simulations . . . . . 88
8.1 Ratio of the first sidelobe and the mainlobe versus output power level for
m = 78, V = 3.3 V, I = 196 mA, f = 2.45 GHz . . . . . . . . . . . . 90
CC cQ c
8.2 Ratio of the first sidelobe and the mainlobe versus output power level for
m = 104, V = 3.3 V, I = 196 mA, f = 2.4 GHz . . . . . . . . . . . . 91
CC cQ c
8.3 Ratio of the first sidelobe and the mainlobe versus output power level for
m = 78, V = 3.5 V, I = 176 mA, f = 2.0 GHz . . . . . . . . . . . . 92
CC cQ c
8.4 Ratio of the first sidelobe and the mainlobe versus current consumption at
P = 24 dBm for m = 78, V = 3.5 V, f = 2.0 GHz . . . . . . . . . . 92
out CC c
8.5 ACPRversusoutputpowerlevelforIS-95modulation,m=78,V =3.5V,
CC
I = 176 mA, f = 2.0 GHz . . . . . . . . . . . . . . . . . . . . . . . . . . 93
cQ c
8.6 Electric field and the variation of length of the collector-base space charge
region for (a) Low collector dopant density (b) High collector dopant density
(c) Shallow buried layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94