Diplexing Distributed Power Amplifier for Mobile

Diplexing Distributed Power Amplifier for
Mobile Applications
Der Technischen Fakultät
der Universität Erlangen-Nürnberg
zur Erlangung des Grades
DOKTOR-INGENIEUR
Vorgelegt von
M. Sc. Wei Wang
Erlangen, März 2012
Verteilte Mehrtor Leistungsverstärker für
Mobilfunkanwendungen mit
Diplexerfunktion
Als Dissertation genehmigt von
der Technischen Fakultät
der Universität Erlangen-Nürnberg
Tag der Einreichung: 11. 08. 2011
Tag der Promotion:
19. 03. 2012
Dekanin:
Prof. Dr.-Ing. Marion Merklein
Berichterstatter:
Prof. Dr.-Ing. Georg Fischer
Prof. Dr.-Ing. Wolfgang Heinrich
Berichte aus der Kommunikationstechnik
Wei Wang
Diplexing Distributed Power Amplifier
for Mobile Applications
D 29 (Diss. Universität Erlangen-Nürnberg)
Shaker Verlag
Aachen 2012
Bibliographic information published by the Deutsche Nationalbibliothek
The Deutsche Nationalbibliothek lists this publication in the Deutsche
Nationalbibliografie; detailed bibliographic data are available in the Internet at
http://dnb.d-nb.de.
Zugl.: Erlangen-Nürnberg, Univ., Diss., 2012
Copyright Shaker Verlag 2012
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Acknowledgements
My foremost appreciation goes to Mr. Christian Korden at TDK-EPC Corporation, Munich
and Prof. Dr.-Ing. Robert Weigel, the Chair of Electronics Engineering at University of
Erlangen-Nuremberg, Germany. They gave me the opportunity to work on this interesting
topic.
I also wish to express my gratitude to Prof. Dr.-Ing. Georg Fischer, who has supervised me
throughout my work. Without his helpful guidance and instruction I wouldn’t have finished
my dissertation.
My sincere thanks also go to Dr. Ir. Léon van den Oever at Radio Semiconductor B.V.
Nijmegen, the Netherlands. As one of the most experienced engineers in the field of mobile
phone power amplifier, he always gave me valuable suggestions and instructions.
Furthermore, I would like to thank my colleagues at the chair of Electronics Engineering at
the University of Erlangen-Nuremberg and at TDK-EPC Corporation for all their assistance
during my PhD study.
Finally I would like express my appreciation to my parents and wife for their support,
understanding and love.
I
Abstract
For the purpose of multiband mobile phone power amplifier (PA) design, the prospect of
using a distributed amplifier (DA) has been investigated, which over the last 50 years is well
known for its excellent broadband behaviour. In order to better adapt the DA to mobile phone
PA applications, a new concept is proposed, namely the linear diplexing tapered DA. To
verify this concept, the following designs have been investigated:
x
x
Single stage PCB demonstrator
Two-stage on-chip design, which has tapered DA as driver and the diplexing
tapered DA as a final PA stage
Due to the unique properties of the (diplexing tapered) DA, some commonly used techniques
in Single-Ended-PA designs are not applicable. Therefore modifications and adaptations are
made. Furthermore, the supplementary properties of the diplexing tapered DA are discussed:
x
x
x
x
Stage bypass for PAE enhancement of DA during large back-off (BO) operation
Due to multiple feedback loops and nonlinear devices, large signal and parametric
stability are characterised by system identification method
Due to the inferior linearity of DA, a special dynamic biasing circuit to
compensate for the gain expansion is proposed
The ability to apply spectrum aggregation and load balancing techniques
II
Kurzfassung
In der vorliegenden Arbeit wurde für die im Mobilfunk eingesetzten
Multibandleistungsverstärker (Multiband PA) die Verwendung von verteilten Verstärker
(Distributed Amplifier - DA) untersucht, die seit langem für ihre ausgezeichnete
Breitbandigkeit bekannt sind. Als neues Konzept wurde der linear verteilte Mehrtorverstärker
mit Diplexerfunktion verwendet. Zur Überprüfung der Funktionsweise wurde ein einstufiger
PCB-Demonstrator mit diskreten Bauteilen aufgebaut und charakterisiert, sowie ein
zweistufiges IC-Design mit einem tapered DA als Treiber und einem tapered Mehrtor-DA
mit Diplexerfunktion als Endstufe verifiziert.
Aufgrund der speziellen Eigenschaften von verteilten Verstärkern mit Diplexerfunktion
lassen sich einige bekannte und häufig verwendete Techniken zur Verbesserung von
Linearität und Wirkungsgrad - wie sie häufig zur Auslegung von Single-Ended-PAs
verwendet werden, nicht anwenden. Daher wurden folgende Techniken adaptiert und neu in
Schaltung und Simulation eingeführt:
x
x
x
x
Bypass-Stufe zur Erhöhung des Verstärkerwirkungsgrads (PAE) im Back-Off
(BO)
Analyse der parametrischen und Großsignalstabilität
Dynamische Bias-Schaltung zur Linearitätsverbesserung bzw. zur Kompensation
der Verstärkungsexpansion
Berücksichtigung von Last-Balancierung- und Spektrum-Aggregationstechniken
III
Table of contents
Acknowledgements ................................................................................................................................ I
Abstract.................................................................................................................................................II
List of abbreviations ........................................................................................................................... VI
1.
Introduction................................................................................................................................... 1
2.
Power amplifier fundamentals ...................................................................................................... 3
2.1.
Efficiency ....................................................................................................................... 4
2.1.2.
Gain ................................................................................................................................ 4
2.1.3.
Maximal output power and back-off .............................................................................. 5
2.1.4.
Linearity ......................................................................................................................... 6
2.2.
3.
Operation class comparison: Class A and Class AB .............................................................. 9
The power amplifier bandwidth .................................................................................................. 12
3.1.
Transistor’s figure of merits ................................................................................................. 12
3.2.
Matching limitation.............................................................................................................. 14
3.2.1.
Bode-Fano limit ........................................................................................................... 14
3.2.2.
Limitation of LC matching ........................................................................................... 15
3.3.
4.
PA characteristics .................................................................................................................. 3
2.1.1.
Broadband amplifier topologies ........................................................................................... 18
3.3.1.
Common source (CS) amplifier .................................................................................... 19
3.3.2.
Lossy matched (LM) amplifier ..................................................................................... 19
3.3.3.
Shunt negative feedback (FB) amplifier ....................................................................... 20
3.3.4.
Balanced amplifier (BA) .............................................................................................. 20
3.3.5.
Distributed amplifier (DA) ........................................................................................... 21
3.3.6.
Comparison of topologies............................................................................................. 21
PAE enhancement method .......................................................................................................... 26
4.1.
Dynamic bias ....................................................................................................................... 26
4.2.
Stage bypass in different circuit topologies.......................................................................... 28
4.2.1.
Stage bypass in conventional multistage PA ................................................................ 28
4.2.2.
Linear switched Doherty amplifier ............................................................................... 29
4.2.3.
Stage bypass in BA. ..................................................................................................... 30
4.2.4.
Distinguished stage bypass in DA ................................................................................ 31
4.3.
Spectrum aggregation and load balancing ............................................................................ 31
IV
5.
6.
Distributed Amplifier for mobile phone ...................................................................................... 34
5.1.
Introduction ......................................................................................................................... 34
5.2.
Design procedure of tapered DA.......................................................................................... 35
5.3.
The linearity of DA .............................................................................................................. 38
5.4.
Stability consideration ......................................................................................................... 39
5.5.
Distinguished stage bypass in DA........................................................................................ 43
Directional Distributed Amplifier based on CRLH structure ...................................................... 48
6.1.
CRLH-TL ............................................................................................................................ 48
6.2.
The diplexing DA ................................................................................................................ 49
6.3.
Linear tapered diplexing DA................................................................................................ 51
6.4.
Circuit application discussion .............................................................................................. 56
6.5.
PCB demonstrator ................................................................................................................ 56
6.5.1.
Circuit description ........................................................................................................ 57
6.5.2.
Measurement results ..................................................................................................... 58
6.6.
6.6.1.
Circuit description ........................................................................................................ 66
6.6.2.
Simulation results ......................................................................................................... 68
6.7.
7.
On-chip demonstrator .......................................................................................................... 66
Triplexing and multiplexing DA opportunity....................................................................... 71
Conclusions and future work ...................................................................................................... 74
Appendix A: The mathematical expression of IMD............................................................................ 76
Appendix B: The system identification process .................................................................................. 77
Biboliography ..................................................................................................................................... 80
Author’s publications .......................................................................................................................... 88
V
List of abbreviations
AC
Alternating Current
ACLR
Adjacent Channel Leakage Ratio
ACPR
Adjacent Channel Power Ratio
ADS
Advanced Design System
AV
Low frequency voltage gain
BO
Back-off level
BW
Band Width
C
Capacitance
CRLH
Composite Right/Left- Handed structure
DA
Distributed Amplifier
DC
Direct Current
EM
ElectroMagnetic
EVM
Error Vector Magnitude
FEM
Front End Module
FET
Field Effect Transistor
fmax
Maximal oscillation frequency
ft
Maximal transit frequency
GaAs
Gallium Arsenide
GSM
Global System for Mobile Communications
GT
Transducer power gain
HB
Harmonic Balance or High Band
HBT
Hetrojunction Bipolar Transistor
HSPA
High Speed Package Access
I
Current
IM
Intermodulation
VI
IMN
Input Matching Network
ISO
Isolation
LB
Low Band
LH
Left Handed structure
LSG
Large Signal Gain
LTE
Long Term Evolution
MAG
Maximal Available Gain
MEMS
Micro- Electro Mechanical System
OFDM
Orthogonal Frequency Division Multiplexing
OMN
Output Matching Network
PA
Power Amplifier
PAE
Power Added Efficiency
PCB
Printed Circuit Board
PHEMT
Pseudo High Electron Mobility Transistor
Q
Quality factor
QAM
Quadrature Amplitude Modulation
QPSK
Quadrature Phase Shift Keying
RF
Radio Frequency
RH
Right Handed structure
RX
Transceiver
SC-FDMA
Single Carrier Frequency Division Multiple Access
SDR/CR
Software Defined Radio/Cognitive Radio
TX
Transmitter
TL
Transmission Line
TWA
Travelling Wave Amplifier
UMTS
Universal Mobile Telecommunications System
Vcc
Supply Voltage
VII
VSWR
Voltage Standing Wave Ratio
WCDMA
Wideband Code Division Multiple Access
WLAN
Wireless Local Area Network
Z0
Characteristic impedance
β
Propagation constant
Γ
Reflecting coefficient
ηD
Drain efficiency
λ
Wavelength
θ
Phase shift
ω
Angular frequency
VIII