Distributed Power Amplifiers for RF and Microwave Communications

441 Pages·2015·17.03 MB·English

Distributed Power Amplifiers for RF and
Microwave Communications
For a listing of recent titles in the
Artech House Microwave Library,
turn to the back of this book.
Distributed Power Amplifiers for RF and
Microwave Communications
Narendra KumarAndrei Grebennikov
Library of Congress Cataloging-in-Publication DataA catalog record for this book is available from the
U.S. Library of Congress
British Library Cataloguing in Publication DataA catalog record for this book is available from the British
Library.
ISBN-13: 978-1-60807-831-8
Cover design by John Gomes
© 2015 Artech House685 Canton St.Norwood, MA 02062
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10 9 8 7 6 5 4 3 2 1
Contents
Preface
CHAPTER 1
Two-Port Network Parameters
1.1 Impedance, Admittance, and ABCD Matrices
1.2 Scattering Parameters
1.3 Conversions Between Two-Port Networks
1.4 Practical Two-Port Networks
1.4.1 Single-Element Networks
1.4.2 π- and T-Type Networks
1.5 Lumped Elements
1.5.1 Inductors
1.5.2 Capacitors
1.6 Transmission Lines
1.6.1 Basic Parameters
1.6.2 Microstrip Line
1.6.3 Coplanar Waveguide
1.7 Noise Figure
References
CHAPTER 2
Power Amplifier Design Fundamentals
2.1 Main Characteristics
2.2 Impedance Matching
2.3 Gain and Stability
2.4 Basic Classes of Operation
2.5 Nonlinear Active Device Models
2.5.1 LDMOSFETs
2.5.2 GaAs MESFETs and GaN HEMTs
2.5.3 Low-Voltage and High-Voltage HBTs
2.6 DC Biasing
2.7 Impedance Transformers and Power Combiners
2.8 Directional Couplers
References
CHAPTER 3
Overview of Broadband Power Amplifiers
3.1 Bode-Fano Criterion
3.2 Matching Networks with Lumped Elements
3.3 Matching Networks with Mixed Lumped and Distributed Elements
3.4 Matching Networks with Transmission Lines
3.5 Lossy Matching Circuits
3.6 Push-Pull and Balanced Power Amplifiers
3.6.1 Basic Push-Pull Configuration
3.6.2 Baluns
3.6.3 Balanced Power Amplifiers
3.7 Practical Broadband RF and Microwave Power Amplifiers
References
CHAPTER 4
Distributed Amplification Concept and Its Design Methodology
4.1 Concept of Distributed Amplification
4.2 Image Impedance Method
4.3 Theoretical Analysis of Distributed Amplification
4.3.1 Analytical Approach to Two-Port Theory
4.3.2 Analytical Approach to Admittance Theory
4.3.3 Analytical Approach to Wave Theory
4.4 Gain/Power-Bandwidth Trade-Off
4.5 Practical Design Methodology
4.5.1 Design Goal/Specifications
4.5.2 Device Selection
4.5.3 Theoretical Analysis (Zero-Order Analysis)
4.5.4 Analysis with VCCS and Cgd (First-Order Analysis)
4.5.5 DC Biasing Circuitry Design
4.5.6 Device Modeling of GaN HEMTs
4.5.7 Loading Device into Distributed Output Network
4.5.8 Synthesizing Distributed Input/Output Networks
4.5.9 Layout Design
4.5.10 Full-Wave Simulation/Layout Optimization
References
CHAPTER 5
Efficiency Analysis of Distributed Amplifiers
5.1 Efficiency Limitations of Distributed Amplifiers
5.2 Virtual Impedance Analysis Using Multicurrent Sources
5.3 Simulation Analysis of Efficiency Analysis
5.4 Design Example of High-Efficiency Distributed Amplifier
5.5 Broadband Impedance Transformer Design
References
CHAPTER 6
Stability Analysis of Distributed Amplifiers
6.1 Motivation for Conducting Stability Analyses
6.2 Method of Stability Analysis
6.2.1 K-Factor Stability of a Two-Port Network
6.2.2 Feedback and NDF Factor
6.2.3 Pole-Zero Identification Method
6.3 Analysis and Conditions of Stability in Distributed Amplifiers
6.4 Parametric Oscillation Detection in Distributed Amplifiers
6.4.1 Stability Analysis of Distributed Amplifiers
6.4.2 Circuit Stabilization Technique
References
CHAPTER 7
Implementation of Distributed Amplifiers
7.1 Vacuum-Tube Distributed Amplifier
7.2 Microwave GaAs FET Distributed Amplifiers
7.2.1 Basic Configuration with Microstrip Lines
7.2.2 Basic Configuration with Lumped Elements
7.2.3 Capacitive Coupling
7.3 Tapered Distributed Amplifier
7.4 Power Combining
7.5 Bandpass Configuration
7.6 Parallel and Series Feedback
7.7 Cascode Distributed Amplifiers
7.8 Extended Resonance Technique
7.9 Cascaded Distributed Amplifiers
7.10 Matrix Distributed Amplifiers
7.11 CMOS Distributed Amplifiers
References
CHAPTER 8
Distributed Power Amplifiers
8.1 Dual-Fed Distributed Power Amplifier
8.2 Tapered Termination Cascaded Distributed Power Amplifier
8.3 Vectorially Combined Distributed Power Amplifier
8.3.1 Overview of Vectorially Combined DPA with Load Pull
Determination
8.3.2 Impedance Transformer Design via Real-Frequency Technique
8.4 Drain-Line High-Power Device Loading Compensation
References
About the Authors
Index
Preface
The main objective of this book is to present all relevant information and
comprehensive design methodologies for wideband amplifiers—
specifically, distributed amplifiers in general and their main components in
particular—in different RF and microwave applications including well-
known historical and recent architectures, theoretical approaches, circuit
simulation, and practical implementation techniques. This comprehensive
book will be useful for lecturing to promote a systematic way of thinking
with analytical calculations and practical verification of wideband
amplifiers providing the link between theory and practice of RF and
microwave distributed amplifiers. Therefore, this book is recommended to
academicians, researchers, and professors, and provides good coverage
to practicing designers and engineers because it contains numerous well-
known and novel practical circuits, architectures, and theoretical
approaches with a detailed description of their operational principles.
Chapter 1 introduces basic two-port networks by describing the
behavior of two-port parameters including impedance, admittance and
ABD matrices, scattering parameters, conversion between two-port
networks, and practical two-port circuits. Lumped elements, particularly
inductors and capacitors, are also discussed. Monolithic implementation of
lumped inductors and capacitors is usually required at microwave
frequencies and for portable devices. Transmission-line theory is
introduced and followed by design formulas; curves are given for several
types of transmission lines including striplines, microstrip lines, slotlines,
and coplanar waveguides. Noise phenomena such as noise figure, additive
white noise, low-frequency fluctuations, and flicker noise are discussed at
the end of the chapter.
In Chapter 2, the design fundamentals of power amplifiers are
presented. Design is generally a complicated procedure where it is
necessary to provide simultaneously accurate active device modeling,
effective impedance matching depending on the technical requirements
and operating conditions, stability during operation, and simplicity in
practical implementation. The main characteristics, principles, and
impedance matching techniques are described. The quality of power
amplifier designs is evaluated by determining the realized maximum
power gain under stable operating conditions with minimum amplifier
stages, and the requirement of linearity or high efficiency can be
considered where it is needed. For stable operation, it is necessary to
evaluate the operating frequency domains where the active device may
be potentially unstable. To avoid parasitic oscillations, the stabilization
circuit technique for different frequency domains (from low frequencies up
to high frequencies close to the device transition frequencies) is
discussed. The device bias conditions, which are generally different for
linearity or efficiency improvement, depend on the power amplifier
operating class and the type of active device. The basic classes, Classes
A, AB, B, and C, of power amplifier operations are introduced, analyzed,
and illustrated. All necessary steps to provide an accurate device
modeling procedure, starting with the determination of a device’s small-
signal equivalent circuit parameters, are described. A variety of nonlinear
models for MOSFET, MESFET, HEMT, and BJT devices including HBTs,
which are very attractive for modern monolithic microwave integrated
circuits, are described. The procedure for designing for dc biasing is
discussed and, finally, an overview of impedance transformers and power
combiners and directional couplers is given.
An overview of broadband power amplifiers is given in Chapter 3. The
chapter begins with the Bode-Fano criterion, explaining about the
bandwidth analysis of a broadband power amplifier. A matching circuit is
crucial to providing maximum power transfer from one point to another
point, in which transformation using lumped elements, mixed-lumped,
and distributed elements will be discussed to give choices to designers
trying to meet technical requirements. In addition, transformation with
transmission lines and power amplifiers with lossy compensation networks
are discussed in this chapter. Push-pull and balanced power amplifier
topologies are discussed to give us an understanding of circuit principles
and design implementation. At the end of the chapter, several practical
broadband RF and microwave power amplifier topologies are introduced.
Chapter 4 introduces the concept of distributed amplification by means
of gain and the bandwidth product of an amplifier stage. The concept
explains how the gain stages are connected such that their capacitances
are isolated, yet the output currents still combine in an additive fashion.
The resulting topology forms an artificial transmission line and is
extended to an image impedance method. A theoretical analysis of the
distributed amplifier is presented with several approaches (i.e., two-port,
admittance, and wave theories). The approach via two-port theory
considers only a unilateral small-signal transistor model. The admittance
method is more general because there is no simplifying assumption
regarding the transistor model. Finally, the wave theory method, which
uses the normalized transmission matrix approach, has the advantage of
displaying the traveling wave nature of a distributed amplifier. The
gain/power-bandwidth trade-off is discussed to give an overview of the
influence a simple bandpass amplifier circuit has over the bandwidth
response. The design methodology for a practical distributed amplifier is
presented, which provides guidelines for designers who desire to realize a
distributed amplifier in a timely manner, without any tedious optimization
at the board level. Layout design guidelines (PCB selection, full-wave
simulation, layout optimization, via-hole simulation, and so forth) should
be taken into consideration during the design stage.
Chapter 5 introduces the limitations of the conventional distributed
amplifier and an analytical approach for achieving high-efficiency
performance in distributed amplifiers, where the multicurrent sources
must be combined to a single load by presenting optimum virtual
impedance to each current source. The systematic generalized design
equations are given and a summary of the equations are presented in
table form. Obviously, to keep the output impedance of the distributed
amplifier closer to 50Ω (and to avoid additional impedance
transformation), the magnitude and phase properties of the current
source (or transistor) must be adjusted. The adjustment can be made
according to the designer’s need, the complexity of the design circuit, and
so forth. A few design examples of high-efficiency distributed amplifiers
are discussed. A parallel coupled-line approach is adopted as a test
vehicle for broadband impedance transformation purposes. As an
important point, note that the design concept presented provides
appropriate guidelines for maximizing the efficiency of a distributed
amplifier.
The basic principle and motivation for using stability analyses (with K-
factor, feedback and NDF factor, and pole-zero identification methods)
with the intent of understanding the strategies are discussed in Chapter 6.
The pole-zero identification technique is applied to a distributed amplifier
to provide an understanding of the origin of oscillation due to the
multiple-loop nature. The analysis considers the distributed amplifier to
be a basic feedback oscillator circuit; that is, a Hartley oscillator using a
simplified transistor model. The origin of the distributed amplifier
oscillation can be traced to the transconductance nature or multiple-loop
nature of the feedback network. An explanation of odd-mode oscillation in
a distributed amplifier topology is discussed, which is useful for practical
applications. Large-signal stability analysis based on pole-zero
identification is applied to analyze the parametric oscillations in high-
efficiency distributed amplifiers. The parametric oscillation is correlated to
a gain expansion phenomenon that directly affects the critical poles of the
circuit. Large-signal stability analysis is then used to stabilize a high-
efficiency distributed amplifier with a minimum impact on circuit
performance.
Chapter 7 introduces the design implementation of a distributed
amplifier. A distributed amplifier overcomes the difficulty of conventional
amplifiers by offering a broadband frequency response. The concept of a
vacuum-tube distributed amplifier based on combining interelectrode
capacitances with series wire inductors is discussed using an analytical
approach. A distributed amplifier with a microwave GaAs FET, including
configuration with microstrip lines, lumped elements, and capacitive
coupling, is discussed. A tapered distributed amplifier offers high-
efficiency performance and eliminates dummy termination. Other
implementations of distributed amplifiers such as power combining,
bandpass, and parallel and series feedback configurations are discussed.
A cascade distributed amplifier topology minimizes the degeneration at
higher frequencies, improves the isolation between inputs and outputs,