[...]... the power consumption of the PA easily dominates over all other electronics and digital processing in a mobile terminal Therefore, high efficiency is essential to extend the operation time of the terminals In fixed-point wireless nodes (e.g., in base stations), efficiency is also important, because the transmitted power levels are essentially higher than in terminals 1 2 1.2 Distortion in RF Power Amplifiers. .. result of which a linear system with memory is introduced Nonlinear effects in electrical systems are caused by one or more nonlinear elements A system comprising linear and nonlinear resistors is known as a memoryless nonlinear system Nonlinear systems with memory, on the other hand, include at least one nonlinear element and one memory introducing element (or a single element introducing both) Table... nonlinear effects in RF power amplifiers, Chapter 2 discusses certain theoretical aspects related to amplifier circuits Since RF power amplifiers are nonlinear, bandwidth-dependent circuits with Introduction 7 memory, it is important to define nonlinearity, bandwidth dependency, and memory, and to examine their associated effects Chapter 2 also introduces a direct calculation method for deriving equations... resulting in higher order distortion components than the degree of the nonlinearity suggests 6 Distortion in RF Power Amplifiers b Distortion is originally generated in form of current, which is converted to a voltage by terminal impedances Thus, the phase and amplitude of the distortion components can be strongly influenced by the terminal impedances, and especially by the impedances of the biasing networks... polynomial predistorter or other simple linearization technique can be significantly increased without a substantial increase in dc power consumption Hence, good cancellation performance can be achieved by linearization techniques that consume little power, enabling the design of linear yet power- efficient PAs Finally, additional supporting information is collected in the appendixes Appendixes A and B... the bandwidth, power level, and the peak power to average power ratio (crest factor) all increase The efficiency of these kinds of power amplifiers is very low, and due to higher total transmitted power, this results in very high power dissipation and serious cooling problems 1.3 Linearization and Memory Effects The goal of this book is to improve the conceptual understanding needed in the development... d The polynomial models can also be used in harmonic balance simulators 5 This book also introduces some circuit techniques for reducing memory effects in power amplifiers The standard method of minimizing memory effects involves attempting to maintain impedances at a constant level over all frequency bands Unfortunately, other design requirements often interfere with this aim and cause memory effects... bandwidth-dependent phenomena 9 10 2.1 Distortion in RF Power Amplifiers Classification of Electrical Systems Electrical systems can be classified into four main categories as listed in Table 2.1: linear and nonlinear systems with or without memory An example of a linear memoryless system is a network consisting of linear resistors Addition of an energy storage element such as a linear capacitance causes memory,... of obtaining this information This is accomplished using pulsed S-parameter measurements over a range of terminal voltages and temperatures 1.5 Outline of the Book The main emphasis of this book is on developing a detailed understanding of the physics underlying distortion mechanisms, while keeping the mathematical formulations in a tractable form To lay the groundwork for the analysis of nonlinear... replacing every nonlinear circuit element (input capacitance, gm, and so forth) by the parallel combination of a linear circuit element (small-signal capacitance, small-signal gm, and so forth) and a nonlinear current source This leads to two important findings: a There are several sources of distortion, and the distortion generated in any of these sources can undergo subsequent mixing processes, resulting . y0 w0 h0" alt="" Distortion in RF Power Amplifiers For a listing of recent titles in the Artech House Microwave Library, turn to the back of this book. Distortion in RF Power Amplifiers Joel Vuolevi Timo. Library Cataloguing in Publication Data Vuolevi, Joel Distortion in RF power amplifiers. — (Artech House microwave library) 1. Power amplifiers 2. Amplifiers, Radio frequency 3. Radio— Interference I Distortion in RF Power Amplifiersvi 2.6 Summary 39 2.7 Key Points to Remember 41 References 41 Chapter 3 Memory Effects in RF Power Amplifiers 43 3.1 Efficiency 43 3.2 Linearization 45 3.2.1 Linearization