Small Signal Microwave Amplifier Design
This book explains techniques and examples for designing stable amplifiers for highfrequency applications, in which the signal is small and the amplifier circuit is linear. An indepth discussion of linear network theory provides the foundation needed to develop actual designs. Examples throughout the book will show you how to apply the knowledge gained in each chapter leading to the complex design of low noise amplifiers. Exercises at the end of each chapter will help students to practice their skills. The solutions to these design problems are available in an accompanying solutions booklet (Small Signal Microwave Amplifier Design: Solutions).
Inspec keywords: microwave amplifiers; network synthesis
Other keywords: output networks; highfrequency amplifier design; small signal microwave amplifier design; microwave frequencies; RF frequencies; input networks
Subjects: Amplifiers; Analogue circuit design, modelling and testing
 Book DOI: 10.1049/SBEW032E
 Chapter DOI: 10.1049/SBEW032E
 ISBN: 9781884932069
 eISBN: 9781613530955
 Page count: 278
 Format: PDF

Front Matter
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1 Introduction
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In this book, we assume that the reader has an engineer's basic understanding of electronics and some experience with transmission lines and electromagnetics. The RF and microwave circuits mentioned here only apply to the highfrequency response of the circuit and the designer will still need to supply the correct bias currents and voltages. The designer will also need to know how to use capacitors to block bias currents, or bypass bias components to prevent inadvertent feedback.

2 Introduction to Networks
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This chapter introduces three types of circuit parameters describing electronic networks. These parameters, called the Z, Y, and chain parameters, are common in designing circuits up to two gigahertz but are not often used in microwave circuit design. We begin with these parameters because they are easy to understand and used in most computeraided design (CAD) programs.

3 Introduction to SParameters
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This chapter describes circuit parameters that are based on power flow. The opencircuit Zparameters and the shortcircuit Yparameters are used in many of the circuit computeraided design (CAD) programs. We can calculate the network parameters of circuits made from wellknown components such as resistors, capacitors, and inductors. However, the circuit parameters of transistors and other types of semiconductors must be measured. As frequencies rise, it becomes increasingly difficult to measure voltage and current on the ports of a circuit.

4 SParameter Circuit Analysis
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Sparameters and transmission lines are the main tools utilized in microwave amplifier design. Before we can design our own circuits, however, we need to study some methods of analysis. In this chapter, we will use mathematical and graphical tools to analyze circuits. These circuits will be networks composed of one or more elements. The methods shown in this chapter assume that the Sparameters of a one or twoport have been found or measured. We will concentrate on analyzing the circuit response of a network and groups of interconnected networks. The tools presented in this chapter as well as in Chapter 3 lay the groundwork for the following chapters on synthesizing microwave circuits and amplifiers.

5 Narrowband Circuit Synthesis
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This chapter discusses the design of impedancematching circuits. It often is necessary to connect components or networks that have different impedances. If these components were to be indiscriminately connected, energy would be reflected between them, causing energy loss and other unwanted effects. We can use impedancematching circuits between components in a network so that power is not 'bounced around' between them. Impedancematching circuits are used in two ways. The most common application is to eliminate reflections between components or networks. Most transistors are not matched to the transmission lines that connect them; hence, small circuits are designed to match the input and output impedance of the transistor to the input and output transmission lines.

6 Amplifier Design
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This chapter focuses on microwave amplifier circuit design. A simple microwave amplifier consists of an active device, such as a transistor, an input and outputmatching circuit, and a power supply bias circuit. We begin with the twoport Sparameters for RF and microwave transistors and an operating environment for the finished amplifier. The transistor Sparameters along with some mapping functions are used to determine the correct impedance, which will terminate the input and output of the transistor. Matching circuits are designed to transform these impedances to the actual source and load impedances where the amplifier is to be used.

7 Introduction to Broadband Matching
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This chapter focuses on broadband matching methods developed for broadband applications and introduces some of the techniques that are effective for broadband amplifier design. The terms wideband and ultrawideband are used loosely in the amplifier design community.

8 Introduction to Noise
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Noise analysis of microwave circuits and systems has been a research issue for many decades. A circuit's noise performance is given in terms of noise figure or noise temperature. The signal energy exiting a generator or antenna is amplified or attenuated in passing from the input to the output of a twoport network. Along this signal path, thermal energy in the components add noise to the signal. In some applications, e. g., in a radar receiver, it is necessary to anticipate the amount of noise that circuits add to the signal path. When receiving a radar pulse, the receiver will also add some noise to the signal. This added noise masks the pulses, which will make it more difficult to detect them. When the ratio of pulse power to noise becomes too low, the pulse and the target cannot be detected. Thus, a receiver that adds the least amount of noise possible is desirable. There is a similar requirement for a microwave radio. A microwave signal is modulated with data and transmitted from an antenna on top of a mountain. A receiver on a neighboring mountain ridge receives this signal and extracts the data. When the signal becomes overwhelmed by noise, however, the data stream can no longer be reconstructed.

9 Low Noise Amplifier Design
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In Chapter 8, we introduced noise and noise figure in mathematical terms. In this chapter, we will show how this information applies to transistor amplifiers. Twoport Sparameters and noise characteristics are published by microwave manufacturers to ensure that the transistor can be easily utilized in an amplifier design. We have introduced a mathematical representation of noise created by a twoport. The noise added by the twoport is characterized by a few quantities that are essential to the twoport and the input reflection coefficient. Some transistor data sheets show noise parameters for a particular transistor at several frequencies.

10 Summary
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This chapter presents the summary of all previous chapters of this book. In the previous chapters, we provided tools and techniques for designing stable amplifiers for highfrequency applications. These amplifiers are intended for applications in which the signal is small and the amplifier circuit is linear.

Back Matter
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