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 computer-aided design (CAD) programs.

S-parameters 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 S-parameters of a one or two-port 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.

This chapter focuses on microwave amplifier circuit design. A simple microwave amplifier consists of an active device, such as a transistor, an input and output-matching circuit, and a power supply bias circuit. We begin with the two-port S-parameters for RF and microwave transistors and an operating environment for the finished amplifier. The transistor S-parameters 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.

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 two-port 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.

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 high-frequency applications. These amplifiers are intended for applications in which the signal is small and the amplifier circuit is linear.