TABLE OF CONTENTS Scattering parameters (s-parameters) or power-wave analysis tools have been a tremendous aid in designing linear two-port amplifiers. Before s-parameters, nonreciprocal active components such as bipolar transistors, microwave field effect transistors, and diodes posed difficult problems in the optimization of RF and microwave circuit designs. For example, transistor-model parameters were difficult to extract from Y- or Z-parameter measurements, which were prone to noise and systematic measurement error at high frequencies. There were few circuit design and performance analysis CAD tools for postprocessing the microwave transistor parameters to see how they influence system design. It is difficult for modern microwave designers to imagine how a 1960s low-noise amplifier (LNA) designer could design, tune, and verify a high-volume robust receiver front-end design. The designer was partially blind without s-parameter device measurements and analysis theory such as simultaneous conjugate match, stability, and gain circles.
This situation is potentially the same situation that a present-day differential low-noise amplifier (DLNA) designer faces with the design and verification of balanced differential RF and microwave circuits. DLNAs are four-terminal multiple active device amplifiers used in balanced differential signal processing systems. This chapter develops the extension of standard two-port single-ended s-parameter techniques to four-port balanced DLNA applications.
Low-frequency applications have used balanced differential circuits for a number of years for providing high-noise immunity and for eliminating the ground connection as the signal-return path. As discussed in Chapter 1, there are three main benefits to balanced differential circuit implementations as compared to single-ended circuits, that...
