TABLE OF CONTENTS Scattering parameters (s-parameters) greatly assist in the design, analysis, simulation and measurement of many linear RF and microwave active devices such as transistors and diodes, and of many passive components such as transmission lines, resistors, capacitors, inductors, and others. Moreover, s-parameter measurement techniques characterize active devices terminated in finite impedances (typically 50 ?.) commonly seen in microwave systems. Other small-signal parameters used in linear analog circuit design such as z-parameters and y-parameters require opens and short circuits during measurement. These parameters are defined and developed in Section 6.2. Microwave design requires s-parameter-based impedance matching to optimize noise and gain. Proper microwave circuit analysis can require designers to calculate parameters such as two-port simultaneous conjugate match ( G t max) and stability ( K). These calculations are complex without the simplification of s-parameters. Moreover, the measured data that can be used for these calculations comes in the form of s-parameters.
This chapter extends the definitions of standard single-ended two-port s-parameters to more complex four-port (differential) microwave circuits and signal processing applications. Single-ended RF/microwave systems have an input port and an output port both referenced to ground. In contrast, differential microwave circuits have even numbers of ports taken in pairs. A four-port differential circuit has one pair of ports at the input and one pair at the output. Signal levels are referenced between the inputs of the pairs of ports.
The four-port differential system can be a far more "natural" system for the microwave IC designer. For...
