Modern Microwave Circuits
Including over 1,200 equations and more than 300 illustrations, this invaluable book explains how microstrip circuits are built and provides in-depth coverage of computer-aided simulation and underlying theories.
TABLE OF CONTENTS Modern Microwave Circuits
1.4: CIRCUIT PARAMETERS
1.4 CIRCUIT PARAMETERS
There are four types of circuit parameters that are commonly used in microwave engineering to uniquely characterize linear microwave circuits: scattering parameters ( S-parameters), Y-parameters, Z-parameters, and ABCD-parameters. Among them, S-parameters are the most frequently used in microwave engineering because their derivation is based on forward- and backward-traveling waves on terminal transmission lines that are easy to measure using directional couplers. On the other hand, Z- (or Y-) and ABCD-parameters are based on terminal voltage and current values that are very difficult to measure directly at microwave frequencies. However, they have applications especially in the modeling of passive circuits due to the relatively simple relationship that exists between the equivalent models and relevant circuit parameters. By using Z- or Y-parameters, it is easy to extract the component values of equivalent lumped-circuit models (even by inspection in most cases), and circuit resonances are more eminent in those parameters.
In the following sections, we will provide definitions of these most commonly used circuit parameters with their applications on some simple circuits.
1.4.1 Scattering Parameters
Scattering parameters are defined using incident and reflected waves on transmission lines that connect a microwave circuit to external circuits [8] , [9]. To give the definition, let us assume a two-port network whose ports are connected to transmission lines as shown in Figure 1.13. We will use voltage waves on the terminals to define the S-parameters of this circuit. Note that the...
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