Читать книгу Introduction To Modern Planar Transmission Lines - Anand K. Verma - Страница 104

The [Z], [Y], and [ABCD] matrix descriptions of any microwave network or component are based on the port voltage and port current relations. The evaluation of these parameters requires the short‐circuiting and open‐circuiting of the ports. At the microwave frequency, usually, it is difficult to measure the voltage and current. Similarly, the short‐circuiting and open‐circuiting of the ports may not be always possible at the microwave frequency. Thus, these parameters are normally not measurable quantities. However, these parameters are useful for the analysis of the microwave circuits built around the lumped and distributed circuit elements. At this stage, another kind of measurable parameters is needed to characterize the microwave circuits. At the microwave frequency, the power could be measured, and also the forward and reflected power waves could be obtained. The frequency and phase of a microwave signal are also measurable quantities. The scattering parameters, also called the S‐parameters, are defined for any two‐port network, or even the multiport microwave network, in terms of the measurable incident and reflected power waves [J.1].