Читать книгу Handbook of Microwave Component Measurements - Joel P. Dunsmore - Страница 132

These reflection conversions are already well known as the models represented by the Smith chart, but a similar conversion can be performed for a simple transmission measurement. In this case, the circuits of Figure 2.40c and Figure 2.40d are the reference circuits for these conversions. They are useful when analyzing the series element models, such as coupling capacitors, and the models for series resistors and inductors. The underlying computation for the transmission conversions is

(2.26)

The Z‐transmission conversion would be well suited to view the series resistance of a coupling capacitor. The Y‐transmission would show the resistive value of a series‐mounted surface‐mount technology (SMT) resistor with a shunt capacitance as a constant conductance with a reactance increasing as 2πf, forming a straight reactance line.

These conversions are often confused with conversion to Y‐ or Z‐parameters, but they are not, in general, related. These provide simple modeling functions based on a single S‐parameter, whereas the Y‐, Z‐, and related parameters provide a matrix result and require knowledge of all four S‐parameters as well as the reference impedance. These other matrix parameters are described in the next section.