Introduction to Electric Circuits

214 Two-port networks

O

v, T

O

Figure 9.7

1~! I2

2-port

network

! I2

O+

O-

and are also particularly useful for the analysis of cascaded two-port networks,
such as are frequently encountered in power systems.
The dependent variables are given by
V 1 --AV2 + B12 (9.33)

I1 = CV2 + DI2 (9.34)

In matrix form

The ABCD matrix is called the transfer matrix of the network. The parameters
for this set are measured by open circuit and short circuit tests on the output
port and are defined as follows:

9 A is measured as V1/V2 with I2 - 0 and, being the ratio of two voltages, it is

dimensionless:

A = (gl/g2)li2= o (9.36)

9 B is measured as V1/I2 with V2 = 0 and, being a ratio of volts to amperes,

has the dimensions of impedance:

B = (V~/I2)l,z=o (9.37)

9 C is measured as I1/V2 with I2 = 0 and, being the ratio of amperes to volts,

it has the dimensions of admittance"

C = (I1/V2)112= o (9.38)

9 D is measured as I~/I2 with V2 = 0 and, being the ratio of two currents, it is

dimensionless:

D = (I~/I2)lv~=o (9.39)

9.7 THE INVERSE TRANSMISSION PARAMETERS

Set 6: If V~ and I~ are the independent variables, then the dependent variables

are given by