Introduction to Electric Circuits

222 Two-port networks

The ABCD-parameters of a T-network

T-networks arc commonly used for LC filters and for attenuation sections.

Example 9.10

Obtain the ABCD-parameters for the T-network shown in Fig. 9.15.

11

V1

--0

Z Z

I I

I2

I--~-o +

v2

O-

Figure 9.15

Solution

This network may be considered to be made up of a series impedance network
followed by a shunt admittance network and then another series impedance
network all connected in cascade. We can then make use of the transfer
matrices in Equations (9.49) and (9.51) to write down the matrix equation for
this circuit:

By multiplication of the first two transfer matrices we get

V~ (I+ZY) (O+Z)

Multiplying the remaining two transfer matrices we have

IV,] = [(1+ ZY+ O)

I1 (Y + O) (zY + 1) /2

Finally

I~ I+ZYJ 12

The transmission parameters for this network are therefore

A - D = I + ZY; B = 2Z + Z2Y; C= Y