Question

The conditions under which a passive two-port network represented by ABCD is reciprocal and symmetrical are

1. AD – BC = 1; A = C
2. AD – BC = 0; A = D
3. AD – BC = 1; D = A
4. AD – BC = 0; C = B

Answer 1

Correct Answer - Option 3 : AD – BC = 1; D = A

A two-port network is said to be symmetrical if the input and output ports can be interchanged without altering the port voltages and currents.

A network is said to be reciprocal if the ratio of the response to the excitation is invariant to an interchange of the positions of the excitation and response of the network.

Conditions of reciprocity and symmetry in terms of different two-port parameters are:

Two Port Parameters	Condition for Symmetry	Condition for Reciprocal
Z Parameters	Z11 = Z22	Z12 = Z21
Y parameters	Y11 = Y22	Y12 = Y21
ABCD parameters	A = D	AD - BC = 1
H parameters	h11h22 - h12h21 = 1	h12 = -h21