Question

The condition for symmetry in ABCD two-port parameters is

• A. \(A=B\)
• B. \(A=D\)
• C. \(B=C\)
• D. \(B=D\)

Hint:

For ABCD parameters: \[ \text{Reciprocity: } AD-BC=1 \] \[ \text{Symmetry: } A=D \] These two conditions are among the most frequently asked results in network theory.

Answer 1

The Correct Option is B

Concept: A two-port network can be represented using transmission parameters (ABCD parameters): \[ \begin{bmatrix} V_1 \\ I_1 \end{bmatrix} = \begin{bmatrix} A & B \\ C & D \end{bmatrix} \begin{bmatrix} V_2 \\ -I_2 \end{bmatrix}. \] Special conditions are used to identify whether the network is reciprocal or symmetric.

Step 1: Recall the condition for reciprocity.
For a reciprocal network, \[ AD-BC=1. \] This condition is frequently used in network analysis.

Step 2: Recall the condition for symmetry.
A network is symmetric when interchanging input and output ports does not change its electrical behavior. For a symmetric two-port network, \[ A=D. \]

Step 3: Identify the correct option.
Comparing with the given options, \[ \boxed{A=D} \] is the required condition. Therefore, the correct answer is option (B).