Question

For a two-port network to be reciprocal, it is necessary that ……..

• A. \( z_{11} = z_{22} \) and \( y_{21} = y_{12} \)
• B. \( z_{11} = z_{22} \) and \( AD - BC = 0 \)
• C. \( h_{11} = -h_{12} \) and \( AD - BC = 0 \)
• D. \( y_{12} = y_{21} \) and \( h_{21} = -h_{12} \)

Hint:

For two-port network reciprocity, remember: \( z_{12} = z_{21} \), \( y_{12} = y_{21} \), \( h_{21} = -h_{12} \), and for ABCD parameters, \( AD - BC = 1 \).

Answer 1

The Correct Option is D

Step 1: A two-port network is reciprocal if its transmission characteristics remain the same when the input and output ports are interchanged. This imposes certain symmetry conditions on the parameter sets.

Step 2: For admittance parameters, the reciprocity condition is \( y_{12} = y_{21} \). For hybrid parameters, the condition is \( h_{21} = -h_{12} \). These ensure that the signal flow is identical in both directions.

Step 3: Checking the given options shows that only option (4) states both conditions correctly.