Topic: Electromagnetics
For a two port network to be reciprocal, its Scattering parameters must satisfy the following condition, for $i=1,2; j=1,2$
- A. $S_{ij}=S_{ji}(i\ne j)$
- B. $S_{ij}=S_{ji}(i=j)$
- C. $S_{ij}=1/S_{ji}(i\ne j)$
- D. $S_{ij}=S_{ji}*(i=j)$
Answer: A. $S_{ij}=S_{ji}(i\ne j)$
Explanation: For a two-port network to be reciprocal, the transmission coefficients in both directions must be equal. Therefore, the scattering matrix must be symmetric, which means $S_{ij} = S_{ji}$ for $i \ne j$ (i.e., $S_{12} = S_{21}$).