Question 17.4: The impedance parameters of a two-port network are z11 = 30Ω......

The impedance matrix for the two-port network is

[\pmb{z}]=\begin{bmatrix}30 &10\\10 &20 \end{bmatrix}

The admittance matrix is the inverse of the impedance matrix and is found as

[\pmb{y}]=[\pmb{z}]^{-1}=\frac{adj[\pmb{z}]}{det[\pmb{z}]}=\frac{\begin{bmatrix}20 &-10\\-10 &30 \end{bmatrix} }{500}

=\begin{bmatrix}0.04& -0.02\\-0.02& 0.06 \end{bmatrix}

Hence, the admittance parameters are y_{11} = 40  mS, y_{12} = y_{21} = -20  mS, and y_{22} = 60 mS.