Editing Two-port network (section)

==Admittance parameters (''y''-parameters)==
[[Image:Y-parameter two-port.PNG|thumbnail|300px| Figure&nbsp;5: Y-equivalent two port showing independent variables {{math|''V''{{sub|1}}}} and {{math|''V''{{sub|2}}}}. Although resistors are shown, general admittances can be used instead.]]
{{main|Admittance parameters}}

:<math> \begin{bmatrix} I_1 \\ I_2 \end{bmatrix} = \begin{bmatrix} y_{11} & y_{12} \\ y_{21} & y_{22} \end{bmatrix} \begin{bmatrix} V_1 \\ V_2 \end{bmatrix} </math>

where

:<math>\begin{align}
  y_{11} &\mathrel{\stackrel{\text{def}}{=}} \left. \frac{I_1}{V_1} \right|_{V_2 = 0} &
  y_{12} &\mathrel{\stackrel{\text{def}}{=}} \left. \frac{I_1}{V_2} \right|_{V_1 = 0} \\
  y_{21} &\mathrel{\stackrel{\text{def}}{=}} \left. \frac{I_2}{V_1} \right|_{V_2 = 0} &
  y_{22} &\mathrel{\stackrel{\text{def}}{=}} \left. \frac{I_2}{V_2} \right|_{V_1 = 0}
\end{align}</math>

All the ''Y''-parameters have dimensions of [[Siemens (unit)|siemens]].

For reciprocal networks {{math|1=''y''{{sub|12}} = ''y''{{sub|21}}}}.  For symmetrical networks {{math|1=''y''{{sub|11}} = ''y''{{sub|22}}}}.  For reciprocal lossless networks all the {{math|''y''{{sub|mn}}}} are purely imaginary.<ref name=Matt29/>