Adam Cooman

YZSHGABT
YY→ZY→SY→HY→GY→AY→BY→T
ZZ→YZ→SZ→HZ→GZ→AZ→BZ→T
SS→YS→ZS→HS→GS→AS→BS→T
HH→YH→ZH→SH→GH→AH→BH→T
GG→YG→ZG→SG→HG→AG→BG→T
AA→YA→ZA→SA→HA→GA→BA→T
BB→YB→ZB→SB→HB→GB→AB→T
TT→YT→ZT→ST→HT→GT→AT→B

From G-parameters to S-parameters

In matrix form, the formula is

S=([−Z1 k100k2] G+[k100−Z2 k2]) ([Z1 k100k2] G+[k100Z2 k2])−1\mathbf{S} =\left(\begin{bmatrix} -Z_{1}\,k_{1} & 0\\ 0 & k_{2} \end{bmatrix}\,\mathbf{G}+\begin{bmatrix} k_{1} & 0\\ 0 & -Z_{2}\,k_{2} \end{bmatrix}\right)\,{\left(\begin{bmatrix} Z_{1}\,k_{1} & 0\\ 0 & k_{2} \end{bmatrix}\,\mathbf{G}+\begin{bmatrix} k_{1} & 0\\ 0 & Z_{2}\,k_{2} \end{bmatrix}\right)}^{-1}

While for each element, we obtain

S11=G22+Z2−G11 G22 Z1+G12 G21 Z1−G11 Z1 Z2G22+Z2+G11 G22 Z1−G12 G21 Z1+G11 Z1 Z2S12=−2 G12 Z1 k1k2 (G22+Z2+G11 G22 Z1−G12 G21 Z1+G11 Z1 Z2)S21=2 G21 Z2 k2k1 (G22+Z2+G11 G22 Z1−G12 G21 Z1+G11 Z1 Z2)S22=−Z2−G22−G11 G22 Z1+G12 G21 Z1+G11 Z1 Z2G22+Z2+G11 G22 Z1−G12 G21 Z1+G11 Z1 Z2\begin{align*}S_{11} &=\frac{G_{22}+Z_{2}-G_{11}\,G_{22}\,Z_{1}+G_{12}\,G_{21}\,Z_{1}-G_{11}\,Z_{1}\,Z_{2}}{G_{22}+Z_{2}+G_{11}\,G_{22}\,Z_{1}-G_{12}\,G_{21}\,Z_{1}+G_{11}\,Z_{1}\,Z_{2}}\\S_{12} &=-\frac{2\,G_{12}\,Z_{1}\,k_{1}}{k_{2}\,\left(G_{22}+Z_{2}+G_{11}\,G_{22}\,Z_{1}-G_{12}\,G_{21}\,Z_{1}+G_{11}\,Z_{1}\,Z_{2}\right)}\\S_{21} &=\frac{2\,G_{21}\,Z_{2}\,k_{2}}{k_{1}\,\left(G_{22}+Z_{2}+G_{11}\,G_{22}\,Z_{1}-G_{12}\,G_{21}\,Z_{1}+G_{11}\,Z_{1}\,Z_{2}\right)}\\S_{22} &=-\frac{Z_{2}-G_{22}-G_{11}\,G_{22}\,Z_{1}+G_{12}\,G_{21}\,Z_{1}+G_{11}\,Z_{1}\,Z_{2}}{G_{22}+Z_{2}+G_{11}\,G_{22}\,Z_{1}-G_{12}\,G_{21}\,Z_{1}+G_{11}\,Z_{1}\,Z_{2}}\\\end{align*}

The formulas are obtained with the methods explained here. The MATLAB implementation can be found in circuitconversions on Gitlab.

Definitions

[I1V2]=G[V1I2]\begin{bmatrix}I_1 \\V_2\end{bmatrix} = \mathbf{G}\begin{bmatrix}V_1 \\I_2\end{bmatrix}

[B1B2]=S[A1A2]\begin{bmatrix}B_1 \\B_2\end{bmatrix} = \mathbf{S}\begin{bmatrix}A_1 \\A_2\end{bmatrix}

The incident and reflected waves are defined as

A1=k1 (V1+I1 Z1)B1=k1 (V1−I1 Z1)A2=k2 (V2+I2 Z2)B2=k2 (V2−I2 Z2)\begin{align*}A_1 &= k_{1}\,\left(V_{1}+I_{1}\,Z_{1}\right)\qquad B_1 &= k_{1}\,\left(V_{1}-I_{1}\,Z_{1}\right)\\A_2 &= k_{2}\,\left(V_{2}+I_{2}\,Z_{2}\right)\qquad B_2 &= k_{2}\,\left(V_{2}-I_{2}\,Z_{2}\right)\\\end{align*}

with Z0,iZ_{0,i} the reference impedance for port ii and kik_i defined as

ki=12ℜ(Z0,i)ki=αℜ(Z0,i)2∣Z0,i∣k_i=\frac{1}{2\sqrt{\Re\left( Z_{0,i}\right) }}\qquad k_i=\alpha\frac{\sqrt{\Re\left( Z_{0,i} \right) }}{2\left|Z_{0,i}\right|}

depending on whether you are using power- or pseudowaves.