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 T-parameters to G-parameters

In matrix form, the formula is

G=([0012k212k2]+[12Z1k112Z1k100]T)([12k112k100]T+[0012Z2k212Z2k2])1\mathbf{G} =\left(\begin{bmatrix} 0 & 0\\ \frac{1}{2\,k_{2}} & \frac{1}{2\,k_{2}} \end{bmatrix}+\begin{bmatrix} \frac{1}{2\,Z_{1}\,k_{1}} & -\frac{1}{2\,Z_{1}\,k_{1}}\\ 0 & 0 \end{bmatrix}\,\mathbf{T}\right)\,{\left(\begin{bmatrix} \frac{1}{2\,k_{1}} & \frac{1}{2\,k_{1}}\\ 0 & 0 \end{bmatrix}\,\mathbf{T}+\begin{bmatrix} 0 & 0\\ -\frac{1}{2\,Z_{2}\,k_{2}} & \frac{1}{2\,Z_{2}\,k_{2}} \end{bmatrix}\right)}^{-1}

While for each element, we obtain

G11=T11+T12T21T22Z1(T11+T12+T21+T22)G12=2Z2k2(T11T22T12T21)Z1k1(T11+T12+T21+T22)G21=2k1k2(T11+T12+T21+T22)G22=Z2(T11T12+T21T22)T11+T12+T21+T22\begin{align*}G_{11} &=\frac{T_{11}+T_{12}-T_{21}-T_{22}}{Z_{1}\,\left(T_{11}+T_{12}+T_{21}+T_{22}\right)}\\G_{12} &=-\frac{2\,Z_{2}\,k_{2}\,\left(T_{11}\,T_{22}-T_{12}\,T_{21}\right)}{Z_{1}\,k_{1}\,\left(T_{11}+T_{12}+T_{21}+T_{22}\right)}\\G_{21} &=\frac{2\,k_{1}}{k_{2}\,\left(T_{11}+T_{12}+T_{21}+T_{22}\right)}\\G_{22} &=\frac{Z_{2}\,\left(T_{11}-T_{12}+T_{21}-T_{22}\right)}{T_{11}+T_{12}+T_{21}+T_{22}}\\\end{align*}

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

Definitions

[A1B1]=T[B2A2]\begin{bmatrix}A_1 \\B_1\end{bmatrix} = \mathbf{T}\begin{bmatrix}B_2 \\A_2\end{bmatrix}

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

The incident and reflected waves are defined as

A1=k1(V1+I1Z1)B1=k1(V1I1Z1)A2=k2(V2+I2Z2)B2=k2(V2I2Z2)\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=12(Z0,i)ki=α(Z0,i)2Z0,ik_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.