The T1 matrix of the device under test is found as:
\begin{equation} T_{1}=\left[\begin{matrix}A & B\\0 & 0\end{matrix}\right] \end{equation}The matrix equation for the two-port (DUT) is found as:
\begin{equation} \left[\begin{matrix}V_{i}\\I_{i}\end{matrix}\right]=\left[\begin{matrix}A V_{o} + B I_{o}\\0\end{matrix}\right] \end{equation}The source-to-load transfer is obtained as:
\begin{equation} A_{v}=\frac{R_{\ell}}{A R_{\ell} + B} \end{equation}The input impedance is found as:
\begin{equation} z_{i}=\tilde{\infty} \left(A R_{\ell} + B\right) \end{equation}The output impedance is found as:
\begin{equation} z_{o}=\frac{B}{A} \end{equation}The numeric values are obtained after solving the equations for $z_o$ and $A_v$ for the target values given below.
Output impedance $z_o$:
\begin{equation} z_{o}=50 \end{equation}Source-to-load voltage transfer $A_v$:
\begin{equation} A_{v}=1 \end{equation}Antenna capacitance $C_A$:
\begin{equation} C_{A}=6.3 \cdot 10^{-12} \end{equation}Value of the current sense resistor: $R_s=5\Omega$
Transformer T1:
\begin{equation} n_{T1}=\frac{1}{5} \end{equation}Transformer T2:
\begin{equation} n_{T2}=2 \end{equation}The T1 matrix of the amplifier:
\begin{equation} T_{1}=\left[\begin{matrix}\frac{1}{2} & 25\\0 & 0\end{matrix}\right] \end{equation}The influence of R2 on the power efficiency and the noise is small if its value is much smaller than that of the load resistance. This is because the output resistance of the amplifier is set by the value of R2 and the turn ratio of T1.
Similar holds for the noise contribution of R2.
The circuit uses a voltage input. Hence, the relatively high source impedance, in combination with a nonlinear Q-V or V-I relation of the EDS device in parallel with the input may cause an unacceptably large distortion.
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Last project update: 2022-04-01 08:22:20