**Class: **rfckt.twowire**Package: **rfckt

Computed S-parameters, noise figure, OIP3, and group delay values

`rfdata.data`

object

Handle to an `rfdata.data`

object
that contains the S-parameters, noise figure, OIP3, and group delay
values computed over the specified frequency range using the `analyze`

method. This property is empty by
default.

The `analyze`

method treats
the transmission line, which can be lossy or lossless, as a 2-port
linear network. It computes the `AnalyzedResult`

property
of a stub or as a stubless line using the data stored in the `rfckt.twowire`

object properties as follows:

If you model the transmission line as a stubless line, the

`analyze`

method first calculates the ABCD-parameters at each frequency contained in the modeling frequencies vector. It then uses the`abcd2s`

function to convert the ABCD-parameters to S-parameters.The

`analyze`

method calculates the ABCD-parameters using the physical length of the transmission line,*d*, and the complex propagation constant,*k*, using the following equations:$$\begin{array}{l}A=\frac{{e}^{kd}+{e}^{-kd}}{2}\\ B=\frac{{Z}_{0}*\left({e}^{kd}-{e}^{-kd}\right)}{2}\\ C=\frac{{e}^{kd}-{e}^{-kd}}{2*{Z}_{0}}\\ D=\frac{{e}^{kd}+{e}^{-kd}}{2}\end{array}$$

*Z*_{0}and*k*are vectors whose elements correspond to the elements of*f*, the vector of frequencies specified in the`analyze`

input argument`freq`

. Both can be expressed in terms of the resistance (*R*), inductance (*L*), conductance (*G*), and capacitance (*C*) per unit length (meters) as follows:$$\begin{array}{c}{Z}_{0}=\sqrt{\frac{R+j2\pi fL}{G+j2\pi fC}}\\ k={k}_{r}+j{k}_{i}=\sqrt{(R+j2\pi fL)(G+j2\pi FC)}\end{array}$$

where

$$\begin{array}{l}R=\frac{1}{\pi a{\sigma}_{cond}{\delta}_{cond}}\\ L=\frac{\mu}{\pi}\text{a}\mathrm{cosh}\left(\frac{D}{2a}\right)\\ G=\frac{\pi \omega {\epsilon}^{\u2033}}{\text{a}\mathrm{cosh}\left(\frac{D}{2a}\right)}\\ C=\frac{\pi \epsilon}{\text{a}\mathrm{cosh}\left(\frac{D}{2a}\right)}\end{array}$$

In these equations:

*w*is the plate width.*d*is the plate separation.*σ*is the conductivity in the conductor._{cond}*μ*is the permeability of the dielectric.*ε*is the permittivity of the dielectric.*ε″*is the imaginary part of*ε*,*ε″*=*ε*_{0}*ε*tan_{r}*δ*, where:*ε*_{0}is the permittivity of free space.*ε*is the_{r}`EpsilonR`

property value.tan

*δ*is the`LossTangent`

property value.

*δ*is the skin depth of the conductor, which the block calculates as $$1/\sqrt{\pi f\mu {\sigma}_{cond}}$$._{cond}*f*is a vector of modeling frequencies determined by the Outport block.

If you model the transmission line as a shunt or series stub, the

`analyze`

method first calculates the ABCD-parameters at the specified frequencies. It then uses the`abcd2s`

function to convert the ABCD-parameters to S-parameters.When you set the

`StubMode`

property to`'Shunt'`

, the 2-port network consists of a stub transmission line that you can terminate with either a short circuit or an open circuit as shown in the following figure.*Z*is the input impedance of the shunt circuit. The ABCD-parameters for the shunt stub are calculated as:_{in}$$\begin{array}{c}A=1\\ B=0\\ C=1/{Z}_{in}\\ D=1\end{array}$$

When you set the

`StubMode`

property to`'Series'`

, the 2-port network consists of a series transmission line that you can terminate with either a short circuit or an open circuit as shown in the following figure.*Z*is the input impedance of the series circuit. The ABCD-parameters for the series stub are calculated as:_{in}$$\begin{array}{c}A=1\\ B={Z}_{in}\\ C=0\\ D=1\end{array}$$

The `analyze`

method uses
the S-parameters to calculate the group delay values at the frequencies
specified in the `analyze`

input
argument `freq`

, as described in
the `analyze`

reference
page.

tx1 = rfckt.twowire; analyze(tx1,[1e9,2e9,3e9]); tx1.AnalyzedResult ans = Name: 'Data object' Freq: [3x1 double] S_Parameters: [2x2x3 double] GroupDelay: [3x1 double] NF: [3x1 double] OIP3: [3x1 double] Z0: 50 ZS: 50 ZL: 50 IntpType: 'Linear'

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