**Class: **rfckt.txline**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.txline`

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}is the specified characteristic impedance.*k*is a vector whose elements correspond to the elements of the input vector`freq`

. The`analyze`

method calculates*k*from the specified properties as*k*=*α*+_{a}*iβ*, where*α*is the attenuation coefficient and_{a}*β*is the wave number. The attenuation coefficient*α*is related to the specified loss,_{a}*α*, by$${\alpha}_{a}=-\mathrm{ln}\left({10}^{\alpha /20}\right)$$

The wave number

*β*is related to the specified phase velocity,*V*, by_{p}$$\beta =\frac{2\pi f}{{V}_{p}},$$

where

*f*is the frequency range specified in the`analyze`

input argument`freq`

. The phase velocity*V*is derived from the_{p}`rfckt.txline`

object properties. It is also known as the*wave propagation velocity*.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.txline; 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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