# Two-Wire Transmission Line

Model two-wire transmission line

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• RF Blockset / Equivalent Baseband / Transmission Lines

## Description

The Two-Wire Transmission Line block models the two-wire transmission line described in the block dialog box in terms of its frequency-dependent S-parameters. A two-wire transmission line is shown in cross-section in the following figure. Its physical characteristics include the radius of the wires a, the separation or physical distance between the wire centers S, and the relative permittivity and permeability of the wires. RF Blockset™ Equivalent Baseband software assumes the relative permittivity and permeability are uniform.

## Parameters

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### Main

Radius of the conducting wires of the two-wire transmission line, specified as a scalar in meters.

Physical distance between the wires, specified as a scalar in meters.

Relative permeability of the dielectric, expressed as the ratio of the permeability of the dielectric to permeability in free space μ0, specified as a scalar.

Relative permittivity of the dielectric, expressed as the ratio of the permittivity of the dielectric to permittivity in free space ε0, specified as a scalar.

Loss tangent of the dielectric, specified as a scalar.

Conductivity of the conductor, specified as a scalar in siemens per meter. Conductivity measures the ease with which current flows in the conductor.

Physical length of the transmission line, specified as a scalar in meters.

The block enables you to model the transmission line as a stub or as a stubless line.

#### Stubless Transmission Line

• `Not a stub`Not a stub

If you model a coaxial transmission line as stubless line, the Coaxial Transmission Line block 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. For more information, see Stub Mode- Not a stub.

#### Shunt Transmission Line

• `Shunt`—This parameter provides a two-port network that consists of a stub transmission line that you can terminate with either a short circuit or an open circuit as shown in these diagrams.

Zin is the input impedance of the shunt circuit. The ABCD-parameters for the shunt stub are calculated as

`$\begin{array}{c}A=1\\ B=0\\ C=1/{Z}_{in}\\ D=1\end{array}$`

#### Series Transmission Line

• `Series`—This mode parameter provides a two-port network that consists of a series transmission line that you can terminate with either a short circuit or an open circuit as show in these diagrams.

Zin is the input impedance of the series circuit. The ABCD-parameters for the series stub are calculated as

`$\begin{array}{c}A=1\\ B={Z}_{in}\\ C=0\\ D=1\end{array}$`

Stub termination for stub modes `Shunt` and `Series`. Choices are `Open` or `Short`

#### Dependencies

To enable this parameter, select `Shunt` or `Series` in Stub mode

### Visualization

Frequency data source, specified as `User-specified`.

Frequency data range, specified as a vector in hertz.

Reference impedance, specified as a nonnegative scalar in ohms.

Type of data plot to visualize using the given data, specified as one of the following:

• `X-Y plane` — Generate a Cartesian plot of the data versus frequency. To create linear, semilog, or log-log plots, set the Y-axis scale and X-axis scale accordingly.

• `Composite data` — Plot the composite data. For more information, see Create Plots.

• `Polar plane` — Generate a polar plot of the data. The block plots only the range of data corresponding to the specified frequencies.

• `Z smith chart`, ```Y smith chart```, and `ZY smith chart` — Generate a Smith® chart. The block plots only the range of data corresponding to the specified frequencies.

Type of parameters to plot, specified as one of the following.

 `S11` `S12` `S21` `S22` `GroupDelay` `GammaIn` `GammaOut` `VSWRIn` `VSWROut` `OIP3` `IIP3` `NF` `NFactor` `NTemp` `TF1` `TF2` `TF3` `Gt` `Ga` `Gp` `Gmag` `Gmsg` `GammaMS` `GammaML` `K` `Delta` `Mu` `MuPrime`

Note

Y parameter1 is disabled when you select Plot type to `Composite data`.

Type of parameters to plot, specified as one of the following.

 `S11` `S12` `S21` `S22` `GroupDelay` `GammaIn` `GammaOut` `VSWRIn` `VSWROut` `OIP3` `IIP3` `NF` `NFactor` `NTemp` `TF1` `TF2` `TF3` `Gt` `Ga` `Gp` `Gmag` `Gmsg` `GammaMS` `GammaML` `K` `Delta` `Mu` `MuPrime`

Note

Y parameter2 is disabled when you select Plot type to `Composite data`.

Plot format, specified as one of the following.

Y parameter1Y format1
`S11`, `S12`, `S21`, `S22`, `GammaIn`, `GammaOut`, `TF1`, `TF2`, `TF3`, `GammaMS`, `GammaML`, and `Delta`.`dB`, `Magnitude (decibels)`, `Abs`, `Mag`, `Magnitude (linear)`, `Angle`, `Angle(degrees)`, `Angle(radians)`, `Real`, `Imag`, and `Imaginary`.
`GroupDelay``ns`, `us`, `ms`, `s`, and `ps`.
`VSWRIn` and `VSWROut`.`Magnitude (decibels)` and `None`.
`OIP3` and `IIP3`.`dBm`, `W`, and `mW`.
`NF` `dB` and `Magnitude (decibels)`.
`NFactor`, `K`, `Mu`, and `MuPrime`.`None`
`NTemp``Kelvin`
`Gt`, `Ga`, `Gp`, `Gmag`, and `Gmsg`.`dB`, `Magnitude (decibels)`, and `None`.

#### Dependencies

To enable Y format1, set Plot type to `X-Y plane`.

Plot format, specified as one of the following.

Y parameter2Y format2
`S11`, `S12`, `S21`, `S22`, `GammaIn`, `GammaOut`, `TF1`, `TF2`, `TF3`, `GammaMS`, `GammaML`, and `Delta`.`dB`, `Magnitude (decibels)`, `Abs`, `Mag`, `Magnitude (linear)`, `Angle`, `Angle(degrees)`, `Angle(radians)`, `Real`, `Imag`, and `Imaginary`.
`GroupDelay``ns`, `us`, `ms`, `s`, and `ps`.
`VSWRIn` and `VSWROut`.`Magnitude (decibels)` and `None`.
`OIP3` and `IIP3`.`dBm`, `W`, and `mW`.
`NF` `dB` and `Magnitude (decibels)`.
`NFactor`, `K`, `Mu`, and `MuPrime`.`None`
`NTemp``Kelvin`
`Gt`, `Ga`, `Gp`, `Gmag`, and `Gmsg`.`dB`, `Magnitude (decibels)`, and `None`.

#### Dependencies

To enable Y format2, set Plot type to `X-Y plane`.

Frequency plot, specified as `Freq`.

Frequency plot format, specified as one of the following.

 `Auto` `Hz` `kHz` `MHz` `GHz` `THz`

Y-axis scale, specified as `Linear` or `Log`.

#### Dependencies

To enable this parameter, set Plot type to ```X-Y plane```.

X-axis scale, specified as `Linear` or `Log`.

#### Dependencies

To enable this parameter, set Plot type to ```X-Y plane```.

Plot the specified data using the plot button.

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## References

[1] Pozar, David M. Microwave Engineering. Hobken, NJ, John Wiley & Sons, Inc., 2005.

Introduced in R2009a