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Model passive network using S-parameters

Black Box Elements sublibrary of the Physical library

The S-Parameters Passive Network block models the two-port passive network described in the block dialog box, in terms of its S-parameters and the frequencies and reference impedance of the S-parameters.

In the **S-Parameters** field of the block
dialog box, provide the S-parameters for each of M frequencies as
a 2-by-2-by-M array. In the **Frequency** field,
specify the frequencies for the S-parameters as an M-element vector.
The elements of the vector must be in the same order as the S-parameters.
All frequencies must be positive. For example, the following figure
shows the correspondence between the S-parameters array and the vector
of frequencies.

The S-Parameters Passive Network block interpolates the given S-parameters to determine their values at the modeling frequencies. The modeling frequencies are determined by the Output Port block. See RF Blockset Equivalent Baseband Algorithms for more details.

**S-Parameters**S-parameters for a two-port passive network in a 2-by-2-by-M array. M is the number of S-parameters.

**Frequency (Hz)**Frequencies of the S-parameters as an M-element vector. The order of the frequencies must correspond to the order of the S-parameters in

**S-Parameters**. All frequencies must be positive.**Reference impedance (ohms)**Reference impedance of the network as a scalar or a vector of length M. The value of this parameter can be real or complex. If you provide a scalar value, then that value is applied to all frequencies.

**Interpolation method**The method used to interpolate the network parameters. The following table lists the available methods describes each one.

Method Description `Linear`

(default)Linear interpolation `Spline`

Cubic spline interpolation `Cubic`

Piecewise cubic Hermite interpolation

For information about plotting, see Create Plots.

The following example specifies S-parameters [-.96-.23i, .03-.12i; .03-.12i, -.96-.23i] and [-.96-.11i, .02-.21i; .02-.21i, -.96-.11i] at frequencies 2.0 GHz and 2.1 GHz respectively. The example then plots these parameters.

The example first uses the MATLAB^{®} `cat`

function
to create the 2-by-2-by-2 S-parameters array.

cat(3,[-.96-.23i, .03-.12i; .03-.12i, -.96-.23i],... [-.96-.11i, .02-.21i; .02-.21i, -.96-.11i])

You could also use the MATLAB `reshape`

function.
The following command produces the same result as previous command.

reshape([-.96-.23i;.03-.12i;.03-.12i;-.96-.23i;... -.96-.11i;.02-.21i;.02-.21i;-.96-.11i],2,2,2)

Type the following command at the MATLAB prompt to create a variable called

`sparams`

that stores the values of the S-parameters.sparams = cat(3,... [-.96-.23i, .03-.12i; .03-.12i, -.96-.23i],... [-.96-.11i, .02-.21i; .02-.21i, -.96-.11i])

Set the S-Parameters Passive Network block parameters on the

**Main**tab as follows:Set the

**S-Parameters**parameter to`sparams`

.Set the

**Frequency (Hz)**parameter to`[2.0e9,2.1e9]`

.

Click

**Apply**. This action applies the specified settings.Set the S-Parameters Passive Network block parameters on the

**Visualization**tab as follows:In the

**Source of frequency data**list, select`User-specified`

.Set the

**Frequency data (Hz)**parameter to`[1.9e9:1.0e8:2.2e9]`

.In the

**Y parameter1**list, select`S21`

.

Click

**Plot**. This action creates an X-Y Plane plot of the magnitude of the S_{21}parameters, in decibels, in the frequency range 1.9 to 2.2 GHz.

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