Model passive network using S-parameters
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 SimRF Equivalent Baseband Algorithms for more details.
S-parameters for a two-port passive network in a 2-by-2-by-M array. M is the number of S-parameters.
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 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.
The method used to interpolate the network parameters. The following table lists the available methods describes each one.
|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.
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 S21 parameters, in decibels, in the frequency range 1.9 to 2.2 GHz.