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Z-Parameters Passive Network

Model passive network using Z-parameters


Black Box Elements sublibrary of the Physical library


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

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

The Z-Parameters Passive Network block uses the RF Toolbox™ z2s function to convert the Z-parameters to S-parameters, and then interpolates the resulting S-parameters to determine their values at the modeling frequencies. The modeling frequencies are determined by the Output Port block. See Map Network Parameters to Modeling Frequencies for more details.


Main Tab


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

Frequency (Hz)

Frequencies of the Z-parameters as an M-element vector. The order of the frequencies must correspond to the order of the Z-parameters in Z-Parameters. All frequencies must be positive.

Interpolation method

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

Linear (default)Linear interpolation
SplineCubic spline interpolation
CubicPiecewise cubic Hermite interpolation

Visualization Tab

For information about plotting, see Create Plots.


Plotting Parameters with the Z-Parameters Passive Network Block

The following example specifies Z-parameters [0.13 - 5.93i, .03-3.16i; 0.03-3.16i, .13-5.93i] and [0.27-2.86i, -.09-5.41i; -.09-5.41i, .27-2.86i] at frequencies 2.0 GHz and 2.1 GHz respectively. It uses the MATLAB® cat function to create the 2-by-2-by-2 Z-parameters array.

cat(3,[0.13-5.93i, .03-3.16i; 0.03-3.16i, .13-5.93i],...
      [0.27-2.86i,-.09-5.41i; -.09-5.41i, .27-2.86i])
  1. Type the following command at the MATLAB prompt to create a variable called zparams that stores the values of the Z-parameters.

    zparams = cat(3,...
          [0.13-5.93i,.03-3.16i; 0.03-3.16i,.13-5.93i],...
          [0.27-2.86i,-.09-5.41i; -.09-5.41i,.27-2.86i])

  2. Set the Z-Parameters Passive Network block parameters on the Main tab as follows:

    • Set the Z-Parameters parameter to zparams.

    • Set the Frequency (Hz) parameter to [2.0e9,2.1e9].

    Click Apply. This action applies the specified settings.

  3. Set the Z-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 S12.

    Click Plot. This action creates an X-Y plane plot of the S12 parameters in the frequency range 1.9 to 2.2 GHz.