RF Blockset™

Z-Parameters Passive Network - Model passive network using Z-parameters

Library

Black Box Elements sublibrary of the Physical library

Description

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 RF Blockset Algorithms for more details.

Dialog Box

Main Tab

Z-Parameters

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.

Method	Description
`Linear` (default)	Linear interpolation
`Spline`	Cubic spline interpolation
`Cubic`	Piecewise cubic Hermite interpolation

Visualization Tab

For information about plotting circuit parameters, see Plotting Model Data.

Examples

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])

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])

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.
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.