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Error Between S-parameters: SModel

Summary

SModel is used to compute the weighted difference between two sets of S-parameters. The weighted difference (error function) calculation method is selected by setting the "Error Function" measurement parameter. This measurement can be used as a goal for optimization when fitting a circuit to measured S-parameter data.

SModel requires that the two sets of S-parameters have the same number of frequencies, and compares them in order, point by point. It does not require that the frequency values be identical. For example, you can use SModel to compare a physically scaled model against the original, even though their operation frequencies are different. You should make sure the frequencies are set correctly on the source of each set of S-parameters.

Parameters

Name Type Range
Data Source Name Subcircuit 1 to 1000 ports
Data Source Name Subcircuit 1 to 1000 ports
Error Function List of options

Average L1 Norm

Average L2 Norm

Maximum L1 Norm

Average Normalized L1 Norm

NOTE: All measurements will have additional parameters that allow you to specify the plotting configuration for swept parameters. These parameters are dynamic; they change based upon which data source is selected. See “Swept Parameter Analysis ” for details on configuring these parameters.

Result

This measurement returns a real value. Select the dB check box to display the absolute value of the real component in dB.

Computational Details

The various error functions are calculated as follows:

Average L1 Norm. The weighted difference is the average magnitude of the difference between each element of the S-parameter matrix:

Average L2 Norm. The weighted difference is the average squared magnitude of the difference between each element of the S-parameter matrix:

Maximum L1 Norm. The maximum difference is the magnitude of the maximum difference between each element of the S-parameter matrix (the magnitude of the largest difference between any pair of entries in the S-parameter matrices):

Average Normalized L1 Norm. The magnitude of the difference between each element of the S-parameter matrix is calculated. Each difference is then normalized by the average magnitude of the two matrix elements (one from each set):

In the previous equations, SA and SB are the two NxN S-parameter matrices.

Options

The two documents specified by the Data Source Name parameters must have the same number of sweep (frequency) points.

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