makepassive

Enforce passivity of rational fit

Syntax

pfit = makepassive(fit,s)

pfit = makepassive(fit,s,'Display','on')

Description

pfit = makepassive(fit,s) produces a passive fit by modifying the input, fit while optimally matching the data of S-parameter input, s. makepassive function does modifies the residues of the fit to make it passive.

example

pfit = makepassive(fit,s,'Display','on') solves as above, but turns on the display of iteration information. The default for 'Display' is 'off'.

Examples

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Make Passive Fit of S-Parameter Rationalfit

Open Live Script

Read a file named passive.s2p and fit the 2x2 S-parameters.

 S = sparameters('passive.s2p');
 fit = rationalfit(S);

Plot the passivity of the 2x2 fit, noting the violations.

 figure
 passivity(fit)

Figure contains an axes object. The axes object with title Fit not passive, max norm(H) is 1+1.79e-02 at 17.7 GHz, xlabel Frequency (GHz), ylabel norm(H) contains 4 objects of type line. One or more of the lines displays its values using only markers

Optimize residues to produce a passive fit still close to S.

 pfit = makepassive(fit,S)

pfit = 
  2x2 rfmodel.rational array with properties:

    A
    C
    D
    Delay
    Name

To display iteration information:

  pfit = makepassive(fit,S,'Display','on' )

Iter	H-infinity norm	Frequency	Error (dB)	Constraints
0		1+1.79e-02		17.7 GHz		-40.4702
1		1+2.69e-04		282 MHz		-40.9169	5
2		1+7.35e-05		376 MHz		-40.9078	8
3		1+1.00e-06		361 MHz		-40.9067	9
4		1-2.55e-06		368 MHz		-40.9062	10

pfit = 
  2x2 rfmodel.rational array with properties:

    A
    C
    D
    Delay
    Name

Plot the passivity of the new fit.

 figure
 passivity(pfit)

Figure contains an axes object. The axes object with title Fit passive, max norm(H) is 1-2.55e-06 at 368 MHz, xlabel Frequency (GHz), ylabel norm(H) contains an object of type line.