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zpk

Compute zeros, poles, and gain of rational object

Since R2020a

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Syntax

[z,p,k,dcgain] = zpk(fit)

Description

example

[z,p,k,dcgain] = zpk(fit) returns the zeros, poles, gain, and DC gain of a rational object.

Examples

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Open Live Script

Create an S-Parameters object from the file named default.s2p. Perform rational fitting of the S-Parameters.

S = sparameters('default.s2p');
fit = rational(S,Display='plot')

Figure contains an axes object. The axes object with title Real part of data and response, xlabel Frequency (Hz), ylabel Data and response contains 12 objects of type line. One or more of the lines displays its values using only markers These objects represent Data, Response, Matched Points.

Figure contains an axes object. The axes object with title Imaginary part of data and response, xlabel Frequency (Hz), ylabel Data and response contains 12 objects of type line. One or more of the lines displays its values using only markers These objects represent Data, Response, Matched Points.

Figure contains an axes object. The axes object with title Error (difference between data and response), xlabel Frequency (Hz), ylabel Error contains 4 objects of type line. This object represents Error.

fit = 
  rational with properties:

      NumPorts: 2
      NumPoles: 52
         Poles: [52x1 double]
      Residues: [2x2x52 double]
    DirectTerm: [2x2 double]
         ErrDB: -22.6872

Calculate the zeros, poles, gain, and DC gain of the rational object.

[z,p,k,dcgain] = zpk(fit)
z=2×2 cell array
    {51x1 double}    {51x1 double}
    {51x1 double}    {51x1 double}


p=2×2 cell array
    {52x1 double}    {52x1 double}
    {52x1 double}    {52x1 double}


k = 2×2
1010 ×

    1.0544   -0.0194
    0.9158    0.0377


dcgain = 2×2

    0.1289   -0.0838
   -0.1209    0.7649

Input Arguments

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Rational fit, specified as a rational or rfmodel.rational object.

Output Arguments

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Zeroes of the fit, returned as a 1-D array of doubles or a 3-D array of doubles.

Poles of the fit, returned as a 1-D array of doubles or a 3-D array of doubles.

Gain of the fit, returned as a 2-D array of doubles. k is the coefficient of the rational function when poles and zeros are expressed as monic polynomials in S.

DC gain of the fit, returned as 2-D array of doubles for zero frequency response.

Version History

Introduced in R2020a

See Also

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