zpk

Compute zeros, poles, and gain of rational object

Syntax

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

Description

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

Examples

Zeros, Poles, Gain, and DC Gain of Fit

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')

fit = 
  rational with properties:

      NumPorts: 2
      NumPoles: 44
         Poles: [44x1 double]
      Residues: [2x2x44 double]
    DirectTerm: [2x2 double]
         ErrDB: -22.6464

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

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

z=2×2 cell array
    {43x1 double}    {43x1 double}
    {43x1 double}    {43x1 double}

p=2×2 cell array
    {44x1 double}    {44x1 double}
    {44x1 double}    {44x1 double}

k = 2×2
109 ×

   -2.5743   -0.0556
   -0.6980   -1.3221

dcgain = 2×2

    0.0933   -0.0302
   -1.1079    0.4746

Input Arguments

fit — Rational fit

rational object

Rational fit, specified as a rational object returned by rational.

Output Arguments

z — Zeroes of fit

1-D array of doubles | 3-D array of doubles

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

p — Poles of fit

1-D array of doubles | 3-D array of doubles

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

k — Gain of fit

2-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.

dcgain — DC gain of fit

2-D array of doubles

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