freqresp

Frequency response of a rational function and rationalfit function object

Description

[response, outputfreq] = freqresp(rationalobject,inputfreq) calculates the frequency response, response of a rational function object, rationalobject at the specified input frequencies, inputfreq.

example

[response, outputfreq] = freqresp(fit,inputfreq) calculates the frequency response of the fit.

Examples

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Compute the frequency response of data stored in the file,|passive.s2p| by reading it into an rfdata object, fitting a rational function object to the data, and using the freqresp method to compute the frequency response of the object

orig_data=read(rfdata.data,'passive.s2p')
orig_data = 
   rfdata.data with properties:

            Freq: [202x1 double]
    S_Parameters: [2x2x202 double]
      GroupDelay: [202x1 double]
              NF: [202x1 double]
            OIP3: [202x1 double]
              Z0: 50.0000 + 0.0000i
              ZS: 50.0000 + 0.0000i
              ZL: 50.0000 + 0.0000i
        IntpType: 'Linear'
            Name: 'Data object'

freq=orig_data.Freq;
data=orig_data.S_Parameters(2,1,:);
fit_data=rationalfit(freq,data)
fit_data = 
   rfmodel.rational with properties:

        A: [6x1 double]
        C: [6x1 double]
        D: 0
    Delay: 0
     Name: 'Rational Function'

[resp,freq]=freqresp(fit_data,freq);

plot(freq/1e9,20*log10(abs(resp)));

figure
plot(freq/1e9,unwrap(angle(resp)));

Input Arguments

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Rational function object, specified as an object handle created using rationalfit.

Example: [resp,freq]=freqresp(fit_data,freq); where fit_data is the rational object handle created using rationalfit.

Data Types: char | string

Input frequencies, specified as a vector of positive frequencies in Hz.

Data Types: double

N-by-N array, specified rfmodel.rational objects returned by rationalfit.

Output Arguments

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Frequency response values, returned as a vector.

Frequency values same as input frequencies, returned as a vector.

Introduced before R2006a