Documentation

This is machine translation

Translated by Microsoft
Mouseover text to see original. Click the button below to return to the English verison of the page.

Note: This page has been translated by MathWorks. Please click here
To view all translated materals including this page, select Japan from the country navigator on the bottom of this page.

freqresp

Frequency response of rational function object

Syntax

[resp,outfreq] = freqresp(h,infreq)

Description

[resp,outfreq] = freqresp(h,infreq) computes the frequency response, resp, of the rational function object, h, at the frequencies specified by freq.

The input h is the handle of a rational function object returned by rationalfit, and infreq is a vector of positive frequencies, in Hz, over which the frequency response is calculated.

The output argument outfreq is a vector that contains the same frequencies as the input frequency vector, in order of increasing frequency. The frequency response, resp, is a vector of frequency response values corresponding to these frequencies. It is computed using the analytical form of the rational function

resp=(k=1nCksAk+D)es*Delay,s=j2π*freq

where A, C, D, and Delay are properties of the rational function object, h.

Examples

collapse all

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')
freq=orig_data.Freq;
data=orig_data.S_Parameters(2,1,:);
fit_data=rationalfit(freq,data)

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

plot(freq/1e9,20*log10(abs(resp)));
figure
plot(freq/1e9,unwrap(angle(resp)));
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'


fit_data = 

   rfmodel.rational with properties:

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

Introduced in R2006b

Was this topic helpful?