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freqrespopts

Options for filter frequency response analysis

Syntax

opts = freqrespopts(H)

Description

opts = freqrespopts(H) uses the settings in the filter System object™, H, to create an object, opts. This object contains parameters and values for estimating the filter frequency response. You pass opts as an input argument to freqrespest to specify values for the input parameters.

freqrespopts allows you to use the same settings for freqrespest with multiple filters without specifying all of the parameters as input arguments to freqrespest.

The following Filter System objects are supported by this analysis function:

In addition, dsp.FarrowRateConverter and dsp.FilterCascade support this analysis method.

Examples

collapse all

This example shows freqrespopts in use for setting options for freqrespest. hd and hd2 are bandpass filters that use different design methods. The opts object makes it easier to set the same conditions for the frequency response estimate in freqrespest.

d = fdesign.bandpass('fst1,fp1,fp2,fst2,ast1,ap,ast2',...
0.25,0.3,0.45,0.5,60,0.1,60);
hd = design(d,'butter','SystemObject',true)
hd = 
  dsp.BiquadFilter with properties:

                   Structure: 'Direct form II'
             SOSMatrixSource: 'Property'
                   SOSMatrix: [18x6 double]
                 ScaleValues: [19x1 double]
           InitialConditions: 0
    OptimizeUnityScaleValues: true

  Show all properties

hd2 = design(d,'cheby2','SystemObject',true)
hd2 = 
  dsp.BiquadFilter with properties:

                   Structure: 'Direct form II'
             SOSMatrixSource: 'Property'
                   SOSMatrix: [9x6 double]
                 ScaleValues: [10x1 double]
           InitialConditions: 0
    OptimizeUnityScaleValues: true

  Show all properties

opts = freqrespopts(hd)
opts =

  struct with fields:

             FreqPoints: 'All'
                   NFFT: 512
    NormalizedFrequency: true
                     Fs: 'Normalized'
          SpectrumRange: 'Half'
               CenterDC: false
opts.NFFT=256; % Same as set(opts,'nfft',256).
opts.NormalizedFrequency=false;
opts.fs=1.5e3;
opts.CenterDC=true
opts =

  struct with fields:

             FreqPoints: 'All'
                   NFFT: 256
    NormalizedFrequency: false
                     Fs: 1500
          SpectrumRange: 'Whole'
               CenterDC: true

With opts configured as needed, use it as an input argument for freqrespest.

[h2,w2]=freqrespest(hd2,20,opts);
[h1,w1]=freqrespest(hd,20,opts);

Introduced in R2011a

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