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DistortionMeasurementsConfiguration

Compute and display harmonic and intermodulation distortion

Since R2022a

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    Description

    Use the DistortionMeasurementsConfiguration object to compute and display harmonic and intermodulation distortion.

    You can specify the distortion type, number of harmonics, and label the harmonics. You can control the distortion settings from the Spectrum Analyzer toolstrip or from the command line. Both the spectrumAnalyzer object and the SpectrumAnalyzerBlockConfiguration object support the DistortionMeasurementsConfiguration object in the command line.

    To modify the distortion settings in the Spectrum Analyzer toolstrip, click the Measurements tab and edit the settings in the Distortion section.

    Snapshot showing distortion measurements.

    Creation

    Syntax

    distmeas = DistortionMeasurementsConfiguration()

    Description

    distmeas = DistortionMeasurementsConfiguration() creates a distortion measurements configuration object distmeas.

    example

    Properties

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    All properties are tunable.

    Type of measurement data to display, specified as "harmonic" or "intermodulation".

    Scope Window Use

    Click the Measurements tab on the Spectrum Analyzer toolstrip. In the Distortion section, set Distortion Type to Harmonic or Intermodulation.

    The Measurements tab appears when you select Spectrum in the Scope tab.

    Data Types: char | string

    Number of harmonics to measure, specified as a positive integer less than or equal to 99.

    Dependency

    To enable this property, set Type to "harmonic".

    Scope Window Use

    Click the Measurements tab on the Spectrum Analyzer toolstrip. In the Distortion section, set Num Harmonics to a positive integer less than or equal to 99.

    The Measurements tab appears when you select Spectrum in the Scope tab.

    Data Types: double

    Label harmonics (for harmonic distortion) and frequencies (for intermodulation distortion), specified as true or false.

    Scope Window Use

    Click the Measurements tab on the Spectrum Analyzer toolstrip. In the Distortion section, select Label Harmonics.

    The Measurements tab appears when you select Spectrum in the Scope tab.

    Data Types: logical

    Enable distortion measurements, specified as true or false.

    Scope Window Use

    Click the Measurements tab on the Spectrum Analyzer toolstrip. In the Distortion section, select Distortion.

    The Measurements tab appears when you select Spectrum in the Scope tab.

    Data Types: logical

    Examples

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    Open Live Script

    Compute and display the power spectrum of a noisy sinusoidal input signal using the spectrumAnalyzer MATLAB® object. Measure the peaks, cursor placements, adjacent channel power ratio, and distortion values in the spectrum by enabling these properties:

    • PeakFinder

    • CursorMeasurements

    • ChannelMeasurements

    • DistortionMeasurements

    Initialization

    The input sine wave has two frequencies: 1000 Hz and 5000 Hz. Create two dsp.SineWave System objects to generate these two frequencies. Create a spectrumAnalyzer object to compute and display the power spectrum.

    Fs = 44100;
Sineobject1 = dsp.SineWave(SamplesPerFrame=1024,PhaseOffset=10,...
    SampleRate=Fs,Frequency=1000);
Sineobject2 = dsp.SineWave(SamplesPerFrame=1024,...
    SampleRate=Fs,Frequency=5000);
SA = spectrumAnalyzer(SampleRate=Fs,SpectrumType="power",...
    PlotAsTwoSidedSpectrum=false,ChannelNames={'Power spectrum of the input'},...
    YLimits=[-120 40],ShowLegend=true);

    Enable Measurements Data

    To obtain the measurements, set the Enabled property to true.

    SA.CursorMeasurements.Enabled = true;
SA.ChannelMeasurements.Enabled = true;
SA.PeakFinder.Enabled = true;
SA.DistortionMeasurements.Enabled = true;

    Use getMeasurementsData

    Stream in the noisy sine wave input signal and estimate the power spectrum of the signal using the spectrumAnalyzer object. Measure the characteristics of the spectrum. Use the getMeasurementsData function to obtain these measurements programmatically. The isNewDataReady function returns true when there is new spectrum data. Store the measured data in the variable data.

    data = [];
for Iter = 1:1000
    Sinewave1 = Sineobject1();
    Sinewave2 = Sineobject2();
    Input = Sinewave1 + Sinewave2;
    NoisyInput = Input + 0.001*randn(1024,1);
    SA(NoisyInput);
     if SA.isNewDataReady
        data = [data;getMeasurementsData(SA)];
     end
end

    The panes at the bottom of the scope window display the measurements that you have enabled. The values in these panes match the values in the last time step of the data variable. You can access the individual fields of data to obtain the various measurements programmatically.

    Compare Peak Values

    Use the PeakFinder property to obtain peak values. Verify that the peak values in the last time step of data match the values in the spectrum analyzer plot.

    peakvalues = data.PeakFinder(end).Value 
    peakvalues = 3×1

   26.3957
   22.7830
  -57.9977


    frequencieskHz = data.PeakFinder(end).Frequency/1000
    frequencieskHz = 3×1

    4.9957
    0.9905
   20.6719

    Version History

    Introduced in R2022a

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    See Also

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