PeakFinderConfiguration

Compute and display the largest calculated peak values on the scope display

Since R2022a

Description

Use the PeakFinderConfiguration object to compute and display peaks in the scope. The scope computes and displays peaks for only the portion of the input signal that is currently on display in the scope.

You can specify the number of peaks you want the scope to display, the minimum height above which you want the scope to detect peaks, the minimum distance between peaks, and label the peaks. You can control the peak finder settings from the scope toolstrip or from the command line. The algorithm defines a peak as a local maximum with lower values present on either side of the peak. It does not consider end points as peaks. For more information on the algorithm, see the findpeaks function.

To modify the peak finder settings in the scope interface, click the Measurements tab and enable Peak Finder. Once you enable the Peak Finder, an arrow appears on the plot at each maxima and a Peaks panel appears at the bottom of the scope window.

The SpectrumAnalyzerBlockConfiguration object supports the PeakFinderConfiguration object in the command line.

Spectrum Analyzer Toolstrip

Time Scope Toolstrip

Array Plot Toolstrip

Dynamic Filter Visualizer Toolstrip

Creation

Syntax

pkfinder = PeakFinderConfiguration()

Description

pkfinder = PeakFinderConfiguration() creates a peak finder configuration object.

Properties

All properties are tunable.

MinHeight — Level above which scope detects peaks

-Inf (default) | real scalar value

Level above which the scope detects peaks, specified as a real scalar.

Scope Window Use

On the Measurements tab, select Peak Finder. In the peak finder settings, specify a real scalar in the Min Height box.

Data Types: double

NumPeaks — Maximum number of peaks to show

3 (default) | positive integer less than 100

Maximum number of peaks to show, specified as a positive integer less than 100.

Scope Window Use

On the Measurements tab, select Peak Finder. In the peak finder settings, specify a positive integer less than 100 in the Num Peaks box.

Data Types: double

MinDistance — Minimum number of samples between adjacent peaks

1 (default) | positive integer

Minimum number of samples between adjacent peaks, specified as a positive integer.

Scope Window Use

On the Measurements tab, select Peak Finder. In the peak finder settings, specify a positive integer in the Min Distance box.

Data Types: double

Threshold — Minimum difference in height of peak and its neighboring samples

0 (default) | nonnegative scalar

Minimum difference in the height of the peak and its neighboring samples, specified as a nonnegative scalar.

Scope Window Use

On the Measurements tab, select Peak Finder. In the peak finder settings, specify a nonnegative scalar in the Threshold box.

Data Types: double

LabelPeaks — Label found peaks

false (default) | true

Label found peaks, specified as true or false. The scope displays the labels (P1, P2, …) above the arrows in the plot.

Scope Window Use

On the Measurements tab, select Peak Finder. In the peak finder settings, select Label Peaks.

Data Types: logical

LabelFormat — Coordinates to display

"x + y" (default) | "x" | "y"

Coordinates to display next to the calculated peak value, specified as "x", "y", or "x + y".

Data Types: char | string

Enabled — Enable peak finder measurements

false (default) | true

Enable peak finder measurements, specified as true or false. Set this property to true to enable the peak finder measurements.

Scope Window Use

On the Measurements tab, select Peak Finder.

Data Types: logical

Examples

Enable Peak Finder Programmatically in a Time Scope Object

Create a sine wave and view it in the Time Scope. Enable the peak finder programmatically.

Initialization

Create the input sine wave using the sin function. Create a timescope MATLAB® object to display the signal. Set the TimeSpan property to 1 second.

f = 100;
fs = 1000;
swv = sin(2.*pi.*f.*(0:1/fs:1-1/fs)).';
scope = timescope(SampleRate=fs,...
    TimeSpanSource="property", ...
    TimeSpan=1);

Peaks

Enable the peak finder and label the peaks. Set the scope to show three peaks and label them.

scope.PeakFinder.Enabled = true;
scope.PeakFinder.LabelPeaks = true;
scope(swv)
release(scope)

Obtain Measurements Data Programmatically for spectrumAnalyzer object

Compute and display the power spectrum of a noisy sinusoidal input signal using the spectrumAnalyzer 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. Label the peak measurements.

SA.CursorMeasurements.Enabled = true;
SA.ChannelMeasurements.Enabled = true;
SA.PeakFinder.Enabled = true;
SA.PeakFinder.LabelPeaks = 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 panels 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

R2023a: Support for Spectrum Analyzer block

The SpectrumAnalyzerBlockConfiguration object now supports the PeakFinderConfiguration object. The PeakFinderConfiguration object enables you to obtain and modify the peak finder measurements of the Spectrum Analyzer block programmatically from the command line.