CursorMeasurementsConfiguration

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);

Data Cursors

Enable data cursors in the scope programmatically by setting the Enabled property of the CursorMeasurementsConfiguration object to true.

scope.CursorMeasurements.Enabled = true;
scope(swv);
release(scope)

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

Open and Inspect the Model

Filter a streaming noisy sinusoidal input signal using a Lowpass Filter block. The input signal consists of two sinusoidal tones: 1 kHz and 15 kHz. The noise is white Gaussian noise with a mean of 0 and a variance of 0.05. The sampling frequency is 44.1 kHz. Open the model and inspect the parameter values in the blocks.

model = 'spectrumanalyzer_measurements.slx';
open_system(model)

Access the configuration properties of the Spectrum Analyzer block using the get_param function.

sablock = 'spectrumanalyzer_measurements/Spectrum Analyzer';
cfg = get_param(sablock,'ScopeConfiguration');

Enable Measurements Data

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

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

Simulate the Model

Run the model. The Spectrum Analyzer block compares the original spectrum with the filtered spectrum.

sim(model)

The panes at the bottom of the spectrum analyzer window display the measurements that you have enabled.

Use getMeasurementsData function

Use the getMeasurementsData function to obtain the measurements programmatically.

data = getMeasurementsData(cfg)

data =

  1x5 table

    SimulationTime    PeakFinder    CursorMeasurements    ChannelMeasurements    DistortionMeasurements
    ______________    __________    __________________    ___________________    ______________________

        9.9962        1x1 struct        1x1 struct            1x1 struct               1x1 struct      

The values shown in the measurement panels match the values shown in data. You can access the individual fields of data to obtain the various measurements programmatically.

Compare Peak Values

As an example, compare the peak values. Verify that the peak values obtained by data.PeakFinder match with the values in the spectrum analyzer window.

peakvalues = data.PeakFinder.Value
frequencieskHz = data.PeakFinder.Frequency/1000

peakvalues =

   26.8237
   26.3370
   -5.3604


frequencieskHz =

   15.0015
    1.0049
   12.2739