ChannelMeasurementsConfiguration
R2026bCompute and display occupied bandwidth or adjacent channel power ratio on the spectrum analyzer
Since R2022a
Description
Use the ChannelMeasurementsConfiguration object to compute and
display the occupied bandwidth or adjacent channel power ratio on the spectrum
analyzer.
You can specify the occupied bandwidth or adjacent channel power ratio (ACPR) settings,
frequency span, center frequency, and start and stop frequencies, and control the channel
measurement settings from the spectrum analyzer toolstrip or from the command line. Both the
spectrumAnalyzer
object and the SpectrumAnalyzerBlockConfiguration object support
the ChannelMeasurementsConfiguration object in the command line.
To enable the channel measurements on the spectrum analyzer toolstrip, select Channel Measurements in the Measurements tab. To modify the channel measurement settings, click the Channel Measurements drop-down arrow.
Creation
Description
channMeas = ChannelMeasurementsConfiguration() creates a channel
measurements configuration object channMeas.
Properties
Examples
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:
PeakFinderCursorMeasurementsChannelMeasurementsDistortionMeasurements
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
