ChannelMeasurementsConfiguration

Compute 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 modify the channel measurement settings on the spectrum analyzer toolstrip, click the Channel Measurements tab.

Creation

Syntax

channMeas = ChannelMeasurementsConfiguration()

Description

channMeas = ChannelMeasurementsConfiguration() creates a channel measurements configuration object channMeas.

Properties

All properties are tunable.

Type — Type of measurement data to display

"occupied-bandwidth" (default) | "acpr"

Type of measurement data to display, specified as either "occupied-bandwidth" or "acpr".

Scope Window Use

Click the Channel Measurements tab on the spectrum analyzer toolstrip. In the Channel Measurements section, set Type to either Occupied BW or ACPR.

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

Data Types: char | string

FrequencySpan — Frequency span mode

"span-and-center-frequency" (default) | "start-and-stop-frequencies"

Frequency span mode, specified as one of the following:

• "span-and-center-frequency" –– Measure over a frequency range specified in Span Hz and around the frequency value specified in CenterFrequency property.

• "start-and-stop-frequencies" –– Measure over the frequency range [StartFrequency, StopFrequency].

Scope Window Use

Click the Channel Measurements tab on the spectrum analyzer toolstrip. In the Frequency Options section, set Frequency Span to either Span and Center Frequency or Start and Stop Frequencies.

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

Data Types: char | string

Span — Frequency span

2000 (default) | positive scalar

Frequency span over which the object computes the channel measurements, specified as a positive scalar in Hz.

Dependency

To enable this property, set the FrequencySpan property to "span-and-center-frequency".

Scope Window Use

Click the Channel Measurements tab on the spectrum analyzer toolstrip. In the Frequency Options section, set Frequency Span to Span and Center Frequency and Span (Hz) to a positive scalar.

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

Data Types: double

CenterFrequency — Center frequency of span

0 (default) | real scalar

Center frequency of the span over which the object computes the channel measurements, specified as a real scalar in Hz.

Dependency

To enable this property, set the FrequencySpan property to "span-and-center-frequency".

Scope Window Use

Click the Channel Measurements tab on the spectrum analyzer toolstrip. In the Frequency Options section, set Frequency Span to Span and Center Frequency and Center Frequency (Hz) to a real scalar.

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

Data Types: double

StartFrequency — Start frequency

-1000 (default) | real scalar

Start frequency over which the object computes the channel measurements, specified as a real scalar in Hz.

Dependency

To enable this property, set the FrequencySpan property to "start-and-stop-frequencies".

Scope Window Use

Click the Channel Measurements tab on the spectrum analyzer toolstrip. In the Frequency Options section, set Frequency Span to Start and Stop Frequencies and Start Frequency (Hz) to a real scalar.

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

Data Types: double

StopFrequency — Stop frequency

1000 (default) | real scalar

Stop frequency over which the object computes the channel measurements, specified as a real scalar in Hz.

Dependency

To enable this property, set the FrequencySpan property to "start-and-stop-frequencies".

Scope Window Use

Click the Channel Measurements tab on the spectrum analyzer toolstrip. In the Frequency Options section, set Frequency Span to Start and Stop Frequencies and Stop Frequency (Hz) to a real scalar.

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

Data Types: double

PercentOccupiedBW — Percentage of power to compute occupied bandwidth

99 (default) | positive scalar

Percentage of power over which the object computes the occupied bandwidth, specified as a positive scalar.

Dependency

To enable this property, set the Type property to "occupied-bandwidth".

Scope Window Use

Click the Channel Measurements tab on the spectrum analyzer toolstrip. In the Channel Measurements section, set Type to Occupied BW and Occupied BW (%) to a positive scalar.

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

Data Types: double

AdjacentBW — Adjacent channel bandwidth

1000 (default) | positive scalar

Adjacent channel bandwidth, specified as a positive scalar.

Dependency

To enable this property, set the Type property to "acpr".

Scope Window Use

Click the Channel Measurements tab on the spectrum analyzer toolstrip. In the Channel Measurements section, set Type to ACPR. In the Adjacent Channels section, set Adjacent BW (Hz) to a positive scalar.

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

Data Types: double

FilterShape — Filter shape

"none" (default) | "gaussian" | "rrc"

Filter shape for main and adjacent channels, specified as "none", "gaussian", or "rrc".

Dependency

To enable this property, set the Type property to "acpr".

Scope Window Use

Click the Channel Measurements tab on the spectrum analyzer toolstrip. In the Channel Measurements section, set Type to ACPR. In the Adjacent Channels section, set Filter Shape.

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

Data Types: char | string

FilterCoeff — Channel filter coefficient

0.5 (default) | real scalar in range [0, 1]

Channel filter coefficient, specified as a real scalar in the range [0, 1].

Dependency

To enable this property, set the Type property to "acpr" and the FilterShape property to either "gaussian" or "rrc".

Scope Window Use

Click the Channel Measurements tab on the spectrum analyzer toolstrip. In the Channel Measurements section, set Type to ACPR.

In the Adjacent Channels section, set:

• Filter Shape to RRC and specify Roll-off Factor as a real scalar in the range [0,1].

• Filter Shape to Gaussian and specify BT Product as a real scalar in the range [0,1].

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

Data Types: double

NumOffsets — Number of adjacent channel pairs

2 (default) | positive integer in range [1, 64]

Number of adjacent channel pairs, specified as a positive integer in the range [1, 64].

Dependency

To enable this property, set the Type property to "acpr".

Scope Window Use

Click the Channel Measurements tab on the spectrum analyzer toolstrip. In the Channel Measurements section, set Type to ACPR. In the Adjacent Channels section, set Num Pairs to a positive integer in the range [1, 64].

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

Data Types: double

ACPROffsets — Frequency of adjacent channel relative to center frequency of main channel

[2000 3500] (default) | vector

Frequency of the adjacent channel relative to the center frequency of the main channel, specified as a real vector of length equal to the number of offset pairs specified in NumOffsets.

Dependency

To enable this property, set the Type property to "acpr".

Scope Window Use

Click the Channel Measurements tab on the spectrum analyzer toolstrip. In the Channel Measurements section, set Type to ACPR. In the Adjacent Channels section, set Offset (Hz).

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

Data Types: double

Enabled — Channel measurements flag

false (default) | true

Channel measurements flag, specified as true or false.

Scope Window Use

Click the Channel Measurements tab on the spectrum analyzer toolstrip. In the Channel Measurements section, select Channel Measurements.

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

Data Types: logical

Examples

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