# dsp.SpectrumAnalyzer

(To be removed) Display frequency spectrum of time-domain signals

• The `dsp.SpectrumAnalyzer` object will be removed in a future release. Use the `spectrumAnalyzer` MATLAB® object instead.

• The `CCDFMeasurements` property of the `dsp.SpectrumAnalyzer` object will be removed in a future release. Use the `powermeter` object instead to compute and visualize CCDF measurements.

## Description

The Spectrum Analyzer System object™ displays the frequency spectrum of time-domain signals. This scope supports variable-size input, which allows the input frame size to change. Frame size is the first dimension of the input vector. The number of input channels must remain constant.

To display the spectra of signals in the Spectrum Analyzer:

1. Create the `dsp.SpectrumAnalyzer` object and set its properties.

2. Call the object with arguments, as if it were a function.

## Creation

### Syntax

``scope = dsp.SpectrumAnalyzer``
``scope = dsp.SpectrumAnalyzer(ports)``
``scope = dsp.SpectrumAnalyzer(Name,Value)``

### Description

````scope = dsp.SpectrumAnalyzer` creates a Spectrum Analyzer System object. This object displays the frequency spectrum of real- and complex-valued floating- and fixed-point signals. `scope = dsp.SpectrumAnalyzer(ports)` creates a Spectrum Analyzer object and sets the `NumInputPorts` property to the value of `ports`.`scope = dsp.SpectrumAnalyzer(Name,Value)` sets properties using one or more name-value pairs. Enclose each property name in single quotes.```

## Properties

expand all

Unless otherwise indicated, properties are nontunable, which means you cannot change their values after calling the object. Objects lock when you call them, and the `release` function unlocks them.

If a property is tunable, you can change its value at any time.

### Frequently Used

Number of input ports, specified as a positive integer. Each signal coming through a separate input becomes a separate channel in the scope. You must invoke the scope with the same number of inputs as the value of this property.

The domain of the input signal you want to visualize, specified as `"Time"` or `"Frequency"`. If you visualize time-domain signals, the Spectrum Analyzer transforms the signal to the frequency spectrum based on the algorithm specified in the `Method` property.

#### Scope Window Use

In the Estimation tab on the Spectrum Analyzer toolstrip, set Input Domain to `Time` or `Frequency`.

Data Types: `char` | `string`

Spectrum type, specified as one of these:

`"Power"` — Power spectrum

`"Power density"` — Power spectral density. The power spectral density is the magnitude squared of the spectrum normalized to a bandwidth of 1 Hz.

`"RMS"` — Root mean square. The root mean square shows the square root of the mean square. Use this option to view the frequency of voltage or current signals.

Tunable: Yes

#### Dependency

To enable this property, set `InputDomain` to `"Time"`.

#### Scope Window Use

In the Analyzer tab on the Spectrum Analyzer toolstrip, select . Click to select `Power`, `Power Density`, or `RMS`.

To enable these options, set the Input Domain on the Estimation tab to `Time`.

Data Types: `char` | `string`

Specify the spectrum type as one of `"Spectrum"`, `"Spectrogram"`, or `"Spectrum and spectrogram"`.

• `"Spectrum"` — Shows the power spectrum.

• `"Spectrogram"` — Shows frequency content over time. Each line of the spectrogram is one periodogram. Time scrolls from the bottom to the top of the display. The most recent spectrogram update is at the bottom of the display.

• `"Spectrum and Spectrogram"` — Shows a dual view of a spectrum and spectrogram.

Tunable: Yes

#### Scope Window Use

In the Analyzer tab on the Spectrum Analyzer toolstrip, select , , or both.

Data Types: `char` | `string`

Specify the sample rate, in hertz, of the input signals as a finite numeric scalar.

#### Scope Window Use

Open the Spectrum Settings. In the Main options section, set Sample rate (Hz).

Spectrum estimation method, specified as one of the following:

• `"Filter bank"` –– Use an analysis filter bank to estimate the power spectrum. Compared to Welch's method, this method has a lower noise floor, better frequency resolution, and lower spectral leakage and requires fewer samples per update.

• `"Welch"` –– Use Welch's method of averaged modified periodograms.

For more details on these methods, see Algorithms.

Tunable: Yes

#### Dependency

To enable this property, set `InputDomain` to `"Time"`.

#### Scope Window Use

In the Estimation tab of the Spectrum Analyzer toolstrip, set Method to `Filter bank` or `Welch`.

To enable this parameter, set Input Domain to `Time` in the Estimation tab.

Data Types: `char` | `string`

Option to plot a two-sided spectrum, specified as one of the following:

• `true` — Compute and plot two-sided spectral estimates. When the input signal is complex valued, you must set this property to `true`.

• `false` — Compute and plot one-sided spectral estimates. If you set this property to `false`, then the input signal must be real valued.

When you set this property to `false`, the Spectrum Analyzer uses power-folding. The y-axis values are twice the amplitude that they would be if you were to set this property to `true`, except at `0` and the Nyquist frequency. A one-sided power spectral density (PSD) contains the total power of the signal in the frequency interval from DC to half the Nyquist rate. For more information, see `pwelch`.

Tunable: Yes

#### Scope Window Use

Click the Spectrum tab or the Spectrogram tab (if enabled) of the Spectrum Analyzer toolstrip. In the section, select Two-Sided Spectrum to compute and plot two-sided spectral estimates.

Data Types: `logical`

Scale to display frequency, specified as one of the following:

• `"Linear"` — Use a linear scale to display frequencies on the x-axis. To use the `"Linear"` setting, you must also set the `PlotAsTwoSidedSpectrum` property to `true`.

• `"Log"` — Use a logarithmic scale to display frequencies on the x-axis. To use the `"Log"` setting, you must also set the `PlotAsTwoSidedSpectrum` property to `false`.

Tunable: Yes

#### Scope Window Use

Click the Spectrum tab or the Spectrogram tab (if enabled) of the Spectrum Analyzer toolstrip. In the section, set the Frequency Scale to `Linear` or `Log`.

To set the Frequency Scale to `Log`, clear the Two-Sided Spectrum check box in the section in the Spectrum or the Spectrogram tab (if enabled). If you select the Two-Sided Spectrum check box, then you must set the Frequency Scale to `Linear`.

Data Types: `char` | `string`

Frequency span mode, specified as one of the following:

Tunable: Yes

#### Dependency

To enable this property, set `InputDomain` to `"Time"`.

#### Scope Window Use

Click the Estimation tab on the Spectrum Analyzer toolstrip. In the section, set Frequency Span to `Full`, ```Span and Center Frequency```, or ```Start and Stop Frequencies```.

To enable the Frequency Span, set Input Domain to `Time`.

Data Types: `char` | `string`

Specify the frequency span, in hertz, over which the Spectrum Analyzer computes and plots the spectrum. The overall span, defined by this property and the `CenterFrequency` property, must fall within the Nyquist Frequency Interval.

Tunable: Yes

#### Dependency

To enable this property, set `FrequencySpan` to `"Span and center frequency"`.

#### Scope Window Use

Open the Spectrum Settings. In the Main options section, clear the Full frequency span check box and set `Span`.

Start of the frequency interval over which spectrum is computed, specified in hertz as a real scalar. The overall span, which is defined by this property and `StopFrequency`, must fall within the Nyquist Frequency Interval.

Tunable: Yes

#### Dependency

To enable this property, set `FrequencySpan` to `"Start and stop frequencies"`.

#### Scope Window Use

Open the Spectrum Settings. In the Main options section, clear the Full frequency span and change `Span` to `FStart`. Set FStart (Hz).

End of the frequency interval over which spectrum is computed, specified in hertz as a real scalar. The overall span, which is defined by this property and the `StartFrequency` property, must fall within the Nyquist Frequency Interval.

Tunable: Yes

#### Dependency

To enable this property, set `FrequencySpan` to `"Start and stop frequencies"`.

#### Scope Window Use

Open the Spectrum Settings. In the Main options section, clear the Full frequency span and change `Span` to `FStart`. Set FStop (Hz).

Specify in hertz the center frequency of the span over which the Spectrum Analyzer computes and plots the spectrum. The overall frequency span, defined by the `Span` and this property, must fall within the Nyquist Frequency Interval.

Tunable: Yes

#### Dependency

To enable this property, set `FrequencySpan` to `"Span and center frequency"`.

#### Scope Window Use

Open the Spectrum Settings. In the Main, clear Full frequency span and set CF (Hz).

Specify the frequency resolution method of the Spectrum Analyzer.

• `"RBW"` - The `RBWSource` and `RBW` properties control the frequency resolution (in Hz) of the analyzer. The FFT length is the window length that results from achieving the specified RBW value or 1024, whichever is larger.

• `"WindowLength"` - Applies only when the `Method` property is set to `"Welch"`. The `WindowLength` property controls the frequency resolution. You can control the number of FFT points only when the `FrequencyResolutionMethod` property is `"WindowLength"`.

• `"NumFrequencyBands"` - Applies only when the `Method` property is set to ```"Filter Bank"```. The `FFTLengthSource` and `FFTLength` properties control the frequency resolution.

Tunable: Yes

#### Dependency

To enable this property, set `InputDomain` to `"Time"`.

#### Scope Window Use

Open the Spectrum Settings. In the Main options section, set the frequency resolution method by selecting the RBW (Hz) dropdown.

Data Types: `char` | `string`

Specify the source of the resolution bandwidth (RBW) as either `"Auto"` or `"Property"`.

• `"Auto"` — The Spectrum Analyzer adjusts the spectral estimation resolution to ensure that there are 1024 RBW intervals over the defined frequency span.

• `"Property"` — Specify the resolution bandwidth directly using the `RBW` property.

Tunable: Yes

#### Dependency

To enable this property, set either:

• `InputDomain` to `"Time"` and `FrequencyResolutionMethod` to `"RBW"`.

• `InputDomain` to `"Frequency"`.

#### Scope Window Use

Open the Spectrum Settings. In the Main options section, set RBW (Hz).

Data Types: `char` | `string`

RBW controls the spectral resolution of Spectrum Analyzer. Specify the resolution bandwidth in hertz as a real positive scalar. You must specify a value to ensure that there are at least two RBW intervals over the specified frequency span. Thus, the ratio of the overall span to RBW must be greater than two:

`$\frac{span}{RBW}>2$`

You can specify the overall span in different ways based on how you set the `FrequencySpan` property.

#### Dependency

To enable, set:

• `RBWSource` to `"Property"`

#### Scope Window Use

Open the Spectrum Settings. In the Main options section, set RBW (Hz).

Control the frequency resolution by specifying the window length, in samples used to compute the spectral estimates. The window length must be an integer scalar greater than 2.

Tunable: Yes

#### Dependencies

To enable this property, set:

• `FrequencyResolutionMethod` to `"WindowLength"`, which controls the frequency resolution based on your window length setting

• `Method` to `"Welch"`

#### Scope Window Use

Open the Spectrum Settings. Change the RBW (Hz) dropdown to `Window length`.

• `"Auto"` - sets the FFT length to the window length specified in the `WindowLength` property or 1024, whichever is larger.

• `"Property"` - number of FFT points using the `FFTLength` property. `FFTLength` must be greater than `WindowLength`.

Tunable: Yes

#### Dependency

To enable this property, set `FrequencyResolutionMethod` to `"WindowLength"`.

#### Scope Window Use

Open the Spectrum Settings. In the Main options section, next to the RBW (Hz) option, enter a number or select `Auto`.

Data Types: `char` | `string`

Specify the length of the FFT that the Spectrum Analyzer uses to compute spectral estimates.

If `FrequencyResolutionMethod` is `"RBW"`, the FFT length is set as the window length required to achieve the specified resolution bandwidth value or 1024, whichever is larger.

Tunable: Yes

#### Dependencies

To use this property, the following must be true:

• `FrequencyResolutionMethod` is set to `"WindowLength"` or `"NumFrequencyBands"`

• `FFTLength` is greater than or equal to the `WindowLength`.

• `FFTLengthSource` is set to `"Property"`.

#### Scope Window Use

Open the Spectrum Settings. In the Main options section, next to the RBW (Hz) option, enter a number or select `Auto`.

Specify the number of filter taps or coefficients for each frequency band. This number must be a positive even integer. This value corresponds to the number of filter coefficients per polyphase branch. The total number of filter coefficients is equal to `NumTapsPerBand` + `FFTLength`.

#### Dependency

To enable this property, set `Method` to ```"Filter Bank"```

#### Scope Window Use

Open the Spectrum Settings. In the Main options section, set Taps per band.

• `"Auto"` — The frequency vector is calculated from the length of the input. See Frequency Vector.

• `"Property"` — Enter a custom vector as the frequency vector.

#### Dependency

To enable this property, set `InputDomain` to `"Frequency"`.

#### Scope Window Use

Open the Spectrum Settings. In the Frequency input options section, set Frequency (Hz).

Data Types: `char` | `string`

Custom frequency vector, specified as a monotonically increasing vector. This vector determines the x-axis of the display. The vector must be monotonically increasing and must have the same length as the input signal frame size.

Tunable: Yes

#### Dependency

To enable this property, set:

• `InputDomain` to `"Frequency"`.

• `FrequencyVectorSource` to `"Property"`.

to .

#### Scope Window Use

Click the Estimation tab on the Spectrum Analyzer toolstrip. In the section, set Frequency (Hz) to a monotonically increasing vector of length equal to the input signal frame size.

To enable the Frequency (Hz), set Input Domain to `Frequency`.

Data Types: `single` | `double` | `int8` | `int16` | `int32` | `int64` | `uint8` | `uint16` | `uint32` | `uint64`

The percentage overlap between the previous and current buffered data segments, specified as a real, scalar value. The overlap creates a window segment that is used to compute a spectral estimate. The value must be greater than or equal to zero and less than 100.

Tunable: Yes

#### Scope Window Use

Open the Spectrum Settings. In the Window options section, set Overlap (%).

Specify a window function for the spectral estimator. The following table shows preset windows. For more information, follow the link to the corresponding function reference in the Signal Processing Toolbox™ documentation.

Window OptionCorresponding Signal Processing Toolbox Function
`"Rectangular"``rectwin`
`"Chebyshev"``chebwin`
`"Flat Top"``flattopwin`
`"Hamming"``hamming`
`"Hann"``hann`
`"Kaiser"``kaiser`
`"Blackman-Harris"``blackmanharris`

To set your own spectral estimation window, set this property to `"Custom"` and specify a custom window function in the `CustomWindow` property.

Tunable: Yes

#### Dependency

To enable this property, set:

• `InputDomain` to `"Time"`.

• `Method` to `"Welch"`

#### Scope Window Use

Click the Estimation tab on the Spectrum Analyzer toolstrip. In the Window Options section, set the Window.

To enable the Window, set Input Domain to `Time` and Method to `Welch` in the Estimation tab on the Spectrum Analyzer toolstrip.

Data Types: `char` | `string`

Name of the custom window function, specified as a character vector or string scalar. The name of the custom window function must be on the MATLAB path. Use this property if you want to customize the window using additional properties available with the Signal Processing Toolbox version of the window function.

Tunable: Yes

#### Example

Define and use a custom window function.

```function w = my_hann(L) w = hann(L, 'periodic') end scope.Window = 'Custom'; scope.CustomWindow = 'my_hann'```

#### Dependency

To use this property, set `Window` to `"Custom"`.

#### Scope Window Use

Click the Estimation tab on the Spectrum Analyzer toolstrip. In the Window Options section, for the Window, enter the name of the custom window function.

Data Types: `char` | `string`

The window sidelobe attenuation, in decibels (dB). The value must be greater than or equal to `45`.

Tunable: Yes

#### Dependency

To enable this property, set `Window` to `"Chebyshev"` or `"Kaiser"`.

#### Scope Window Use

Open the Spectrum Settings. In the Window options section, set Attenuation (dB).

Select the units of the frequency-domain input. This property allows the Spectrum Analyzer to scale frequency data if you choose a different display unit with the `SpectrumUnits` property.

#### Dependency

This option is only available when `InputDomain` is set to `Frequency`.

#### Scope Window Use

Open the Spectrum Settings. In the Frequency input options section, set Input units.

Data Types: `char` | `string`

Specify the units in which the Spectrum Analyzer displays power values.

Tunable: Yes

#### Dependency

The spectrum units available depend on the value you specify in the `SpectrumType` property.

`InputDomain``SpectrumType`Allowed `SpectrumUnits`
`"Time"``"Power"``"dBm"`, `"dBW"`, `"dBFS"`, `"Watts"`
`"Power density"``"dBm/Hz"`, `"dBW/Hz"`,`"dBFS/Hz"`, `"Watts/Hz"`
`"RMS"``"dBV"`, `"Vrms"`
`"Frequency"``"Auto"`, `"dBm"`, `"dBV"`, `"dBW"`, `"Vrms"`, `"Watts"`

If you set the `InputDomain` property to `"Frequency"` and the `SpectrumUnits` property to `"Auto"`, the Spectrum Analyzer assumes the spectrum units to be equal to input units specified in the `InputUnits` property. If you set `InputDomain` to `"Time"` and `SpectrumUnits` to any option other than `"Auto"`, then the Spectrum Analyzer converts the units specified in `InputUnits` to the units specified in `SpectrumUnits`.

#### Scope Window Use

Click the Spectrum tab on the Spectrum Analyzer toolstrip. In the section, set Spectrum Unit.

Data Types: `char` | `string`

Specify the source of the dBFS scaling factor as either `"Auto"` or `"Property"`.

• `"Auto"` –– The Spectrum Analyzer adjusts the scaling factor based on the input data.

• `"Property"` –– Specify the full-scale scaling factor using the `FullScale` property.

Tunable: Yes

#### Dependency

To enable this property, set:

• `InputDomain` to `"Time"`

• `SpectrumType` to `"Power"` or `"Power density"`

• `SpectrumUnits` to `"dBFS"` or `"dBFS/Hz"` (when spectrum type is set to `"Power density"`)

#### Scope Window Use

Click the Spectrum tab on the Spectrum Analyzer toolstrip. In the section, set the Full Scale to either `Auto` or a positive scalar.

To enable the Full Scale:

• In the Analyzer tab, set the spectrum type to `Power` or ```Power Density```.

• In the Estimation tab, set Input Domain to `Time`.

• In the Spectrum tab, set Spectrum Unit to `dBFS` or `dBFS/Hz` (when spectrum type is set to `Power Density`).

Data Types: `char` | `string`

Specify a real positive scalar for the `dBFS` full scale.

Tunable: Yes

#### Dependency

To enable this option set:

• `SpectrumUnits` to `"dBFS"`

• `FullScaleSource` to `"Property"`

#### Scope Window Use

Open the Spectrum Settings. In the Trace options section, set Full scale to `Auto` or enter a number.

Averaging method, specified as one of the following:

• `"VBW"` — Video bandwidth method. The object uses a lowpass filter to smooth the trace and decrease noise. Use the `VBWSource` and `VBW` properties to specify the VBW value.

• `"Exponential"` — Weighted average of samples. The object computes the average over samples weighted by an exponentially decaying forgetting factor. Use the `ForgettingFactor` property to specify the weighted forgetting factor.

Tunable: Yes

#### Dependency

To enable this property, set `InputDomain` to `"Time"`.

#### Scope Window Use

Click the Estimation tab on the Spectrum Analyzer toolstrip. In the section, set Averaging Method to `VBW` or `Exponential`.

To enable the Averaging Method, set Input Domain to `Time`.

Data Types: `char` | `string`

The Spectrum Analyzer computes the current power spectrum estimate by computing a running average of the last N power spectrum estimates. This property defines N.

Tunable: Yes

#### Dependency

To enable this property, set `ViewType` to `"Spectrum"`.

#### Dependency

This property applies only when the `AveragingMethod` is `"Running"`.

#### Scope Window Use

Open the Spectrum Settings. In the Trace options section, set Averages.

Specify the exponential weighting as a scalar value greater than 0 and less than or equal to 1.

#### Dependency

This property applies only when the `AveragingMethod` is `"Exponential"`.

#### Scope Window Use

Open the Spectrum Settings. In the Trace options section, set Forgetting factor.

The load the scope uses as a reference to compute power levels.

Tunable: Yes

#### Scope Window Use

Open the Spectrum Settings. In the Trace options section, set Ref. load (Ohms).

• Scalar — Apply the same frequency offset to all channels, specified in hertz as a character vector.

• Vector — apply a specific frequency offset for each channel, specify a vector of frequencies. The vector length must be equal to number of input channels.

The frequency-axis values are offset by the values specified in this property. The overall span must fall within the Nyquist Frequency Interval. You can control the overall span in different ways based on how you set the `FrequencySpan` property.

Tunable: Yes

#### Scope Window Use

Open the Spectrum Settings. In the Trace options section, set Offset (Hz).

### Spectrogram

Specify the channel for which the spectrogram is plotted, as a real, positive scalar integer in the range [1 N], where N is the number of input channels.

Tunable: Yes

#### Dependency

To enable this property, set `ViewType` to `"Spectrogram"` or ```"Spectrum and spectrogram"```.

#### Scope Window Use

Open the Spectrum Settings. In the Spectrogram options section, select a Channel.

Specify the source for the time resolution of each spectrogram line as either `"Auto"` or `"Property"`. The `TimeResolution` property shows the time resolution for the different frequency resolution methods and time resolution properties.

Tunable: Yes

#### Dependency

To enable this property, set `ViewType` to `"Spectrogram"` or ```"Spectrum and spectrogram"```.

#### Scope Window Use

Click the Spectrogram tab on the Spectrum Analyzer toolstrip. In the Time Options section, set the Time Resolution (s) to `Auto` or enter a positive scalar.

To enable the Time Resolution (s), select Spectrogram in the Analyzer tab.

Data Types: `char` | `string`

Specify the time resolution of each spectrogram line as a positive scalar, expressed in seconds.

The Spectrum Analyzer determines the time resolution value based on the frequency resolution method, RBW, and time resolution properties.

MethodRBWTime ResolutionResulting Time Resolution in Seconds
`Welch` or ```Filter Bank````Auto``Auto`1/RBW
`Welch` or ```Filter Bank````Auto`Manually entered1/Time Resolution Hz
`Welch` or ```Filter Bank```Manually entered`Auto`1/RBW seconds
`Welch` or ```Filter Bank```Manually enteredManually enteredEqual to or greater than the minimum attainable time resolution 1/RBW. The Spectrum Analyzer combines several spectral estimates into one spectrogram line to obtain the desired time resolution. It uses interpolation to obtain time resolution values that are not integer multiples of 1/RBW.

Tunable: Yes

#### Dependency

To enable this property, set:

• `ViewType` to `"Spectrogram"` or `"Spectrum and spectrogram"`

• `TimeResolutionSource` to `"Property`.

#### Scope Window Use

Open the Spectrum Settings. In the Spectrogram options section, in the Time res (s) box, enter a number.

Source for the time span of the spectrogram, specified as either `"Auto"` or `"Property"`. If you set this property to `"Auto"`, the spectrogram displays 100 spectrogram lines at any given time. If you set this property to `"Property"`, the spectrogram uses the time duration you specify in seconds in the `TimeSpan` property.

Tunable: Yes

#### Dependency

To enable this property, set `ViewType` to `"Spectrogram"` or ```"Spectrum and spectrogram"```.

#### Scope Window Use

Click the Spectrogram tab on the Spectrum Analyzer toolstrip. In the Time Options section, set the Time Span (s) to `Auto` or enter a positive scalar.

Data Types: `char` | `string`

Specify the time span of the spectrogram display in seconds. You must set the time span to be at least twice as large as the duration of the number of samples required for a spectral update.

Tunable: Yes

#### Dependency

To enable this property, set:

• `ViewType` to `"Spectrogram"` or `"Spectrum and spectrogram"`.

• `TimeSpanSource` to `"Property"`.

#### Scope Window Use

Open the Spectrum Settings. In the Spectrogram options section, in the Time span (s) box, enter a number.

### Measurements

Channel for which the measurements are obtained, specified as a real, positive integer greater than 0 and less than or equal to 100. The maximum number you can specify is the number of channels (columns) in the input signal.

Tunable: Yes

#### Scope Window Use

Click on > and open the Trace Selection settings.

Data Types: `double`

Specify whether to display upper and lower spectral mask lines on a spectrum plot. This property uses properties from a `SpectralMaskSpecification` object to enable and configure the spectral masks.

Tunable: Yes

#### Scope Window Use

Open the Spectral Mask pane and modify the Settings options.

Peak finder measurement, specified as a `PeakFinderConfiguration` object. Enable peak finder to compute and display the largest calculated peak values. All `PeakFinderConfiguration` properties are tunable.

Tunable: Yes

#### Dependency

To enable this property, set `ViewType` to `"Spectrum"` or ```"Spectrum and spectrogram"```.

#### Scope Window Use

Click the Measurements tab on the Spectrum Analyzer toolstrip and modify the peak finder measurements in the Peaks section.

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

Cursor measurements, specified as a `CursorMeasurementsConfiguration` object. Enable cursor measurements to display waveform cursors. All `CursorMeasurementsConfiguration` properties are tunable.

Tunable: Yes

#### Dependency

To enable this property, set `ViewType` to `"Spectrum"` or `"Spectrum and spectrogram"`.

#### Scope Window Use

Click the Measurements tab on the Spectrum Analyzer toolstrip and modify the cursor measurements in the Cursors section.

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

Enable channel measurements to compute and display the occupied bandwidth or adjacent channel power ratio. The `ChannelMeasurements` property uses the `ChannelMeasurementsSpecification` properties.

The `ChannelMeasurementsSpecification` properties are:

• `Algorithm` –– Type of measurement data to display, specified as either `"Occupied BW"` or `"ACPR"`.

Default: `"Occupied BW"`

• `FrequencySpan` –– Frequency span mode, specified as either `"Span and center frequency"` or ```"Start and stop frequencies"```

Default: `"Span and center frequency"`

• `Span` –– Frequency span over which the channel measurements are computed, specified as a real, positive scalar in Hz. This property applies when you set the `FrequencySpan` property to `"Span and center frequency"`.

Default: `2000` Hz

• `CenterFrequency` –– Center frequency of the span over which the channel measurements are computed, specified as a real scalar in Hz. This property applies when you set the `FrequencySpan` property to ```"Span and center frequency"```.

Default: `0` Hz

• `StartFrequency` –– Start frequency over which the channel measurements are computed, specified as a real scalar in Hz. This property applies when you set the `FrequencySpan` property to `"Start and stop frequencies"`.

Default: `-1000` Hz

• `StopFrequency` –– Stop frequency over which the channel measurements are computed, specified as a real scalar in Hz. This property applies when you set the `FrequencySpan` property to `"Start and stop frequencies"`.

Default: `1000` Hz

• `PercentOccupiedBW` –– Percent of power over which to compute the occupied bandwidth, specified as a positive real scalar. This property applies when you set the `Algorithm` property to `"Occupied BW"`.

Default: `99`

• `NumOffsets` –– Number of adjacent channel pairs, specified as a real, positive integer. This property applies when you set the `Algorithm` property to `"ACPR"`.

Default: `2`

• `AdjacentBW` –– Adjacent channel bandwidth, specified as a real, positive scalar. This property applies when you set the `Algorithm` property to `"ACPR"`.

Default: `1000`

• `FilterShape` –– Filter shape for both main and adjacent channels, specified as `"None"`, `"Gaussian"`, or `"RRC"`. This property applies when you set the `Algorithm` property to `"ACPR"`.

Default: `"None"`

• `FilterCoeff` –– Channel filter coefficient, specified as a real scalar between `0` and `1`. This property applies when you set the `Algorithm` property to `"ACPR"` and the `FilterShape` property to either `"Gaussian"` or `"RRC"`.

Default: `0.5`

• `ACPROffsets` –– 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`. This property applies when you set the `Algorithm` property to `"ACPR"`.

Default: `[2000 3500]`

• `Enable` –– Set this property to `true` to enable channel measurements. Valid values are `true` or `false`.

Default: `false`

All `ChannelMeasurementsSpecification` properties are tunable.

#### Scope Window Use

Open the Channel Measurements pane () and modify the Measurement and Channel Settings options.

Distortion measurements, specified as a `DistortionMeasurementsConfiguration` object. Enable distortion measurements to compute and display the harmonic distortion and intermodulation distortion. All `DistortionMeasurementsConfiguration` properties are tunable.

Tunable: Yes

#### Dependency

To enable this property, set `ViewType` to `"Spectrum"` or `"Spectrum and spectrogram"`.

#### Scope Window Use

Click the Measurements tab on the Spectrum Analyzer toolstrip and modify the distortion measurements in the Distortion section.

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

### Visualization

Caption to display in the scope window, specified as a character vector or string scalar.

Tunable: Yes

Data Types: `char` | `string`

Spectrum Analyzer window position in pixels, specified by the size and location of the scope window as a four-element double vector of the form [left bottom width height]. You can place the scope window in a specific position on your screen by modifying the values to this property.

By default, the window appears in the center of your screen with a width of `800` pixels and height of `450` pixels. The exact center coordinates depend on your screen resolution.

Tunable: Yes

Plot type to display normal traces, specified as `"Line"` or `"Stem"`. Normal traces are traces that display free-running spectral estimates.

Tunable: Yes

#### Dependencies

To enable this property, set:

• `ViewType` to `"Spectrum"` or `"Spectrum and spectrogram"`.

• `PlotNormalTrace` to `true`.

#### Scope Window Use

Click the Analyzer tab on the Spectrum Analyzer toolstrip, navigate to the section and click . In the Spectrum Analyzer Settings window, under Display and Labels, set Plot Type to `Line` or `Stem`.

To enable the Plot Type, you must:

• Select in the Views section of the Analyzer tab.

• Enable the Normal Trace check box in the Trace Options section of the Spectrum tab.

Data Types: `char` | `string`

To remove normal traces from the display, set this property to `false`. These traces display the free-running spectral estimates. The Spectrum Analyzer continues its spectral computations even when you set this property to `false`.

Tunable: Yes

#### Dependency

To enable this property, set `ViewType` to `"Spectrum"` or ```"Spectrum and spectrogram"```.

#### Scope Window Use

Click the Spectrum tab on the Spectrum Analyzer toolstrip and select the Normal Trace check box in the Trace Options section.

To enable the Normal Trace check box, select Spectrum in the Analyzer tab.

Data Types: `logical`

To compute and plot the maximum-hold spectrum of each input channel, set this property to `true`. The maximum-hold spectrum at each frequency bin is computed by keeping the maximum value of all the power spectrum estimates. When you toggle this property, the Spectrum Analyzer resets its maximum-hold computations.

Tunable: Yes

#### Dependency

To enable this property, set `ViewType` to `"Spectrum"` or ```"Spectrum and spectrogram"```.

#### Scope Window Use

Click the Spectrum tab on the Spectrum Analyzer toolstrip and select the Max-Hold Trace check box in the Trace Options section.

To enable the Max-Hold Trace check box, select Spectrum in the Analyzer tab.

Data Types: `logical`

To compute and plot the minimum-hold spectrum of each input channel, set this property to `true`. The minimum-hold spectrum at each frequency bin is computed by keeping the minimum value of all the power spectrum estimates. When you toggle this property, the Spectrum Analyzer resets its minimum-hold computations.

Tunable: Yes

#### Dependency

To enable this property, set `ViewType` to `"Spectrum"` or ```"Spectrum and spectrogram"```.

#### Scope Window Use

Click the Spectrum tab on the Spectrum Analyzer toolstrip and select the Min-Hold Trace check box in the Trace Options section.

To enable the Min-Hold Trace check box, select Spectrum in the Analyzer tab.

Data Types: `logical`

Display title, specified as a character vector or a string scalar.

Tunable: Yes

#### Scope Window Use

Click the Analyzer tab on the Spectrum Analyzer toolstrip. In the Configuration section, click . In the Spectrum Analyzer Settings window that opens up, under Display and labels, enter Title.

Data Types: `char` | `string`

y-axis label, specified as a character vector or a string scalar. The Spectrum Analyzer displays the label to the left of the y-axis.

Regardless of the value of this property, Spectrum Analyzer always displays power units as one of the `SpectrumUnits` values.

Tunable: Yes

#### Dependency

To enable this property, set `ViewType` to `"Spectrum"` or ```"Spectrum and spectrogram"```.

#### Scope Window Use

Click the Analyzer tab on the Spectrum Analyzer toolstrip. In the Configuration section, click . In the Spectrum Analyzer Settings window that opens up, under Display and labels, enter Y-Label.

To enable the Y-Label, select Spectrum in the Analyzer tab.

Data Types: `char` | `string`

Flag to show the legend, specified as `true` or `false`. To show a legend with the input names, set this property to `true`.

Use the legend to control which signals are visible. In the scope legend, click a signal name to hide the signal in the scope. To show the signal, click the signal name again. To show only one signal, right-click the signal name. To show all signals, press Esc.

Tunable: Yes

#### Dependencies

To enable this property, set the `ViewType` property to `"Spectrum"` or `"Spectrum and spectrogram"`.

#### Scope Window Use

Click the Analyzer tab on the Spectrum Analyzer toolstrip. To see the legend, click in the Configuration section.

To enable the Legend, select Spectrum in the Analyzer tab.

Data Types: `logical`

Channel names in the input data, specified as a cell array of character vectors or an array of strings. The names you specify in this property appear in the following locations:

• Legend

• Spectrum Analyzer Settings > Color and styling section

• Measurements and Channel Measurements tabs

If you do not specify channel names, the Spectrum Analyzer names the channels as `Channel 1`, ```Channel 2```, and so on.

Tunable: Yes

#### Dependency

To see the channel names, set `ShowLegend` to `true`.

#### Scope Window Use

Click the Analyzer tab on the Spectrum Analyzer toolstrip. To see the legend, click in the Configuration section.

Data Types: `char`

Flag to show the grid, specified as `true` or `false`. Set this property to `true` to show grid lines in the plot.

Tunable: Yes

#### Scope Window Use

Click the Analyzer tab on the Spectrum Analyzer toolstrip. In the Configuration section, click . In the Spectrum Analyzer Settings window that appears, under Display and Labels, select Show Grid.

Data Types: `logical`

y-axis limits, specified as a two-element numeric vector of the form [`ymin ymax`]. The units of the y-axis limits depend on the `SpectrumUnits` property.

Example: `scope.YLimits = [-10,20]`

Tunable: Yes

#### Dependencies

• To enable this property, set the `ViewType` property to `"Spectrum"` or ```"Spectrum and spectrogram"```.

• The units directly depend upon the `SpectrumUnits` property.

#### Scope Window Use

Click the Analyzer tab on the Spectrum Analyzer toolstrip. In the Configuration section, click . In the Spectrum Analyzer Settings window that opens up, under Display and Labels, enter Y-Axis Limits.

To enable the Y-Axis Limits, select Spectrum in the Analyzer tab.

Color limits of the spectrogram, specified as a two-element numeric vector of the form [`colorMin colorMax`]. The units of the color limits directly depend upon the `SpectrumUnits` property.

Example: `scope.ColorLimits = [-10,20]`

Tunable: Yes

#### Dependencies

• To enable this property, set the `ViewType` property to `"Spectrogram"` or ```"Spectrum and spectrogram"```.

• The units directly depend upon the `SpectrumUnits` property.

#### Scope Window Use

Click the Analyzer tab on the Spectrum Analyzer toolstrip. In the Configuration section, click . In the Spectrum Analyzer Settings window that opens up, under Display and Labels, enter Color Limits.

To enable the Color Limits, select Spectrogram in the Analyzer tab.

Axes scaling mode, specified as one of these:

• `"Auto"` — The scope scales the axes to fit the data, both during and after simulation.

• `"Manual"` — The scope does not scale the axes automatically.

• `"OnceAtStop"` — The scope scales the axes when the simulation stops.

• `"Updates"` — The scope scales the axes after a specific number of visual updates. It determines the number of updates using the `AxesScalingNumUpdates` property.

Tunable: Yes

Data Types: `char` | `string`

Layout of the axes, specified as one of `"Vertical"` or `"Horizontal"`. A vertical layout stacks the spectrum above the spectrogram. A horizontal layout puts the two views side-by-side.

Tunable: Yes

#### Dependency

To enable this property, set `ViewType` to ```"Spectrum and spectrogram"```.

#### Scope Window Use

Click the Analyzer tab on the Spectrum Analyzer toolstrip. Select Spectrum and Spectrogram. In the Configuration section, select and update Layout.

Data Types: `char` | `string`

## Usage

### Syntax

``scope(signal)``
``scope(signal1,signal2,...,signalN)``

### Description

````scope(signal)` updates the spectrum of the signal in the spectrum analyzer.```

example

````scope(signal1,signal2,...,signalN)` displays multiple signals in the spectrum analyzer. The signals must have the same frame length, but can vary in number of channels. You must set the `NumInputPorts` property to enable multiple input signals. ```

### Input Arguments

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Specify one or more input signals to visualize in the `dsp.SpectrumAnalyzer`. Signals can have a different number of channels, but must have the same frame length.

Example: `scope(signal1, signal2)`

Data Types: `single` | `double` | `int8` | `int16` | `int32` | `int64` | `uint8` | `uint16` | `uint32` | `uint64` | `fi`

## Object Functions

To use an object function, specify the System object as the first input argument. For example, to release system resources of a System object named `obj`, use this syntax:

`release(obj)`

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 `generateScript` Generate MATLAB script to create scope with current settings `getMeasurementsData` Get the current measurement data displayed on the spectrum analyzer `getSpectralMaskStatus` Get test results of current spectral mask `getSpectrumData` Save spectrum data shown in spectrum analyzer `isNewDataReady` Check spectrum analyzer for new data
 `show` Display scope window `hide` Hide scope window `isVisible` Determine visibility of scope
 `step` Run System object algorithm `release` Release resources and allow changes to System object property values and input characteristics `reset` Reset internal states of System object

If you want to restart the simulation from the beginning, call `reset` to clear the scope window displays. Do not call `reset` after calling `release`.

## Examples

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View a one-sided power spectrum made from the sum of fixed real sine waves with different amplitudes and frequencies.

```Fs = 100e6; % Sampling frequency fSz = 5000; % Frame size sin1 = dsp.SineWave(1e0, 5e6,0,'SamplesPerFrame',fSz,'SampleRate',Fs); sin2 = dsp.SineWave(1e-1,15e6,0,'SamplesPerFrame',fSz,'SampleRate',Fs); sin3 = dsp.SineWave(1e-2,25e6,0,'SamplesPerFrame',fSz,'SampleRate',Fs); sin4 = dsp.SineWave(1e-3,35e6,0,'SamplesPerFrame',fSz,'SampleRate',Fs); sin5 = dsp.SineWave(1e-4,45e6,0,'SamplesPerFrame',fSz,'SampleRate',Fs); scope = dsp.SpectrumAnalyzer; scope.SampleRate = Fs; scope.SpectralAverages = 1; scope.PlotAsTwoSidedSpectrum = false; scope.RBWSource = 'Auto'; scope.PowerUnits = 'dBW'; for idx = 1:1e2 y1 = sin1(); y2 = sin2(); y3 = sin3(); y4 = sin4(); y5 = sin5(); scope(y1+y2+y3+y4+y5+0.0001*randn(fSz,1)); end```

Run the `release` method to let property values and input characteristics change. The scope automatically scales the axes.

`release(scope)`

Run the `clear` function to close the Spectrum Analyzer window.

`clear('scope');`

View a two-sided power spectrum of a sine wave with noise on the Spectrum Analyzer.

```sin = dsp.SineWave('Frequency',100,'SampleRate',1000); sin.SamplesPerFrame = 1000; scope = dsp.SpectrumAnalyzer('SampleRate',sin.SampleRate); for ii = 1:250 x = sin() + 0.05*randn(1000,1); scope(x); end```

Run the `release` method to change property values and input characteristics. The scope automatically scales the axes. It updates the display one more time if any data is in the internal buffer.

`release(scope);`

Run the MATLAB `clear` function to close the Spectrum Analyzer window.

`clear('scope');`

This example shows the spectrogram for a chirp signal with added random noise.

```Fs = 233e3; frameSize = 20e3; chirp = dsp.Chirp('SampleRate',Fs,... 'SamplesPerFrame',frameSize,... 'InitialFrequency',11e3,... 'TargetFrequency',11e3+55e3); scope = dsp.SpectrumAnalyzer('SampleRate',Fs); scope.ViewType = 'Spectrogram'; scope.RBWSource = 'Property'; scope.RBW = 500; scope.TimeSpanSource = 'Property'; scope.TimeSpan = 2; scope.PlotAsTwoSidedSpectrum = false; for idx = 1:50 y = chirp()+ 0.05*randn(frameSize,1); scope(y); end release(scope) ```

Use the Spectrum Analyzer to display frequency input from spectral estimates of sinusoids embedded in white Gaussian noise.

Initialization

Initialize two `dsp.SpectrumEstimator` objects to display. Set one object to use the Welch-based spectral estimation technique with a Hann window, set the other object use a filter bank estimation. Specify a noisy sine wave input signal with four sinusoids at 0.16, 0.2, 0.205, and 0.25 cycles/sample. View the spectral estimate using a third object, a spectrum analyzer, set to process frequency input.

```FrameSize = 420; Fs = 1; Frequency = [0.16 0.2 0.205 0.25]; sinegen = dsp.SineWave('SampleRate',Fs,'SamplesPerFrame',FrameSize,... 'Frequency',Frequency,'Amplitude',[2e-5 1 0.05 0.5]); NoiseVar = 1e-10; numAvgs = 8; hannEstimator = dsp.SpectrumEstimator('PowerUnits','dBm',... 'Window','Hann','FrequencyRange','onesided',... 'SpectralAverages',numAvgs,'SampleRate',Fs); filterBankEstimator = dsp.SpectrumEstimator('PowerUnits','dBm',... 'Method','Filter bank','FrequencyRange','onesided',... 'SpectralAverages',numAvgs,'SampleRate',Fs); spectrumPlotter = dsp.SpectrumAnalyzer('InputDomain','Frequency',... 'SampleRate',Fs,... 'SpectrumUnits','dBm','YLimits',[-120,40],... 'PlotAsTwoSidedSpectrum',false,... 'ChannelNames',{'Hann window','Filter bank'},'ShowLegend',true); ```

Streaming

Stream the input. Compare the spectral estimates in the spectrum analyzer.

```for i = 1:1000 x = sum(sinegen(),2) + sqrt(NoiseVar)*randn(FrameSize,1); Pse_hann = hannEstimator(x); Pfb = filterBankEstimator(x); spectrumPlotter([Pse_hann,Pfb]) end ```

Compute and display the power spectrum of a noisy sinusoidal input signal using the `dsp.SpectrumAnalyzer` System object. Measure the peaks, cursor placements, adjacent channel power ratio, and distortion in the spectrum by enabling the following 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 `dsp.SpectrumAnalyzer` System 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 = dsp.SpectrumAnalyzer('SampleRate',Fs,'Method','Filter bank',... 'SpectrumType','Power','PlotAsTwoSidedSpectrum',false,... 'ChannelNames',{'Power spectrum of the input'},... 'YLimits',[-120 40],'ShowLegend',true);```

Enable Measurements Data

To obtain the measurements, set the `Enable` property of the measurements to `true`.

```SA.CursorMeasurements.Enable = true; SA.ChannelMeasurements.Enable = true; SA.PeakFinder.Enable = true; SA.DistortionMeasurements.Enable = true;```

Use `getMeasurementsData`

Stream in the noisy sine wave input signal and estimate the power spectrum of the signal using the spectrum analyzer. Measure the characteristics of the spectrum. Use the `getMeasurementsData` function to obtain these measurements programmatically. The `isNewDataReady` function indicates when there is new spectrum data. The measured data is stored 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 right side of the spectrum analyzer shows the enabled measurement panes. The values shown in these panes match with the values shown 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

Peak values are obtained by the `PeakFinder` property. Verify that the peak values obtained in the last time step of `data` match the values shown on the spectrum analyzer plot.

`peakvalues = data.PeakFinder(end).Value `
```peakvalues = 3×1 26.9851 24.1735 -51.1973 ```
`frequencieskHz = data.PeakFinder(end).Frequency/1000`
```frequencieskHz = 3×1 4.9957 0.9905 0.2369 ```

## Tips

• To close the scope window and clear its associated data, use the MATLAB `clear` function.

• To hide or show the scope window, use the `hide` and `show` functions.

• Use the MATLAB `mcc` function to compile code containing a Spectrum Analyzer.

You cannot open Spectrum Analyzer configuration dialog boxes if you have more than one compiled component in your application.

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## Version History

Introduced in R2012b

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