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dsp.DynamicFilterVisualizer

Display time-varying magnitude and phase response of digital filters

Description

The dsp.DynamicFilterVisualizer object displays the magnitude response and phase response of time-varying digital filters or time-varying filter coefficients. The input to this object can be a filter coefficients vector or a filter System object™.

Using the dynamic filter visualizer, you can configure the plot settings, find the peak values, enable cursor measurements, and even generate script to recreate the plot with the current settings from the visualizer interface. For details, see Configure Dynamic Filter Visualizer.

Creation

Description

example

dfv = dsp.DynamicFilterVisualizer returns a dynamic filter visualizer object, dfv, that displays the magnitude response of digital filters or filter coefficients.

dfv = dsp.DynamicFilterVisualizer(nfft) returns a dynamic filter visualizer with the FFTLength property set to nfft.

dfv = dsp.DynamicFilterVisualizer(nfft,Fs) returns a dynamic filter visualizer with the FFTLength property set to nfft and the SampleRate property set to Fs.

dfv = dsp.DynamicFilterVisualizer(nfft,Fs,range) returns a dynamic filter visualizer with the FFTLength property set to nfft, the SampleRate property set to Fs, and the FrequencyRange property set to range.

example

dfv = dsp.DynamicFilterVisualizer(Name=Value) returns a dynamic filter visualizer with each specified property set to the specified value. You can specify name-value pair arguments in any order.

Properties

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Frequently Used

FFT length that the dynamic filter visualizer uses to compute spectral estimates, specified as a positive integer.

Tunable: Yes

Scope Window Use

In the Configuration section on the Plot tab of the Dynamic Filter Visualizer toolstrip, click Settings. In the Filter Visualizer Settings window that opens, under Data and Axes, set FFT Length to a positive integer.

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

Sampling rate of the input signal, specified as a real positive scalar in Hz.

Tunable: Yes

Scope Window Use

In the Configuration section on the Plot tab of the Dynamic Filter Visualizer toolstrip, click Settings. In the Filter Visualizer Settings window that opens, under Data and Axes, set Sample Rate (Hz) to a positive scalar.

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

Range of the frequency axis, specified as a two-element numeric vector that is monotonically increasing and of the form [fmin, fmax]. The upper limit must be less than or equal to Fs/2, where Fs is the value specified in SampleRate.

Tunable: Yes

Scope Window Use

In the Configuration section on the Plot tab of the Dynamic Filter Visualizer toolstrip, click Settings. In the Filter Visualizer Settings window that opens, under Data and Axes, set Frequency Range to a two-element numeric vector.

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

X-axis scale, specified as either 'Linear' or 'Log'.

Tunable: Yes

Scope Window Use

In the Configuration section on the Plot tab of the Dynamic Filter Visualizer toolstrip, click Settings. In the Filter Visualizer Settings window that opens, under Data and Axes, set X-Scale to Linear or Log.

Y-axis units, specified as one of the following:

  • 'Magnitude'

  • 'Magnitude (dB)'

  • 'Magnitude squared'

Tunable: Yes

Scope Window Use

In the Configuration section on the Plot tab of the Dynamic Filter Visualizer toolstrip, click Settings. In the Filter Visualizer Settings window that opens, under Data and Axes, set Display Unit to Magnitude, Magnitude (dB), or Magnitude Squared.

  • true – The filter visualizer plots the magnitude and phase responses of the filter on two separate axes.

  • false – The filter visualizer plots only the magnitude response of the filter.

Tunable: Yes

Scope Window Use

In the Configuration section on the Plot tab of the Dynamic Filter Visualizer toolstrip, click the Magnitude Phase button.

Specify the type of plot to use in the filter visualizer window as one of these:

  • "Line" – The filter visualizer connects each point on the magnitude and phase response plot with a line.

  • "Stairs" – The filter visualizer displays the filter response (magnitude, phase, or both) as a stair-step graph. A stair-step graph is made up of only horizontal lines and vertical lines. Each horizontal line represents the filter response over a frequency value and is connected to two vertical lines. Each vertical line represents a change in values occurring at a frequency.

  • "Stem" – The filter visualizer displays the frequency response as circles with vertical lines extending down to the x-axis at each of the frequency values.

Tunable: Yes

Scope Window Use

In the Configuration section on the Plot tab of the Dynamic Filter Visualizer toolstrip, click Settings. In the Filter Visualizer Settings window that opens, under Data and Axes, set Plot Type to Line, Stairs, or Stem.

Specify the scaling mode for the axes as one of these:

  • "Auto" — The filter visualizer scales the axes as needed to fit the data, both during and after simulation.

  • "Manual" — The filter visualizer does not scale the axes automatically.

  • "OnceAtStop" — The filter visualizer scales the axes when the simulation stops.

  • "Updates" — The filter visualizer scales the axes limits once after a set number of visual updates. The number of updates is determined by the value of the AxesScalingNumUpdates property.

Tunable: Yes

Scope Window Use

Hover over the filter visualizer to see the maximize Maximize button, pan Panning icon, zoom Zoom icon, and autoscale autoscale icon buttons. You can also zoom and pan using your mouse.

Data Types: char | string

Specify the number of updates before scaling as a real, positive scalar integer.

Tunable: Yes

Dependency

To enable this property, set AxesScaling to "Updates".

Data Types: double

Measurements

Channel for which to obtain measurements, specified as a positive integer in the range [1 N], where N is the number of input channels.

Tunable: Yes

Scope Window Use

Click the Measurements tab on the Dynamic Filter Visualizer toolstrip. In the Channel section, select a Channel.

Data Types: double

Cursor measurements to display waveform cursors, specified as a CursorMeasurementsConfiguration object.

All CursorMeasurementsConfiguration properties are tunable.

Tunable: Yes

Scope Window Use

Click the Measurements tab on the Dynamic Filter Visualizer toolstrip and modify the cursor measurements in the Cursors section.

Peak finder measurements to compute and display the largest calculated peak values, specified as a PeakFinderConfiguration object.

All PeakFinderConfiguration properties are tunable.

Tunable: Yes

Scope Window Use

Click the Measurements tab on the Dynamic Filter Visualizer toolstrip and modify the peak finder measurements in the Peaks section.

Visualization

Caption to display on the Dynamic Filter Visualizer window, specified as a character vector or a string scalar.

Example: 'Dynamic Filter Visualizer'

Example: "Dynamic Filter Visualizer"

Tunable: Yes

Scope window position in pixels, specified as a four-element double vector of the form [left bottom width height]. The default value of this property is dependent on the screen resolution, and is such that the window is positioned in the center of the screen, with a width and height of 800 and 500 pixels, respectively.

Tunable: Yes

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

Specify whether to display the filter visualizer in maximized-axes mode. In this mode, the axes are expanded to fit into the entire display. To conserve space, labels do not appear in each display. Instead, tick-mark values appear on top of the plotted data. You can select one of the following options:

  • "Auto" — The axes appear maximized in all displays only if the Title and YLabel properties are empty for every display. If you enter any value in any display for either of these properties, the axes are not maximized.

  • "On" — The axes appear maximized in all displays. Any values entered into the Title and YLabel properties are hidden.

  • "Off" — None of the axes appear maximized.

Tunable: Yes

Scope Window Use

Hover over the Dynamic Filter Visualizer window to see the maximize axes button .

Data Types: char | string

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

Example: 'Magnitude Response'

Example: "Magnitude Response"

Tunable: Yes

Scope Window Use

In the Configuration section on the Plot tab of the Dynamic Filter Visualizer toolstrip, click Settings. In the Filter Visualizer Settings window that opens, under Display and Labels, set Title to a character vector or a string scalar.

Y-axis limits, specified as a two-element numeric row vector with the second element greater than the first element and of the form [ymin, ymax].

Tunable: Yes

Scope Window Use

In the Configuration section on the Plot tab of the Dynamic Filter Visualizer toolstrip, click Settings. In the Filter Visualizer Settings window that opens, under Data and Axes, set Y-Axis Limits to a two-element numeric vector.

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

When this property is set to false, no legend is displayed. When this property is set to true, a legend with automatic string labels for each input filter is displayed.

Tunable: Yes

Scope Window Use

In the Configuration section on the Plot tab of the Dynamic Filter Visualizer toolstrip, click Legend.

Data Types: logical

Names to label the input filters in the legend, specified as a cell array of character vectors or an array of strings. The default is an empty cell array. When this property is set to an empty cell array, the filters are named by default names, such as Filter 1, Filter 2, and so on.

Tunable: Yes

Scope Window Use

In the Configuration section on the Plot tab of the Dynamic Filter Visualizer toolstrip, click Legend. In the legend that appears on the plot, click the filter name.

Set this property to true to show grid lines on the plot.

Scope Window Use

In the Configuration section on the Plot tab of the Dynamic Filter Visualizer toolstrip, click Settings. In the Filter Visualizer Settings window that opens, under Data and Axes, select Grid.

Upper limit spectral mask, specified as a two-column matrix. The first column represents the frequency values (Hz), and the second column represents the magnitude spectrum of the upper limit mask.

Tunable: Yes

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

Lower limit spectral mask, specified as a two-column matrix. The first column represents the frequency values (Hz), and the second column represents the magnitude spectrum of the lower limit mask.

Tunable: Yes

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

Usage

Description

dfv(filt) displays the time-varying magnitude response of the object filter, filt, in the Dynamic Filter Visualizer figure, as long as filt has a valid freqz() implementation.

dfv(B,A) displays the magnitude response for the digital filters with numerator and denominator polynomial coefficients stored in B1 and A1, B2 and A2, ..., and BN and AN, respectively.

Input Arguments

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Input filter System object with a valid freqz() implementation.

Numerator polynomial coefficients, specified as a row vector.

Data Types: single | double

Denominator polynomial coefficients, specified as a:

  • scalar –– The filter is an FIR filter.

  • row vector –– The filter is an IIR filter.

Data Types: single | double

Object Functions

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stepDisplay time-varying magnitude response
showDisplay scope window
hideHide scope window
isVisibleDetermine visibility of scope
generateScriptGenerate MATLAB script to create scope with current settings

Examples

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Design an FIR filter with time-varying magnitude and phase response. Plot this varying response on a dynamic filter visualizer.

Create a dsp.DynamicFilterVisualizer object. Set the PlotAsMagnitudePhase property to true.

dfv = dsp.DynamicFilterVisualizer(PlotAsMagnitudePhase=1,...
    Title='Magnitude and Phase Response',...
    FilterNames=["FIR Filter","FIR Filter"])
dfv = 
  dsp.DynamicFilterVisualizer with properties:

               FFTLength: 2048
              SampleRate: 44100
          FrequencyRange: [0 22050]
                  XScale: 'Linear'
        MagnitudeDisplay: 'Magnitude (dB)'
    PlotAsMagnitudePhase: 1
                PlotType: 'Line'
             AxesScaling: 'Auto'

  Show all properties

Vary the cutoff frequency of the FIR filter, k, from 0.1 to 0.5 in increments of 0.001. View the varying magnitude and phase response using the dynamic filter visualizer.

for k = 0.1:0.001:0.5
    b = fir1(90,k);
    dfv(b,1);
end

Visualize the varying magnitude response of the variable bandwidth FIR filter using the dynamic filter visualizer.

Create a dsp.DynamicFilterVisualizer object.

dfv = dsp.DynamicFilterVisualizer(YLimits=[-160 10],...
    FilterNames="Variable Bandwidth FIR Filter")
dfv = 
  dsp.DynamicFilterVisualizer with properties:

               FFTLength: 2048
              SampleRate: 44100
          FrequencyRange: [0 22050]
                  XScale: 'Linear'
        MagnitudeDisplay: 'Magnitude (dB)'
    PlotAsMagnitudePhase: 0
                PlotType: 'Line'
             AxesScaling: 'Manual'

  Show all properties

Design a bandpass variable bandwidth FIR filter with a center frequency of 5 kHz and a bandwidth of 4 kHz.

Fs = 44100;
vbw = dsp.VariableBandwidthFIRFilter(FilterType='Bandpass',...
    FilterOrder=100,...
    SampleRate=Fs,...
    CenterFrequency=5e3,...
    Bandwidth=4e3);

Vary the center frequency of the filter. Visualize the varying magnitude response of the filter using the dsp.DynamicFilterVisualizer object.

for idx  = 1:100
    dfv(vbw);
    vbw.CenterFrequency = vbw.CenterFrequency + 20;
end

Version History

Introduced in R2018b

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