dsp.DynamicFilterVisualizer

Display time-varying magnitude response of digital filters

Description

The dsp.DynamicFilterVisualizer object displays the magnitude 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™.

Creation

Syntax

dfv = dsp.DynamicFilterVisualizer

dfv = dsp.DynamicFilterVisualizer(nfft)

dfv = dsp.DynamicFilterVisualizer(nfft,Fs)

dfv = dsp.DynamicFilterVisualizer(nfft,Fs,range)

dfv = dsp.DynamicFilterVisualizer(Name,Value)

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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`FFTLength` — FFT length
`2048` (default) | positive integer

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

`SampleRate` — Sampling rate of input
`44100` (default) | positive scalar

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

`FrequencyRange` — Range of frequency axis
[`20` `20e3`] (default) | two-element numeric vector

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

`XScale` — x-axis scale
`'Log'` (default) | `'Linear'`

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

Tunable: Yes

`MagnitudeDisplay` — y-axis units
`'Magnitude (dB)'` (default) | `'Magnitude'`|`'Magnitude squared'`

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

'Magnitude'
'Magnitude (dB)'
'Magnitude squared'

Tunable: Yes

Visualization

`Name` — Caption to display on Dynamic Filter Visualizer window
`'Dynamic Filter Visualizer'` (default) | character vector | string scalar

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

`Title` — Display title
`''` (default) | character vector | string scalar

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

Example: 'Magnitude Response'

Example: "Magnitude Response"

Tunable: Yes

`YLimits` — y-axis limits
[`-25` `25`] (default) | two-element numeric vector

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

Tunable: Yes

`ShowLegend` — Show or hide legend
`false` (default) | `true`

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

Data Types: logical

`FilterNames` — Names for input filters
`{''}` (default) | cell array of character vectors

Set this property to a cell array of character vectors to label the input filters in the legend. 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

`UpperMask` — Upper limit mask
`Inf` (default) | two-column matrix

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.

`LowerMask` — Lower limit mask
`-Inf` (default) | two-column matrix

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.

`Position` — Scope window position in pixels
`[880 495 800 450]` (default) | four-element double vector

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 410 and 300 pixels, respectively.

Tunable: Yes

Usage

Syntax

dfv(filt)

dfv(B,A)

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 B_N and A_N, respectively.

Input Arguments

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`filt` — Input filter
filter System object

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

`B` — Numerator polynomial coefficients
row vector

Numerator polynomial coefficients, specified as a row vector.

Data Types: single | double

`A` — Denominator polynomial coefficients
scalar | row vector

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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Specific to dsp.DynamicFilterVisualizer

step Display time-varying magnitude response

Specific to Scopes

`show`	Display scope window
`hide`	Hide scope window

Examples

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Plot Time-Varying Magnitude Response of FIR Filter

Open Live Script

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

Create a dsp.DynamicFilterVisualizer object.

dfv = dsp.DynamicFilterVisualizer('YLimits',[-120 10])

dfv = 
  DynamicFilterVisualizer with properties:

           FFTLength: 2048
          SampleRate: 44100
      FrequencyRange: [0 22050]
              XScale: 'Linear'
    MagnitudeDisplay: 'Magnitude (dB)'

   Visualization
                Name: 'Dynamic Filter Visualizer'
               Title: 'Magnitude Response'
             YLimits: [-120 10]
          ShowLegend: 0
         FilterNames: {''}
           UpperMask: Inf
           LowerMask: -Inf
            Position: [240 262 800 500]

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

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

Plot Time-Varying Magnitude Response of Variable Bandwidth FIR Filter

Open Live Script

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

Create a dsp.DynamicFilterVisualizer object.

dfv = dsp.DynamicFilterVisualizer('YLimits',[-160 10])

dfv = 
  DynamicFilterVisualizer with properties:

           FFTLength: 2048
          SampleRate: 44100
      FrequencyRange: [0 22050]
              XScale: 'Linear'
    MagnitudeDisplay: 'Magnitude (dB)'

   Visualization
                Name: 'Dynamic Filter Visualizer'
               Title: 'Magnitude Response'
             YLimits: [-160 10]
          ShowLegend: 0
         FilterNames: {''}
           UpperMask: Inf
           LowerMask: -Inf
            Position: [240 262 800 500]

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

Documentation

dsp.DynamicFilterVisualizer

Description

Creation

Syntax

Description

Properties

`FFTLength` — FFT length
`2048` (default) | positive integer

`SampleRate` — Sampling rate of input
`44100` (default) | positive scalar

`FrequencyRange` — Range of frequency axis
[`20` `20e3`] (default) | two-element numeric vector

`XScale` — x-axis scale
`'Log'` (default) | `'Linear'`

`MagnitudeDisplay` — y-axis units
`'Magnitude (dB)'` (default) | `'Magnitude'`|`'Magnitude squared'`

Visualization

`Name` — Caption to display on Dynamic Filter Visualizer window
`'Dynamic Filter Visualizer'` (default) | character vector | string scalar

`Title` — Display title
`''` (default) | character vector | string scalar

`YLimits` — y-axis limits
[`-25` `25`] (default) | two-element numeric vector

`ShowLegend` — Show or hide legend
`false` (default) | `true`

`FilterNames` — Names for input filters
`{''}` (default) | cell array of character vectors

`UpperMask` — Upper limit mask
`Inf` (default) | two-column matrix

`LowerMask` — Lower limit mask
`-Inf` (default) | two-column matrix

`Position` — Scope window position in pixels
`[880 495 800 450]` (default) | four-element double vector

Usage

Syntax

Description

Input Arguments

`filt` — Input filter
filter System object

`B` — Numerator polynomial coefficients
row vector

`A` — Denominator polynomial coefficients
scalar | row vector

Object Functions

Specific to dsp.DynamicFilterVisualizer

Specific to Scopes

Examples

Plot Time-Varying Magnitude Response of FIR Filter

Plot Time-Varying Magnitude Response of Variable Bandwidth FIR Filter

See Also

Functions

Objects

Topics

DSP System Toolbox Documentation

Support

Documentation

dsp.DynamicFilterVisualizer

Description

Creation

Syntax

Description

Properties

FFTLength — FFT length 2048 (default) | positive integer

SampleRate — Sampling rate of input 44100 (default) | positive scalar

FrequencyRange — Range of frequency axis [20 20e3] (default) | two-element numeric vector

XScale — x-axis scale 'Log' (default) | 'Linear'

MagnitudeDisplay — y-axis units 'Magnitude (dB)' (default) | 'Magnitude'|'Magnitude squared'

Visualization

Name — Caption to display on Dynamic Filter Visualizer window 'Dynamic Filter Visualizer' (default) | character vector | string scalar

Title — Display title '' (default) | character vector | string scalar

YLimits — y-axis limits [-25 25] (default) | two-element numeric vector

ShowLegend — Show or hide legend false (default) | true

FilterNames — Names for input filters {''} (default) | cell array of character vectors

UpperMask — Upper limit mask Inf (default) | two-column matrix

LowerMask — Lower limit mask -Inf (default) | two-column matrix

Position — Scope window position in pixels [880 495 800 450] (default) | four-element double vector

Usage

Syntax

Description

Input Arguments

filt — Input filter filter System object

B — Numerator polynomial coefficients row vector

A — Denominator polynomial coefficients scalar | row vector

Object Functions

Specific to dsp.DynamicFilterVisualizer

Specific to Scopes

Examples

Plot Time-Varying Magnitude Response of FIR Filter

Plot Time-Varying Magnitude Response of Variable Bandwidth FIR Filter

See Also

Functions

Objects

Topics

DSP System Toolbox Documentation

Support

`FFTLength` — FFT length
`2048` (default) | positive integer

`SampleRate` — Sampling rate of input
`44100` (default) | positive scalar

`FrequencyRange` — Range of frequency axis
[`20` `20e3`] (default) | two-element numeric vector

`XScale` — x-axis scale
`'Log'` (default) | `'Linear'`

`MagnitudeDisplay` — y-axis units
`'Magnitude (dB)'` (default) | `'Magnitude'`|`'Magnitude squared'`

`Name` — Caption to display on Dynamic Filter Visualizer window
`'Dynamic Filter Visualizer'` (default) | character vector | string scalar

`Title` — Display title
`''` (default) | character vector | string scalar

`YLimits` — y-axis limits
[`-25` `25`] (default) | two-element numeric vector

`ShowLegend` — Show or hide legend
`false` (default) | `true`

`FilterNames` — Names for input filters
`{''}` (default) | cell array of character vectors

`UpperMask` — Upper limit mask
`Inf` (default) | two-column matrix

`LowerMask` — Lower limit mask
`-Inf` (default) | two-column matrix

`Position` — Scope window position in pixels
`[880 495 800 450]` (default) | four-element double vector

`filt` — Input filter
filter System object

`B` — Numerator polynomial coefficients
row vector

`A` — Denominator polynomial coefficients
scalar | row vector