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FVTool

(To be removed) Filter Visualization Tool

FVTool will be removed in a future release. Use Filter Analyzer instead. For more information, see Version History.

Description

Filter Visualization Tool is an interactive app that enables you to display and analyze the responses, coefficients, and other information of a filter. You can also synchronize FVTool and Filter Designer to immediately visualize any changes made to a filter design.

In the app, you can view:

  • Magnitude response

  • Phase response

  • Group delay

  • Phase delay

  • Impulse response

  • Step response

  • Pole-zero plot

  • Filter coefficients

  • Filter information

For more information, see Analysis Types.

If you have installed the DSP System Toolbox™, FVTool can also visualize the frequency response of a filter System object™. If you need to filter streaming data in real time, using System objects is the recommended approach. For more information, see fvtool (DSP System Toolbox).

Filter Visualization Tool

Open the FVTool

FVTool can be opened programmatically using one of the methods described in Programmatic Use.

Examples

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Consider a 6th-order elliptic filter with a passband ripple of 3 dB, a stopband attenuation of 50 dB, a sample rate of 1 kHz, and a normalized passband edge of 300 Hz. Display the magnitude response of the filter.

[b,a] = ellip(6,3,50,300/500);
fvtool(b,a)

Magnitude response of an elliptic filter in FVTool.

Related Examples

Programmatic Use

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fvtool(b,a) opens FVTool and displays the magnitude response of the digital filter defined with numerator b and denominator a. Specify b and a coefficients in ascending order of power z-1.

fvtool(sos) opens FVTool and displays the magnitude response of the digital filter defined by the L-by-6 matrix of second order sections:

sos=[b01b11b211a11a21b02b12b221a12a22b0Lb1Lb2L1a1La2L]

The rows of sos contain the numerator and denominator coefficients bik and aik of the cascade of second-order sections of H(z):

H(z)=gk=1LHk(z)=gk=1Lb0k+b1kz1+b2kz21+a1kz1+a2kz2.

The number of sections L must be greater than or equal to 2. If the number of sections is less than 2, fvtool considers the input to be a numerator vector.

fvtool(d) opens FVTool and displays the magnitude response of a digital filter d. Use designfilt to generate d based on frequency-response specifications.

fvtool(b1,a1,b2,a2,...,bN,aN) opens FVTool and displays the magnitude responses of multiple filters defined with numerators b1, …, bN and denominators a1, ..., aN.

fvtool(sos1,sos2,...,sosN) opens FVTool and displays the magnitude responses of multiple filters defined with second order section matrices sos1, sos2, ..., sosN.

fvtool(Hd) opens FVTool and displays the magnitude responses for the dfilt filter object Hd or the array of dfilt filter objects.

fvtool(Hd1,Hd2,...,HdN) opens FVTool and displays the magnitude responses of the filters in the dfilt objects Hd1, Hd2, ..., HdN.

h = fvtool(___) returns a figure handle h. You can use this handle to interact with FVTool from the command line. For more information, see Controlling FVTool from the MATLAB Command Line.

More About

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Version History

Introduced before R2006a

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R2024b: FVTool will be removed

FVTool will be removed in a future release. Use Filter Analyzer instead. There are differences that require updates to your code.

Consider these filters:

[b,a] = ellip(5,5,60,[0.2 0.45]);
dFd = designfilt("bandpassfir", ...
    SampleRate=2e3,PassbandRipple=5, ...
    StopbandFrequency1=500,PassbandFrequency1=600, ...
    StopbandAttenuation1=80, ...
    PassbandFrequency2=750,StopbandFrequency2=900, ...
    StopbandAttenuation2=40);

Given the filter numerator coefficients b, denominator coefficients a, and the digitalFilter object dFd, you must make the following updates to your code.

Original Code in R2024a or EarlierUpdated Code in R2024b
fvtool(b,a,dFd)
filterAnalyzer(b,a,dFd)
fvtool(b,a,dFd,Analysis="freq")
filterAnalyzer(b,a,dFd, ...
    Analysis="magnitude",Overlay="phase")
fvtool(b,a,Fs=1000)
filterAnalyzer(b,a,SampleRates=1000)
fvtool(b,a,dFd,NumberofPoints=512, ...
    FrequencyRange="[0, 2pi)",FrequencyScale="Log")
filterAnalyzer(b,a,dFd,NFFT=512, ...
    FrequencyRange="twosided",FrequencyScale="log")
hfvt = fvtool(dFd);
addfilter(hfvt,dfilt.df1(b,a))
fa = filterAnalyzer(dFd);
addFilters(fa,b,a)
hfvt = fvtool(dFd);
setfilter(hfvt,dfilt.df1(b,a))
fa = filterAnalyzer(dFd,FilterNames="df");
replaceFilters(fa,b,a,FilterNames="df")
hfvt = fvtool(b,a,dFd);
deletefilter(hfvt,2)
fa = filterAnalyzer(b,a,dFd,FilterNames=["ba" "dFd"]); 
deleteFilters(fa,FilterNames="dFd")
hfvt = fvtool(b,a,dFd);
legend(hfvt,"ba","dFd")
filterAnalyzer(b,a,dFd,FilterNames=["ba" "dFd"])
hfvt = fvtool(b,a,dFd);
zoom(hfvt,[0.4 0.7 -30 0])
fa = filterAnalyzer(b,a,dFd);
zoom(fa,"xy",[0.4 0.7 -30 0])
fvtool(b,a,dFd,Analysis="noisepower")
filterAnalyzer(b,a,dFd,Analysis="noisepsd")

The second order sections (SOS) format is not supported in Filter Analyzer. Use the Cascaded Transfer Functions format instead. Given a filter specified as an SOS matrix sos, you must make the following updates to your code.

Original Code in R2024a or EarlierUpdated Code in R2024b
fvtool(sos)
filterAnalyzer(sos(:,1:3),sos(:,4:6))

or

[ctfNum,ctfDen] = sos2ctf(sos);
filterAnalyzer(ctfNum,ctfDen)
hfvt = fvtool(sos);
set(hfvt.SOSViewSettings,View="cumulative")
[ctfNum,ctfDen] = sos2ctf(sos);
fa = filterAnalyzer(ctfNum,ctfDen,CTFAnalysisMode="cumulative");
hfvt = fvtool(sos);
set(hfvt.SOSViewSettings,View="userdefined",UserDefined={3,1})
[ctfNum,ctfDen] = sos2ctf(sos);
fa = filterAnalyzer(ctfNum,ctfDen, ...
    CTFAnalysisMode="specify",CTFAnalysisSections={3,1});