designBandstopFIR

Design and implement bandstop FIR filter

Since R2023b

Syntax

B = designBandstopFIR

B = designBandstopFIR(Name=Value)

Description

B = designBandstopFIR designs a bandstop FIR filter with the filter order of 100, center frequency of 0.5, bandwidth of 0.1, and a Hamming window. B is a vector of filter coefficients of length 101.

The System object™ argument is false by default. To implement the filter, assign the filter coefficients in B to a dsp.FIRFilter object.

B = designBandstopFIR(Name=Value) specifies options using one or more name-value arguments.

For example, B = designBandstopFIR(FilterOrder=30,CenterFrequency=0.4,Window="hann",SystemObject=true) designs a bandstop FIR filter with the filter order of 30, center frequency of 0.4, and a Hann window. As the SystemObject argument is true, the function designs and implements the bandstop FIR filter. B is a dsp.FIRFilter System object in this case.

When you specify only a partial list of filter parameters, the function designs the filter by setting the other design parameters to their default values.

When you specify any of the numeric input arguments in single precision, the function designs the filter coefficients in single precision. Alternatively, you can use the Datatype and like arguments to control the coefficients data type. (since R2024b)

Examples

Design and Implement Bandstop FIR Filter with Tunable Center Frequency

Create a dsp.FIRFilter object, and set the NumeratorSource property to 'Input port' so that you can vary the FIR filter coefficients through the input during simulation.

firFilt = dsp.FIRFilter(NumeratorSource="Input port")

firFilt = 
  dsp.FIRFilter with properties:

            Structure: 'Direct form'
      NumeratorSource: 'Input port'
    InitialConditions: 0

  Use get to show all properties

Create a spectrumAnalyzer object to visualize the spectra of the input and output signals.

spectrumScope = spectrumAnalyzer(SampleRate=44100,PlotAsTwoSidedSpectrum=false,...
    ChannelNames=["Input Signal","Filtered Signal"]);

Create a dsp.DynamicFilterVisualizer object to visualize the magnitude response of the varying filter.

filterViz = dsp.DynamicFilterVisualizer(NormalizedFrequency=true);

Stream in random data and filter the signal using the dsp.FIRFilter object. Use the designBandstopFIR function to design the filter coefficients. By default, this function returns a vector of FIR filter coefficients. Assign these coefficients to the dsp.FIRFilter object.

Vary the center frequency of the filter during simulation. The designBandstopFIR function redesigns the coefficients based on the updated filter specifications. Pass these updated coefficients to the FIR filter. Visualize the spectra of the input and filtered signals using the spectrum analyzer.

Fc = 0.5;
for idx = 1:500
    num = designBandstopFIR(FilterOrder=30,CenterFrequency=Fc,Bandwidth=0.2,Window="hann");
    x = randn(1024,1);
    y = firFilt(x,num);
    spectrumScope(x,y);
    filterViz(num);
    Fc = Fc + 0.0001;
end

Design and Implement Bandstop FIR Filter Object

Design and implement a bandstop FIR filter object using the designBandstopFIR function. The function returns a dsp.FIRFilter object when you set the SystemObject argument to true. To design the filter in single-precision, use the Datatype or like argument. Alternatively, you can specify any of the numerical arguments in single-precision.

firFilt = designBandstopFIR(FilterOrder=30,CenterFrequency=0.5,Bandwidth=0.3,Window="hann",...
    Datatype="single",SystemObject=true)

firFilt = 
  dsp.FIRFilter with properties:

            Structure: 'Direct form'
      NumeratorSource: 'Property'
            Numerator: [0 1.5217e-04 -3.2176e-19 0.0030 -2.0714e-17 -0.0158 1.1893e-17 0.0208 -3.3379e-18 0.0213 -2.0490e-17 -0.1252 3.4516e-17 0.2442 -1.7349e-17 0.7027 -1.7349e-17 0.2442 3.4516e-17 -0.1252 -2.0490e-17 0.0213 ... ] (1x31 single)
    InitialConditions: 0

  Use get to show all properties

Create a dsp.DynamicFilterVisualizer object to visualize the magnitude response of the varying filter.

filterViz = dsp.DynamicFilterVisualizer(NormalizedFrequency=true);
filterViz(firFilt)

Create a spectrumAnalyzer object to visualize the spectra of the input and output signals.

spectrumScope = spectrumAnalyzer(SampleRate=44100,PlotAsTwoSidedSpectrum=false,...
    ChannelNames=["Input Signal","Filtered Signal"]);

Stream in random data and filter the signal using the dsp.FIRFilter object. Visualize the spectra of the input and filtered signals using the spectrum analyzer.

for idx = 1:500
    x = randn(1024,1);
    y = firFilt(x);
    spectrumScope(x,y);
end

Input Arguments

Name-Value Arguments

Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Example: designBandstopFIR(FilterOrder=30,CenterFrequency=0.3,Bandwidth=0.2)

FilterOrder — Order of bandstop FIR filter

100 (default) | even nonnegative integer

Order of the bandstop FIR filter, N, specified as an even nonnegative integer.

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

CenterFrequency — Center frequency of bandstop FIR filter

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

Center frequency of the bandstop FIR filter, Fc, specified as a normalized scalar in the range (0,1].

Data Types: single | double

Bandwidth — Bandwidth of bandstop FIR filter

0.1 (default) | scalar in the range (0,1]

Bandwidth of the bandstop FIR filter, BW, specified as a normalized scalar in the range (0,1].

Data Types: single | double

Window — Window design method

"hamming" (default) | "hann" | "blackman" | "blackman-harris" | "chebyshev" | "kaiser" | "custom"

Window design method, specified as one of these options:

• "hamming"

• "hann"

• "blackman"

• "blackman-harris"

• "chebyshev" –– The default sidelobe attenuation is 60 dB.

• "kaiser"

• "custom" –– Specify the custom window vector in the CustomWindow argument.

Data Types: char | string

CustomWindow — Custom window vector

vector

Custom window vector, specified as a vector of length FilterOrder + 1.

Data Types: single | double

Datatype — Data type of filter coefficients by type name

"double" (default) | "single"

Since R2024b

Data type of the filter coefficients, specified by type name as "double" or "single".

You can use the Dataype or the like argument to specify the data type of the filter coefficients, but you cannot use both arguments at the same time.

If you specify the data type of the filter coefficients using this argument, the function ignores the data types of the other numeric arguments.

Data Types: char | string

like — Data type of filter coefficients by prototype

real floating-point value

Since R2024b

Data type of the filter coefficients, specified as a prototype of a real floating-point value.

You can use the Dataype or the like argument to specify the data type of filter coefficients, but you cannot use both arguments at the same time.

If you specify the data type of the filter coefficients using this argument, the function ignores the data types of the other numeric arguments.

Example: B = designBandstopFIR(FilterOrder=N,CenterFrequency=Fc,like=single(N))

Example: N = single(110); B = designBandstopFIR(FilterOrder=N,CenterFrequency=Fc,like=N)

Data Types: single | double

SystemObject — Option to create System object

false (default) | true

Option to create System object, specified as one of these:

• false –– The function returns a vector of FIR filter coefficients.

• true –– The function returns a dsp.FIRFilter object.

Data Types: logical

Verbose — Option to print function call in MATLAB^®

false (default) | true

Option to print function call in MATLAB, specified as one of these:

• false –– The function does not print the function call.

• true –– The function prints the entire function call including the default values of the Name=Value arguments that you did not specify when calling the function.

  Use this argument to view all the values used by the function to design and implement the filter.

Data Types: logical

Output Arguments

B — Filter coefficients or filter object

row vector | dsp.FIRFilter object

Bandstop FIR filter coefficients or filter object, returned as one of these:

• Row vector –– The function returns a row vector of length FilterOrder + 1 when you set the SystemObject argument to false.

  If you specify single-precision values in any of the input arguments, the function designs single-precision filter coefficients. (since R2024a)

  If you specify the data type using the Datatype or the like argument, the function ignores the data types of the other numeric arguments. (since R2024b)

• dsp.FIRFilter System object –– The function returns a filter object when you set the SystemObject argument to true.

Data Types: single | double

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

When you set the SystemObject argument to false, the function supports code generation with no limitations.

When you set the SystemObject argument to true, the inputs to the function must be constants when generating code.

This function supports strict single precision in generated code. If any of the input arguments are in single precision, or you use the Datatype and like arguments to specify single-precision (since R2024b), the code you generate uses strictly single-precision arithmetic. (since R2024a)

Version History

Introduced in R2023b

R2024b: Specify data type of filter coefficients explicitly

You can now specify the data type of filter coefficients explicitly using the Datatype and like arguments.

R2024a: Support for strict single precision

When you specify single-precision values in any of the input arguments, the function designs single-precision filter coefficients both in simulation and in generated code.