Design bandstop filter
DSP System Toolbox / Filtering / Filter Designs
This block brings the filter design capabilities of the filterbuilder
function to the Simulink^{®} environment.
This block supports SIMD code generation. For details, see Code Generation.
Port_1
— Input signalInput signal to filter, specified as a scalar, vector, or matrix.
Data Types: single
 double
Port_1
— Filtered output signalFiltered output signal, specified as a scalar, vector, or matrix.
Data Types: single
 double
View Filter Response
— Open Filter Visualization Toolbutton
This button opens the Filter Visualization Tool (fvtool
) from the
Signal Processing Toolbox™ product. You can use the tool to display:
Magnitude response, phase response, and group delay in the frequency domain.
Impulse response and step response in the time domain.
Polezero information.
The tool also helps you evaluate filter performance by providing information about filter order, stability, and phase linearity. For more information on FVTool, see the Signal Processing Toolbox documentation.
Impulse response
— FIR or IIR filterFIR
(default)  IIR
Specify whether the block implements an FIR
or
IIR
filter.
Note
The design methods and structures for FIR filters are not the same as the methods and structures for IIR filters.
Order mode
— Mode of specifying filter orderMinimum
(default)  Specify
Select Minimum
to have the block implement a
filter with minimum order. When you select
Specify
, you must enter the filter order
using the Order parameter.
Tip
When you set the Impulse response to
IIR
, you can specify different numerator and
denominator orders. To specify a different denominator order, select the
Denominator order check box.
Order
— Filter order20
(default)  positive integerSpecify the filter order as a positive integer.
To enable this parameter, set Order mode to
Specify
.
Denominator order
— Specify denominator orderoff
(default)  on
Select this check box to specify a different denominator order. When you select this check box, you can specify the denominator order as a positive integer in the resulting text box.
To enable this parameter, set the Impulse
response to IIR
and the
Order mode to
Specify
.
Filter type
— Type of filterSinglerate
(default)  Decimator
 Interpolator
 Samplerate converter
Select the type of filter to implement. Your choice determines the type of filter and the design methods and structures that are available to implement your filter.
This parameter applies only when you set Impulse
response to
FIR
.
Selecting Decimator
or
Interpolator
activates the
Decimation Factor or the
Interpolation Factor options
respectively.
Selecting Samplerate converter
activates both factors.
Decimation Factor
— Decimation factor2
(default)  positive integerSpecify the decimation factor as a positive integer.
To enable this parameter, set the Filter type to
Decimator
or Samplerate
converter
.
Interpolation Factor
— Interpolation factor2
(default)  positive integerSpecify the interpolation factor as a positive integer.
To enable this parameter, set the Filter type to
Interpolator
or Samplerate
converter
.
Frequency constraints
— Frequency response constraintsPassband and stopband
edges
(default)  Passband edges
 Half power (3dB) frequencies
 Half power (3dB) frequencies and passband
width
 Half power (3dB) frequencies and stopband
width
 Cutoff (6dB) frequencies
When you set the Order mode to
Specify
, this parameter allows you to choose
the filter features that the block uses to define the frequency response
characteristics. Depending on the Impulse response you
choose, you can set the Frequency constraints to one
of:
Passband and stopband edges
— Specify the frequencies for the edges for the stop and
passbands.
Passband edges
— For IIR
filters, define the filter by specifying frequencies for the
edges of the passband.
Stopband edges
— For IIR filters,
define the filter by specifying frequencies for the edges of the
stopbands.
Half power (3dB) frequencies
— For IIR filters, define the filter response by
specifying the locations of the 3 dB points. The 3 dB point is
the frequency for the point three decibels below the passband
value.
Half power (3dB) frequencies and passband
width
— For IIR filters, define the
filter by specifying frequencies for the 3 dB points in the
filter response and the width of the passband.
Half power (3dB) frequencies and stopband
width
— For IIR filters, define the
filter by specifying frequencies for the 3 dB points in the
filter response and the width of the stopband.
Cutoff (6dB) frequencies
—
For FIR filters, define the filter response by specifying the
locations of the 6 dB points. The 6 dB point is the frequency
for the point 6 dB below the passband value.
To enable this parameter, set the Order mode to
Specify
. The available
Frequency constraints will depend on whether
the Impulse response is
FIR
or
IIR
.
Frequency units
— Frequency unitsNormalized (0 to 1)
(default)  Hz
 kHz
 MHz
 GHz
Use this parameter to specify whether your frequency settings are
normalized or in absolute frequency. Select Normalized (0 to
1)
to enter frequencies in normalized form. To enter
frequencies in absolute values, select one of the frequency units from the
dropdown list—Hz
,
kHz
, MHz
, or
GHz
.
Input sample rate
— Input sample rate2
(default)  positive scalarFs
, specified in the units you selected for
Frequency units, defines the sampling frequency at
the filter input. When you provide an input sampling frequency, all
frequencies in the specifications are in the selected units as well.
To enable this parameter, set Filter type to
Singlerate
,
Decimator
, or Samplerate
converter
and Frequency units to
one of the unit options (Hz
,
kHz
, MHz
, or
GHz
).
Output sample rate
— Output sample rate2
(default)  positive scalarWhen you design an interpolator, Fs
represents the
sampling frequency at the filter output rather than the filter input.
To enable this parameter, set Filter type to
Interpolator
and Frequency
units to one of the unit options
(Hz
, kHz
,
MHz
, or
GHz
).
Passband frequency 1
— Frequency at edge of end of first passband0.35
(default)  positive scalarEnter the frequency at the edge of the end of the first passband. Specify the value in either normalized frequency units or the absolute units you select in Frequency units.
Stopband frequency 1
— Frequency at edge of start of stopband0.45
(default)  positive scalarEnter the frequency at the edge of the start of the stopband. Specify the value in either normalized frequency units or the absolute units you select in Frequency units.
Stopband frequency 2
— Frequency at edge of end of stopband0.55
(default)  positive scalarEnter the frequency at the edge of the end of the stopband. Specify the value in either normalized frequency units or the absolute units you select in Frequency units.
Passband frequency 2
— Frequency at edge of start of second passband0.65
(default)  positive scalarEnter the frequency at the edge of the start of the second passband. Specify the value in either normalized frequency units or the absolute units you select in Frequency units.
Half power (3dB) frequency 1
— Lower frequency 3 dB point0.4
(default)  positive scalarSpecify the lower frequency 3 dB point as a positive scalar between zero and one.
To enable this parameter, set Impulse response to
IIR
, Order mode to
Specify
, and Frequency
constraints to Half power (3dB)
frequencies
, Half power (3dB) frequencies
and passband width
, or Half power (3dB)
frequencies and stopband width
.
Half power (3dB) frequency 2
— Higher frequency 3 dB point0.6
(default)  positive scalarSpecify the higher frequency 3 dB point as a positive scalar between zero and one.
To enable this parameter, set Impulse response to
IIR
, Order mode to
Specify
, and Frequency
constraints to Half power (3dB)
frequencies
, Half power (3dB) frequencies
and passband width
, or Half power (3dB)
frequencies and stopband width
.
Cutoff (6dB) frequency 1
— Lower frequency 6 dB point0.4
(default)  positive scalarSpecify the lower frequency 6 dB point as a positive scalar between zero and one.
To enable this parameter, set Frequency
constraints to Cutoff (6dB)
frequencies
.
Cutoff (6dB) frequency 2
— Higher frequency 6 dB point0.6
(default)  positive scalarSpecify the higher frequency 6 dB point as a positive scalar between zero and one.
To enable this parameter, set Frequency
constraints to Cutoff (6dB)
frequencies
.
Passband width
— Passband width0.25
(default)  positive scalarSpecify the width of the passband as a positive scalar, in units corresponding to the Frequency units parameter.
To enable this parameter, set Frequency
constraints to Half power (3dB) frequencies
and passband width
.
Stopband width
— Width of stopband0.15
(default)  positive scalarSpecify the width of the stopband as a positive scalar, in units corresponding to the Frequency units parameter.
To enable this parameter, set Frequency
constraints to Half power (3dB) frequencies
and stopband width
.
Magnitude constraints
— Magnitude constraintsUnconstrained
(default)  Constrained bands
 Passband ripples and stopband
attenuation
Specify the magnitude constraints for the filter design.
To enable this parameter, set Order mode to
Specify
. The available options depend on
the value of the Frequency constraints
parameter.
Magnitude units
— Units for magnitude specificationsdB
(default)  Linear
 Squared
Specify the units for any parameter you provide in magnitude specifications:
Linear
— Specify the
magnitude in linear units.
dB
— Specify the magnitude
in decibels (default).
Squared
— Specify the
magnitude in squared units.
To enable this parameter, set Order mode to
Minimum
.
Passband ripple 1
— Allowable filter ripple in first passband1
(default)  realvalued positive scalarSpecify the filter ripple allowed in the first passband in the units you choose for Magnitude units. Values must be real, positive scalars. If you are specifying values in linear units, they must be smaller than 1.
To enable this parameter, set the Order mode to
Minimum
.
Stopband attenuation
— Stopband attenuation60
(default)  realvalued positive scalarEnter the filter attenuation in the stopband in the units you choose for Magnitude units. Values must be real, positive scalars. If you are specifying values in linear units, they must be smaller than 1.
To enable this parameter, set the Order mode to
Minimum
.
Passband ripple 2
— Allowable filter ripple in second passband1
(default)  realvalued positive scalarEnter the filter ripple allowed in the second passband in the units you choose for Magnitude units. Values must be real, positive scalars. If you are specifying values in linear units, they must be smaller than 1.
To enable this parameter, set the Order mode to
Minimum
.
Design method
— Filter design methodEquiripple
(default)  Kaiser window
 Butterworth
 Chebyshev type I
 Chebyshev type II
 Elliptic
Lists the design methods available for the frequency and magnitude
specifications you entered. When you change the specifications for a filter,
such as changing the impulse response, the methods available to design
filters changes as well. The default IIR design method is usually
Butterworth
, and the default FIR method is
Equiripple
.
Scale SOS filter coefficients to reduce chance of overflow
— Scale filter coefficientson
(default)  off
Selecting this parameter directs the design to scale the filter coefficients to reduce the chances that the inputs or calculations in the filter overflow and exceed the representable range of the filter. Clearing this option removes the scaling.
To enable this parameter, set Impulse response to
IIR
.
Density factor
— Density factor16
(default)  positive scalarDensity factor controls the density of the frequency grid over which the design method
optimization evaluates your filter response function. The number of equally
spaced points in the grid is the value you enter for Density
factor times (filter order
+ 1.
Increasing the value creates a filter that more closely approximates an ideal equiripple
filter but increases the time required to design the filter. The default
value of 16
represents a reasonable balance between the
accurate approximation to the ideal filter and the time to design the
filter.
To enable this parameter, set Impulse response to
FIR
and Design
method to Equiripple
.
Phase constraint
— Phase constraintLinear
(default)  Maximum
 Minimum
Specify the phase constraint of the filter as Linear
,
Maximum
, or Minimum
.
To enable this parameter, set Impulse response to
FIR
and Design
method to Equiripple
.
Minimum order
— Minimum filter orderAny
(default)  Even
When you select this parameter, the design method determines and designs a minimum order filter to meet your specifications.
To enable this parameter, set Impulse response to
FIR
, Order mode to
Minimum
, and Design
method to Kaiser
window
.
Match exactly
— Match passband, stopband, or bothStopband
(default)  Passband
 Both
Specifies that the resulting filter design matches either the passband, stopband, or both bands.
To enable this parameter, set Impulse response to
IIR
.
Structure
— Filter structureDirectform FIR
(default)  Directform FIR transposed
 Directform symmetric FIR
 Cascade minimummultiplier allpass
 Cascade wave digital filter allpass
 Directform I SOS
 Directform I transposed SOS
 Directform II SOS
 Directform II transposed SOS
For the filter specifications and design method you select, this parameter lists the filter structures available to implement your filter. By default, FIR filters use directform structure, and IIR filters use directform II filters with SOS.
Use basic elements to enable filter customization
— Implement filter with basic Simulink blocksoff
(default)  on
Select this check box to implement the filter as a subsystem of basic Simulink blocks. Clear the check box to implement the filter as a highlevel subsystem.
The highlevel implementation provides better compatibility across various filter structures, especially filters that would contain algebraic loops when constructed using basic elements.
When you select this check box, the block enables the following optimization parameters:
Optimize for zero gains — Terminate chains that contain Gain blocks with a gain of zero.
Optimize for unit gains — Remove Gain blocks that scale by a factor of one.
Optimize for delay chains — Substitute delay chains made up of n unit delays with a single delay of n.
Optimize for negative gains — Use subtraction in Sum blocks instead of negative gains in Gain blocks.
Optimize for unit scale values
— Optimize unit scale valuesoff
(default)  on
Select this check box to scale unit gains between sections in SOS filters.
To enable this parameter, set Impulse response to
IIR
.
Rate options
— Enforce singlerate or allow multirate processingEnforce singlerate
processing
(default)  Allow multirate processing
When the Filter type parameter specifies a multirate filter, select the rate processing rule for the block:
Enforce singlerate processing
—
When you select this option, the block maintains the sample rate of
the input.
Allow multirate processing
—
When you select this option, the block adjusts the rate at the
output to accommodate an increased or reduced number of
samples.
To enable this parameter, set the Impulse
response to FIR
and set
Filter type to a multirate filter.
Use symbolic names for coefficients
— Specify coefficients with MATLAB variablesoff
(default)  on
Select this check box to enable the specification of coefficients using MATLAB^{®} variables. The available coefficient names differ depending on the filter structure. Using symbolic names allows tuning of filter coefficients in generated code.
Data Types 

Multidimensional Signals 

VariableSize Signals 

The Bandstop Filter block supports SIMD code generation using Intel AVX2 technology under these conditions:
Impulse response is set to
FIR
.
Filter type is set to
Singlerate
.
Structure is set to Directform
FIR
or Directform FIR
transposed
.
Use basic elements to enable filter customization parameter is not selected.
Input processing is set to Columns
as channels (frame based)
.
Input signal has a data type of single
or
double
.
The SIMD technology significantly improves the performance of the generated code.
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