dsp.FIRFilter
Static or time-varying FIR filter
Description
The dsp.FIRFilter
System object™ filters each channel of the input using static or time-varying FIR filter
implementations.
To filter each channel of the input:
Create the
dsp.FIRFilter
object and set its properties.Call the object with arguments, as if it were a function.
To learn more about how System objects work, see What Are System Objects?
This object supports C/C++ code generation and SIMD code generation under certain conditions. For more information, see Code Generation.
Creation
Description
returns a finite impulse
response (FIR) filter object, fir
= dsp.FIRFilterfir
, which independently filters each
channel of the input over time using a specified FIR filter implementation.
returns an FIR filter System object, fir
= dsp.FIRFilter(num
)fir
, with the Numerator
property
set to num
.
returns an FIR filter System object, fir
= dsp.FIRFilter(Name,Value
)fir
, with each property set to the specified
value.
Properties
Unless otherwise indicated, properties are nontunable, which means you cannot change their
values after calling the object. Objects lock when you call them, and the
release
function unlocks them.
If a property is tunable, you can change its value at any time.
For more information on changing property values, see System Design in MATLAB Using System Objects.
Structure
— Filter structure
Direct form
(default) | Direct form symmetric
| Direct form antisymmetric
| Direct form transposed
| Lattice MA
Specify the filter structure. You can specify the filter structure as one of
Direct form
| Direct form symmetric
|
Direct form antisymmetric
| Direct form
transposed
| Lattice MA
.
NumeratorSource
— Source of filter coefficients
Property
(default) | Input port
Specify the source of the filter coefficients as Property
or
Input port
. When you specify Input port
, the
filter object updates the time-varying filter once every frame.
Dependencies
This applies when you set the Structure
to
Direct form
| Direct form symmetric
|
Direct form antisymmetric
| Direct form
transposed
.
ReflectionCoefficientsSource
— Source of filter coefficients
Property
(default) | Input port
Specify the source of the Lattice filter coefficients as Property
or Input port
. When you specify Input port
, the
filter object updates the time-varying filter once every frame.
Dependencies
This applies when you set the Structure
to
Lattice MA
.
Numerator
— Numerator coefficients
[0.5 0.5]
(default) | row vector
Specify the filter coefficients as a real or complex numeric row vector.
Tunable: Yes
Dependencies
This property applies when you set the NumeratorSource
property to Property
, and the Structure property is set to Direct
form
, Direct form symmetric
, Direct form
antisymmetric
, or Direct form transposed
.
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
Complex Number Support: Yes
ReflectionCoefficients
— Reflection coefficients of lattice filter structure
[0.5 0.5]
(default) | row vector
Specify the reflection coefficients of a lattice filter as a real or complex numeric row vector.
Tunable: Yes
Dependencies
This property applies when you set the Structure property to Lattice
MA
, and the ReflectionCoefficientsSource
property to
Property
.
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
Complex Number Support: Yes
InitialConditions
— Initial conditions for the FIR filter
0
(default) | scalar | vector | matrix
Specify the initial conditions of the filter states. The number of states or delay elements equals the number of reflection coefficients for the lattice structure, or the number of filter coefficients–1 for the other direct form structures.
You can specify the initial conditions as a scalar, vector, or matrix. If you specify a scalar value, the FIR filter object initializes all delay elements in the filter to that value. If you specify a vector whose length equals the number of delay elements in the filter, each vector element specifies a unique initial condition for the corresponding delay element. The object applies the same vector of initial conditions to each channel of the input signal.
If you specify a vector whose length equals the product of the number of input channels and the number of delay elements in the filter, each element specifies a unique initial condition for the corresponding delay element in the corresponding channel.
If you specify a matrix with the same number of rows as the number of delay elements in the filter, and one column for each channel of the input signal, each element specifies a unique initial condition for the corresponding delay element in the corresponding channel.
Tunable: Yes
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
Fixed-Point Properties
FullPrecisionOverride
— Full precision override for fixed-point arithmetic
true
(default) | false
Specify whether to use full precision rules. If you set FullPrecisionOverride
to true
, which is the default,
the object computes all internal arithmetic and output data types using full precision
rules. These rules provide the most accurate fixed-point numerics. It also turns off
the display of other fixed-point properties because they do not apply individually.
These rules guarantee that no quantization occurs within the object. Bits are added,
as needed, to ensure that no roundoff or overflow occurs. If you set FullPrecisionOverride
to false
,
fixed-point data types are controlled through individual fixed-point property
settings. For more information, see Full Precision for Fixed-Point System Objects.
RoundingMethod
— Rounding method for fixed-point operations
Floor
(default) | Ceiling
| Convergent
| Nearest
| Round
| Simplest
| Zero
Specify the rounding method.
Dependencies
This property applies only if the object is not in full precision mode.
OverflowAction
— Overflow action for fixed-point operations
Wrap
(default) | Saturate
Specify the overflow action as Wrap
or
Saturate
.
Dependencies
This property applies only if the object is not in full precision mode.
CoefficientsDataType
— Coefficients word and fraction lengths
Same word length as input
(default) | Custom
Specify the coefficients fixed-point data type as Same word length as
input
or Custom
.
Dependencies
This property applies when you set the NumeratorSource
property to Property
.
CustomCoefficientsDataType
— Custom coefficients word and fraction lengths
numerictype(true,16,15)
(default) | numerictype
Specify the coefficients fixed-point type as a signed or unsigned numerictype
(Fixed-Point Designer) object.
Dependencies
This property applies when you set the CoefficientsDataType
property to Custom
.
ReflectionCoefficientsDataType
— Reflection coefficients word and fraction lengths
Same word length as input
(default) | Custom
Specify the reflection coefficients fixed-point data type as Same word
length as input
or Custom
.
Dependencies
This property applies when you set the
ReflectionCoefficientsSource
property to
Property
.
CustomReflectionCoefficientsDataType
— Custom reflection coefficients word and fraction lengths
numerictype(true,16,15)
(default) | numerictype
Specify the reflection coefficients fixed-point type as a signed or unsigned
numerictype
(Fixed-Point Designer) object.
Dependencies
This property applies when you set the
ReflectionCoefficientsDataType
property to
Custom
.
ProductDataType
— Product word and fraction lengths
Full precision
(default) | Same as input
| Custom
Specify the product fixed-point data type as Full precision
,
Same as input
, or Custom
.
CustomProductDataType
— Custom product word and fraction lengths
numerictype(true,32,30)
(default) | numerictype
Specify the product fixed-point type as a signed or unsigned scaled numerictype
(Fixed-Point Designer) object.
Dependencies
This property applies when you set the ProductDataType
property to Custom
.
AccumulatorDataType
— Accumulator word and fraction lengths
Full precision
(default) | Same as input
| Same as product
| Custom
Specify the accumulator fixed-point data type to Full
precision
, Same as input
, Same as
product
, or Custom
.
CustomAccumulatorDataType
— Custom accumulator word and fraction lengths
numerictype(true,32,30)
(default) | numerictype
Specify the accumulator fixed-point type as a signed or unsigned scaled numerictype
(Fixed-Point Designer) object.
Dependencies
This property applies when you set the AccumulatorDataType
property to Custom
.
StateDataType
— State word and fraction lengths
Same as accumulator
(default) | Same as input
| Custom
Specify the state fixed-point data type as one of Same as
input
, Same as accumulator
, or
Custom
.
Dependencies
This property does not apply to any of the direct form or direct form I filter structures.
CustomStateDataType
— Custom state word and fraction lengths
numerictype(true,16,15)
(default) | numerictype
Specify the state fixed-point type as a signed or unsigned scaled numerictype
(Fixed-Point Designer) object.
Dependencies
This property applies when you set the StateDataType
property to Custom
.
OutputDataType
— Output word and fraction lengths
Same as accumulator
(default) | Same as input
| Custom
Specify the output fixed-point data type as one of Same as
input
, Same as accumulator
, or
Custom
.
CustomOutputDataType
— Custom output word and fraction lengths
numerictype(true,16,15)
(default) | numerictype
Specify the output fixed-point type as a signed or unsigned scaled numerictype
(Fixed-Point Designer) object.
Dependencies
This property applies when you set the OutputDataType property to
Custom
.
Usage
Description
Input Arguments
x
— Data input
vector | matrix
Data input, specified as a vector or a matrix. When the input data is of a
fixed-point type, it must be signed when the structure is set to Direct form
symmetric
or Direct form antisymmetric
. The FIR filter
object operates on each channel of the input signal independently over successive
calls to the object.
This System object supports variable-size input.
Data Types: single
| double
| int8
| int16
| int32
| uint8
| uint16
| uint32
| fi
Complex Number Support: Yes
coeff
— Filter coefficients
row vector
Time-varying filter coefficients, specified as a row vector. The data and coefficient inputs must have the same data type.
Data Types: single
| double
| int8
| int16
| int32
| uint8
| uint16
| uint32
| fi
Complex Number Support: Yes
Output Arguments
y
— Filtered output
vector | matrix
Filtered output, returned as a vector or a matrix. The output has the same size as
the input. For single
and double
inputs, the
output data type matches the input data type. For integer and fixed-point inputs, the
output data type depends on the setting of the
FullPrecisionOverride
and OutputDataType
properties.
Data Types: single
| double
| int8
| int16
| int32
| uint8
| uint16
| uint32
| fi
Complex Number Support: Yes
Object Functions
To use an object function, specify the
System object as the first input argument. For
example, to release system resources of a System object named obj
, use
this syntax:
release(obj)
Specific to dsp.FIRFilter
freqz | Frequency response of discrete-time filter System object |
filterAnalyzer | Analyze filters with Filter Analyzer app |
impz | Impulse response of discrete-time filter System object |
info | Information about filter System object |
coeffs | Returns the filter System object coefficients in a structure |
cost | Estimate cost of implementing filter System object |
grpdelay | Group delay response of discrete-time filter System object |
generatehdl | Generate HDL code for quantized DSP filter (requires Filter Design HDL Coder) |
outputDelay | Determine output delay of single-rate or multirate filter |
Examples
Lowpass Filter a Sinusoid Signal Using FIRFilter object
Use an FIR filter to apply a lowpass filter to a waveform with two sinusoidal components.
t = (0:1000)'/8e3; xin = sin(2*pi*0.3e3*t)+sin(2*pi*3e3*t); sr = dsp.SignalSource; sr.Signal = xin; sink = dsp.SignalSink; fir = dsp.FIRFilter(designLowpassFIR(FilterOrder=10,CutoffFrequency=0.5)); sa = spectrumAnalyzer(... SampleRate=8e3,... Method='welch',... PlotAsTwoSidedSpectrum=false,... OverlapPercent=80,... SpectrumUnits='dBW',... YLimits=[-150 -10]); while ~isDone(sr) input = sr(); filteredOutput = fir(input); sink(filteredOutput); sa(filteredOutput) end
filteredResult = sink.Buffer; filterAnalyzer(fir,SampleRates=8000)
Design an FIR filter as a System object.
N = 10; Fc = 0.4; firFiltObj = designLowpassFIR(FilterOrder=N,CutoffFrequency=Fc,SystemObject=true)
firFiltObj = dsp.FIRFilter with properties: Structure: 'Direct form' NumeratorSource: 'Property' Numerator: [-1.2414e-18 -0.0126 -0.0247 0.0635 0.2748 0.3981 0.2748 0.0635 -0.0247 -0.0126 -1.2414e-18] InitialConditions: 0 Use get to show all properties
filterAnalyzer(firFiltObj)
Design and Implement Lowpass FIR Filter with Tunable Cutoff Frequency
Create a dsp.FIRFilter
object, and set the NumeratorSource
property to 'Input port'
so that you can vary the coefficients of the FIR filter through the input port 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 designLowpassFIR
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 cutoff frequency of the filter during simulation. The designLowpassFIR
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.
Fcut = 0.5; for idx = 1:500 num = designLowpassFIR(FilterOrder=30,CutoffFrequency=Fcut,Window="hann"); x = randn(1024,1); y = firFilt(x,num); spectrumScope(x,y); filterViz(num); Fcut = Fcut + 0.0005; end
Design and Implement Lowpass FIR Filter Object
Design and implement a lowpass FIR filter object using the designLowpassFIR
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 = designLowpassFIR(FilterOrder=30,CutoffFrequency=0.5,Window="hann",... Datatype="single",SystemObject=true)
firFilt = dsp.FIRFilter with properties: Structure: 'Direct form' NumeratorSource: 'Property' Numerator: [0 2.1297e-19 0.0011 -1.8613e-18 -0.0048 4.8729e-18 0.0122 -8.7270e-18 -0.0251 1.2757e-17 0.0477 -1.6267e-17 -0.0960 1.8649e-17 0.3148 0.5000 0.3148 1.8649e-17 -0.0960 -1.6267e-17 0.0477 1.2757e-17 -0.0251 ... ] (1x31 single) InitialConditions: 0 Use get to show all properties
Create a dsp.DynamicFilterVisualizer
object to visualize the magnitude response of the 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
Design and Implement Equiripple FIR Halfband Filter
Design an equiripple FIR halfband filter with the order of 24 and a transition width of 0.1 using the designHalfbandFIR
function. Assign the filter coefficients to a dsp.FIRFilter
System object.
b = designHalfbandFIR(FilterOrder=24,DesignMethod='equiripple');
hbFIR = dsp.FIRFilter(b);
Create a dsp.DynamicFilterVisualizer
object and visualize the magnitude response of the filter.
dfv = dsp.DynamicFilterVisualizer(NormalizedFrequency=true); dfv(hbFIR);
Create a spectrumAnalyzer
object to visualize the spectra of the input and output signals.
scope = spectrumAnalyzer(SampleRate=2, PlotAsTwoSidedSpectrum=false,... ChannelNames=["Input Signal","Filtered Signal"]);
Stream in random data and filter the signal using the FIR halfband filter.
for i = 1:1000 x = randn(1024, 1); y = hbFIR(x); scope(x,y); end
Design Lowpass FIR Filter Using designfilt
Since R2023b
Design a lowpass FIR filter using the designfilt
function.
The filter is a minimum order filter with a passband frequency of 0.45 and a stopband frequency of 0.55 in normalized frequency units. The passband ripple is 1 dB and the stopband attenuation is 60 dB. Use the Kaiser window
design method and set the SystemObject
argument to true
.
With these specifications, the designfilt
function generates a dsp.FIRFilter
System object™.
lpFIRFilter = designfilt('lowpassfir', ... 'PassbandFrequency',0.45,'StopbandFrequency',0.55, ... 'PassbandRipple',1,'StopbandAttenuation',60, ... 'DesignMethod','kaiserwin','SystemObject',true)
lpFIRFilter = dsp.FIRFilter with properties: Structure: 'Direct form' NumeratorSource: 'Property' Numerator: [1.2573e-04 -1.9141e-04 -2.7282e-04 3.7207e-04 4.9141e-04 -6.3325e-04 -8.0016e-04 9.9490e-04 0.0012 -0.0015 -0.0018 0.0021 0.0025 -0.0029 -0.0034 0.0040 0.0046 -0.0053 -0.0060 0.0069 0.0079 -0.0090 -0.0102 0.0116 ... ] (1x74 double) InitialConditions: 0 Use get to show all properties
Visualize the magnitude and phase responses of this filter using freqz
.
freqz(lpFIRFilter.Numerator)
Algorithms
This object implements the algorithm, inputs, and outputs described on the Discrete FIR Filter (Simulink) block reference page. The object properties correspond to the block parameters.
Extended Capabilities
C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.
Usage notes and limitations:
Only the
Numerator
property is tunable for code generation.See System Objects in MATLAB Code Generation (MATLAB Coder).
The dsp.FIRFilter
System object supports SIMD code generation using Intel® AVX2 code replacement library under these conditions:
Filter structure is set to
'Direct form'
or'Direct form transposed'
.Input signal is real-valued with real filter coefficients.
When the filter structure is set to
'Direct form'
, the input signal can also be complex-valued with real or complex filter coefficients.Input signal has a data type of
single
ordouble
.
The SIMD technology significantly improves the performance of the generated code. For more information, see SIMD Code Generation. To generate SIMD code from this object, see Use Intel AVX2 Code Replacement Library to Generate SIMD Code from MATLAB Algorithms.
HDL Code Generation
Generate VHDL, Verilog and SystemVerilog code for FPGA and ASIC designs using HDL Coder™.
This object supports HDL code generation with the HDL Coder™ or Filter Design HDL Coder™ products. For HDL Coder workflow and limitations, see HDL Code Generation for System Objects (HDL Coder). For Filter Design HDL Coder workflow and limitations, see Generate HDL Code for Filter System Objects (Filter Design HDL Coder).
Version History
Introduced in R2012aR2023b: The designfilt
function and the Design Filter Live Editor task support dsp.FIRFilter
object
The designfilt
function generates a
dsp.FIRFilter
object when you specify 'lowpassfir'
and 'highpassfir'
filter responses and set the
'SystemObject'
flag to 'true'
.
lpFIRFilter = designfilt('lowpassfir', ... 'PassbandFrequency',0.45,'StopbandFrequency',0.55, ... 'PassbandRipple',1,'StopbandAttenuation',60, ... 'DesignMethod','kaiserwin','SystemObject',true)
lpFIRFilter = dsp.FIRFilter with properties: Structure: 'Direct form' NumeratorSource: 'Property' Numerator: [1.2573e-04 -1.9141e-04 -2.7282e-04 3.7207e-04 … ] (1×74 double) InitialConditions: 0
The Design
Filter Live Editor task generates a dsp.FIRFilter
object
for lowpass FIR and highpass FIR filter responses when you select the Use a System
object to implement filter check box in the task UI and run the
designfilt
code the task generates.
See Also
Functions
freqz
|filterAnalyzer
|impz
|info
|coeffs
|cost
|grpdelay
|generatehdl
|outputDelay
|designLowpassFIR
|designBandpassFIR
|designBandstopFIR
|designHighpassFIR
|designFracDelayFIR
|designHalfbandFIR
Objects
Blocks
- Discrete FIR Filter (Simulink)
MATLAB 명령
다음 MATLAB 명령에 해당하는 링크를 클릭했습니다.
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