dsp.AllpoleFilter

IIR Filter with no zeros

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Description

The dsp.AllpoleFilter object filters each channel of the input using allpole filter implementations.

To filter each channel of the input:

Create the dsp.AllpoleFilter 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?

Creation

Syntax

allpole = dsp.AllpoleFilter

allpole = dsp.AllpoleFilter(Name,Value)

Description

allpole = dsp.AllpoleFilter returns an allpole filter System object™, allpole, which independently filters each channel of the input over successive calls to the algorithm. This System object uses a specified allpole filter implementation.

example

allpole = dsp.AllpoleFilter(Name,Value) returns an allpole filter System object, allpole, with each property set to the specified value.

Properties

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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 transposed` | `Lattice AR`

Specify the filter structure as one of | Direct form | Direct form transposed | Lattice AR. Analysis methods are not supported for fixed-point processing if the structure is Direct form or Direct form transposed. This property is nontunable.

`Denominator` — Filter denominator coefficients
`[1 0.1]` (default) | row vector

Specify the denominator coefficients as a numeric row vector.

Tunable: Yes

Dependencies

This property is applicable when the Structure property is set to one of Direct form | Direct form transposed.

`ReflectionCoefficients` — Lattice filter coefficients
`[0.2 0.4]` (default) | row vector

Specify the lattice filter coefficients as a numeric row vector.

Tunable: Yes

Dependencies

This property is applicable when the Structure property is set to Lattice AR.

`InitialConditions` — Initial conditions for the filter states
`0` (default) | scalar | vector | matrix

Specify the initial conditions of the filter states.

You can specify the initial conditions as a scalar, vector, or matrix. If you specify a scalar value, this System object initializes all delay elements in the filter to that value. You can also specify a vector whose length equals the number of delay elements in the filter. When you do so, 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.

You can also 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. In this case, each element specifies a unique initial condition for the corresponding delay element in the corresponding channel.

Tunable: Yes

`CoefficientsDataType` — Denominator coefficients word- and fraction-length designations
`Same word length as input` (default) | `Custom`

Specify the denominator coefficients fixed-point data type as one of Same word length as input | Custom. This property is nontunable.

`ReflectionCoefficientsDataType` — Reflection coefficients word- and fraction-length designations
`Same word length as input` (default) | `Custom`

Specify the reflection coefficients fixed-point data type as one of Same word length as input | Custom. This property is nontunable.

Fixed-Point Properties

`ProductDataType` — Product word- and fraction-length designations
`Full precision` (default) | `Same as input` | `Custom`

Specify the product fixed-point data type as one of | Full precision | Same as input | Custom |. This property is nontunable.

`AccumulatorDataType` — Accumulator word- and fraction-length designations
`Full precision` (default) | `Same as input` | `Same as product` | `Custom`

`OutputDataType` — Output word- and fraction-length designations
`Same as input` (default) | `Same as accumulator` | `Custom`

Specify the output fixed-point data type as one of | Same as accumulator | Same as input | Custom |. This property is nontunable.

`StateDataType` — State word- and fraction-length designations
`Same as accumulator` (default) | `Same as input` | `Custom`

Specify the state fixed-point data type as one of | Same as input | Same as accumulator | Custom. This property is nontunable.

`CustomCoefficientsDataType` — Custom denominator word- and fraction-lengths
`numerictype ([],16,15)` (default) | `numerictype`

Specify the denominator coefficients fixed-point type as an autosigned numerictype (Fixed-Point Designer) object. This property is nontunable.

Dependencies

This property is applicable when the CoefficientsDataType property is Custom.

`CustomReflectionCoefficientsDataType` — Custom reflection coefficients word- and fraction-lengths
`numerictype ([],16,15)` (default) | `numerictype`

Specify the denominator coefficients fixed-point type as an autosigned numerictype (Fixed-Point Designer) object. This property is nontunable.

Dependencies

This property is applicable when the ReflectionCoefficientsDataType property is Custom.

`CustomProductDataType` — Custom Product word- and fraction-lengths
`numerictype ([],32,30)` (default) | `numerictype`

Specify the product fixed-point type as an autosigned scaled numerictype (Fixed-Point Designer) object. This property is nontunable.

Dependencies

This property applies when you set the ProductDataType property to Custom.

`CustomAccumulatorDataType` — Custom accumulator word- and fraction-lengths
`numerictype([],32,30)` (default) | `numerictype`

Specify the accumulator fixed-point type as an autosigned scaled numerictype (Fixed-Point Designer) object. This property is nontunable.

Dependencies

This property applies when you set the AccumulatorDataType property to Custom.

`CustomStateDataType` — Custom state word- and fraction-lengths
`numerictype([],16,15)` (default) | `numerictype`

Specify the state fixed-point type as an autosigned scaled numerictype (Fixed-Point Designer) object. This property is nontunable.

Dependencies

This property applies when you set the StateDataType property to Custom.

`CustomOutputDataType` — Custom output word- and fraction-lengths
`numerictype([],16,15)` (default) | `numerictype`

Specify the output fixed-point type as an autosigned scaled numerictype (Fixed-Point Designer) object. This property is nontunable.

Dependencies

This property applies when you set the OutputDataType property to Custom.

Usage

Syntax

y = allpole(x)

Description

y = allpole(x) filters the real or complex input signal x using an allpole filter to produce the output y.

example

Input Arguments

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`x` — Data input
vector | matrix

Data input, specified as a vector or a matrix. This object also accepts variable-size inputs. Once the object is locked, you can change the size of each input channel, but you cannot change the number of channels.

When the input data is of a fixed-point type, it must be signed. The allpole filter object operates on each channel of the input signal independently over successive calls to the algorithm.

Output Arguments

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`y` — Filtered output
vector | matrix

Filtered output, returned as a vector or a matrix. The size, data type, and complexity of the output signal matches that of the input signal.

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)

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Specific to `dsp.AllpoleFilter`

`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
`outputDelay`	Determine output delay of single-rate or multirate filter
`phasez`	Phase response of discrete-time filter System object (unwrapped)

Common to All System Objects

`step`	Run System object algorithm
`release`	Release resources and allow changes to System object property values and input characteristics
`reset`	Reset internal states of System object

Examples

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Lowpass Filter a Waveform with Two Frequencies

Open Live Script

Use an Allpole filter to apply a lowpass filter to a waveform with two sinusoidal frequencies.

 t = (0:1000)./8e3;
 xin = sin(2*pi*1e3*t)+sin(2*pi*3e3*t);
 
 src = dsp.SignalSource(xin', 4);
 sink = dsp.SignalSink;
 allpole = dsp.AllpoleFilter;
 tt = (-25:25)';
 xsinc = 0.4*sinc(0.4*tt);
 asinc = lpc(xsinc,51);
 allpole.Denominator = asinc;

 sa = spectrumAnalyzer('SampleRate',8e3,...
     'Method','welch',...
    'PlotAsTwoSidedSpectrum',false,...
    'OverlapPercent',80,'SpectrumUnits','dBW',...
    'YLimits',[-150 50]);
 
while ~isDone(src)
      input = src();
      filteredOutput = allpole(input);
      sink(filteredOutput);
      sa(filteredOutput)
 end

 filteredResult = sink.Buffer;
 filterAnalyzer(allpole,SampleRates=8000)

Algorithms

This object implements the algorithm, inputs, and outputs described on the Allpole Filter 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 Denominator property is tunable for code generation.
See System Objects in MATLAB Code Generation (MATLAB Coder).

Version History

Introduced in R2012b

dsp.AllpoleFilter

Description

Creation

Syntax

Description

Properties

Structure — Filter structure Direct form (default) | Direct form transposed | Lattice AR

Denominator — Filter denominator coefficients [1 0.1] (default) | row vector

Dependencies

ReflectionCoefficients — Lattice filter coefficients [0.2 0.4] (default) | row vector

Dependencies

InitialConditions — Initial conditions for the filter states 0 (default) | scalar | vector | matrix

CoefficientsDataType — Denominator coefficients word- and fraction-length designations Same word length as input (default) | Custom

ReflectionCoefficientsDataType — Reflection coefficients word- and fraction-length designations Same word length as input (default) | Custom

Fixed-Point Properties

ProductDataType — Product word- and fraction-length designations Full precision (default) | Same as input | Custom

AccumulatorDataType — Accumulator word- and fraction-length designations Full precision (default) | Same as input | Same as product | Custom

OutputDataType — Output word- and fraction-length designations Same as input (default) | Same as accumulator | Custom

StateDataType — State word- and fraction-length designations Same as accumulator (default) | Same as input | Custom

CustomCoefficientsDataType — Custom denominator word- and fraction-lengths numerictype ([],16,15) (default) | numerictype

Dependencies

CustomReflectionCoefficientsDataType — Custom reflection coefficients word- and fraction-lengths numerictype ([],16,15) (default) | numerictype

Dependencies

CustomProductDataType — Custom Product word- and fraction-lengths numerictype ([],32,30) (default) | numerictype

Dependencies

CustomAccumulatorDataType — Custom accumulator word- and fraction-lengths numerictype([],32,30) (default) | numerictype

Dependencies

CustomStateDataType — Custom state word- and fraction-lengths numerictype([],16,15) (default) | numerictype

Dependencies

CustomOutputDataType — Custom output word- and fraction-lengths numerictype([],16,15) (default) | numerictype

Dependencies

Usage

Syntax

Description

Input Arguments

x — Data input vector | matrix

Output Arguments

y — Filtered output vector | matrix

Object Functions

Specific to dsp.AllpoleFilter

Common to All System Objects

Examples

Lowpass Filter a Waveform with Two Frequencies

Algorithms

Extended Capabilities

C/C++ Code Generation Generate C and C++ code using MATLAB® Coder™.

Version History

See Also

Functions

Objects

Topics

`Structure` — Filter structure
`Direct form` (default) | `Direct form transposed` | `Lattice AR`

`Denominator` — Filter denominator coefficients
`[1 0.1]` (default) | row vector

`ReflectionCoefficients` — Lattice filter coefficients
`[0.2 0.4]` (default) | row vector

`InitialConditions` — Initial conditions for the filter states
`0` (default) | scalar | vector | matrix

`CoefficientsDataType` — Denominator coefficients word- and fraction-length designations
`Same word length as input` (default) | `Custom`

`ReflectionCoefficientsDataType` — Reflection coefficients word- and fraction-length designations
`Same word length as input` (default) | `Custom`

`ProductDataType` — Product word- and fraction-length designations
`Full precision` (default) | `Same as input` | `Custom`

`AccumulatorDataType` — Accumulator word- and fraction-length designations
`Full precision` (default) | `Same as input` | `Same as product` | `Custom`

`OutputDataType` — Output word- and fraction-length designations
`Same as input` (default) | `Same as accumulator` | `Custom`

`StateDataType` — State word- and fraction-length designations
`Same as accumulator` (default) | `Same as input` | `Custom`

`CustomCoefficientsDataType` — Custom denominator word- and fraction-lengths
`numerictype ([],16,15)` (default) | `numerictype`

`CustomReflectionCoefficientsDataType` — Custom reflection coefficients word- and fraction-lengths
`numerictype ([],16,15)` (default) | `numerictype`

`CustomProductDataType` — Custom Product word- and fraction-lengths
`numerictype ([],32,30)` (default) | `numerictype`

`CustomAccumulatorDataType` — Custom accumulator word- and fraction-lengths
`numerictype([],32,30)` (default) | `numerictype`

`CustomStateDataType` — Custom state word- and fraction-lengths
`numerictype([],16,15)` (default) | `numerictype`

`CustomOutputDataType` — Custom output word- and fraction-lengths
`numerictype([],16,15)` (default) | `numerictype`

`x` — Data input
vector | matrix

`y` — Filtered output
vector | matrix

Specific to `dsp.AllpoleFilter`

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.