BandFilter Class Reference

Algorithm to create and apply several types of low pass, high pass, band pass and band stop filters. More...

#include <BandFilter.h>

Collaboration diagram for BandFilter:

List of all members.

Public Types

enum FilterType { CHEBYSHEVI = 0, CHEBYSHEVII = 1, BUTTERWORTH = 2, BESSEL = 3 }

Specifies the type of the filter. More...

enum BandType { LOWPASS = 0, HIGHPASS = 1, BANDPASS = 2, BANDSTOP = 3 }

Specifies the type of the band. More...

Public Member Functions

BandFilter (int order=4, Real lowFrequency=0.0, Real highFrequency=1.0, BandType bandType=LOWPASS, FilterType filterType=CHEBYSHEVII, Real ripplePass=0.05, Real attenuationStop=40.0)

void process (const MatrixXR &samples, MatrixXR *filtered)

void a (MatrixXR *a) const

void b (MatrixXR *b) const

int order () const

void setOrder (int order, bool callSetup=true)

Real lowFrequency () const

void setLowFrequency (Real frequency, bool callSetup=true)

Real highFrequency () const

void setHighFrequency (Real frequency, bool callSetup=true)

FilterType filterType () const

void setFilterType (FilterType type, bool callSetup=true)

BandType bandType () const

void setBandType (BandType type, bool callSetup=true)

Real passRipple () const

void setPassRipple (Real rippleDB, bool callSetup=true)

Real stopAttenuation () const

void setStopAttenuation (Real attenuationDB, bool callSetup=true)

Detailed Description

Algorithm to create and apply several types of low pass, high pass, band pass and band stop filters.

This class represents an object to create and apply several types of band filters. Additionally the coefficients, zeros, poles and gains of the created filters can be retrieved.

4 types of bands are implemented:

Low Pass
High Pass
Band Pass
Band Stop

The band type can be selected using the setBandType() taking as argument a BandType.

The critical frequencies are specified using setLowFrequency() and setHighFrequency(). Note that for low pass and high pass filters which have one single critical frequency only setLowFrequency() has an effect.

4 types of filters are implemented:

Chebyshev I
Chebyshev II
Bessel
Butterworth

The filter type can be selected using the setFilterType() taking as argument a FilterType.

The order of the filters can be specified using setOrder().

For Chebyshev I filters the pass band ripple can be specified using setPassRipple(). Note that this method has no effect if a different type of filter is used.

For Chebyshev II filters the stop band attenuation is specified using setStopAttenuation(). Note that this method has no effect if a different type of filter is used.

Author:: Ricard Marxer

See also:: Filter

Member Enumeration Documentation

enum FilterType

Specifies the type of the filter.

See also:: filterType

Enumerator:

CHEBYSHEVI	Chebyshev Type-I filter
CHEBYSHEVII	Chebyshev Type-II filter
BUTTERWORTH	Butterworth filter
BESSEL	Bessel filter

enum BandType

Specifies the type of the band.

See also:: bandType

Enumerator:

LOWPASS	Low pass filter
HIGHPASS	High pass filter
BANDPASS	Band pass filter
BANDSTOP	Band stop filter

Constructor & Destructor Documentation

BandFilter	(	int	order = `4`,
		Real	lowFrequency = `0.0`,
		Real	highFrequency = `1.0`,
		BandType	bandType = `LOWPASS`,
		FilterType	filterType = `CHEBYSHEVII`,
		Real	ripplePass = `0.05`,
		Real	attenuationStop = `40.0`
	)

Constructs a band pass filter object with the given order, lowFrequency, highFrequency, filterType, ripplePass and attenuationStop parameters given.

References setBandType(), setFilterType(), setHighFrequency(), setLowFrequency(), setOrder(), setPassRipple(), and setStopAttenuation().

Member Function Documentation

void process	(	const MatrixXR &	samples,
		MatrixXR *	filtered
	)

Performs a filtering of each of the columns of samples. Puts the resulting filtered in the columns of filtered.

Parameters:

	samples	matrix of Real values. A column represents a channel and a row represents a time index.
	filtered	pointer to a matrix of Real values for the output. The matrix should have the same number of rows and columns as samples.

Note that if the output matrix is not of the required size it will be resized, reallocating a new memory space if necessary.

See also:: Filter::process

References Filter::process().

void a ( MatrixXR * a ) const

Return in a the single column matrix a coefficients.

See also:: b

References Filter::a().

void b ( MatrixXR * b ) const

Return in b the single column matrix b coefficients.

See also:: a

References Filter::b().

int order ( ) const

Return the order of the filter. The default is 4.

See also:: setOrder

void setOrder	(	int	order,
		bool	callSetup = `true`
	)

Specifies the order of the filter. The given order must be higher than 0. Note that orders higher than 25 are not allowed for Bessel filters.

See also:: order

Referenced by BandFilter().

Real lowFrequency ( ) const

Return the low frequency of the filter. The default is 0.0.

See also:: lowFrequency, highFrequency, setLowFrequency, setHighFrequency

void setLowFrequency	(	Real	frequency,
		bool	callSetup = `true`
	)

Specifies the low normalized frequency of the filter. The given frequency must be in the range of 0 to 1.

See also:: lowFrequency, highFrequency, setHighFrequency

Referenced by BandFilter().

Real highFrequency ( ) const

Return the stop frequency of the filter. The default is 1.0.

See also:: lowFrequency, setLowFrequency, setHighFrequency

void setHighFrequency	(	Real	frequency,
		bool	callSetup = `true`
	)

Specifies the stop normalized frequency of the filter. The given frequency must be in the range of 0 to 1.

See also:: lowFrequency, highFrequency, setLowFrequency

Referenced by BandFilter().

BandFilter::FilterType filterType ( ) const

Return the filter type. The default is CHEBYSHEVII. The given frequency must be in the range of 0 to 1.

See also:: setFilterType, order, setOrder

void setFilterType	(	FilterType	type,
		bool	callSetup = `true`
	)

Specifies the filter type.

See also:: lowFrequency, highFrequency, setLowFrequency

Referenced by BandFilter().

BandFilter::BandType bandType ( ) const

Return the type of the band of the filter.

By default it is LOWPASS.

See also:: setBandType()

void setBandType	(	BandType	type,
		bool	callSetup = `true`
	)

Specifies the type of the band of the filter.

See also:: bandType()

Referenced by BandFilter().

Real passRipple ( ) const

Returns the ripple of the pass band in dB

Note that this property only has an effect if the filter type used is CHEBYSHEVI. By default it is 0.05.

See also:: setPassRipple(), stopAttenuation(), setStopAttenuation()

void setPassRipple	(	Real	rippleDB,
		bool	callSetup = `true`
	)

Specifies the ripple of the pass band in dB

Note that this property only has an effect if the filter type used is CHEBYSHEVI.

See also:: passRipple(), stopAttenuation(), setStopAttenuation()

Referenced by BandFilter().

Real stopAttenuation ( ) const

Returns the attenuation of the stop band in dB

Note that this property only has an effect if the filter type used is CHEBYSHEVII. By default it is 40.0.

See also:: passRipple(), setPassRipple(), setStopAttenuation()

void setStopAttenuation	(	Real	attenuationDB,
		bool	callSetup = `true`
	)

Specifies the attenuation of the stop band in dB

Note that this property only has an effect if the filter type used is CHEBYSHEVII.

See also:: passRipple(), setPassRipple(), stopAttenuation()

Referenced by BandFilter().

The documentation for this class was generated from the following files:

BandFilter.h
BandFilter.cpp


Public Types
enum	FilterType { CHEBYSHEVI = 0, CHEBYSHEVII = 1, BUTTERWORTH = 2, BESSEL = 3 }
	Specifies the type of the filter. More...
enum	BandType { LOWPASS = 0, HIGHPASS = 1, BANDPASS = 2, BANDSTOP = 3 }
	Specifies the type of the band. More...
Public Member Functions
	BandFilter (int order=4, Real lowFrequency=0.0, Real highFrequency=1.0, BandType bandType=LOWPASS, FilterType filterType=CHEBYSHEVII, Real ripplePass=0.05, Real attenuationStop=40.0)
void	process (const MatrixXR &samples, MatrixXR *filtered)
void	a (MatrixXR *a) const
void	b (MatrixXR *b) const
int	order () const
void	setOrder (int order, bool callSetup=true)
Real	lowFrequency () const
void	setLowFrequency (Real frequency, bool callSetup=true)
Real	highFrequency () const
void	setHighFrequency (Real frequency, bool callSetup=true)
FilterType	filterType () const
void	setFilterType (FilterType type, bool callSetup=true)
BandType	bandType () const
void	setBandType (BandType type, bool callSetup=true)
Real	passRipple () const
void	setPassRipple (Real rippleDB, bool callSetup=true)
Real	stopAttenuation () const
void	setStopAttenuation (Real attenuationDB, bool callSetup=true)