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Description
D = fdesign.bandpass
constructsa bandpass filter specification object D
, applyingdefault values for the properties Fstop1
, Fpass1
, Fpass2
, Fstop2
, Astop1
, Apass
,and Astop2
— one possible set of valuesyou use to specify a bandpass filter.D = fdesign.bandpass(SPEC)
constructsobject D
and sets its Specification
propertyto SPEC
. Entries in the SPEC
representvarious filter response features, such as the filter order, that governthe filter design. Valid entries for SPEC
are shownbelow and used to define the bandpass filter. These entries are notcase sensitive.Note
Specifications marked with an asterisk require the DSP System Toolbox™ software.
'Fst1,Fp1,Fp2,Fst2,Ast1,Ap,Ast2'
(defaultspec
)'N,F3dB1,F3dB2'
'N,F3dB1,F3dB2,Ap'
*'N,F3dB1,F3dB2,Ast'
*'N,F3dB1,F3dB2,Ast1,Ap,Ast2'
*'N,F3dB1,F3dB2,BWp
*'N,F3dB1,F3dB2,BWst'
*'N,Fc1,Fc2'
'N,Fc1,Fc2,Ast1,Ap,Ast2'
'N,Fp1,Fp2,Ap'
'N,Fp1,Fp2,Ast1,Ap,Ast2'
'N,Fst1,Fp1,Fp2,Fst2'
'N,Fst1,Fp1,Fp2,Fst2,C'
*'N,Fst1,Fp1,Fp2,Fst2,Ap'
*'N,Fst1,Fst2,Ast'
'Nb,Na,Fst1,Fp1,Fp2,Fst2'
*
The filter specifications are defined as follows:
Ap
— amount of ripple allowedin the pass band. Also called Apass.Ast1
— attenuation in thefirst stop band in decibels (the default units). Also called Astop1.Ast2
— attenuation in thesecond stop band in decibels (the default units). Also called Astop2.BWp
— bandwidth of the filterpassband. Specified in normalized frequency units.BWst
— bandwidth of thefilter stopband. Specified in normalized frequency units.C
— Constrained band flag.This enables you to specify passband ripple or stopband attenuationfor fixed-order designs in one or two of the three bands.In the specification'N,Fst1,Fp1,Fp2,Fst2,C'
,you cannot specify constraints in both stopbands and the passbandsimultaneously. You can specify constraints in any one or two bands.F3dB1
— cutoff frequencyfor the point 3 dB point below the passband value for the first cutoff.Specified in normalized frequency units. (IIR filters)F3dB2
— cutoff frequencyfor the point 3 dB point below the passband value for the second cutoff.Specified in normalized frequency units. (IIR filters)Fc1
— cutoff frequency forthe point 6 dB point below the passband value for the first cutoff.Specified in normalized frequency units. (FIR filters)Fc2
— cutoff frequency forthe point 6 dB point below the passband value for the second cutoff.Specified in normalized frequency units. (FIR filters)Fp1
— frequency at the edgeof the start of the pass band. Specified in normalized frequency units.Also called Fpass1.Fp2
— frequency at the edgeof the end of the pass band. Specified in normalized frequency units.Also called Fpass2.Fst1
— frequency at theedge of the start of the first stop band. Specified in normalizedfrequency units. Also called Fstop1.Fst2
— frequency at theedge of the start of the second stop band. Specified in normalizedfrequency units. Also called Fstop2.N
— filter order for FIRfilters. Or both the numerator and denominator orders for IIR filterswhen na and nb are not provided.Na
— denominator order forIIR filtersNb
— numerator order forIIR filters
Graphically, the filter specifications look similar to thoseshown in the following figure.
Regions between specification values like
Fst1
and Fp1
aretransition regions where the filter response is not explicitly defined.The filter design methods that apply to a bandpass filter specificationobject change depending on the
Specification
. Use designmethods
to determine which designmethods apply to an object and the Specification
propertyvalue.Use
designopts
to determinethe design options for a given design method. Enter help(D,METHOD)
atthe MATLAB® command line to obtain detailed help on the designoptions for a given design method, METHOD
.D = fdesign.bandpass(spec,specvalue1,specvalue2,...)
constructsan object D
and sets its specifications at constructiontime.D = fdesign.bandpass(specvalue1,specvalue2,specvalue3,
specvalue4,...specvalue4,specvalue5,specvalue6)
constructs D
withthe default Specification
property, using the valuesyou provide as input arguments for specvalue1,specvalue2,specvalue3,specvalue4,specvalue4,specvalue5,specvalue6
and specvalue7
.D = fdesign.bandpass(...,Fs)
addsthe argument Fs
, specified in Hz to define thesampling frequency to use. In this case, all frequencies in the specificationsare in Hz as well.D = fdesign.bandpass(...,MAGUNITS)
specifiesthe units for any magnitude specification you provide in the inputarguments. MAGUNITS
can be one of'linear'
— specify the magnitudein linear units'dB'
— specify the magnitudein dB (decibels)'squared'
— specify themagnitude in power units
When you omit the
MAGUNITS
argument, fdesign
assumesthat all magnitudes are in decibels. Note that fdesign
storesall magnitude specifications in decibels (converting to decibels whennecessary) regardless of how you specify the magnitudes.