Package: dsp
Variable bandwidth IIR filter
The VariableBandwidthIIRFilter
object filters
each channel of the input using IIR filter implementations. It does
so while having the capability of tuning the bandwidth. This filter
supports double and single precision inputs.
To filter each channel of the input:
Define and set up your variable bandwidth IIR filter. See Construction.
Call step
to filter
each channel of the input according to the properties of dsp.VariableBandwidthIIRFilter
.
The behavior of step
is specific to each object in
the toolbox.
Note:
Starting in R2016b, instead of using the 
vbwIIR = dsp.VariableBandwidthIIRFilter
returns
a System object, vbwIIR
, which independently
filters each channel of the input over successive calls to the step
method.
This System object uses a specified IIR filter implementation.
The filter's passband frequency may be tuned during the filtering
operation. The variable bandwidth IIR filter is designed using the
elliptical method. The filter is tuned using IIR spectral transformations
based on allpass filters.
vbwIIR = dsp.VariableBandwidthIIRFilter('
returns a variable bandwidth IIR filter System object, PropertyName
',PropertyValue
,
...)vbwIIR
,
with each property set to the specified value. You can specify additional
namevalue pair arguments in any order as (Name1,Value1,...,NameN,ValueN
).

Input sample rate Specify the sampling rate of the input in Hertz as a finite numeric scalar. The default is 44.1 kHz. This property is nontunable. 

Filter type Specify the type of the filter as one of 

IIR filter order Specify the order of the IIR filter as a positive integer scalar. The default is 8. This property is nontunable. 

Filter passband frequency Specify the filter passband frequency in Hz as a real, positive
scalar, smaller than the 

Filter center frequency Specify the filter center frequency in Hz as a real, positive
scalar, smaller than 

Filter bandwidth Specify the filter bandwidth in Hertz as a real, positive scalar,
smaller than 

Filter passband ripple Specify the filter passband ripple as a real, positive scalar in decibels (dB). The default is 1 dB. This property is nontunable. 

Filter Stopband attenuation Specify the filter stopband attenuation as a real, positive scalar in decibels (dB). The default is 60 dB. This property is nontunable. 
reset  Reset internal states of variable bandwidth IIR filter 
step  Filter signal using variable bandwidth algorithm 
More Analysis Methods for Filter System Objects.
Common to All System Objects  

clone  Create System object with same property values 
getNumInputs  Expected number of inputs to a System object 
getNumOutputs  Expected number of outputs of a System object 
isLocked  Check locked states of a System object (logical) 
release  Allow System object property value changes 
This filter covers frequency transformations. A lowpass IIR
prototype is designed, using the elliptical method by specifying its
order, passband frequency, passband ripple and stopband attenuation.
The passband ripple and stopband attenuation are equal to the values
of the PassbandRipple
and StopbandAttenuation
properties.
The prototype passband frequency is set to 0.5. If the FilterType
property
is 'Lowpass'
or 'Highpass'
,
the prototype's order is equal to the value of FilterOrder
.
If the FilterType
property is 'Bandpass'
or 'Bandstop'
,
the prototype filter order is equal to FilterOrder/2
.
The prototype is a Direct Form II Transposed cascade of secondorder
sections (Biquad filter). The prototype is transformed into the desired
filter using the algorithms used in Digital Frequency Transformations. Each prototype
SOS section is transformed separately. When FilterType
is 'Lowpass'
or 'Highpass'
,
the resulting filter remains a Direct Form II Transposed cascade of
second order sections. If the FilterType
is 'Bandpass'
or 'Bandstop'
,
the resulting filter is a cascade of Direct Form II Transposed cascade
of fourth order sections.
[1] A. G. Constantinides. "Spectral transformations for digital filters", Proc. Inst. Elect. Eng. Vol. 117, No. 8, 1970, pp. 15851590.
dsp.AllpoleFilter
 dsp.BiquadFilter
 dsp.FIRFilter
 dsp.IIRFilter
 dsp.VariableBandwidthFIRFilter
 Variable Bandwidth FIR Filter  Variable Bandwidth IIR Filter