dsp.VariableBandwidthIIRFilter
Variable bandwidth IIR filter
Description
The dsp.VariableBandwidthIIRFilter
object filters each channel of the
input using IIR filter implementations. It does so while having the capability of tuning the
bandwidth.
To filter each channel of the input:
Create the
dsp.VariableBandwidthIIRFilter
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
Description
returns a System object™, vbwIIR
= dsp.VariableBandwidthIIRFiltervbwIIR
, which independently filters each channel of
the input over successive calls to the algorithm. 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.
returns a variable bandwidth IIR filter System object, vbwIIR
= dsp.VariableBandwidthIIRFilter(Name,Value
)vbwIIR
, with each property set to the specified value.
You can specify additional name-value pair arguments in any order as
(Name1,Value1,...,NameN,ValueN
).
Properties
Usage
Syntax
Description
filters
the real or complex input signal y
= vbwIIR(x
)x
using a variable bandwidth IIR
filter to produce the output y
. The variable bandwidth IIR filter
object operates on each channel, which means the object filters every column of the input
signal independently over successive calls to the algorithm.
Input Arguments
Output Arguments
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)
Examples
Algorithms
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 second-order 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.
References
[1] A. G. Constantinides. “Spectral transformations for digital filters”, Proc. Inst. Elect. Eng. Vol. 117, No. 8, 1970, pp. 1585-1590.
Extended Capabilities
Version History
Introduced in R2014a