IIR comb filter specification object
fdesign.comb specifies a peaking or notching
comb filter. Comb filters amplify or attenuate a set of harmonically
a notching comb filter specification object and applies default values
for the filter order (
N=10) and quality factor
a comb filter specification object of the specified type and applies
default values for the filter order and quality factor. The valid
combtype are shown in the following
table. The entries are not case-sensitive.
|creates a comb filter that attenuates a set of harmonically related frequencies.|
|creates a comb filter that amplifies a set of harmonically related frequencies.|
a comb filter specification object of type
Specification property to
default values. The entries in
the number of peaks or notches in the comb filter as well as their
bandwidth and slope. Valid entries for
shown below. The entries are not case-sensitive.
The following table describes the arguments in
|Bandwidth of the notch or peak. By default the bandwidth is
calculated at the point –3 dB down from the center frequency
of the peak or notch. For example, setting |
|Gain at which the bandwidth is measured. This allows the user to specify the bandwidth of the notch or peak at a gain different from the –3 dB default.|
|Upsampling factor for a shelving filter of order |
|Filter order. Specifies a filter with |
| Shelving filter order. |
|Peak or notch quality factor. |
an IIR comb filter specification object of type
Specification property to the values
an IIR comb filter specification object using the sampling frequency,
of the signal to be filtered. The function assumes that
in Hertz and must be specified as a scalar trailing all other provided
These examples demonstrate how to create IIR comb filter specification objects.
First, create a default specification object.
d = fdesign.comb; %#ok
In the next example, create a notching filter of order 8 with a bandwidth of 0.02 (normalized frequency) referenced to the -3 dB point.
d = fdesign.comb('notch','N,BW',8,0.02); Hd = design(d,'SystemObject',true); fvtool(Hd);
Next, create a peaking comb filter with 5 peaks and a quality factor of 25.
d = fdesign.comb('peak','N,Q',5,25); Hd = design(d,'SystemObject',true); fvtool(Hd);
In the next example, create a notching filter to remove interference at 60 Hz and its harmonics. The following code creates a filter with 10 notches and a notch bandwidth of 5 Hz referenced to the -4dB level. The filter has a shelving filter order of 4 and a sampling frequency of 600 Hz. Because the notches are equidistantly spaced in the interval [-300, 300] Hz, they occur at multiples of 60 Hz.
d = fdesign.comb('notch','L,BW,GBW,Nsh',10,5,-4,4,600); Hd=design(d,'SystemObject',true); fvtool(Hd);