Digital Signal Processing Reference
In-Depth Information
bandpass lter. A bandstop lter is the opposite of the bandpass lter; it attenuates
frequencies within a certain range, while passing through any frequencies above or
below that range. In Figure 3.21 we see an example bandstop lter, made with the
same parameters as the bandpass lter, but obviously these two have an opposite
eect on a signal.
Bandpass filter with cutoff freqs 30% and 50%
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Figure 3.20: Frequency magnitude response for a bandpass lter.
Bandstop filter with cutoff freqs 30% and 50%
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Figure 3.21: Frequency magnitude response for a bandstop lter.
Two other example lters' responses are shown, as special cases of the above.
Figure 3.22 shows a bandstop lter with a very narrow frequency range being at-
tenuated. Notch lters like this one eliminate noise at a specic frequency. Finally,
Figure 3.23 shows the frequency magnitude response for a bandpass lter, except
that it has two passbands. Such a lter would be great for getting rid of parts of
the signal with undesired frequencies, allowing frequencies in one band or the other
