Biomedical Engineering Reference
In-Depth Information
FIGURE 5-20
Comparison of the
group delay of
Butterworth,
Chebyshev, and
Bessel low-pass
filters.
FIGURE 5-21
Frequency response
of Butterworth
high-pass filters.
down to a point where it begins to roll off. A standard reference point for this roll-off is
the point where the amplitude has decreased by 3 dB, to 70.7% of its original amplitude.
The region from infinity to the point where the amplitude is down 3 dB is defined as the
passband of the filter. The range of frequencies from the 3 dB point down to zero (or near
zero) is defined as the stopband of the filter.
