Biomedical Engineering Reference
In-Depth Information
FIGURE 11.7
:
Chebyshev band-reject filter. Response of a fourth-order Chebyshev notch filter
as shown by on an oscilloscope
The transfer function for the band-reject filter is given by (11.10). Band-reject
filters must be of second or higher order, since the filters require two slopes (high and
low). Note that band-reject filters are not All-Pole filters, since the equation shows a pair
of zeros in the numerator (
s
2
).
A
BR
(
s
2
2
+
ω
0
)
H
(
s
)
=
(11.10)
+
ω
Q
s
2
0
s
2
+
ω
Figure 11.7 shows the response of a fourth-order Chebyshev band-reject (notch)
filter. It should be noted that the maximum attenuation of the band-reject filter is the
magnitude at the center frequency,
ω
0
.
11.2 DIGITAL FILTERS
11.2.1 Classification of Digital Filters
The classification of digital filters is similar to the classification of analog filters
1.
Chebyshev filters: low-pass or high-pass (Figs. 11.8 and 11.9)
a. Underdamped, can oscillate
b. Ripple factor
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