Biomedical Engineering Reference
In-Depth Information
1.0
Passband
Passband
0.8
Transition bands
0.6
0.4
0.2
Stopband
0
0
p
Frequency (rad)
FIGURE 11.13
:
Band-reject filter. Note the narrow transition bands in the band-reject filter
in the IIR direct version becomes the FIR direct-form implementation equation, as in
(11.12).
b
−1
b
−
L
H
(
z
)
=
B
(
z
)
=
b
0
+
+···+
(11.12)
1
Z
LZ
The difference equation corresponding to the FIR direct-form implementation equation
(11.12) is given by (11.13), and the “Direct” FIR design is shown in Fig. 11.14.
L
y
k
=
b
n
x
k
−
n
(11.13)
n
=
0
X
k—
1
X
k—
2
X
k—
1
X
k
Z
-1
Z
-1
Z
-1
b
0
b
1
b
L—
1
b
L
+
+
+
+
y
k
+
+
+
FIGURE 11.14
:
Direct-form FIR digital filter. The numerator coefficients are the
b
L
terms, and
since the
a
L
terms are unity there are no denominator coefficients
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