28.11.6 Filter Characteristics - Renesas Hitachi H8S/2194 Series Hardware Manual

28.11.6 Filter Characteristics

(1) Lag-Lead Filter
A filter required for a servo loop is built in the hardware. This filter uses an IIR (Infinite
Impulse Response) type digital filter (another type of the digital filter is FIR, i.e. Finite
Impulse Response type). This digital filter circuit implements a lag-lead filter, as shown in
figure 28.40.
The transfer function G (S) is expressed by the following equation.
Transfer function G (S) =
f =1/2πC (R1+R2)
1
f =1/2πCR2
2
Rev. 2.0, 11/00, page 736 of 1037
R1
INPUT
Figure 28.40 Lag-lead Filter
S
1+
2πf
2
S
1+
2πf
1
OUTPUT
R2
+
C