Renesas Hitachi H8S/2191, Hardware Manual

Page: 764 / 1065

Rev. 2.0, 11/00, page 737 of 1037
(2) Frequency Characteristics
The computation circuit repeats computation of the function, which is obtained by s-z
conversion according to bi-linear approximation of the transfer function on the s-plane.
Figure 28.41 shows the frequency characteristics of the lag-lead filter.
f1
0
f2
Frequency (Hz)
20log(f1/f2)
gain(dB)
phase(deg)
Figure 28.41 Frequency Characteristics of the Lag-Lead Filter
The pulse transfer function G(Z) is obtained by the bi-linear approximation of the transfer
function G (S).
In the transfer G (S),
2 1
−
Z
-1
S=
⋅
Ts 1+Z
-1
Where, assumed that Z
-1
= e
-j
ω
Ts
,
2 1+AZ
-1
G (Z) = G
⋅ ⋅
Ts 1+BZ
-1
1 1 1
Ts+ Ts
−
Ts
−
π
f
2
π
f
2
π
f
1
G (Z) = A = B =
1 1 1
Ts+ Ts+ Ts+
π
f
1
π
f
2
π
f
1
Ts: Sampling cycle (sec)