Intel 2920 Design Handbook page 64

SUMMARY OF FILTER CHARACTERISTICS
OP Dest Source Shift Comments
LOA YI, YO,
ROO
;YI =YO
LOA YO, X, R04
SUB YO,
X,
R06
ADD
YO, X, R08
SUB YO, X, RIO ; YO = G*X
SUB YO, Yl, R04
ADD
YO, YI, R06
SUB YO,
YI,
R08
ADD
YO, YI, RIO ; YO = G*X
+
(B-1) *YI
ADD
YO, YI, ROO
5.6.2 Simulating Complex Conjugate Pole Parts
Figure 5-12 shows a sampled realization of a complex
pole pair with the 2920. Again the blocks labeled X are
multipliers, those labeled z-I are unit (one sample inter-
val) delays, and the block labeled L is an adder. Coeffi-
cients BI and B2 control the frequency parameters, and
G adjusts the overall gain.
x
0-t:\
Y o
_~1
J2
- t
~Z-l
Z-l
0\0
'-61
X
61
=
2e- oT cos wT
62
=
,e,20T
where
0
=
real part 01 pole
w
=
imaginary
T
=
sample period
DC
Gain
=
G/(1,61,62)
Max Gain
=
G/«1
+
621
V
1
+
(612/462) )
atl
=
L
COS,1(6 1 (1,6 2
»)
20 T
----:rn;-
H(S)
=
2 G 2 2 H(Z)
s +20s +(0 +w ) 1-61 Z,1 + 62 Z ,2
Figure 5-12. Realization Of Complex Conjugate
Pole Pair
5-13
Figure 5-13 shows the frequency response of this type of
stage. The choice of parameter values determine both
the frequency at which the gain peaks, and the
Q
or
sharpness of the peak.
50
z
;;
"
FREQUENCY I 2rr
{LC
Figure 5-13. Gain Of Complex Conjugate Pole
Pair Section
The FORTRAN equations for a complex conjugate pole
pair section are as follows:
Y2 = YI
YI = YO
YO = BI *YI
+
B2*Y2
+
G*X
Once the coefficients of the third equation are found,
the equations can be converted to 2920 code using the
procedures described above. Thus the major portion of
the design consists of finding values for the coefficients
which meet the design requirements, yet take the
minimum numbers of 2920 steps to realize. The pro-
cedures are shown in Design Example No.2.
Design Example No. 2.-For a sample interval of
76.8 I-lsec, realize a resonance at 1000 Hz
±
0.5070 with a
Q in the range
75 ~
Q
~ 100.
The peak gain should be
1.0
±
10070.
A complex conjugate pair of s plane poles at s
=
-a±jw
has an impulse response which rings at a frequency
f
=
w I2rr and a value for Q given by
Q = 2~