HP 8901B Operation And Calibration Manual page 27

Model 8901B
General Information
modulation index. If the peak amplitude is called
P
and the trough amplitude is called T, the modulation
index
rn
(usually expressed in
%)
is defined as
P - T
m=-
+
x 100%.
In the example of Figure 1-3,
P
=
1.5
and
T
= 0.5; therefore,
1.5
-
0.5
m =
x 100% = 50%.
1.5
+
0.5
Figure
1-4
shows AM signals with modulation indexes varying from
0
to
100%.
(a) 0% AM (CW)
(b)
30%
AM
(c) 70% AM
(d) 100% AM
Figure
1-4.
AM for Various Depths
1-13