Digital Signal Processing Reference
In-Depth Information
m
(
t
)
x
(
t
)
m
(
t
) cos
c
t
c
(
t
)
cos
c
t
(a)
m
(
t
)
t
(b)
c
(
t
)
2
c
• • •
• • •
t
(c)
x
(
t
)
t
(d)
Figure 6.32
DSB/SC-AM modulation.
wave with the frequency of
c(t)
and with the amplitude varying directly with the
information signal
m(t):
x(t) = m(t)c(t) = m(t) cos(v
c
t).
Using Euler's identity for the cosine wave, we write this as
1
2
[e
jv
c
t
+ e
-jv
c
t
]
x(t) = m(t) *
1
1
2
m(t)e
jv
c
t
2
m(t)e
-jv
c
t
=
+
.
