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354
AM, FM, and Digital Modulated Systems Chap. 5
1
BINARY DATA
0 1 0
1 0
1
T b = ––
R
(a) Unipolar
Modulation
(b) Polar
Modulation
m(t)
m(t)
t
t
(c) OOK Signal
s(t)
t
(d) BPSK Signal
s(t)
(e) FSK Signal
s(t)
(f) DSB-SC with
Pulse Shaping
of the Baseband
Digital Signal
s(t)
Figure 5–19
Bandpass digitally modulated signals.
where m(t) is a unipolar baseband data signal, as shown in Fig. 5–19a. Consequently, the
complex envelope is simply
(5–71)
and the PSD of this complex envelope is proportional to that for the unipolar signal. Using
Eq. (3–39b), we find that this PSD is
g (f) = A c 2
g(t) = A c m(t) for OOK
2 cd(f) + T ba sin pfT b
pfT b
2
b d (for OOK)
(5–72)