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Sec. 5–5 Asymmetric Sideband Signals 327
Baseband processing
m(t)
m(t)
Modulation
input
90° phase
shift across
band of m(t)
^
m(t)
s (t)
SSB signal
Oscillator
f=f c
90° phase
shift
at f=f c
A c sin( c t)
(a) Phasing Method
A c cos( c t)
m(t)
Modulation
input
A c cos( c t)
Sideband filter (bandpass
filter on either
upper or lower
sideband)
s(t)
SSB signal
Oscillator
f=f c
(b) Filter Method
Figure 5–5
Generation of SSB.
This is described by Fig. P5–15 and Prob. P5–15. A practical SSB transmitter incorporates an
up converter to translate the SSB signal to the desired operating frequency and uses a Class B
amplifier to amplify the signal to the desired power level.
SSB signals have both AM and PM. Using Eq. (5–15), we have, for the AM component
(real envelope),
R(t) = |g(t)| = A c 3m 2 (t) + [mN (t)] 2
(5–27)
and for the PM component,
u(t) = lg(t)
= tan -1 c ; mN(t) d
m(t)
(5–28)
SSB signals may be received by using a superheterodyne receiver that incorporates a
product detector with u 0 = 0. Thus, the receiver output is
v out (t) = K Re{g(t)e -ju 0
} = KA c m(t)
(5–29)