B. P. Lathi, Zhi Ding - Modern Digital and Analog Communication Systems-Oxford University Press (2009)

either utilize or remove the 100% spectral redundancy:
4.4 Bandwidth-Efficient Amplitude Modulations 159
· Single-sideband (SSB) modulation, which removes either the LSB or the USB that uses only
bandwidth of B Hz for one message signal m(t);
· Quadrature amplitude modulation (QAM), which utilizes the spectral redundancy by sending
two messages over the same bandwidth of 2B Hz.
Amplitude Modulation: Single Sideband (SSB)
As shown in Fig. 4.13, either the LSB or the USB can be suppressed from the DSB signal
via bandpass filtering. Such a scheme in which only one sideband is transmitted is known as
single-sideband (SSB) transmission, and requires only one-half the bandwidth of the DSB
signal.
Figure 4.12
(a) Original
message
spectrum. (b) The
redundant
bandwidth
consumption in
DSB
modulations.
-B
-fc
0
fc 1-
(a)
,_ 2B
(b)
Figure 4. 13
55B spectra from
suppressing one
DSB sideband.
-B 0
B
1-
(a) Baseband
Upper
sideband
-le
.....
I
I
-le
....' '
Lower
sideband
0
0
Lower
sideband
... ...
I
I
le
..... ' \
1-
Upper
sideband
(b) DSB
1-
1-
(c) USB
(d) LSB
-2lc
2lc 1-
( e)