<s>
In	O
radio	O
communications	O
,	O
single-sideband	B-Device
modulation	I-Device
(	O
SSB	O
)	O
or	O
single-sideband	B-Device
suppressed-carrier	I-Device
modulation	B-Application
(	O
SSB-SC	O
)	O
is	O
a	O
type	O
of	O
modulation	B-Application
used	O
to	O
transmit	O
information	O
,	O
such	O
as	O
an	O
audio	O
signal	O
,	O
by	O
radio	O
waves	O
.	O
</s>
<s>
A	O
refinement	O
of	O
amplitude	B-Device
modulation	I-Device
,	O
it	O
uses	O
transmitter	O
power	O
and	O
bandwidth	B-Algorithm
more	O
efficiently	O
.	O
</s>
<s>
Amplitude	B-Device
modulation	I-Device
produces	O
an	O
output	O
signal	O
the	O
bandwidth	B-Algorithm
of	O
which	O
is	O
twice	O
the	O
maximum	O
frequency	O
of	O
the	O
original	O
baseband	B-Algorithm
signal	I-Algorithm
.	O
</s>
<s>
Single-sideband	B-Device
modulation	I-Device
avoids	O
this	O
bandwidth	B-Algorithm
increase	O
,	O
and	O
the	O
power	O
wasted	O
on	O
a	O
carrier	O
,	O
at	O
the	O
cost	O
of	O
increased	O
device	O
complexity	O
and	O
more	O
difficult	O
tuning	O
at	O
the	O
receiver	O
.	O
</s>
<s>
In	O
AM	B-Device
transmitters	O
this	O
mixing	O
usually	O
takes	O
place	O
in	O
the	O
final	O
RF	O
amplifier	O
(	O
high	O
level	O
modulation	B-Application
)	O
.	O
</s>
<s>
Thus	O
the	O
resulting	O
signal	O
has	O
a	O
spectrum	O
whose	O
bandwidth	B-Algorithm
is	O
twice	O
the	O
maximum	O
frequency	O
of	O
the	O
original	O
input	O
audio	O
signal	O
.	O
</s>
<s>
In	O
addition	O
,	O
the	O
occupied	O
spectrum	O
is	O
less	O
than	O
half	O
that	O
of	O
a	O
full	O
carrier	O
AM	B-Device
signal	O
.	O
</s>
<s>
SSB	O
reception	O
requires	O
frequency	O
stability	O
and	O
selectivity	O
well	O
beyond	O
that	O
of	O
inexpensive	O
AM	B-Device
receivers	O
which	O
is	O
why	O
broadcasters	O
have	O
seldom	O
used	O
it	O
.	O
</s>
<s>
The	O
first	O
U.S.	O
patent	O
application	O
for	O
SSB	O
modulation	B-Application
was	O
filed	O
on	O
December	O
1	O
,	O
1915	O
,	O
by	O
John	O
Renshaw	O
Carson	O
.	O
</s>
<s>
The	O
U.S.	O
Navy	O
experimented	O
with	O
SSB	O
over	O
its	O
radio	O
circuits	O
before	O
World	O
War	O
I	O
.	O
SSB	O
first	O
entered	O
commercial	O
service	O
on	O
January	O
7	O
,	O
1927	O
,	O
on	O
the	O
longwave	B-Algorithm
transatlantic	O
public	O
radiotelephone	O
circuit	O
between	O
New	O
York	O
and	O
London	O
.	O
</s>
<s>
SSB	O
was	O
also	O
used	O
over	O
long-distance	O
telephone	O
lines	O
,	O
as	O
part	O
of	O
a	O
technique	O
known	O
as	O
frequency-division	B-Protocol
multiplexing	I-Protocol
(	O
FDM	O
)	O
.	O
</s>
<s>
With	O
this	O
technology	O
,	O
many	O
simultaneous	O
voice	O
channels	O
could	O
be	O
transmitted	O
on	O
a	O
single	O
physical	O
circuit	O
,	O
for	O
example	O
in	O
L-carrier	B-Protocol
.	O
</s>
<s>
With	O
SSB	O
,	O
channels	O
could	O
be	O
spaced	O
(	O
usually	O
)	O
only	O
4,000	O
Hz	O
apart	O
,	O
while	O
offering	O
a	O
speech	O
bandwidth	B-Algorithm
of	O
nominally	O
300Hz	O
to	O
3,400	O
Hz	O
.	O
</s>
<s>
Single-sideband	B-Device
has	O
the	O
mathematical	O
form	O
of	O
quadrature	O
amplitude	B-Device
modulation	I-Device
(	O
QAM	O
)	O
in	O
the	O
special	O
case	O
where	O
one	O
of	O
the	O
baseband	B-Algorithm
waveforms	O
is	O
derived	O
from	O
the	O
other	O
,	O
instead	O
of	O
being	O
independent	O
messages	O
:	O
</s>
<s>
where	O
is	O
the	O
message	O
(	O
real-valued	O
)	O
,	O
is	O
its	O
Hilbert	B-Algorithm
transform	I-Algorithm
,	O
and	O
is	O
the	O
radio	O
carrier	O
frequency	O
.	O
</s>
<s>
Coherent	O
demodulation	O
of	O
to	O
recover	O
is	O
the	O
same	O
as	O
AM	B-Device
:	O
multiply	O
by	O
and	O
lowpass	B-Algorithm
to	O
remove	O
the	O
"	O
double-frequency	O
"	O
components	O
around	O
frequency	O
.	O
</s>
<s>
which	O
is	O
the	O
classic	O
model	O
of	O
suppressed-carrier	B-Device
double	O
sideband	O
AM	B-Device
.	O
</s>
<s>
Most	O
often	O
,	O
the	O
carrier	O
is	O
reduced	O
or	O
removed	O
entirely	O
(	O
suppressed	O
)	O
,	O
being	O
referred	O
to	O
in	O
full	O
as	O
single	B-Device
sideband	I-Device
suppressed	B-Device
carrier	I-Device
(	O
SSBSC	B-Device
)	O
.	O
</s>
<s>
Assuming	O
both	O
sidebands	O
are	O
symmetric	O
,	O
which	O
is	O
the	O
case	O
for	O
a	O
normal	O
AM	B-Device
signal	O
,	O
no	O
information	O
is	O
lost	O
in	O
the	O
process	O
.	O
</s>
<s>
Since	O
the	O
final	O
RF	O
amplification	O
is	O
now	O
concentrated	O
in	O
a	O
single	B-Device
sideband	I-Device
,	O
the	O
effective	O
power	O
output	O
is	O
greater	O
than	O
in	O
normal	O
AM	B-Device
(	O
the	O
carrier	O
and	O
redundant	O
sideband	O
account	O
for	O
well	O
over	O
half	O
of	O
the	O
power	O
output	O
of	O
an	O
AM	B-Device
transmitter	O
)	O
.	O
</s>
<s>
Though	O
SSB	O
uses	O
substantially	O
less	O
bandwidth	B-Algorithm
and	O
power	O
,	O
it	O
cannot	O
be	O
demodulated	O
by	O
a	O
simple	O
envelope	B-Algorithm
detector	I-Algorithm
like	O
standard	O
AM	B-Device
.	O
</s>
<s>
An	O
alternate	O
method	O
of	O
generation	O
known	O
as	O
a	O
Hartley	O
modulator	B-Application
,	O
named	O
after	O
R	O
.	O
V	O
.	O
L	O
.	O
Hartley	O
,	O
uses	O
phasing	O
to	O
suppress	O
the	O
unwanted	O
sideband	O
.	O
</s>
<s>
To	O
generate	O
an	O
SSB	O
signal	O
with	O
this	O
method	O
,	O
two	O
versions	O
of	O
the	O
original	O
signal	O
are	O
generated	O
,	O
mutually	O
90°	O
out	O
of	O
phase	O
for	O
any	O
single	O
frequency	O
within	O
the	O
operating	O
bandwidth	B-Algorithm
.	O
</s>
<s>
Shifting	O
the	O
baseband	B-Algorithm
signal	I-Algorithm
90°	O
out	O
of	O
phase	O
cannot	O
be	O
done	O
simply	O
by	O
delaying	O
it	O
,	O
as	O
it	O
contains	O
a	O
large	O
range	O
of	O
frequencies	O
.	O
</s>
<s>
Modulation	B-Application
using	O
this	O
method	O
is	O
again	O
gaining	O
popularity	O
in	O
the	O
homebrew	O
and	O
DSP	B-Architecture
fields	O
.	O
</s>
<s>
This	O
method	O
,	O
utilizing	O
the	O
Hilbert	B-Algorithm
transform	I-Algorithm
to	O
phase	O
shift	O
the	O
baseband	B-Algorithm
audio	O
,	O
can	O
be	O
done	O
at	O
low	O
cost	O
with	O
digital	O
circuitry	O
.	O
</s>
<s>
Another	O
variation	O
,	O
the	O
Weaver	B-Device
modulator	I-Device
,	O
uses	O
only	O
lowpass	B-Algorithm
filters	I-Algorithm
and	O
quadrature	O
mixers	O
,	O
and	O
is	O
a	O
favored	O
method	O
in	O
digital	O
implementations	O
.	O
</s>
<s>
In	O
Weaver	O
's	O
method	O
,	O
the	O
band	O
of	O
interest	O
is	O
first	O
translated	O
to	O
be	O
centered	O
at	O
zero	O
,	O
conceptually	O
by	O
modulating	O
a	O
complex	O
exponential	O
with	O
frequency	O
in	O
the	O
middle	O
of	O
the	O
voiceband	O
,	O
but	O
implemented	O
by	O
a	O
quadrature	O
pair	O
of	O
sine	O
and	O
cosine	O
modulators	B-Application
at	O
that	O
frequency	O
(	O
e.g.	O
</s>
<s>
This	O
complex	O
signal	O
or	O
pair	O
of	O
real	O
signals	O
is	O
then	O
lowpass	B-Algorithm
filtered	O
to	O
remove	O
the	O
undesired	O
sideband	O
that	O
is	O
not	O
centered	O
at	O
zero	O
.	O
</s>
<s>
Then	O
,	O
the	O
single-sideband	B-Device
complex	O
signal	O
centered	O
at	O
zero	O
is	O
upconverted	O
to	O
a	O
real	O
signal	O
,	O
by	O
another	O
pair	O
of	O
quadrature	O
mixers	O
,	O
to	O
the	O
desired	O
center	O
frequency	O
.	O
</s>
<s>
Conventional	O
amplitude-modulated	O
signals	O
can	O
be	O
considered	O
wasteful	O
of	O
power	O
and	O
bandwidth	B-Algorithm
because	O
they	O
contain	O
a	O
carrier	O
signal	O
and	O
two	O
identical	O
sidebands	O
.	O
</s>
<s>
When	O
the	O
carrier	O
is	O
removed	O
from	O
the	O
transmitted	O
signal	O
,	O
it	O
is	O
called	O
suppressed-carrier	B-Device
SSB	O
.	O
</s>
<s>
This	O
mode	B-Application
of	I-Application
transmission	I-Application
is	O
called	O
reduced-carrier	B-Device
single-sideband	B-Device
.	O
</s>
<s>
In	O
other	O
cases	O
,	O
it	O
may	O
be	O
desirable	O
to	O
maintain	O
some	O
degree	O
of	O
compatibility	O
with	O
simple	O
AM	B-Device
receivers	O
,	O
while	O
still	O
reducing	O
the	O
signal	O
's	O
bandwidth	B-Algorithm
.	O
</s>
<s>
This	O
can	O
be	O
accomplished	O
by	O
transmitting	O
single-sideband	B-Device
with	O
a	O
normal	O
or	O
slightly	O
reduced	B-Device
carrier	I-Device
.	O
</s>
<s>
This	O
mode	O
is	O
called	O
compatible	O
(	O
or	O
full-carrier	O
)	O
SSB	O
or	O
amplitude	B-Device
modulation	I-Device
equivalent	O
(	O
AME	O
)	O
.	O
</s>
<s>
In	O
typical	O
AME	O
systems	O
,	O
harmonic	O
distortion	O
can	O
reach	O
25%	O
,	O
and	O
intermodulation	O
distortion	O
can	O
be	O
much	O
higher	O
than	O
normal	O
,	O
but	O
minimizing	O
distortion	O
in	O
receivers	O
with	O
envelope	B-Algorithm
detectors	I-Algorithm
is	O
generally	O
considered	O
less	O
important	O
than	O
allowing	O
them	O
to	O
produce	O
intelligible	O
audio	O
.	O
</s>
<s>
A	O
second	O
,	O
and	O
perhaps	O
more	O
correct	O
,	O
definition	O
of	O
"	O
compatible	O
single	B-Device
sideband	I-Device
"	O
(	O
CSSB	O
)	O
refers	O
to	O
a	O
form	O
of	O
amplitude	O
and	O
phase	O
modulation	B-Application
in	O
which	O
the	O
carrier	O
is	O
transmitted	O
along	O
with	O
a	O
series	O
of	O
sidebands	O
that	O
are	O
predominantly	O
above	O
or	O
below	O
the	O
carrier	O
term	O
.	O
</s>
<s>
Since	O
phase	O
modulation	B-Application
is	O
present	O
in	O
the	O
generation	O
of	O
the	O
signal	O
,	O
energy	O
is	O
removed	O
from	O
the	O
carrier	O
term	O
and	O
redistributed	O
into	O
the	O
sideband	O
structure	O
similar	O
to	O
that	O
which	O
occurs	O
in	O
analog	B-Application
frequency	I-Application
modulation	I-Application
.	O
</s>
<s>
The	O
signals	O
feeding	O
the	O
phase	O
modulator	B-Application
and	O
the	O
envelope	B-Algorithm
modulator	B-Application
are	O
further	O
phase-shifted	O
by	O
90°	O
with	O
respect	O
to	O
each	O
other	O
.	O
</s>
<s>
This	O
places	O
the	O
information	O
terms	O
in	O
quadrature	O
with	O
each	O
other	O
;	O
the	O
Hilbert	B-Algorithm
transform	I-Algorithm
of	O
information	O
to	O
be	O
transmitted	O
is	O
utilized	O
to	O
cause	O
constructive	O
addition	O
of	O
one	O
sideband	O
and	O
cancellation	O
of	O
the	O
opposite	O
primary	O
sideband	O
.	O
</s>
<s>
Since	O
phase	O
modulation	B-Application
is	O
employed	O
,	O
higher-order	O
terms	O
are	O
also	O
generated	O
.	O
</s>
<s>
In	O
one	O
system	O
,	O
the	O
phase-modulated	O
term	O
is	O
actually	O
the	O
log	O
of	O
the	O
value	O
of	O
the	O
carrier	O
level	O
plus	O
the	O
phase-shifted	O
audio/information	O
term	O
.	O
</s>
<s>
This	O
produces	O
an	O
ideal	O
CSSB	O
signal	O
,	O
where	O
at	O
low	O
modulation	B-Application
levels	O
only	O
a	O
first-order	O
term	O
on	O
one	O
side	O
of	O
the	O
carrier	O
is	O
predominant	O
.	O
</s>
<s>
As	O
the	O
modulation	B-Application
level	O
is	O
increased	O
,	O
the	O
carrier	O
level	O
is	O
reduced	O
while	O
a	O
second-order	O
term	O
increases	O
substantially	O
in	O
amplitude	O
.	O
</s>
<s>
At	O
the	O
point	O
of	O
100%	O
envelope	B-Algorithm
modulation	B-Application
,	O
6dB	O
of	O
power	O
is	O
removed	O
from	O
the	O
carrier	O
term	O
,	O
and	O
the	O
second-order	O
term	O
is	O
identical	O
in	O
amplitude	O
to	O
carrier	O
term	O
.	O
</s>
<s>
At	O
the	O
point	O
of	O
100%	O
modulation	B-Application
,	O
the	O
spectrum	O
appears	O
identical	O
to	O
a	O
normal	O
double-sideband	O
AM	B-Device
transmission	O
,	O
with	O
the	O
center	O
term	O
(	O
now	O
the	O
primary	O
audio	O
term	O
)	O
at	O
a	O
0dB	O
reference	O
level	O
,	O
and	O
both	O
terms	O
on	O
either	O
side	O
of	O
the	O
primary	O
sideband	O
at	O
−6dB	O
.	O
</s>
<s>
At	O
levels	O
below	O
100%	O
modulation	B-Application
,	O
the	O
sideband	O
structure	O
appears	O
quite	O
asymmetric	O
.	O
</s>
<s>
The	O
result	O
is	O
that	O
the	O
signal	O
occupies	O
approximately	O
1/2	O
the	O
normal	O
bandwidth	B-Algorithm
of	O
a	O
full-carrier	O
,	O
DSB	O
signal	O
.	O
</s>
<s>
At	O
negative	O
100%	O
modulation	B-Application
,	O
the	O
term	O
is	O
driven	O
to	O
zero	O
(	O
0	O
)	O
,	O
and	O
the	O
modulator	B-Application
becomes	O
undefined	O
.	O
</s>
<s>
Strict	O
modulation	B-Application
control	O
must	O
be	O
employed	O
to	O
maintain	O
stability	O
of	O
the	O
system	O
and	O
avoid	O
splatter	O
.	O
</s>
<s>
One	O
example	O
of	O
this	O
method	O
was	O
also	O
used	O
to	O
generate	O
one	O
of	O
the	O
Kahn	O
independent-sideband	B-Device
(	O
ISB	O
)	O
AM	B-Device
stereo	O
signals	O
.	O
</s>
<s>
Later	O
,	O
the	O
system	O
was	O
further	O
improved	O
by	O
use	O
of	O
an	O
arcsine-based	O
modulator	B-Application
that	O
included	O
a	O
1-0.52E	O
term	O
in	O
the	O
denominator	O
of	O
the	O
arcsin	O
generator	O
equation	O
.	O
</s>
<s>
E	O
represents	O
the	O
envelope	B-Algorithm
term	O
;	O
roughly	O
half	O
the	O
modulation	B-Application
term	O
applied	O
to	O
the	O
envelope	B-Algorithm
modulator	B-Application
is	O
utilized	O
to	O
reduce	O
the	O
second-order	O
term	O
of	O
the	O
arcsin	O
"	O
phase	O
"	O
-modulated	O
path	O
;	O
thus	O
reducing	O
the	O
second-order	O
term	O
in	O
the	O
undesired	O
sideband	O
.	O
</s>
<s>
A	O
multi-loop	O
modulator/demodulator	O
feedback	O
approach	O
was	O
used	O
to	O
generate	O
an	O
accurate	O
arcsin	O
signal	O
.	O
</s>
<s>
An	O
additional	O
audio	O
processing	O
device	O
further	O
improved	O
the	O
sideband	O
structure	O
by	O
selectively	O
applying	O
pre-emphasis	O
to	O
the	O
modulating	B-Application
signals	I-Application
.	O
</s>
<s>
Since	O
the	O
envelope	B-Algorithm
of	O
all	O
the	O
signals	O
described	O
remains	O
an	O
exact	O
copy	O
of	O
the	O
information	O
applied	O
to	O
the	O
modulator	B-Application
,	O
it	O
can	O
be	O
demodulated	O
without	O
distortion	O
by	O
an	O
envelope	B-Algorithm
detector	I-Algorithm
such	O
as	O
a	O
simple	O
diode	O
.	O
</s>
<s>
In	O
a	O
practical	O
receiver	O
,	O
some	O
distortion	O
may	O
be	O
present	O
,	O
usually	O
at	O
a	O
low	O
level	O
(	O
in	O
AM	B-Device
broadcast	O
,	O
always	O
below	O
5%	O
)	O
,	O
due	O
to	O
sharp	O
filtering	O
and	O
nonlinear	O
group	O
delay	O
in	O
the	O
IF	O
filters	O
of	O
the	O
receiver	O
,	O
which	O
act	O
to	O
truncate	O
the	O
compatibility	O
sideband	O
–	O
those	O
terms	O
that	O
are	O
not	O
the	O
result	O
of	O
a	O
linear	O
process	O
of	O
simply	O
envelope	B-Algorithm
modulating	O
the	O
signal	O
as	O
would	O
be	O
the	O
case	O
in	O
full-carrier	O
DSB-AM	O
–	O
and	O
rotation	O
of	O
phase	O
of	O
these	O
compatibility	O
terms	O
such	O
that	O
they	O
no	O
longer	O
cancel	O
the	O
quadrature	O
distortion	O
term	O
caused	O
by	O
a	O
first-order	O
SSB	O
term	O
along	O
with	O
the	O
carrier	O
.	O
</s>
<s>
The	O
Kahn	O
CSSB	O
method	O
was	O
also	O
briefly	O
used	O
by	O
Airphone	B-Application
as	O
the	O
modulation	B-Application
method	O
employed	O
for	O
early	O
consumer	O
telephone	O
calls	O
that	O
could	O
be	O
placed	O
from	O
an	O
aircraft	O
to	O
ground	O
.	O
</s>
<s>
This	O
was	O
quickly	O
supplanted	O
by	O
digital	O
modulation	B-Application
methods	O
to	O
achieve	O
even	O
greater	O
spectral	O
efficiency	O
.	O
</s>
<s>
While	O
CSSB	O
is	O
seldom	O
used	O
today	O
in	O
the	O
AM/MW	O
broadcast	O
bands	O
worldwide	O
,	O
some	O
amateur	O
radio	O
operators	O
still	O
experiment	O
with	O
it	O
.	O
</s>
<s>
The	O
front	O
end	O
of	O
an	O
SSB	O
receiver	O
is	O
similar	O
to	O
that	O
of	O
an	O
AM	B-Device
or	O
FM	B-Application
receiver	O
,	O
consisting	O
of	O
a	O
superheterodyne	O
RF	O
front	O
end	O
that	O
produces	O
a	O
frequency-shifted	O
version	O
of	O
the	O
radio	O
frequency	O
(	O
RF	O
)	O
signal	O
within	O
a	O
standard	O
intermediate	O
frequency	O
(	O
IF	O
)	O
band	O
.	O
</s>
<s>
To	O
recover	O
the	O
original	O
signal	O
from	O
the	O
IF	O
SSB	O
signal	O
,	O
the	O
single	B-Device
sideband	I-Device
must	O
be	O
frequency-shifted	O
down	O
to	O
its	O
original	O
range	O
of	O
baseband	B-Algorithm
frequencies	O
,	O
by	O
using	O
a	O
product	O
detector	O
which	O
mixes	O
it	O
with	O
the	O
output	O
of	O
a	O
beat	O
frequency	O
oscillator	O
(	O
BFO	O
)	O
.	O
</s>
<s>
In	O
other	O
words	O
,	O
it	O
is	O
just	O
another	O
stage	O
of	O
heterodyning	B-Algorithm
.	O
</s>
<s>
The	O
baseband	B-Algorithm
frequency	O
it	O
needs	O
to	O
be	O
shifted	O
to	O
is	O
=	O
2000Hz	O
.	O
</s>
<s>
(	O
The	O
unwanted	O
components	O
at	O
can	O
be	O
removed	O
by	O
a	O
lowpass	B-Algorithm
filter	I-Algorithm
;	O
for	O
which	O
an	O
output	O
transducer	O
or	O
the	O
human	O
ear	O
may	O
serve	O
)	O
.	O
</s>
<s>
SSB	O
techniques	O
can	O
also	O
be	O
adapted	O
to	O
frequency-shift	O
and	O
frequency-invert	O
baseband	B-Algorithm
waveforms	O
(	O
voice	O
inversion	O
)	O
.	O
</s>
<s>
This	O
voice	O
scrambling	O
method	O
was	O
made	O
by	O
running	O
the	O
audio	O
of	O
one	O
side	O
band	O
modulated	B-Application
audio	O
sample	O
through	O
its	O
opposite	O
(	O
e.g.	O
</s>
<s>
running	O
an	O
LSB	O
modulated	B-Application
audio	O
sample	O
through	O
a	O
radio	O
running	O
USB	O
modulation	B-Application
)	O
.	O
</s>
<s>
Limitation	O
of	O
single-sideband	B-Device
modulation	I-Device
being	O
used	O
for	O
voice	O
signals	O
and	O
not	O
available	O
for	O
video/TV	O
signals	O
leads	O
to	O
the	O
usage	O
of	O
vestigial	O
sideband	O
.	O
</s>
<s>
Television	O
broadcasts	O
(	O
in	O
analog	O
video	O
formats	O
)	O
use	O
this	O
method	O
if	O
the	O
video	O
is	O
transmitted	O
in	O
AM	B-Device
,	O
due	O
to	O
the	O
large	O
bandwidth	B-Algorithm
used	O
.	O
</s>
<s>
It	O
may	O
also	O
be	O
used	O
in	O
digital	O
transmission	O
,	O
such	O
as	O
the	O
ATSC	B-Device
standardized	O
8VSB	B-Device
.	O
</s>
<s>
The	O
broadcast	O
or	O
transport	O
channel	O
for	O
TV	O
in	O
countries	O
that	O
use	O
NTSC	O
or	O
ATSC	B-Device
has	O
a	O
bandwidth	B-Algorithm
of	O
6MHz	O
.	O
</s>
<s>
To	O
conserve	O
bandwidth	B-Algorithm
,	O
SSB	O
would	O
be	O
desirable	O
,	O
but	O
the	O
video	O
signal	O
has	O
significant	O
low-frequency	O
content	O
(	O
average	O
brightness	O
)	O
and	O
has	O
rectangular	O
synchronising	O
pulses	O
.	O
</s>
<s>
In	O
vestigial	O
sideband	O
,	O
the	O
full	O
upper	O
sideband	O
of	O
bandwidth	B-Algorithm
W2	O
=	O
4.0MHz	O
is	O
transmitted	O
,	O
but	O
only	O
W1	O
=	O
0.75MHz	O
of	O
the	O
lower	O
sideband	O
is	O
transmitted	O
,	O
along	O
with	O
a	O
carrier	O
.	O
</s>
<s>
This	O
effectively	O
makes	O
the	O
system	O
AM	B-Device
at	O
low	O
modulation	B-Application
frequencies	O
and	O
SSB	O
at	O
high	O
modulation	B-Application
frequencies	O
.	O
</s>
<s>
When	O
single-sideband	B-Device
is	O
used	O
in	O
amateur	O
radio	O
voice	O
communications	O
,	O
it	O
is	O
common	O
practice	O
that	O
for	O
frequencies	O
below	O
10MHz	O
,	O
lower	O
sideband	O
(	O
LSB	O
)	O
is	O
used	O
and	O
for	O
frequencies	O
of	O
10MHz	O
and	O
above	O
,	O
upper	O
sideband	O
(	O
USB	O
)	O
is	O
used	O
.	O
</s>
<s>
Extended	O
single	B-Device
sideband	I-Device
is	O
any	O
J3E	B-Device
(	O
SSB-SC	O
)	O
mode	O
that	O
exceeds	O
the	O
audio	O
bandwidth	B-Algorithm
of	O
standard	O
or	O
traditional	O
2.9kHz	O
SSB	O
J3E	B-Device
modes	O
(	O
ITU	O
2K90J3E	O
)	O
to	O
support	O
higher-quality	O
sound	O
.	O
</s>
<s>
Amplitude-companded	O
single	B-Device
sideband	I-Device
(	O
ACSSB	B-Device
)	O
is	O
a	O
narrowband	O
modulation	B-Application
method	O
using	O
a	O
single	B-Device
sideband	I-Device
with	O
a	O
pilot	O
tone	O
,	O
allowing	O
an	O
expander	O
in	O
the	O
receiver	O
to	O
restore	O
the	O
amplitude	O
that	O
was	O
severely	O
compressed	O
by	O
the	O
transmitter	O
.	O
</s>
<s>
It	O
offers	O
improved	O
effective	O
range	O
over	O
standard	O
SSB	O
modulation	B-Application
while	O
simultaneously	O
retaining	O
backwards	O
compatibility	O
with	O
standard	O
SSB	B-Device
radios	I-Device
.	O
</s>
<s>
ACSSB	B-Device
also	O
offers	O
reduced	O
bandwidth	B-Algorithm
and	O
improved	O
range	O
for	O
a	O
given	O
power	O
level	O
compared	O
with	O
narrow	O
band	O
FM	B-Application
modulation	B-Application
.	O
</s>
<s>
The	O
generation	O
of	O
standard	O
SSB	O
modulation	B-Application
results	O
in	O
large	O
envelope	B-Algorithm
overshoots	O
well	O
above	O
the	O
average	O
envelope	B-Algorithm
level	O
for	O
a	O
sinusoidal	O
tone	O
(	O
even	O
when	O
the	O
audio	O
signal	O
is	O
peak-limited	O
)	O
.	O
</s>
<s>
The	O
standard	O
SSB	O
envelope	B-Algorithm
peaks	O
are	O
due	O
to	O
truncation	O
of	O
the	O
spectrum	O
and	O
nonlinear	O
phase	O
distortion	O
from	O
the	O
approximation	O
errors	O
of	O
the	O
practical	O
implementation	O
of	O
the	O
required	O
Hilbert	B-Algorithm
transform	I-Algorithm
.	O
</s>
<s>
It	O
was	O
recently	O
shown	O
that	O
suitable	O
overshoot	O
compensation	O
(	O
so-called	O
controlled-envelope	B-Device
single-sideband	I-Device
modulation	I-Device
or	O
CESSB	B-Device
)	O
achieves	O
about	O
3.8dB	O
of	O
peak	O
reduction	O
for	O
speech	O
transmission	O
.	O
</s>
<s>
Although	O
the	O
generation	O
of	O
the	O
CESSB	B-Device
signal	O
can	O
be	O
integrated	O
into	O
the	O
SSB	O
modulator	B-Application
,	O
it	O
is	O
feasible	O
to	O
separate	O
the	O
generation	O
of	O
the	O
CESSB	B-Device
signal	O
(	O
e.g.	O
</s>
<s>
in	O
form	O
of	O
an	O
external	O
speech	O
preprocessor	O
)	O
from	O
a	O
standard	O
SSB	B-Device
radio	I-Device
.	O
</s>
<s>
This	O
requires	O
that	O
the	O
standard	O
SSB	B-Device
radio	I-Device
's	O
modulator	B-Application
be	O
linear-phase	O
and	O
have	O
a	O
sufficient	O
bandwidth	B-Algorithm
to	O
pass	O
the	O
CESSB	B-Device
signal	O
.	O
</s>
<s>
If	O
a	O
standard	O
SSB	O
modulator	B-Application
meets	O
these	O
requirements	O
,	O
then	O
the	O
envelope	B-Algorithm
control	O
by	O
the	O
CESSB	B-Device
process	O
is	O
preserved	O
.	O
</s>
<s>
In	O
1982	O
,	O
the	O
International	O
Telecommunication	O
Union	O
(	O
ITU	O
)	O
designated	O
the	O
types	O
of	O
amplitude	B-Device
modulation	I-Device
:	O
</s>
