<s>
Sensitivity	B-Algorithm
time	I-Algorithm
control	I-Algorithm
(	O
STC	O
)	O
,	O
also	O
known	O
as	O
swept-gain	O
control	O
,	O
is	O
a	O
system	O
used	O
to	O
attenuate	O
the	O
very	O
strong	O
signals	O
returned	O
from	O
nearby	O
ground	O
clutter	O
targets	O
in	O
the	O
first	O
few	O
range	B-Algorithm
gates	I-Algorithm
of	O
a	O
radar	B-Application
receiver	O
.	O
</s>
<s>
This	O
is	O
used	O
in	O
air	B-Application
traffic	I-Application
control	I-Application
systems	I-Application
and	O
has	O
an	O
influence	O
on	O
the	O
shape	O
of	O
the	O
elevation	O
pattern	O
of	O
the	O
surveillance	O
antenna	O
.	O
</s>
<s>
It	O
is	O
represented	O
in	O
terms	O
of	O
numerical	O
value	O
typically	O
expressed	O
in	O
decibels	O
(	O
dB	O
)	O
,	O
starting	O
from	O
zero	O
,	O
indicating	O
that	O
there	O
is	O
no	O
muting	O
and	O
that	O
the	O
radar	B-Application
system	I-Application
is	O
accepting	O
all	O
returns	O
.	O
</s>
<s>
The	O
radar	B-Application
equation	O
is	O
based	O
on	O
,	O
meaning	O
that	O
doubling	O
the	O
range	O
to	O
a	O
target	O
results	O
in	O
sixteen	O
times	O
less	O
energy	O
being	O
returned	O
.	O
</s>
<s>
In	O
the	O
case	O
of	O
a	O
long-range	O
radar	B-Application
with	O
high	O
power	O
outputs	O
,	O
the	O
return	O
from	O
nearby	O
targets	O
can	O
be	O
so	O
powerful	O
that	O
it	O
causes	O
the	O
amplifiers	O
to	O
saturate	O
,	O
producing	O
a	O
blank	O
area	O
on	O
the	O
screen	O
beyond	O
which	O
nothing	O
can	O
be	O
detected	O
until	O
the	O
amplifiers	O
return	O
to	O
normal	O
operation	O
again	O
.	O
</s>
<s>
For	O
early	O
radar	B-Application
systems	I-Application
,	O
the	O
solution	O
was	O
to	O
point	O
the	O
signal	O
away	O
from	O
the	O
ground	O
.	O
</s>
<s>
This	O
can	O
be	O
difficult	O
for	O
ground	O
or	O
ship-based	O
radars	B-Application
,	O
which	O
required	O
other	O
solutions	O
.	O
</s>
<s>
In	O
the	O
case	O
of	O
the	O
ground-based	O
AMES	O
Type	O
7	O
,	O
for	O
instance	O
,	O
the	O
radars	B-Application
were	O
installed	O
in	O
natural	O
dish-like	O
depressions	O
so	O
that	O
all	O
returns	O
below	O
a	O
certain	O
angle	O
were	O
cut	O
off	O
very	O
close	O
to	O
the	O
radar	B-Application
.	O
</s>
<s>
The	O
downside	O
to	O
this	O
approach	O
is	O
that	O
it	O
permanently	O
hides	O
any	O
signal	O
below	O
a	O
certain	O
angle	O
,	O
which	O
for	O
a	O
very	O
long-range	O
system	O
might	O
prevent	O
it	O
from	O
seeing	O
anything	O
near	O
the	O
radar	B-Application
site	O
.	O
</s>
<s>
STC	O
addresses	O
this	O
problem	O
by	O
implementing	O
a	O
reverse	O
gain	O
curve	O
with	O
the	O
same	O
characteristics	O
as	O
the	O
radar	B-Application
equation	O
,	O
that	O
is	O
,	O
a	O
dependency	O
or	O
some	O
function	O
close	O
to	O
that	O
(	O
often	O
there	O
are	O
discrete	O
steps	O
)	O
.	O
</s>
<s>
The	O
gain	O
modification	O
is	O
reduced	O
over	O
time	O
,	O
until	O
it	O
reaches	O
zero	O
at	O
some	O
selected	O
distance	O
from	O
the	O
radar	B-Application
site	O
,	O
often	O
on	O
the	O
order	O
of	O
.	O
</s>
<s>
Because	O
the	O
system	O
works	O
by	O
muting	O
nearby	O
signals	O
,	O
it	O
may	O
have	O
the	O
side-effect	O
of	O
eliminating	O
small	O
targets	O
near	O
the	O
radar	B-Application
.	O
</s>
<s>
This	O
is	O
fine	O
for	O
many	O
applications	O
,	O
like	O
air	B-Application
traffic	I-Application
control	I-Application
,	O
where	O
the	O
targets	O
are	O
large	O
and	O
nearby	O
aircraft	O
are	O
often	O
guided	O
using	O
a	O
local-area	O
radar	B-Application
.	O
</s>
