<s>
This	O
is	O
a	O
list	O
of	O
different	O
types	B-Algorithm
of	I-Algorithm
radar	I-Algorithm
.	O
</s>
<s>
Search	O
radars	B-Application
scan	O
great	O
volumes	O
of	O
space	O
with	O
pulses	O
of	O
short	O
radio	O
waves	O
.	O
</s>
<s>
The	O
radar	B-Application
measures	O
the	O
distance	O
to	O
the	O
reflector	O
by	O
measuring	O
the	O
time	O
of	O
the	O
roundtrip	O
from	O
emission	O
of	O
a	O
pulse	O
to	O
reception	O
,	O
dividing	O
this	O
by	O
two	O
,	O
and	O
then	O
multiplying	O
by	O
the	O
speed	O
of	O
light	O
.	O
</s>
<s>
The	O
radar	B-Application
determines	O
the	O
direction	O
because	O
the	O
short	O
radio	O
waves	O
behave	O
like	O
a	O
search	O
light	O
when	O
emitted	O
from	O
the	O
reflector	O
of	O
the	O
radar	B-Application
set	O
's	O
antenna	O
.	O
</s>
<s>
Targeting	O
radars	B-Application
utilize	O
the	O
same	O
principle	O
but	O
scan	O
smaller	O
volumes	O
of	O
space	O
far	O
more	O
often	O
,	O
usually	O
several	O
times	O
a	O
second	O
or	O
more	O
,	O
while	O
a	O
search	O
radar	B-Application
will	O
scan	O
a	O
larger	O
volume	O
less	O
frequently	O
.	O
</s>
<s>
Missile	O
lock-on	O
describes	O
the	O
scenario	O
where	O
a	O
targeting	O
radar	B-Application
has	O
acquired	O
a	O
target	O
,	O
and	O
the	O
fire	O
control	O
can	O
calculate	O
a	O
path	O
for	O
the	O
missile	O
to	O
the	O
target	O
;	O
in	O
semi-active	O
radar	B-Application
homing	O
systems	O
,	O
this	O
implies	O
that	O
the	O
missile	O
can	O
"	O
see	O
"	O
the	O
target	O
that	O
the	O
targeting	O
radar	B-Application
is	O
"	O
illuminating	O
"	O
.	O
</s>
<s>
Some	O
targeting	O
radars	B-Application
have	O
a	O
range	O
gate	O
that	O
can	O
track	O
a	O
target	O
,	O
to	O
eliminate	O
clutter	O
and	O
electronic	O
countermeasures	O
.	O
</s>
<s>
Instrumentation	O
radars	B-Application
are	O
used	O
to	O
test	O
aircraft	O
,	O
missiles	O
,	O
rockets	O
,	O
and	O
munitions	O
on	O
government	O
and	O
private	O
test	O
ranges	O
.	O
</s>
<s>
Radar	B-Application
proximity	O
fuzes	O
are	O
attached	O
to	O
anti-aircraft	O
artillery	O
shells	O
or	O
other	O
explosive	O
devices	O
,	O
and	O
detonate	O
the	O
device	O
when	O
it	O
approaches	O
a	O
large	O
object	O
.	O
</s>
<s>
They	O
use	O
a	O
small	O
rapidly	O
pulsing	O
omnidirectional	O
radar	B-Application
,	O
usually	O
with	O
a	O
powerful	O
battery	O
that	O
has	O
a	O
long	O
storage	O
life	O
,	O
and	O
a	O
very	O
short	O
operational	O
life	O
.	O
</s>
<s>
Weather	B-Application
radars	I-Application
can	O
resemble	O
search	O
radars	B-Application
.	O
</s>
<s>
This	O
radar	B-Application
uses	O
radio	O
waves	O
along	O
with	O
horizontal	O
,	O
dual	O
(	O
horizontal	O
and	O
vertical	O
)	O
,	O
or	O
circular	O
polarization	O
.	O
</s>
<s>
The	O
frequency	O
selection	O
of	O
weather	B-Application
radar	I-Application
is	O
a	O
performance	O
compromise	O
between	O
precipitation	O
reflectivity	O
and	O
attenuation	O
due	O
to	O
atmospheric	O
water	O
vapor	O
.	O
</s>
<s>
Some	O
weather	B-Application
radars	I-Application
uses	O
doppler	B-Algorithm
shift	I-Algorithm
to	O
measure	O
wind	O
speeds	O
and	O
dual-polarization	O
for	O
identification	O
of	O
types	O
of	O
precipitations	O
.	O
</s>
<s>
Navigational	O
radars	B-Application
resemble	O
search	O
radar	B-Application
,	O
but	O
use	O
very	O
short	O
waves	O
that	O
reflect	O
from	O
earth	O
and	O
stone	O
.	O
</s>
<s>
Marine	O
radars	B-Application
are	O
used	O
by	O
ships	O
for	O
collision	O
avoidance	O
and	O
navigation	O
purposes	O
.	O
</s>
<s>
The	O
frequency	O
band	O
of	O
radar	B-Application
used	O
on	O
most	O
ships	O
is	O
X	B-Algorithm
band	I-Algorithm
(	O
9GHz/3cm	O
)	O
,	O
but	O
S	B-Algorithm
band	I-Algorithm
(	O
3GHz/10cm	O
)	O
radar	B-Application
is	O
also	O
installed	O
on	O
most	O
oceangoing	O
ships	O
to	O
provide	O
better	O
detection	O
of	O
ships	O
in	O
rough	O
sea	O
and	O
heavy	O
rain	O
condition	O
.	O
</s>
<s>
Vessel	O
traffic	O
services	O
also	O
use	O
marine	O
radars	B-Application
(	O
X	O
or	O
S	B-Algorithm
band	I-Algorithm
)	O
for	O
tracking	O
ARPA	B-Algorithm
and	O
provides	O
collision	O
avoidance	O
or	O
traffic	O
regulation	O
of	O
ships	O
in	O
the	O
surveillance	O
area	O
.	O
</s>
<s>
General	O
purpose	O
radars	B-Application
are	O
increasingly	O
being	O
substituted	O
for	O
pure	O
navigational	O
radars	B-Application
.	O
</s>
<s>
These	O
generally	O
use	O
navigational	O
radar	B-Application
frequencies	O
,	O
but	O
modulate	O
the	O
pulse	O
so	O
the	O
receiver	O
can	O
determine	O
the	O
type	O
of	O
surface	O
of	O
the	O
reflector	O
.	O
</s>
<s>
The	O
best	O
general-purpose	O
radars	B-Application
distinguish	O
the	O
rain	O
of	O
heavy	O
storms	O
,	O
as	O
well	O
as	O
land	O
and	O
vehicles	O
.	O
</s>
<s>
Air	B-Application
traffic	I-Application
control	I-Application
uses	O
primary	O
and	O
secondary	O
radars	B-Application
.	O
</s>
<s>
Primary	O
radars	B-Application
are	O
a	O
"	O
classical	O
"	O
radar	B-Application
which	O
reflects	O
all	O
kind	O
of	O
echoes	O
,	O
including	O
aircraft	O
and	O
clouds	O
.	O
</s>
<s>
Secondary	O
radar	B-Application
emits	O
pulses	O
and	O
listens	O
for	O
special	O
answer	O
of	O
digital	O
data	O
emitted	O
by	O
an	O
Aircraft	O
Transponder	B-Architecture
as	O
an	O
answer	O
.	O
</s>
<s>
Transponders	B-Architecture
emit	O
different	O
kind	O
of	O
data	O
like	O
a	O
4	O
octal	O
ID	O
(	O
mode	O
A	O
)	O
,	O
the	O
onboard	O
calculated	O
altitude	O
(	O
mode	B-Architecture
C	I-Architecture
)	O
or	O
the	O
Callsign	O
(	O
not	O
the	O
flight	O
number	O
)	O
(	O
mode	O
S	O
)	O
.	O
</s>
<s>
Military	O
use	O
transponders	B-Architecture
to	O
establish	O
the	O
nationality	O
and	O
intention	O
of	O
an	O
aircraft	O
,	O
so	O
that	O
air	O
defenses	O
can	O
identify	O
possibly	O
hostile	O
radar	B-Application
returns	O
.	O
</s>
<s>
This	O
military	O
system	O
is	O
called	O
IFF	O
(	O
Identification	B-Device
Friend	I-Device
or	I-Device
Foe	I-Device
)	O
.	O
</s>
<s>
Radar	B-Application
altimeters	O
measure	O
an	O
aircraft	O
's	O
true	O
height	O
above	O
ground	O
.	O
</s>
<s>
Mapping	O
radars	B-Application
are	O
used	O
to	O
scan	O
a	O
large	O
region	O
for	O
remote	B-Application
sensing	I-Application
and	O
geography	O
applications	O
.	O
</s>
<s>
They	O
generally	O
use	O
synthetic	B-Application
aperture	I-Application
radar	I-Application
,	O
which	O
limits	O
them	O
to	O
relatively	O
static	O
targets	O
,	O
normally	O
terrain	O
.	O
</s>
<s>
Specific	O
radar	B-Application
systems	I-Application
can	O
sense	O
a	O
human	O
behind	O
walls	O
.	O
</s>
<s>
However	O
,	O
since	O
humans	O
reflect	O
far	O
less	O
radar	B-Application
energy	O
than	O
metal	O
does	O
,	O
these	O
systems	O
require	O
sophisticated	O
technology	O
to	O
isolate	O
human	O
targets	O
and	O
moreover	O
to	O
process	O
any	O
sort	O
of	O
detailed	O
image	O
.	O
</s>
<s>
Through-the-wall	O
radars	B-Application
can	O
be	O
made	O
with	O
Ultra	O
Wideband	O
impulse	O
radar	B-Application
,	O
micro-Doppler	O
radar	B-Application
,	O
and	O
synthetic	B-Application
aperture	I-Application
radar	I-Application
(	O
SAR	O
)	O
.	O
</s>
<s>
Radar	B-Application
range	O
and	O
wavelength	O
can	O
be	O
adapted	O
for	O
different	O
surveys	O
of	O
bird	O
and	O
migration	O
and	O
daily	O
habits	O
.	O
</s>
<s>
Surveillance	O
radar	B-Application
(	O
mostly	O
X	O
and	O
S	B-Algorithm
band	I-Algorithm
,	O
i.e.	O
</s>
<s>
Tracking	O
radar	B-Application
(	O
mostly	O
X	B-Algorithm
band	I-Algorithm
,	O
i.e.	O
</s>
<s>
Wearable	O
radar	B-Application
and	O
miniature	O
radar	B-Application
systems	I-Application
are	O
used	O
as	O
electric	O
seeing	O
aids	O
for	O
the	O
visually	O
impaired	O
,	O
as	O
well	O
as	O
early	O
warning	O
collision	O
detection	O
and	O
situational	O
awareness	O
.	O
</s>
