<s>
Bistatic	B-Algorithm
radar	I-Algorithm
is	O
a	O
radar	B-Application
system	I-Application
comprising	O
a	O
transmitter	O
and	O
receiver	O
that	O
are	O
separated	O
by	O
a	O
distance	O
comparable	O
to	O
the	O
expected	O
target	O
distance	O
.	O
</s>
<s>
Conversely	O
,	O
a	O
conventional	O
radar	B-Application
in	O
which	O
the	O
transmitter	O
and	O
receiver	O
are	O
co-located	O
is	O
called	O
a	O
monostatic	B-Algorithm
radar	I-Algorithm
.	O
</s>
<s>
A	O
system	O
containing	O
multiple	O
spatially	O
diverse	O
monostatic	O
or	O
bistatic	B-Algorithm
radar	I-Algorithm
components	O
with	O
a	O
shared	O
area	O
of	O
coverage	O
is	O
called	O
multistatic	B-Algorithm
radar	I-Algorithm
.	O
</s>
<s>
Many	O
long-range	O
air-to-air	O
and	O
surface-to-air	O
missile	O
systems	O
use	O
semi-active	O
radar	B-Application
homing	O
,	O
which	O
is	O
a	O
form	O
of	O
bistatic	B-Algorithm
radar	I-Algorithm
.	O
</s>
<s>
Some	O
radar	B-Application
systems	I-Application
may	O
have	O
separate	O
transmit	O
and	O
receive	O
antennas	O
,	O
but	O
if	O
the	O
angle	O
subtended	O
between	O
transmitter	O
,	O
target	O
and	O
receiver	O
(	O
the	O
bistatic	B-Algorithm
angle	I-Algorithm
)	O
is	O
close	O
to	O
zero	O
,	O
then	O
they	O
would	O
still	O
be	O
regarded	O
as	O
monostatic	O
or	O
pseudo-monostatic	O
.	O
</s>
<s>
For	O
example	O
,	O
some	O
very	O
long	O
range	O
HF	O
radar	B-Application
systems	I-Application
may	O
have	O
a	O
transmitter	O
and	O
receiver	O
which	O
are	O
separated	O
by	O
a	O
few	O
tens	O
of	O
kilometres	O
for	O
electrical	O
isolation	O
,	O
but	O
as	O
the	O
expected	O
target	O
range	O
is	O
of	O
the	O
order	O
1000	O
–	O
3500km	O
,	O
they	O
are	O
not	O
considered	O
to	O
be	O
truly	O
bistatic	O
and	O
are	O
referred	O
to	O
as	O
pseudo-monostatic	O
.	O
</s>
<s>
In	O
some	O
configurations	O
,	O
bistatic	B-Algorithm
radars	I-Algorithm
may	O
be	O
designed	O
to	O
operate	O
in	O
a	O
fence-like	O
configuration	O
,	O
detecting	O
targets	O
which	O
pass	O
between	O
the	O
transmitter	O
and	O
receiver	O
,	O
with	O
the	O
bistatic	B-Algorithm
angle	I-Algorithm
near	O
180	O
degrees	O
.	O
</s>
<s>
This	O
is	O
a	O
special	O
case	O
of	O
bistatic	B-Algorithm
radar	I-Algorithm
,	O
known	O
as	O
a	O
forward	O
scatter	O
radar	B-Application
,	O
after	O
the	O
mechanism	O
by	O
which	O
the	O
transmitted	O
energy	O
is	O
scattered	O
by	O
the	O
target	O
.	O
</s>
<s>
In	O
forward	O
scatter	O
,	O
the	O
scattering	O
can	O
be	O
modeled	O
using	O
Babinet	O
's	O
principle	O
and	O
is	O
a	O
potential	O
countermeasure	O
to	O
stealth	O
aircraft	O
as	O
the	O
radar	B-Application
cross	O
section	O
(	O
RCS	O
)	O
is	O
determined	O
solely	O
by	O
the	O
silhouette	O
of	O
the	O
aircraft	O
seen	O
by	O
the	O
transmitter	O
,	O
and	O
is	O
unaffected	O
by	O
stealth	O
coatings	O
or	O
shapings	O
.	O
</s>
<s>
The	O
RCS	O
in	O
this	O
mode	O
is	O
calculated	O
as	O
σ	O
=	O
4πA²/λ²	O
,	O
where	O
A	O
is	O
the	O
silhouette	O
area	O
and	O
λ	O
is	O
the	O
radar	B-Application
wavelength	O
.	O
</s>
<s>
However	O
,	O
target	O
may	O
vary	O
from	O
place	O
to	O
place	O
location	O
and	O
tracking	O
is	O
very	O
challenging	O
in	O
forward	O
scatter	O
radars	B-Application
,	O
as	O
the	O
information	O
content	O
in	O
measurements	O
of	O
range	O
,	O
bearing	O
and	O
Doppler	O
becomes	O
very	O
low	O
(	O
all	O
these	O
parameters	O
tend	O
to	O
zero	O
,	O
regardless	O
of	O
the	O
location	O
of	O
the	O
target	O
in	O
the	O
fence	O
)	O
.	O
</s>
<s>
A	O
multistatic	B-Algorithm
radar	I-Algorithm
system	O
is	O
one	O
in	O
which	O
there	O
are	O
at	O
least	O
three	O
components	O
-	O
for	O
example	O
,	O
one	O
receiver	O
and	O
two	O
transmitters	O
,	O
or	O
two	O
receivers	O
and	O
one	O
transmitter	O
,	O
or	O
multiple	O
receivers	O
and	O
multiple	O
transmitters	O
.	O
</s>
<s>
It	O
is	O
a	O
generalisation	O
of	O
the	O
bistatic	B-Algorithm
radar	I-Algorithm
system	O
,	O
with	O
one	O
or	O
more	O
receivers	O
processing	O
returns	O
from	O
one	O
or	O
more	O
geographically	O
separated	O
transmitter	O
.	O
</s>
<s>
A	O
bistatic	O
or	O
multistatic	B-Algorithm
radar	I-Algorithm
that	O
exploits	O
non-radar	O
transmitters	O
of	O
opportunity	O
is	O
termed	O
a	O
passive	O
coherent	O
location	O
system	O
or	O
passive	O
covert	O
radar	B-Application
.	O
</s>
<s>
Any	O
radar	B-Application
which	O
does	O
not	O
send	O
active	O
electro-magnetic	O
pulse	O
is	O
known	O
as	O
passive	O
radar	B-Application
.	O
</s>
<s>
Passive	O
coherent	O
location	O
also	O
known	O
as	O
PCL	O
is	O
a	O
special	O
type	O
of	O
passive	O
radar	B-Application
,	O
which	O
exploits	O
the	O
transmitters	O
of	O
opportunity	O
especially	O
the	O
commercial	O
signals	O
in	O
the	O
environment	O
.	O
</s>
<s>
The	O
principal	O
advantages	O
of	O
bistatic	O
and	O
multistatic	B-Algorithm
radar	I-Algorithm
include	O
:	O
</s>
<s>
Possible	O
enhanced	O
radar	B-Application
cross	O
section	O
of	O
the	O
target	O
due	O
to	O
geometrical	O
effects	O
.	O
</s>
<s>
The	O
principal	O
disadvantages	O
of	O
bistatic	O
and	O
multistatic	B-Algorithm
radar	I-Algorithm
include	O
:	O
</s>
<s>
The	O
bistatic	B-Algorithm
angle	I-Algorithm
is	O
the	O
angle	O
subtended	O
between	O
the	O
transmitter	O
,	O
target	O
and	O
receiver	O
in	O
a	O
bistatic	B-Algorithm
radar	I-Algorithm
.	O
</s>
<s>
When	O
it	O
is	O
exactly	O
zero	O
the	O
radar	B-Application
is	O
a	O
monostatic	B-Algorithm
radar	I-Algorithm
,	O
when	O
it	O
is	O
close	O
to	O
zero	O
the	O
radar	B-Application
is	O
pseudo-monostatic	O
,	O
and	O
when	O
it	O
is	O
close	O
to	O
180	O
degrees	O
the	O
radar	B-Application
is	O
a	O
forward	O
scatter	O
radar	B-Application
.	O
</s>
<s>
Elsewhere	O
,	O
the	O
radar	B-Application
is	O
simply	O
described	O
as	O
a	O
bistatic	B-Algorithm
radar	I-Algorithm
.	O
</s>
<s>
The	O
bistatic	B-Algorithm
angle	I-Algorithm
is	O
an	O
important	O
factor	O
in	O
determining	O
the	O
radar	B-Application
cross	O
section	O
of	O
the	O
target	O
.	O
</s>
<s>
Bistatic	O
range	O
refers	O
to	O
the	O
basic	O
measurement	O
of	O
range	O
made	O
by	O
a	O
radar	B-Application
or	O
sonar	B-Application
system	O
with	O
separated	O
transmitter	O
and	O
receiver	O
.	O
</s>
<s>
If	O
the	O
target	O
is	O
at	O
range	O
Rrx	O
from	O
the	O
receiver	O
and	O
range	O
Rtx	O
from	O
the	O
transmitter	O
,	O
and	O
the	O
receiver	O
and	O
transmitter	O
are	O
a	O
distance	O
L	O
apart	O
,	O
then	O
the	O
bistatic	O
range	O
is	O
Rrx+	O
Rtx-L	O
.	O
Motion	O
of	O
the	O
target	O
causes	O
a	O
rate	O
of	O
change	O
of	O
bistatic	O
range	O
,	O
which	O
results	O
in	O
bistatic	B-Algorithm
Doppler	I-Algorithm
shift	I-Algorithm
.	O
</s>
<s>
Bistatic	B-Algorithm
Doppler	I-Algorithm
shift	I-Algorithm
is	O
a	O
specific	O
example	O
of	O
the	O
Doppler	O
effect	O
that	O
is	O
observed	O
by	O
a	O
radar	B-Application
or	O
sonar	B-Application
system	O
with	O
a	O
separated	O
transmitter	O
and	O
receiver	O
.	O
</s>
<s>
In	O
a	O
bistatic	B-Algorithm
radar	I-Algorithm
with	O
wavelength	O
λ	O
,	O
where	O
the	O
distance	O
between	O
transmitter	O
and	O
target	O
is	O
Rtx	O
and	O
distance	O
between	O
receiver	O
and	O
target	O
is	O
Rrx	O
,	O
the	O
received	O
bistatic	O
Doppler	O
frequency	O
shift	O
is	O
calculated	O
as	O
:	O
</s>
<s>
Bistatic	O
imaging	O
is	O
a	O
radar	B-Algorithm
imaging	I-Algorithm
technique	O
using	O
bistatic	B-Algorithm
radar	I-Algorithm
(	O
two	O
radar	B-Application
instruments	O
,	O
with	O
one	O
emitting	O
and	O
one	O
receiving	O
)	O
.	O
</s>
<s>
The	O
result	O
is	O
a	O
more	O
detailed	O
image	O
than	O
would	O
have	O
been	O
rendered	O
with	O
just	O
one	O
radar	B-Application
instrument	O
.	O
</s>
<s>
Bistatic	O
imaging	O
can	O
be	O
useful	O
in	O
differentiating	O
between	O
ice	O
and	O
rock	O
on	O
the	O
surface	O
of	O
a	O
remote	O
target	O
,	O
such	O
as	O
the	O
moon	O
,	O
due	O
to	O
the	O
different	O
ways	O
that	O
radar	B-Application
reflects	O
off	O
these	O
objectswith	O
ice	O
,	O
the	O
radar	B-Application
instruments	O
would	O
detect	O
"	O
volume	O
scattering	O
"	O
,	O
and	O
with	O
rock	O
,	O
the	O
more	O
traditional	O
surface	O
scattering	O
would	O
be	O
detected	O
.	O
</s>
