<s>
The	O
Spectrally	O
Agile	O
Frequency-Incrementing	O
Reconfigurable	O
(	O
SAFIRE	O
)	O
radar	O
is	O
a	O
vehicle-mounted	O
,	O
forward-looking	O
ground-penetrating	B-Algorithm
radar	I-Algorithm
(	O
FLGPR	O
)	O
system	O
designed	O
to	O
detect	O
buried	O
or	O
hidden	O
explosive	O
hazards	O
.	O
</s>
<s>
It	O
was	O
developed	O
by	O
the	O
U.S.	O
Army	O
Research	O
Laboratory	O
(	O
ARL	O
)	O
in	O
2016	O
as	O
part	O
of	O
a	O
long	O
generation	O
of	O
ultra-wideband	O
(	O
UWB	O
)	O
and	O
synthetic	B-Application
aperture	I-Application
radar	I-Application
(	O
SAR	O
)	O
systems	O
created	O
to	O
combat	O
buried	O
landmines	O
and	O
IEDs	O
.	O
</s>
<s>
Past	O
iterations	O
include	O
the	O
railSAR	B-Algorithm
,	O
the	O
boomSAR	B-Algorithm
,	O
and	O
the	O
SIRE	B-Algorithm
radar	I-Algorithm
.	O
</s>
<s>
The	O
SAFIRE	B-Algorithm
radar	I-Algorithm
was	O
initially	O
conceived	O
as	O
a	O
response	O
to	O
the	O
increasing	O
congestion	O
of	O
the	O
radio	O
frequency	O
(	O
RF	O
)	O
spectrum	O
due	O
to	O
the	O
recent	O
growth	O
of	O
wireless	O
technology	O
.	O
</s>
<s>
As	O
part	O
of	O
an	O
effort	O
to	O
improve	O
upon	O
the	O
existing	O
SIRE	B-Algorithm
radar	I-Algorithm
system	O
,	O
the	O
U.S.	O
Army	O
Research	O
Laboratory	O
designed	O
the	O
SAFIRE	B-Algorithm
radar	I-Algorithm
as	O
a	O
UWB	O
radar	O
that	O
could	O
match	O
or	O
exceed	O
the	O
performance	O
of	O
the	O
SIRE	B-Algorithm
radar	I-Algorithm
while	O
operating	O
in	O
congested	O
RF	O
environments	O
.	O
</s>
<s>
The	O
SAFIRE	B-Algorithm
radar	I-Algorithm
was	O
also	O
designed	O
to	O
be	O
highly	O
reconfigurable	O
due	O
to	O
its	O
nature	O
as	O
an	O
experimental	O
radar	O
.	O
</s>
<s>
The	O
SAFIRE	B-Algorithm
radar	I-Algorithm
differs	O
from	O
past	O
UWB	O
SAR	O
systems	O
developed	O
by	O
ARL	O
like	O
the	O
boomSAR	B-Algorithm
and	O
the	O
SIRE	B-Algorithm
radar	I-Algorithm
in	O
that	O
it	O
utilizes	O
a	O
stepped-frequency	O
system	O
rather	O
than	O
a	O
short-pulse	O
one	O
.	O
</s>
<s>
One	O
of	O
the	O
main	O
challenges	O
caused	O
by	O
the	O
nature	O
of	O
the	O
SIRE	B-Algorithm
radar	I-Algorithm
as	O
an	O
impulse	O
UWB	O
system	O
was	O
its	O
high	O
susceptibility	O
to	O
in-band	O
radio	O
frequency	O
interference	O
(	O
RFI	O
)	O
.	O
</s>
<s>
Furthermore	O
,	O
while	O
impulse	O
UWB	O
radars	O
like	O
the	O
SIRE	B-Algorithm
radar	I-Algorithm
must	O
avoid	O
transmitting	O
signals	O
in	O
certain	O
reserved	O
frequency	O
bands	O
,	O
stepped-frequency	O
radars	O
possess	O
the	O
flexibility	O
to	O
transmit	O
signals	O
that	O
conform	O
to	O
any	O
spectral	O
shape	O
,	O
so	O
long	O
as	O
the	O
return	O
signals	O
are	O
processed	O
to	O
minimize	O
the	O
noise	O
.	O
</s>
<s>
The	O
resulting	O
radar	O
imagery	O
of	O
this	O
approach	O
may	O
feature	O
bands	O
of	O
frequencies	O
over	O
the	O
operating	O
bandwidth	B-Algorithm
with	O
no	O
data	O
as	O
a	O
consequence	O
.	O
</s>
<s>
Due	O
to	O
these	O
configurations	O
,	O
the	O
SAFIRE	B-Algorithm
radar	I-Algorithm
is	O
capable	O
of	O
performing	O
ultra-wideband	O
operations	O
with	O
comparable	O
range	O
resolution	O
and	O
penetration	O
abilities	O
while	O
avoiding	O
spectral	O
areas	O
congested	O
with	O
high	O
RF	O
content	O
.	O
</s>
<s>
Once	O
development	O
was	O
completed	O
,	O
the	O
SAFIRE	B-Algorithm
radar	I-Algorithm
was	O
later	O
subjected	O
to	O
a	O
series	O
of	O
field	O
trials	O
at	O
an	O
arid	O
Army	O
test	O
site	O
in	O
2016	O
and	O
2017	O
,	O
where	O
it	O
was	O
tasked	O
with	O
detecting	O
several	O
anti-tank	O
landmines	O
hidden	O
throughout	O
the	O
site	O
and	O
buried	O
at	O
different	O
depths	O
.	O
</s>
<s>
According	O
to	O
the	O
results	O
of	O
these	O
experiments	O
,	O
the	O
SAFIRE	B-Algorithm
radar	I-Algorithm
was	O
shown	O
to	O
be	O
capable	O
of	O
detecting	O
and	O
imaging	O
broadside-oriented	O
landmines	O
that	O
were	O
buried	O
as	O
deep	O
as	O
8	O
inches	O
in	O
the	O
soil	O
.	O
</s>
<s>
The	O
SAFIRE	B-Algorithm
radar	I-Algorithm
operates	O
at	O
a	O
bandwidth	B-Algorithm
ranging	O
from	O
300MHz	O
to	O
2GHz	O
with	O
a	O
minimum	O
frequency	O
step	O
size	O
of	O
1MHz	O
.	O
</s>
<s>
While	O
an	O
increase	O
in	O
bandwidth	B-Algorithm
may	O
improve	O
the	O
resolution	O
and	O
the	O
signal-to-clutter	O
ratio	O
,	O
SAFIRE	O
's	O
radar	O
resolution	O
was	O
specifically	O
chosen	O
to	O
be	O
comparable	O
to	O
the	O
dimensions	O
of	O
a	O
typical	O
anti-personnel	O
(	O
AP	O
)	O
landmine	O
.	O
</s>
<s>
When	O
the	O
SAFIRE	B-Algorithm
radar	I-Algorithm
is	O
not	O
in	O
listen-only	O
mode	O
,	O
the	O
signal	O
is	O
sent	O
to	O
the	O
Tx-LR	O
switch	O
,	O
which	O
is	O
used	O
to	O
cycle	O
between	O
the	O
left	O
and	O
right	O
transmitters	O
.	O
</s>
<s>
This	O
first	O
mixing	O
stage	O
serves	O
to	O
collapse	O
the	O
1700-MHz	O
operating	O
bandwidth	B-Algorithm
into	O
a	O
narrowband	O
IF	O
,	O
which	O
is	O
then	O
amplified	O
and	O
filtered	O
.	O
</s>
<s>
The	O
SAFIRE	B-Algorithm
radar	I-Algorithm
also	O
features	O
two	O
electro-optical	O
(	O
EO	O
)	O
Point	O
Grey	O
Flea	O
2G	O
HD	O
cameras	O
and	O
two	O
long-wave	O
infrared	O
(	O
LWIR	O
)	O
Xenics	O
Gobi	O
640	O
cameras	O
.	O
</s>
<s>
The	O
data	O
generated	O
from	O
these	O
four	O
cameras	O
can	O
be	O
superimposed	O
with	O
the	O
collected	O
radar	O
data	O
to	O
produce	O
a	O
stereoscopic	O
augmented	B-General_Concept
reality	I-General_Concept
display	O
for	O
the	O
user	O
that	O
allows	O
them	O
to	O
view	O
all	O
the	O
sensor	O
data	O
simultaneously	O
.	O
</s>
<s>
A	O
GPS	O
receiver	O
and	O
an	O
inertial	O
measurement	O
unit	O
(	O
IMU	O
)	O
are	O
both	O
incorporated	O
into	O
the	O
SAFIRE	B-Algorithm
radar	I-Algorithm
to	O
collect	O
and	O
determine	O
the	O
position	O
and	O
movements	O
of	O
the	O
platform	O
as	O
it	O
travels	O
on	O
top	O
of	O
its	O
designated	O
vehicle	O
.	O
</s>
