
RCS
Calibration
f.
Turn
Gating
ON
by
pressing
4
PRIOR
MENU
5
NNNNNNNNNNNNNNNNNNNNNNN
GATE
ON
.
g.
P
osition
the
gate
around
the
target
response
.
If
your
target
is
a
sphere
,
the
placement
of
the
gate
is
critical.
Spheres
produce
a
secondary
reection
caused
by
RF
energy
propagating
around
the
back
of
the
sphere
,
which
ultimately
arrives
back
at
the
receive
antenna.
This
produces
the
secondary
reection,
known
as
a
\creeping
wave
."
If
the
creeping
clearly
separate
from
the
main
target
response
,
place
the
gate
around
just
the
main
response
.
In
this
case
make
sure
you
select
the
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
OPTICAL
SPHERE
model
when
you
dene
the
RCS
target
(the
next
step).
If
the
main
target
response
and
the
creeping
wave
are
not
clearly
distinct
and
separate
,
position
the
gate
around
both
of
them.
In
this
case
make
sure
you
select
the
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
TARGET:
SPHERE
model
when
you
dene
the
RCS
target
(the
next
step).
Do
not
attempt
to
gate
out
very
large
background
reections
,
or
subsequent
measurements
will
not
be
accurate
.
Dene
the
RCS
T
arget
The
next
step
is
to
select
they
type
of
RCS
target
you
use
during
calibration,
and
enter
its
physical
dimensions
.
3.
Press
4
CAL
5
N
NNNNNNNNNNNNN
MORE
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
DEFINE
RCS
TARGT
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
TARGET
SELECTION
.
4.
Select
the
type
of
calibration
target
by
pressing
one
of
the
following:
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
TARGET:
SPHERE
NNNNNNNNNNNNNNNNN
PLATE
NNNNNNNNNNNNNNNNNNNNNNNNNNNNN
TRIHEDRAL
NNNNNNNNNNNNNNNNNNNNNNNNNN
CYLINDER
NNNNNNNNNNNNNNNNNNNNNNNNNN
DIHEDRAL
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
OPTICAL
SPHERE
If
Y
ou
are
Using
a
Sphere:
If
you
are
NOT
using
gating
during
the
calibration,
always
select
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
TARGET:
SPHERE
.
The
Dierence
between
Sphere
and
Optical
Sphere
The
top
selection,
N
NNNNNNNNNNNNNNNNNNN
SPHERE
,
computes
the
exact
solution
for
the
radar
cross
section
of
a
perfectly
conducting
sphere
.
The
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
OPTICAL
SPHERE
selection
computes
the
radar
cross
section
of
the
sphere
based
on
geometric
optics
-
in
which
the
RF
signal
is
treated
as
\optical
rays"
according
to
physical
principles
of
reection
and
refraction.
The
optical
sphere
selection
is
best
used
when
the
wavelength
of
the
RF
energy
is
large
enough
that
it
approximates
the
behavior
of
light.
This
is
called
the
\optical
region"
of
the
sphere
.
The
RF
energy
is
in
the
sphere's
\optical
region"
when
the
following
relationship
between
wavelength
and
sphere
radius
is
true:
(2
r
4
)
>
10
Where
is
wavelength
and
r
is
the
radius
of
the
sphere
.
NOTE:
Radar
Cross
Section
data
for
all
target
types
except
NNNNNNNNNNNNNNNNNNNN
SPHERE
are
based
on
geometric
optics
.
5.
Press
4
PRIOR
MENU
5 .
6.
Enter
the
required
(metric)
dimensions
of
the
target
using
the
appropriate
dimension
softkeys
for
each
type
of
target:
Menus
Block
5-21
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