presentation: analyze
TRANSCRIPT
Analysis of mm-wave radar system capabilities for concealed objects identification
Yuri Álvarez, Borja González, Jose Ángel Martínez Lorenzo, Richard Moore, Carey M. Rappaport, Fernando Las-Heras
Outer bumps – original geometry Inner bumps – original geometry
x axis (m)
z ax
is (m
)
x axis (m)
AIR
AIR PECPEC
The field acquisition domain is a semi-cylindrical domain of R = 0.75 m, from 0º to 180º in f, and from -0.6 to +0.6 m in z, ensuring that most of the backscattered field is collected.
The field scattered by the object-under-test is calculated using a Physical Optics (PO) code. A full wave Method-of-Moments method could have been used, but in order to speed up the forward problem, PO fulfills this requirement providing accurate results.
The incident field on the object-under-test is a z-polarized spherical wave, generated by a reflector antenna capable of providing a narrow beam along z direction. At 60 GHz, the -3 dB beamwidth is about 1.5 cm, thus being possible to consider just one slice of the object having 3 cm thickness in z.
The working frequency band is taken from 60 to 66 GHz, in 600 MHz-steps (11 frequencies).
Problem description
The field observation domain is sampled each 0.63º in f and each 27.3 mm in z, resulting in 12672 observation points.
An equivalent current distribution is reconstructed from the scattered field acquired on the observation domain on several slices along z axis. 19 slices from -135 to +135 mm in z axis, separated 15 mm each are considered. Each slice has a size of 300 x 200 mm, being discretized in 2.25 x 2.25 mm square patches.
Retrieved mesh is obtained from the combination of the SAR images on each slice.
Inverse procedure
Scattered field on the acquisition surface
x axis (m)
z ax
is (m
)
x axis (m) y axis (m)y axis (m)
z ax
is (m
)
Normalized amplitude (dB)
Outer bumps case
Crosspolar component (E_XP) Copolar component (E_XP)
x axis (m)
y axis (m)
z ax
is (m
)
FMM division in groups
Outer bumps – SAR slices (some of them)
Nor
mal
ized
am
plitu
de (d
B)
Nor
mal
ized
am
plitu
de (d
B)
Nor
mal
ized
am
plitu
de (d
B)
x axis (m)
x axis (m)
x axis (m)
x axis (m)
x axis (m)
y ax
is (m
)y
axis
(m)
y ax
is (m
)y
axis
(m)
y ax
is (m
)
Reconstructed equivalent currents
No bump
Smallest bump
Biggest bump
Second smallest bump
Second biggest bump
Outer bumps – SAR slices (some of them) and original geometry
z ax
is (m
)
x axis (m)
Rec
onst
ruct
ed e
quiv
alen
t cur
rent
s (n
orm
aliz
ed a
mpl
itude
, dB
)
y axis (m)
z = -0.135
z = -0.105
z = -0.045
z = +0.015
z = +0.045
z = +0.105
Outer bumps – original geometry Outer bumps – retrieved mesh
z ax
is (m
)
z ax
is (m
)
x axis (m)x axis (m)
y axis (m)y axis (m)
y-axis depth (m)
z axis (m)
y ax
is (m
)
X ray image (YZ plane)
6 cm 3 cm
2 cm 1 cm
2 cm1 cm
3.5 cm5 cm
Outer bumps – original geometry (YZ plane)
Retrieved mesh
y ax
is (m
)
y-ax
is d
epth
(m)
Inner bumps – original geometry Inner bumps – retrieved mesh
x axis (m)x axis (m)
y axis
(m)
y axis
(m)
z ax
is (m
)y-axis depth (m)
z ax
is (m
)
z axis (m)
y ax
is (m
)
Inner bumps – original geometry (YZ plane)
Retrieved mesh
6 cm3 cm
2 cm
1 cm1.25 cm
0.75 cm2 cm4 cm
y ax
is (m
)
y-axis depth (m)