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    Presentation: Analyze Presentation: Analyze Presentation 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 axis (m) x axis (m) AIR AIR PEC PEC
    • 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 axis (m) x axis (m) y axis (m) y axis (m) z axis (m) Normalized amplitude (dB) Outer bumps case Crosspolar component (E_XP) Copolar component (E_XP)
    • x axis (m) y axis (m) z axis (m) FMM division in groups
    • Outer bumps – SAR slices (some of them) Normalized amplitude (dB) Normalized amplitude (dB) Normalized amplitude (dB) x axis (m) x axis (m) x axis (m) x axis (m) x axis (m) y axis (m) y axis (m) y axis (m) y axis (m) y axis (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 axis (m) x axis (m) Reconstructed equivalent currents (normalized amplitude, 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 axis (m) z axis (m) x axis (m) x axis (m) y axis (m) y axis (m) y-axis depth (m)
    • z axis (m) y axis (m) X ray image (YZ plane) 6 cm 3 cm 2 cm 1 cm 2 cm 1 cm 3.5 cm 5 cm Outer bumps – original geometry (YZ plane) Retrieved mesh y axis (m) y-axis depth (m)
    • Inner bumps – original geometry Inner bumps – retrieved mesh x axis (m) x axis (m) y axis (m) y axis (m) z axis (m) y-axis depth (m) z axis (m)
    • z axis (m) y axis (m) Inner bumps – original geometry (YZ plane) Retrieved mesh 6 cm 3 cm 2 cm 1 cm 1.25 cm 0.75 cm 2 cm 4 cm y axis (m) y-axis depth (m)