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Introduction of Research Activities at Remote Sensing Laboratory

Teaching Staff : Yoshio Yamaguchi, Hiroyoshi Yamada

We like electromagnetic wave because of its physical and mathematical nature. There still exist uncertain portions of the property when applied to actual field, and hence it attracts me. We have been engaged in the research of fully utilizing the properties of electromagnetic wave (especially, polarization and phase) for what can be done and for future possibilitites. The research interests include the following;

SAR image data analysis

Remotely sensed polarimetric image data obtained by Japanese Phased Array L-band Synthetic Aperture Radar (PALSAR), NASA Shuttle Imaging Radar -C/X SAR, Shuttle Radar Topography Mission (SRTM) and AIRSAR, NASDA/CRL's Polarimetric Interferometric SAR (PI-SAR), and our own FM-CW Polarimetric SAR are currently under investigation aimed at,
provided by CRLNiigata University - Ikarashi Campus

Platforms and data:
    Satellite    NASDA/MITIJERS-1
                 ALOS-PALSAR
    Shuttle      Shuttle Imaging Radar (SIR-C/X-SAR)(Aug, 13, 2000)
                 Shuttle Radar Topography Mission
    Airborne     CRL/NASDA Polarimetric Interferometric SAR
                 NASA/JPL AIRSAR

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Radar polarimetry

Radar polarimetry, i.e., the full utilization of vector nature of electromagnetic wave information, is one of the most advanced technologies in modern radar sensing. Polarization is a trace of the extremity of the electric field vector as a function of time at a fixed location in space, when viewed along the direction of propagation. Since the polarimetric scattering nature from a target depends highly on target orientation, aspect angle, frequency, etc., it is possible to obtain target information by analyzing polarimetric scattering characteristics. Fully polarimetric radar has many advantages such as;
This technology may be applicable to communication polarimetry.

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Interferometry

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FM-CW Radar

FM-CW (Frequency Modulated Continuous Wave) radar determines a target range by measuring the beat frequency between a transmitted signal and the received signal from the target. The transmitted radar signal is linearly swept. Since the beat frequency is proportional to a range, the range can be recovered by Fourier Transform. Therefore, FM-CW radar can be regarded as frequency domain version of pulse (time-domain) radar.
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    Snow and wave interaction

    We live in snowy country where snow depth becomes 2-4 meters in mountenious area. It is important to understand wave interaction with snow for communication, sensing, etc.

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    Propagation in tunnel structures

    One of the important problem to be solved in mobile communication has been the propagation loss in tunnel structures such as road tunnel, railway tunnel, underground street, etc. These structures can be regarded as oversized waveguides surrounded by lossy medium. The propagation constant of mode analysis revealed that the attenuation decreases with increasing frequency up to 1-2 GHz regardless of the cross sectional shape of tunnel.

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    Propagation in lossy media

    The significant feature of microwave is the penetration of wave into opaque media such as cloud, snow, soil, etc. This characteristic benefits us to detect objects in such media by radar system. For the efficient detection, we tried to select most suitable frequencies, measuring attenuation in these media. For example, 1-2 GHz for wet snow application, 100-1000 MHz for subsurface detection, etc. These basic data is ulilized to the design of radar antennas (e.g., Ultra-wide-band T-bar fed slot antenna for soil)

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    Scattering with respect to shape, permittivity, conductivity

    Scattered wave from object depends on target parameters (shape, orientation, size, etc) and radio system parameters (frequency, incidence angle, polarization, etc.). The forward problem pursuits scattered wave if these parameters are given. The inverse problem tries to determine the object information provided that scattered wave is given. Inverse problem is related to remote sensing. We try to obtain target information by FDTD and other simulations using polarimetric scattering characteristics both theoretically and experimentally.

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    Diffraction Tomograph

    Diffraction phenomenon appears when the size of an object becomes comparable to the wavelength. Diffraction tomography incorporates the phenomena and pursuits reconstruction of the object based on a spacial distribution function of permittivity and/or conductivity. At present situation, we deal with:
    • Reconstruction simulation
    • Reconstruction experiment using a network analyzer
    • Polarimetric experiment


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