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Introduction |
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A common issue in the electromagnetic inverse scattering community is the lack of open access measurement data from experimental laboratory set-ups or prototype systems. Data available from the Ipswich (e.g. McGahan and Kleinman, [1, 2]) and Fresnel (e.g. Geffrin and Sabouroux, [3, 4]) databases have addressed this insufficiency. These data were collected with a bi-static, mechanically scanned system with antennas located in the far-field. However, there are many applications, such as biomedical imaging or non-destructive testing, for which scattering data are better collected with a mechanically static near-field system. Advantages of near-field imaging include higher resolution, but additional complications such as antenna coupling and a complicated incident field do occur. We are aware of only one repository of near-field multi-static data (Mallorqui et. al. [5]), but this dataset is available pre-calibrated, with closely coupled antennas removed, and only for a single frequency.
With the goal of stimulating research with respect to near-field multi-static imaging calibration and inversion, we present a database of microwave scattering measurements. All of the measurement data are presented uncalibrated. The measurements were taken with the imaging system outlined in a previous publication (Gilmore et. al, [6]). Tar- gets were elongated in the z-direction, and the linearly polarized antennas were oriented in the same direction. Thus we intend for the 2D Transverse Magnetic (scalar) approximation to apply. Several dielectric and metallic targets were interrogated in free-space under two different schemes labled tomographic and radar. The tomographic data are multi-static (i.e. Sa;b) in the frequency range of 3 to 6 GHz in 0.5 GHz steps, and the radar data are reflection data only (i.e. Sx;x) for 1601 linearly spaced frequencies from 3 to 10 GHz.