Ms. Ingrid Ullmann Profile

Ingrid Ullmann

at Friedrich-Alexander-Univ Erlangen-Nürnberg

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Publications (2)

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Proceedings Article | 12 September 2021 Presentation + Paper

Close range ISAR imaging with target velocity determination for security screening applications

Konstantin Root, Ingrid Ullmann, Stefan Gmehling, Martin Vossiek

Proceedings Volume 11868, 118680M (2021) https://doi.org/10.1117/12.2602072

KEYWORDS: Radar, Antennas, Velocity measurements, Synthetic aperture radar, Image resolution, Scanners, Radar imaging, Imaging arrays

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State-of-the-art personnel screening systems reconstruct images by using multiple-input-multiple-output (MIMO) radars, which require a large number of transmit and receive channels along a two-dimensional array. We propose a novel concept for security screening which does not require the person to stand still and only employs a one- dimensional array: Our approach is built on the use of inverse synthetic aperture radar (ISAR) imaging based on a vertical line array. This means that the moving person inversely samples a synthetic aperture along the horizontal dimension. In order to reconstruct an image by the ISAR principle, the test subject's velocity relative to the radar aperture needs to be known. Therefore, we employ an additional radar module which measures the person's velocity, assuming that the person is moving parallel to the aperture plane. Experiments with a mannequin carrying threat objects were performed. The mannequin was moved on a traversing rail with 1 m/s and its velocity was estimated by a commercial radar module emitting a chirp sequence signal. The estimation was in very good accordance with the rail's real moving speed. With the determined target velocity an image was reconstructed along the horizontal direction by the ISAR principle. Along the vertical direction, the focusing was performed using a MIMO line array of 45 transmitter and 24 receiver channels with a total height of 60 cm. That way, and by employing broadband signals (70 GHz - 80 GHz), three-dimensional high-resolution images were obtainable. Promising results were obtained from the measurements and different threat objects were made visible.

Proceedings Article | 20 September 2020 Paper

Circular polarization millimeter wave SAR imaging using 3D-printed helix antennas

Ingrid Ullmann, Konstantin Root, Konstantin Lomakin, Gerald Gold, Michael Gottinger, Klaus Helmreich, Martin Vossiek

Proceedings Volume 11541, 1154108 (2020) https://doi.org/10.1117/12.2573952

KEYWORDS: Antennas, Synthetic aperture radar, Polarization, Radar imaging, Additive manufacturing, Millimeter wave imaging, Dielectric polarization, Imaging systems, Polarimetry, Image sensors

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We propose the use of 3D-printed helix antennas for millimeter-wave radar imaging. This concept is promising for a number of reasons: Additive manufacturing involving 3D-printing is a relatively cost efficient fabrication technique and offers increased geometrical freedom of design compared to conventional manufacturing processes. From an imaging point of view, using helix antennas is advantageous because of the circular polarization the antennas emit. That way, imaging thin dipole-like structures is possible regardless of their orientation. In contrast, imaging systems using linearly polarized antennas are unable to image dipoles orientated orthogonally to their polarization direction. Radar systems using circular polarization additionally enable polarimetric imaging and decomposition. In security screening this can achieve a higher classification accuracy in discriminating threat objects and reduce false alarms. Furthermore, the thin helix antennas (typical coil diameter: ca. 1.5 mm) can be mounted very closely to each other, which is interesting for array design. A security screening example was investigated for demonstration: A cardboard box with metallic and dielectric threat objects was screened at 70 GHz – 90 GHz by a quasi-monostatic synthetic aperture radar consisting of two 3D-printed helix antennas, one right-hand and one left-hand circularly polarized. As a reference, the same object was screened with split-block linearly polarized horn antennas. With the proposed setup, the resolution of the reconstruction images was comparable to that of the reference system. However, the circular polarization was able to depict thin structures in a better fashion than the linearly polarized reference system.

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