Short-Range SAR Imaging From GHz to THz Waves

Batra, Aman; Barowski, Jan; Damyanov, D.; Wiemeler, Michael; Rolfes, Ilona; Schultze, Thorsten; Balzer, Jan C.; Göhringer, Diana; Kaiser, Thomas

doi:10.1109/jmw.2021.3063343

Cited by 44 publications

(28 citation statements)

References 30 publications

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“…Scanning the object from above allows layer-by-layer evaluation of the different plastic components. The GPU backprojection [29] processed SAR image of the acquired non-focused IF datasets has an image resolution of ≈1 mm x 1 mm x 2.7 mm (X/Y/Z). The resolution in depth is limited by the system bandwidth and the XY resolution depends on the open waveguide aperture size, i.e.…”

Section: B Hi-res Sar Imaging Setupmentioning

confidence: 99%

Versatile 126–182 GHz UWB D-Band FMCW Radar for Industrial and Scientific Applications

Küppers¹,

Jaeschke²,

Pohl

et al. 2022

IEEE Sens. Lett.

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In this paper a D-band frequency modulated continuous wave (FMCW) radar for industrial and scientific applications is presented. It covers an ultra-wide 56 GHz sweep bandwidth (126 GHz-182 GHz, 36.4%) and is based on a custom 1 TRX + 2 RX SiGe transceiver MMIC manufactured in Infineon's B11HFC 130 nm BiCMOS process with an T of 250 GHz and max of 370 GHz. An innovative versatile multichannel edge-launch waveguide frontend-module architecture allows covering applications requiring dual polarization sensing or azimuth & elevation angle-of-arrival estimation based on the same mm-wave circuit board. The FMCW sweeper is based on measurement equipment grade commercial fractional-N PLL synthesizers in an offset dual-loop configuration for highly linear wideband FMCW sweep generation with a phase noise of better than -80 dBc/Hz ( off > 10 kHz) and superior performance even for ultra-fast ramp slopes of more than 56 GHz / 1 ms. Intermediate frequency (IF) signals of a single target measurement are presented to demonstrate the dynamic range capabilities of the FMCW radar. An SNR of 81 dB is achieved using a metal plate reflector target in free space. Due to the ultra-wide bandwidth and the resulting calibrated range resolution of 2.7 mm (-3 dB width, Tukey window), target separation is even possible in dense multi-target environments. Additionally, synthetic aperture radar (SAR) images are presented as an example application utilizing the high range resolution capabilities.

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Section: B Hi-res Sar Imaging Setupmentioning

confidence: 99%

Versatile 126–182 GHz UWB D-Band FMCW Radar for Industrial and Scientific Applications

Küppers¹,

Jaeschke²,

Pohl

et al. 2022

IEEE Sens. Lett.

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“…The novelty of the proposed object recognition can be expanded by further evaluating the robustness based on rotated object image and SAR image at a different frequency spectrum, which is accomplished with an imaging technique other than the SAR such as inverse-SAR [ 5 , 8 ]. The principle of inverse-SAR to acquire high angular resolution is similar to SAR.…”

Section: Object Classificationmentioning

confidence: 99%

“…The important measurement parameters can be briefly described as

and the aperture length along both the y - and z -axis is

with a step-size of

. The detailed description of the VNA-based measurement setup for the spectrum of 220–

, such as employed antenna dimensions and half power beamwidth, is available in [ 8 ]. In reference to Equations ( 3 ) and ( 4 ), a high-resolution SAR image similar to the spectrum of 325–

can be reconstructed in the selected spectrum of 220–

.…”

Section: Object Classificationmentioning

confidence: 99%

“…The novel extension of SAR to the THz spectrum enables a new era of SAR applications. Due to the available large bandwidth, smaller wavelengths, and compact antennas at the THz spectrum, sub-mm spatial resolution is achievable [ 8 ]. In comparison to the microwave spectrum, the THz spectrum is limited in sensing range due to higher atmospheric attenuation, free space path loss, and lower transmit power [ 9 , 10 ].…”

Section: Introductionmentioning

confidence: 99%

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Object Recognition in High-Resolution Indoor THz SAR Mapped Environment

Batra

Sheikh

Khaliel

et al. 2022

Sensors

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Synthetic aperture radar (SAR) at the terahertz (THz) spectrum has emerging short-range applications. In comparison to the microwave spectrum, the THz spectrum is limited in propagation range but benefits from high spatial resolution. The THz SAR is of significant interest for several applications which necessitate the mapping of indoor environments to support various endeavors such as rescue missions, map-assisted wireless communications, and household robotics. This paper addresses the augmentation of the high-resolution indoor mapped environment for object recognition, which includes detection, localization, and classification. Indoor object recognition is currently dominated by the usage of optical and infrared (IR) systems. However, it is not widely explored by radar technologies due to the limited spatial resolution at the most commonly used microwave frequencies. However, the THz spectrum provides a new paradigm of possible adaptation of object recognition in the radar domain by providing image quality in good compliance to optical/IR systems. In this paper, a multi-object indoor environment is foremost mapped at the THz spectrum ranging from 325 to 500 GHz in order to investigate the imaging in highly scattered environments and accordingly create a foundation for detection, localization, and classification. Furthermore, the extraction and clustering of features of the mapped environment are conducted for object detection and localization. Finally, the classification of detected objects is addressed with a supervised machine learning-based support vector machine (SVM) model.

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“…For example, in [8][9][10], SAR imaging is performed at 0.3 THz, and, in [11,12], the imaging has been implemented at frequencies 0.6 THz and 0.75 THz, respectively. Recent results include imaging at 1.1 THz that have been published in [13].…”

Section: Introductionmentioning

confidence: 99%

Interpolation Methods with Phase Control for Backprojection of Complex-Valued SAR Data

Ivanenko

Batra

et al. 2022

Sensors

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Time-domain backprojection algorithms are widely used in state-of-the-art synthetic aperture radar (SAR) imaging systems that are designed for applications where motion error compensation is required. These algorithms include an interpolation procedure, under which an unknown SAR range-compressed data parameter is estimated based on complex-valued SAR data samples and backprojected into a defined image plane. However, the phase of complex-valued SAR parameters estimated based on existing interpolators does not contain correct information about the range distance between the SAR imaging system and the given point of space in a defined image plane, which affects the quality of reconstructed SAR scenes. Thus, a phase-control procedure is required. This paper introduces extensions of existing linear, cubic, and sinc interpolation algorithms to interpolate complex-valued SAR data, where the phase of the interpolated SAR data value is controlled through the assigned a priori known range time that is needed for a signal to reach the given point of the defined image plane and return back. The efficiency of the extended algorithms is tested at the Nyquist rate on simulated and real data at THz frequencies and compared with existing algorithms. In comparison to the widely used nearest-neighbor interpolation algorithm, the proposed extended algorithms are beneficial from the lower computational complexity perspective, which is directly related to the offering of smaller memory requirements for SAR image reconstruction at THz frequencies.

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Short-Range SAR Imaging From GHz to THz Waves

Cited by 44 publications

References 30 publications

Versatile 126–182 GHz UWB D-Band FMCW Radar for Industrial and Scientific Applications

Versatile 126–182 GHz UWB D-Band FMCW Radar for Industrial and Scientific Applications

Object Recognition in High-Resolution Indoor THz SAR Mapped Environment

Interpolation Methods with Phase Control for Backprojection of Complex-Valued SAR Data

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