| 1. |
- Batra, Aman, et al.
(författare)
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Experimental analysis of high resolution indoor THz SAR imaging
- 2020
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Ingår i: WSA 2020 - 24th International ITG Workshop on Smart Antennas. - : VDE Verlag GmbH. - 9783800752003
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Konferensbidrag (refereegranskat)abstract
- Synthetic Aperture Radar (SAR) technology is most commonly used in the frequency span of sub-30 GHz which provides the spatial resolution in the range of sub-cm. This technology is being extended to higher frequencies such as millimeter wave and THz region to achieve higher resolution in the range of sub-mm. This expands the SAR applications for material characterization, classification and sub-mm localization. However, the region is suitable for short propagation distance such as an indoor environment. Therefore, to investigate the achieved resolution and quality of the SAR images at THz, an indoor SAR testbed based on vector network analyzer has been setup for the measurements. This paper explains the indoor SAR geometry and describes the associated testbed along with the system parameters. The measurements are performed at a centre frequency of 275 GHz with a bandwidth of 110 GHz. The measurement results are analyzed for the theoretical resolution with the Backprojection Algorithm and the findings are presented in this paper. The sub-mm spatial resolution imaging of two small size metallic objects are performed. © WSA 2020.
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| 2. |
- Batra, Aman, et al.
(författare)
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Sub-mm Resolution Indoor THz Range and SAR Imaging of Concealed Object
- 2020
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Ingår i: 2020 IEEE MTT-S International Conference on Microwaves for Intelligent Mobility, ICMIM 2020. - : Institute of Electrical and Electronics Engineers Inc.. - 9781728167558
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Konferensbidrag (refereegranskat)abstract
- In radar systems, the frequency range is being extended to high frequencies such as THz for sub-mm resolution. The spectrum offers high resolution but on the contrary, propagation distance and penetration depth are limited because of smaller wavelength. It suffers from higher atmospheric absorption in comparison to sub-GHz systems. In comparison to optical technology, the radar technique majorly benefits with respect to the penetration property such as cloud/smoke cover penetration and detection of concealed objects. However, the THz range and synthetic aperture radar (SAR) imaging of concealed objects are not very well established. Therefore, this paper examines this property at THz. A testbed has been set up with a bandwidth of 110 GHz at a carrier frequency of 275 GHz. The imaging is performed of a very small metal object. Firstly, the sub-mm resolution is validated with the experiment after that the range and SAR imaging are performed in which this object is covered with different types of materials. The backscattered data is processed with the image reconstruction algorithms and the results are presented in this paper with respect to sub-mm resolution and detection. © 2020 IEEE.
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| 3. |
- Ivanenko, Yevhen, et al.
(författare)
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Interpolation Methods with Phase Control for Backprojection of Complex-Valued SAR Data†
- 2022
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Ingår i: Sensors. - : MDPI. - 1424-8220. ; 22:13
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Tidskriftsartikel (refereegranskat)abstract
- 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. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
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| 4. |
- Vu, Viet Thuy, 1977-, et al.
(författare)
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Fourier Transform of SAR Data Cube and 3-D Range Migration Algorithm
- 2022
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Ingår i: IEEE Transactions on Aerospace and Electronic Systems. - : Institute of Electrical and Electronics Engineers Inc.. - 0018-9251 .- 1557-9603. ; 58:3, s. 2584-2591
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Tidskriftsartikel (refereegranskat)abstract
- To develop a 3-D imaging synthetic aperture radar(SAR) algorithm, a theoretical expression for a Fourier transform of data cube is required. In this article, we introduce a function representing the Fourier transform of 3-D SAR data cube. The function is derived using the method of stationary phase and similar to the one used for 2-D data matrix. For verification and evaluation, a 3-D range migration algorithm using this function for bulk compression is examined. The simulation results based on the parameters of an experimental terahertz indoor SAR testbed show that the algorithm can well focus the 3-D image and, hence, verify the derived function. The image quality assessments such as spatial resolutions and peak sidelobe ratio are used to further evaluate the function and the algorithm. The measured results are compared with the ones provided by a backprojection algorithm.
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| 5. |
- Vu, Viet Thuy, 1977-, et al.
(författare)
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Implementing Backprojection at Base Station for Precise Localization in Indoor Environment
- 2023
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Ingår i: Proceedings - 2023 RIVF International Conference on Computing and Communication Technologies, RIVF 2023. - : Institute of Electrical and Electronics Engineers (IEEE). - 9798350315844 ; , s. 212-217
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Konferensbidrag (refereegranskat)abstract
- Mobile equipment with an integrated radar system allows active localization by realizing monostatic, bistatic, multistatic and passive SAR. For mobile user localization, it is also possible by implementing backprojection at base station. In the paper, an approach for precise mobile user localization by implementing backprojection at base station is proposed. The simulation shows the feasibility of the proposal. Some technical issues such as accuracy and backprojection ambiguity, are also addressed. The practicality of the proposal is also demonstrated with a practical frequency-modulated continuous wave (FMCW) radar system and a monostatic radar measurement based on the system. © 2023 IEEE.
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| 6. |
- Vu, Viet Thuy, 1977-, et al.
(författare)
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Multiple Mobile Equipment Localization in Indoor Environment Based on Cell Sectoring
- 2023
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Ingår i: Industrial Networks and Intelligent Systems. - : Springer Science+Business Media B.V.. - 9783031473586 ; , s. 119-131
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Konferensbidrag (refereegranskat)abstract
- Precise mobile equipment localization in indoor environment is possible for mobile equipment with an integrated radar system. Deploying an omni-directional antenna at a base station allows localizing a single mobile unit at a time slot and a frequency resource block. With cell sectoring, an approach to cope with increasing capacity in a cell of a mobile network, helps to localize multiple mobile units at a time slot and a frequency resource block. Most importantly, cell sectoring helps to avoid localization ambiguity caused by the backprojection process. The paper presents the precise multiple mobile equipment localization approach in indoor environment based on cell sectoring. The simulation illustrates the benefit of the approach. The practicality of the approach is also addressed in the paper. © 2023, © ICST Institute for Computer Sciences, Social Informatics and Telecommunications Engineering.
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