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Characterization of Pedestrian Electromagnetic Scattering at 76-77GHz
Chen, Ming

2013, Doctor of Philosophy, Ohio State University, Electrical and Computer Engineering.
Automobile safety system has received tremendous attention in the past few years. Radar used in such system must be capable of detecting not only other vehicles but also pedestrian. Automobile radar working at 24GHz has been used in blind-spot detection (BSD) and automatic cruise control (ACC) system to track the distance and relative speed of on-road object. However, existing radars are limited to short detection range (30m) and low spatial resolution, making them less useful for pedestrian detection. A new frequency band 76-77GHz, recently designated by the Federal Communication Commission (FCC), the International Telecommunication Union (ITU) in Europe, and the Ministry of Internal Affairs and Communications (MIC) in Japan for vehicular radar. At such high frequencies, a longer detection range (100m-150m) and better resolution can be achieved. As such, it will enable more reliable detection of pedestrians in front of vehicles with lower false alarm rate. In on-road environment, multiple radar reflections may be generated from clutters like trees, trash cans, road surface, curbs and other vehicles. Therefore, it is necessary to identify unique pedestrian radar signatures in the 76-77GHz band to help discriminate them from clutters.

Experimental characterization of radar response of human targets at such high frequencies is not trivial and often inaccurate due to extremely short wavelength which makes radar measurement very sensitive to uncertainties associated with body position, orientation, and breathing motion. The variations produced by these uncertainties severely affect the reliability of the radar features extracted from measurement. In addition, the almost infinite combination of clothes, accessories and body postures significantly increase the time and resource required by this approach.

In this dissertation, analysing pedestrian radar signatures in the 76-77GHz band via numerical simulations is proposed to overcome the issues with measurements. Without the impact of human body motion and posture uncertainties, it should be more reliable and cost effective to study pedestrian scattering signature via numerical model simulations. The trade-off between simulation accuracy and computation efficiency was studied for different mesh sizes. Simplified human model using maximal acceptable mesh size was adopted to substantially reduce the computer memory and simulation time while maintaining desired accuracy.

Utilizing optimized numerical simulation setup, pedestrian radar signatures study were carried out for human with different body features and in different postures. Several significant radar features as well as the corresponding feature extraction methods were proposed and studied. Measured radar response of human subjects using a custom designed 76-78GHz up/down converter module was employed to validate the radar signatures from numerical simulations. Measurement system requirement to obtain reliable data was analysed. Clutter removal processing was introduced to remove the undesired environment impact on the human RCS response. Good agreement between simulations and measurements confirmed the effectiveness and reliability of the radar features extracted from simulation.

Based on radar response study of human subjects, a radar mannequin was designed by the Ohio State University (OSU) and Indiana University-Purdue University Indianapolis (IUPUI) to reproduce radar response of human at all observation angle. The mannequin can then be used to evaluate the effectiveness of a radar based active safety system mounted on vehicle. As part of this effort, a novel multi-layered artificial skin design was proposed and demonstrated to have similar reflectivity to the actual human skin. This artificial skin was adopted to cover the mannequin. Measured RCS patterns of mannequin showed similar radar features to human subjects of similar shapes.
Chi-Chih Chen (Advisor)
John Volakis (Advisor)
Baker Christopher (Committee Member)
Olli Tuovinen (Committee Member)
108 p.

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Chen, M. (2013). Characterization of Pedestrian Electromagnetic Scattering at 76-77GHz. (Electronic Thesis or Dissertation). Retrieved from https://etd.ohiolink.edu/

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Chen, Ming. "Characterization of Pedestrian Electromagnetic Scattering at 76-77GHz." Electronic Thesis or Dissertation. Ohio State University, 2013. OhioLINK Electronic Theses and Dissertations Center. 25 Nov 2017.

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Chen, Ming "Characterization of Pedestrian Electromagnetic Scattering at 76-77GHz." Electronic Thesis or Dissertation. Ohio State University, 2013. https://etd.ohiolink.edu/

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