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Exploring Electromagnetic Horizons: Dielectrics, Radars, and Biomedical Imaging

Hossain, Maruf
http://orcid.org/0000-0002-3331-2217
http://rave.ohiolink.edu/etdc/view?acc_num=osu1713446392044886

Abstract Details

2024, Doctor of Philosophy, Ohio State University, Electrical and Computer Engineering.
The central theme of this dissertation is to explore material interaction with electromagnetic waves in millimeter-wave (mmWave) and terahertz (THz) frequency bands spanning the range from 30 GHz to 3 THz. The implications of these interactions in the context of on-vehicle integration of mmWave automotive radars is discussed. Furthermore, specific mechanisms are exploited for broadband material characterization, and biomedical imaging. First, this research outlines the traditional broadband methods to characterize the electromagnetic properties of isotropic non-magnetic dielectric materials. In mmWave and THz regime, this data is not readily available in many cases. Utilizing established free-space techniques such as terahertz time-domain spectroscopy (THz-TDS) and quasi-optical transmission measurements, this research extracts this data for a diverse range of materials. In particular, we discuss the challenges related to the reliability of the permittivity extraction process in situations where the measurement may not have a high SNR across the bandwidth of interest. We circumvent this problem by cross-validating the data across multiple modalities to ensure consistency. Additionally, for thin dielectric films for which conventional methods fail, this research proposes a novel permittivity extraction technique from calibrated two-port S-parameter measurements of a coplanar waveguide. Interaction of mmWave radar signal with the near zone radome and bumper layers can impair the radar performance through reduction of signal-to-noise ratio and distortion of the pattern. Therefore, towards the goal of a `transparent' radome, the dissertation proposes a novel textured radome design aimed at optimizing transmission efficiency for mmWave automotive radar. Through a strategic optimization based on first-principles, this design exhibits an enhanced signal transmission throughout the entire automotive radar band of 76 – 81 GHz. The optimized design demonstrates an average 3-dB increase in the signal-to-noise ratio within a ±30° field-of-view when compared to the standard radomes, which translates to an increase of the radar range. Moreover, this research also discusses the challenges associated with integrating the radar behind curved dielectric bumpers, and proposes a workflow to determine the optimal installation criteria. A careful modification in the asymptotic simulation resulted in higher accuracy with minimal increase in simulation expenses. The data obtained from the developed process exhibits high-correlation with the data obtained from the full-wave simulations as well as measurements, 4 times faster and using only 3% memory. Additionally, a custom code is developed automating different components of the simulation process which enables engineers to optimize radar placements in vehicle designs rapidly, cutting down the design cycle from months to weeks or possibly just days. In a separate investigation, the dissertation also explores the potential of polarized THz beams in biomedical tissue imaging. Built entirely with commercially available off-the-shelf components, the proposed imaging system enables detection of tissue anisotropy in formalin-fixed paraffin embedded brain tissues at an unprecedented three times finer resolution than the free-space diffraction limit. This opens new avenues for diagnosis of degenerative diseases such as Alzheimer's disease by detecting the distortion of tissue boundaries, showcasing the capabilities of polarized THz beams in high-resolution imaging of tissues.
Niru Nahar (Advisor)
Kubilay Sertel (Committee Member)
Asimina Kiourti (Committee Member)
Alebel Arage (Committee Member)
205 p.
Electrical Engineering; Electromagnetics
mmWave, THz, biomedical imaging, material characterization, automotive radars

Recommended Citations

Citations

  • Hossain, M. (2024). Exploring Electromagnetic Horizons: Dielectrics, Radars, and Biomedical Imaging [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1713446392044886

    APA Style (7th edition)

  • Hossain, Maruf. Exploring Electromagnetic Horizons: Dielectrics, Radars, and Biomedical Imaging. 2024. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1713446392044886.

    MLA Style (8th edition)

  • Hossain, Maruf. "Exploring Electromagnetic Horizons: Dielectrics, Radars, and Biomedical Imaging." Doctoral dissertation, Ohio State University, 2024. http://rave.ohiolink.edu/etdc/view?acc_num=osu1713446392044886

    Chicago Manual of Style (17th edition)

osu1713446392044886
© 2024, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.