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Passive Radar Imaging with Multiple Transmitters

Brandewie, Aaron
http://orcid.org/0000-0002-3671-2769
http://rave.ohiolink.edu/etdc/view?acc_num=osu1638201848893416

Abstract Details

2021, Doctor of Philosophy, Ohio State University, Electrical and Computer Engineering.
Passive radar systems use signals of opportunity to illuminate targets instead of dedicated radar transmitters. The signals of opportunity have lower bandwidth than dedicated active radar systems, leading to poor downrange resolution. Multiple signals of opportunity can be coherently combined to increase the overall bandwidth of the system, and therefore create finer resolution images. These signals are usually separated in the frequency domain (non-contiguous), which causes large unwanted grating lobe artifacts in the image when using back-projection or Fourier transform based imaging. Additionally, the signals of opportunity may be completely uncorrelated and transmitting from different locations. This dissertation investigates methods of combining these signals to create images with higher resolution than if only a single signal of opportunity were used. A method to quickly estimate bistatic scattered electric fields from complex targets is augmented with new models. The targets are first decomposed into a set of canonical geometries with closed-form solutions. Then the total scattered field of the target is found as the superposition of the scattered fields from the individual geometries. The canonical geometries used are plates, dihedrals, and trihedrals. A closed-form solution for the non-90° dihedral is introduced and verified with iterative physical optics. Bistatic SAR images of complex targets can be predicted in seconds using the total scattered fields from the canonical geometries, whereas it would take hours using a physical optics solver. Approaches of combining signals for 1D passive radar imaging are then examined. The signals may be non-contiguous in frequency, and originate from transmitters not located at the same position. A calibration method is developed to align the downrange responses, and coherently combine the two signals. A compressive sensing-based algorithm is used to combine the non-contiguous frequency data, and is shown to mitigate the grating lobe artifacts that occur when using a back-projection algorithm. This approach is verified using simulated data, and experimental data of commercial aircraft collected with the ElectroScience Lab (ESL) digital television passive (DTV) passive radar system. It is shown that the compressive sensing-based algorithm can provide finer resolution images, without the presence of grating lobes when the frequency is non-contiguous. The imaging approach developed for 1D downrange profiles is then extended for 2D Inverse Synthetic Aperture Radar (ISAR) imaging. A measurement duration is multiple seconds for ISAR imaging, due to the need of collecting scattered signals from multiple aspect angles for increased cross-range resolution. A motion compensation algorithm is developed to estimate the uncooperative target’s kinematics, and to keep the imaging plane focused on the target as it moves. This algorithm is demonstrated using both simulated, and experimental data of commercial aircraft collected with the ESL DTV passive radar system. Additionally, it is demonstrated that the compressive sensing-based algorithm is able to improve the resolution of the image and resolve point scatterers that cannot be observed in a back-projection image.
Robert Burkholder (Advisor)
Brian Joseph (Committee Member)
Fernando Teixeira (Committee Member)
Joel Johnson (Committee Member)
143 p.
Electrical Engineering
passive radar; radar imaging; bistatic radar; multistatic radar; compressive sensing; range-Doppler imaging

Recommended Citations

Citations

  • Brandewie, A. (2021). Passive Radar Imaging with Multiple Transmitters [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1638201848893416

    APA Style (7th edition)

  • Brandewie, Aaron. Passive Radar Imaging with Multiple Transmitters. 2021. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1638201848893416.

    MLA Style (8th edition)

  • Brandewie, Aaron. "Passive Radar Imaging with Multiple Transmitters." Doctoral dissertation, Ohio State University, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu1638201848893416

    Chicago Manual of Style (17th edition)

osu1638201848893416
125
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This open access ETD is published by The Ohio State University and OhioLINK.