Loading...

Design, Simulation and Image Reconstruction in Frequency-scan Millimeter-Wave Imaging System

Esmailzade, Mahin | 2017

2051 Viewed
  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 49815 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Kavehvash, Zahra
  7. Abstract:
  8. Frequency-scan millimeter-wave imaging systems are of high interest due to their low cost and acceptable performance in many applications such as concealed-weapon-detection. In recent years, the performance of this system in view of imaging time, image quality and cost has been improved via its implementation based on metamaterial apertures. These structures take advantage from the famous theory of single pixel imaging in optics. Through using the compressive sensing principle, the number of required imaging modes for obtaining diffraction limited resolution is reduced which in turn lessens the imaging time and more importantly the required bandwidth. Still, the image quality and resolution of these systems is diffraction limited which is here analyzed theoretically based on the derived reconstruction relations. Consequently, the metamaterial-based frequency-scan structure is redesigned for obtaining improved resolution. Super-resolution is obtained based on the theory of structureillumination which is widely used in optical microscopy for overcoming the diffraction limit. In this theory, by illuminating the target with appropriate fringe patterns, it frequency contents is shifted in frequency domain and this way its high frequency components will pass through the band-limited low-pass diffraction filter. In the proposed structure, utilizing a Fresnelzone- plate designed based on non-resonant metamaterial elements, the spherical wave from a dipole transmitter is collimated as a plane-wave. Subsequently, the resultant plane wave will pass through the frequency-scan metamaterial aperture producing random patterns on the target plane. By inclining the location of transmitter antenna from the lens axis, the produced plane-wave is tilted accordingly, resulting in tilted random patterns on the targeted scene after passing through the metamaterial aperture. The combination of the images resulted from normal and tilted illuminations will yield an image of improved bandwidth and thus higher resolution. The numerical electromagnetic simulation results confirms the superiority of the proposed structure compared to previous metamaterial-based frequency-scan structures in view of the image quality and resolution
  9. Keywords:
  10. Image Reconstruction ; Frequency Scanning Antenna ; Fresnel Lens ; Three Dimentional Millimeter Wave Imaging ; Image Resolution ; Structured Illumination ; Metamaterial Aperture

 Digital Object List

 Bookmark

...see more