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Performance Improvement of the Millimeter-wave Imaging System in Image Acquisition and Reconstruction

Nili, Vahid Amin | 2016

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 48910 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Kavehvash, Zahra; Fakharzadeh, Mohammad
  7. Abstract:
  8. Thesedays, personnel surveillance at security checkpoints, such as airports, is becoming increasingly important. Improvements in various fields of imaging techniques provided an attractive opportunity for automatic personnel servaillance at high security checkpoints. Millimeter-wave imaging systems are capable of penetrating through clothes and thin layers to form an image of a person with very high resolution and without no health hazard at moderate power levels. Therefore millimeter-wave imaging is becoming an important method for surveillance purposes. Typically, there are two common methods for microwave imaging, including synthetic aperture imaging and phased-array imaging. Synthetic aperture imaging is more conventional for surveillance purposes and many systems are designed based on this method but one important problem in these systems is unwanted signals like background clutter, antenna coupling and segmentation of the concealed object from the image. This work reviews some methods like clutter map, histogram, image fusion and polarization for clutter rejction and object separation and verifies most of these methods with experimental results. After that one method based on spectral behavior of objects is presented for clutter rejection and object separation based on their material. It will be shown that this method is capable of detection objects behind strong reflectors like wet leather. One method based on statistical behavior of complex data versus frequency is provided, which is able to distinguish between objects according to depth distance then determine actual range distance and finally reconstruct 2-D images of separated objects each one at its own depth. Also, this method is capable of rejection coupling between antennas. As it is mentioned before, another method for imaging is phased-array structure, but implementation of this method is too expensive. Frequency scanning antenna is similar to this structure although it is cost efficient, which is suitable for imaging purposes. A proper image reconstruction algorithm could proof the ability of this system. In this work a method for 2-D and 3-D image reconstruction in the structure of combined frequency scanning-mechanical scanning system is presented and resolution analysis is discussed for all three direction. Finally the method is verified with simulation in FEKO
  9. Keywords:
  10. Spectral Analysis ; Image Reconstruction ; Principal Component Analysis (PCA) ; Three Dimentional Millimeter Wave Imaging ; Clutter Suppression ; Resolution ; Frequency Scanning Array

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