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Design and Analysis of a Reflector System for Millimeter Wave Active Standoff Imaging

Koohi Ghamsari, Mohammad Hossein | 2022

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 55218 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Ahmadi Boroujeni, Mehdi
  7. Abstract:
  8. In this dissertation, to improve the specifications of the available standoff imaging system in the THz and far-infrared Lab. of the electrical engineering department, we designed and analyzed some examples of reflective optical configurations as an optics of active millimeter-wave imaging systems. The superiority of reflective optics versus refractive optics due to the specifications such as loss reduction, broadband frequency response, proper aberration control, beam scanning capability, and easier transmitter and receiver positioning justifies the utilization of reflective configurations for designing millimeter-wave imaging optics. The defined design goals of this dissertation are as follows:Field of View (FoV) Aperture Standoff distance Resolution 40 ~ 5 cm< 1 m 1 ~ 5 m < 3 cm In the first step, we designed and simulated the classical Gregorian structure and examined its performance by ray-tracing and optical simulations. Then, a modified Gregorian-based 4-mirror optics is designed. For this purpose, first, an initial on-axis configuration is considered. Then, by examining the defects of the structure, we tried to optimize the optics in terms of standoff distance spot diameter and scanning performance by using the off-axis technique.In the second step, by summarizing the obtained results, we proposed a new on-axis reflective optics. First, the secondary reflector's general geometry and the synthesis process are explained. Then, the structure's ability for focusing the rays at a standoff distance and scanning the object plane was investigated. Using ray-tracing and full-wave simulations, we showed that the proposed configuration, compared to the previously proposed structures, reduces the wave blockage losses and increases the radiation efficiency of the antenna structure without increasing the cost and complicating the manufacturing process. Therefore, the proposed configuration can be used as reflective optics of millimeter-wave imaging systems
  9. Keywords:
  10. Millimeter-Wave Imaging ; Stand-Off Imaging ; Ray Tracing ; Gregorian Reflective Structure ; Reflective Optics Structure

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