A millimeter-wave diffraction system and its applications

• Main Author: 袁景濱
• Other Authors: 張存續
• Format: Others
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/73415525830226665607

博士 === 國立清華大學 === 物理系 === 100 === A compact diffraction apparatus is developed with millimeter wave propagation between two parallel plates. Micro-fabricated model crystals are individually mounted on a rotatable structure. In contrast to previous work, the experimental results agree well with Bragg's predictions because multiple scattering is minimized in this configuration. Factors that affect the resolution and signal strength, such as the number of scatterers, cylinder radius, and the distance between the detector and model crystal, are analyzed. The effects of (atomic) form factor can be observed in the millimeter-wave Bragg diffraction, which affects the amplitude of scattering wave. Another important factor that affects the amplitude of the scattering wave is from the multiple scattering. Here we used many two-dimensional lattice types of metal-stub structures. Furthermore, a computer-automatically-controlled rotary platform was used to speed up the measurements. The diversification of intensity can not be briefly summarized, but the intensity of scattering wave can be predicted by these two effects. The calculations also matched well with the experimental results. With a better understanding of these two effects, the phenomena of angle offset to Bragg’s law perdition also have further explanations. The apparatus can also be using to measure the photonic band gap. A theoretical method is presented to solve metal-stub photonic-band-gap (PBG) problems based on modal analysis. The automatic millimeter-wave diffraction system has also potential applications in two-dimensional meta-material electromagnetic cloak.