Permittivity and Permeability Iron-based Studies of Nanocrystalline Composite Materials by the Cavity Perturbation Method

• Main Authors: Wen-fan Liang, 梁文凡
• Other Authors: Ruey-bin Yang
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/49472337934415582048

碩士 === 逢甲大學 === 航太與系統工程所 === 96 === Resonant cavity perturbation method is a technique to obtain the complex permittivity and permeability of bulk materials or thin films at microwave frequencies. This method uses a microwave resonant circuit to measure the shift of resonant frequency and the change of quality factor in a closed rectangular or circular waveguide. In this study, the accuracy of the resonant cavity perturbation is evaluated by changing the samples sizes and lengths of Teflon and RT/duroid. To verify the formulae used in the calculation of the complex permittivity and permeability, a numerical simulation is also carried out by using Ansoft HFSS to analyze the electromagnetic disturbance in a rectangular waveguide with an open slot for the test samples. Microwave absorbing composites are fabricated by mixing epoxy resin with carbonyl iron, nano-Fe3O4, and conductive carbon black for different weight ratios and then molded in rod shapes. Using the resonant perturbation method, these microwave absorbing composites are measured in X-band and compared with the transmission/reflection method by using a coaxial line. The results show either complex permittivity or permeability of these two methods are rather consistent. The discrepancy becomes large for high permittivity materials. This research provides a simple and reliable method to measure the electromagnetic properties of materials in the microwave frequency range and may benefit the development of new microwave materials and microwave devices.