Characterization of the permeability tensors for ferrites in a bias magnetic field

碩士 === 國立清華大學 === 物理系 === 103 === Ferrite materials biased under DC magnetic field have been intensely studied for the past decades due to their wide applications in microwave region, such as isolator, circulator, and high-density magnetic recording media. The magnetic property (tensor-form permeabi...

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Bibliographic Details
Main Authors: Chang, Wei Chen, 張韋臻
Other Authors: Chang, Tsun Hsu
Format: Others
Language:zh-TW
Published: 2015
Online Access:http://ndltd.ncl.edu.tw/handle/98608772937845836334
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Summary:碩士 === 國立清華大學 === 物理系 === 103 === Ferrite materials biased under DC magnetic field have been intensely studied for the past decades due to their wide applications in microwave region, such as isolator, circulator, and high-density magnetic recording media. The magnetic property (tensor-form permeability) of the biased ferrites must be clearly characterized for designing and further applications. In this study, we insert the bulk under-test ferrite into a rectangular waveguide. The whole system is biased by a uniform DC magnetic field parallel to short edge of the rectangular waveguide. The permeability of the loaded ferrite will strongly modulate the eigenmodes’ dispersions, making their field distributions deviate from their counterparts under the case without a bias field. The changes of eigenmodes’ field distributions under the bias field further imply that the strong modal effect would occur as the guided wave transmits through the air-ferrite interfaces. How those eigenmodes jointly satisfy boundary conditions intricately relates to their scattering parameters (necessary for retrieving ferrite characteristics), and so understanding the modal coupling process is of vital importance. In this work, we exactly analyze the behaviors of TEm0 modes, including the dispersions and field distributions in a rectangular waveguide loaded with ferrite material and biased by a DC magnetic field. Based on these eigenmodes’ properties, the transmission and reflection for the EM wave (TE 10 mode) passing through the ferrite loaded in the rectangular waveguide can be also analyzed. These solutions could be further employed to retrieve the permeability tensor of the under-test ferrite material as long as the overall transmission and reflection measured by the experiment are provided.