本研究致力於微波材料特性，主要研究分為兩項。一種是等向性材料（銀納米顆粒/環氧樹脂複合材料）且具有可控的電磁特性，另一種是量測磁各向異性材料（鐵氧體）的方法架構。

可控性電磁性質奈米銀/環氧樹脂複合材料
材料的電磁特性通常與電磁波頻率相關。一般在狹窄頻率範圍內，可以簡單地達到控制複合材料的介電常數和磁導率。這項研究使用穿透/反射法量測奈米銀顆粒/環氧樹脂複合材料的電磁特性。隨著奈米銀體積濃度的增加，奈米銀顆粒可視為電偶極子並增加了介電常數。另一方面，在快速變化的磁場下，導電銀顆粒上激發感應電流從而導致負極化率，而在長波長的限制下，巨觀磁化率是負的。此複合材料，電磁特性可以藉由調整奈米銀顆粒來調控，並且在8 GHz到110 GHz非常寬的頻率範圍內變化很小。

量測鐵氧體的微波特性
我們提出一個只需運用一套全負載波導系統來量測鐵氧體的高頻電磁特性，並且建立一個四步驟高精密度的標準作業程序。首先，在沒有外加任何磁場的情況下，使用穿透反射法(Nicolson-Ross-Weir method)量測初步的介電常數與介電損耗。其次，操作在鐵磁共振頻率下，從鐵磁共振的強吸收行為中量測初步的鐵氧體飽和磁化量。根據這兩個初步的值可以幫助我們確保實驗的操作條件。在操作條件下，我們可以運用單一值磁場強度去近似外加在鐵氧體上的磁場以描述波在鐵氧體中的行為。最後，藉由模式分析，我們運用散射頻譜上的特徵頻率同時量測出鐵氧體的四個電磁特性 (包括複介電常數、飽和磁化量和磁性線寬)。此研究測試了四個具有不同電磁特性的樣品，量測結果、高頻結構模擬與廠商提供的規格有不錯的一致性。

The research is devoted to the material characterization in microwave. There are two major studies. One is attribute to the isotropic material (silver nanoparticle/epoxy composite) with controllable electromagnetic properties over a wide bandwidth. The other is magnetic anisotropic material (ferrite) for characterization method.

Manipulating the Permittivities and Permeabilities of Epoxy/Silver Nanocomposites Over a Wide Bandwidth
The electromagnetic properties of materials are generally frequency-dependent. Controlling the permittivities and the permeabilities of composites are commonly achieved in a narrow frequency range. This work characterizes the electromagnetic properties of the epoxy/silver nanocomposites using transmission/reflection method. The silver nanoparticles serving as electric dipoles enhance the permittivity as the volume fraction increases. On the other hand, the rapidly changing magnetic field induces current on the conducting silver particles resulting in a negative polarizability. The macroscopic magnetic susceptivities are negative under the long-wavelength limit. The electromagnetic properties are controllable and just slightly change over a very broad frequency range from 8 GHz to 110 GHz.


Characterization of Ferrite Using Fully-loaded Rectangular Waveguide System in Microwave
We developed a single and compact fully-loaded waveguide system to characterize the electromagnetic properties of ferrites. A standard characterization procedure with four steps and high precision is proposed. Firstly, a preliminary complex permittivity was extracted using the Nicolson-Ross-Weir (N.R.W.) method without any magnetic field. Secondly, a rough saturation magnetization was measured from the behavior of ferromagnetic resonance near the ferromagnetic frequency. These two preliminary data can help determine the operating condition, a suitable bias that guarantees the single-value magnetic field approximation. Finally, we can retrieve the full electromagnetic properties simultaneously, including the complex permittivity, the saturation magnetization and the linewidth with the correction of the intrinsic magnetization under the consideration of the modal effect (excited high-order modes owing to impedance matching at the interface of two different material). Four samples with distinctive electromagnetic characteristics were tested, and the results show great agreement with the HFSS simulations and the specifications offered by the vendors.

Acknowledgements ii
摘要 iii
Abstract v
Content vii
List of Figures ix
List of Tables xii
Chapter 1 Introduction 1
1.1 Introduction to Epoxy/Silver nanocomposites 1
1.2 Introduction to Characterization Method of Ferrite 3
Chapter 2 Experimental Setup 5
2.1 Sample Preparation for Epoxy/Silver nanocomposites 5
2.2 Sample Preparation for Ferrite 6
2.3 Experimental Setup 7
Chapter 3 Characterization Method 9
3.1 Nicolson-Ross-Weir (N.R.W.) Method 9
3.2 Characterization Method of Ferrite 12
Modal Analysis 13
Dispersion of Ferrite inside Rectangular Waveguide 14
Chapter 4 Experimental Results and Discussion 18
4.1 Results of Epoxy/Silver nanocomposites 18
4.2 Results of Ferrite Characterization 24
Air-gap Mode 24
Silver Conductive Paste Coating 25
Determination of Saturation Magnetization 28
Determination of Operating Condition 31
Experimental Results 32
4.3 Discussion 36
Error Discussion 36
Error in Mismatch versus Nonuniformity of Magnetic Bias 38
Complex Permittivity (Comparison with Traditional Method) 39
Saturation Magnetization (Comparison with Traditional Method : VSM) 40
Linewidth (Comparison with Traditional Method) 41
Influence on Operating in Region V 43
Restrictions to Ferrite Characterization Method 45
Uniformity of Ha and H0 48
Three-step Fitting Procedure 49
Right-hand and Left-hand Circularly-polarized Wave in Fully-loaded Rectangular Waveguide 53
4.4 Future work 58
Chapter 5 Conclusions 59
References 60

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