近年來，快速發展的無線通訊系統滿足了個人通訊之需求。而價格低廉、尺寸縮小化、多功能化、及製造簡單化，是現今無線通訊元件的發展重點。為達到前述之目的，在此研究論文中我們使用了介電係數約為9.4之高品質因數氧化鋁(Al2O3)陶瓷基板來製造一系列的雙模態濾波器。雙模態共振諧振器和介電諧振器，廣泛應用於衛星無線通訊系統上，所以在本篇論文中，我們設計了一系列具有輕薄、小型化、價格低廉、容易製作等優點的雙模態濾波器。
本研究中所敘述的濾波器其製程非常簡單，其濾波饋入幾何形狀包括方形、圓形，以及迂迴型式，每個結構由兩條50Ω傳輸線當成輸入及輸出端，且成900饋入結構的中心。製造前先利用IE3D軟體於氧化鋁陶瓷基板上加以模擬，而模擬之頻率為位於微波頻段，接著再將所須之濾波器形狀加以蒸鍍於氧化鋁陶瓷基板即可。模擬結果顯示，隨著傳輸線饋入深度的增加，會使得濾波器的特性變好，即穿透損失(S21)會降低，返回損失(S11)會升高，同時結構中的擾亂源亦影響著濾波器的頻寬及諧振頻率。最後我們也在製造後的濾波器量測結果中顯示，實作之濾波器結果與模擬結果相吻合。

Recently, the evolutions of wireless communication systems are growing rapidly to satisfy the personal communication requirements. Compact, small size, low cost, easy fabrication, and multi-function are the major developing trends among these modern wireless communication devices. In this research, high quality Al2O3 ceramic materials are used as a substrate to fabricate modifiable dual-mode bandpass filters with the advantages of light weight, small size, and high performance.
Dual mode cavity and dielectric resonator filters are the mainstay of satellite communications. In this research, a class generation of planar dual mode filters are introduced which significantly offers the advantages of small size, light weight, and low cost. The proposed bandpass filters are first simulated on Al2O3 (er=9.4) substrate for microwave frequency, and the proposed structures consist one square-typed patch, one circle-typed patch, or one meander-typed patch. Each pattern is connected with two 50Ω microstrip line, one for input and another for output. Two 50Ω microstrip lines are connected to the central of the patch with two notches, and the patch will act as the elliptic-function bandpass filters. Before the fabrication of a bandpass filter, IE3D microwave simulation software is used to simulate the designed filters. With a metal mask, the filter patterns are fabricated on the Al2O3 substrate by using evaporation method. It is found that as the length of notches increase, the three of structures band-pass filters reveal better filtering effect, i.e., the smaller insertion loss (S21), and larger return loss (S11), and the perturbation in the patch facilitates coupling between two orthogonal modes within the resonator, i.e., the perturbation size can modify bandwidth and resonator frequency. After the measurement of the fabricated filters, it is found that the measured results will match the simulated results.

Contents
Chapter 1 Introduction……...……………………………………….………1
Chapter 2 Theory and physical description…...…………………………….3
2-1 TM wave in rectangular waveguides..………………...………….3
2-2 Transmission line theory…………………………….…………...5
2-2-1 The lumped element circuit model for a
transmissionline……………………………………………………..…...5
2-2-2 The quarter wave transformer………………......…………..6
2-2-3 Formulas for effective dielectric constant
characteristicimpedance, and attenuation…………………....…...7
2-3 Physical description………………………………………..………9
Chapter 3 Pattern design, simulation, and fabrication……………………..11
Chapter 4 Results and Discussion……………...……………………...…...13
4-1 The influences of notch width d on the return loss and insertion
loss…………………………………….………….………………….13
4-2 The dependence of coupling mode on the size of perturbation
element……………………………………………………….….15
4-3 Miniaturization of dual-mode filter design－simulation and
measurement…………………………………………………….17
4-4 Planar dual-mode filters－simulation and measurement…………18
Chapter 5 Conclusion……………………………………………………....20
References………………………………………………..….……………..22

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