本論文之主要目地是將研製平面多重耦合雙頻帶濾波器所得到之心得加以歸納，整理出設計此類雙頻帶濾波器時，所須遵循的電路設計準則。並且將各式多重耦合結構依其諧振條件與饋入方式的不同加以整理，並針對實現在真實電路上的不同極限，經詳盡的運算後列表整理，以提供往後設計及製作相關電路時的參考資料。

本論文是由平面耦合濾波器的基本耦合結構開始，採用漸進的方式，先討論其相關電場性、磁場性與電磁場混合性耦合的部分，接著再探討多重耦合的特殊型式，延伸利用在雙頻帶濾波器的設計中。利用諧振器間的多重耦合機制，使其能同時滿足雙頻諧振之特性又能同時達到兩個頻帶所需之耦合量的情形下，做詳細的探討。最後再利用所需滿足的諧振器負載品質因素之條件，得到 阻抗匹配的饋入方法，使其訊號連接方式更為簡便，能有效的符合電路體積縮小化之要求，最後實作出此類雙頻帶濾波器。

在無線通訊系統前端，常需要三種被動元件，其一為收發切換器，另一個為帶通濾波器，最後是能將非平衡式訊號與平衡式訊號作轉換的Balun。本論文的最後，是探討如何使耦合帶通濾波器的構成組件，同時能夠包含有Balun的基本特性，那麼設計出的雙頻帶濾波器便能同時具有Balun的功能。此結果對於現今通訊電路逐漸走向輕薄短小化的趨勢下具有相當大的意義。

In recent years, dual-band wireless LAN and portable telephones become quite popular due to the need of wireless mobile communications. Dual-band filters become key components in the front end of these communication systems and have been studied in several literatures.

In this thesis, we used multiple coupling mechanism to design a planar dual-band filter which has better performance and the feed-in structures are more compact. Lately, stepped-impedance transmission-line sections are used in dual-band filter design, because they have the dual-band property and their harmonic frequencies are tunable. It is found that dual-band filter realized by synchronously tuned coupled stepped-impedance resonator circuits have all the needed of proposed dual-band resonators and coupling coefficient between resonators. However multiple coupling structures are also required to establish matching networks at the input and output stage. Therefore, feed-in point is also found by the external quality factors of the input and output resonators, for both passbands.

The design procedure of dual-band filters has been verified by several design examples. Also the results have been summarized as design guide rules which could be followed for similar work in the future. In the last part of this thesis, multiple coupling structures is also applied to the design of balun filter, which is the combination of bandpass filter and balun at the front end of wireless communication system. Thus, the whole system block could be smaller and cheaper.

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