本論文提出分枝線共振器的設計方法，利用調整共振器上開路傳輸線的電氣 長度可以設計所需要的傳輸零點，並且若將分枝線共振器置於輸入或輸出端時，
該共振器還可以獨立設計帶通濾波器的外部品質因素。本論文分兩章分別討論輸 入與輸出共振器和耦合路徑上設計傳輸零點的方式。首先驗證可以單獨在輸入與 輸出端產生傳輸零點，再推展到同時在輸入與輸出端設計，最後利用增加傳輸零 點的方式來說明只要在可實現的範圍內，不論是多少個傳輸零點都可以獨立設 計。接下來專注於在耦合路徑上產生傳輸零點，先假設當開路傳輸線的位置在有 與其他共振器耦合的地方，傳輸零點的位置將不容易預測，因此特別將設計傳輸 零點的開路傳輸線放在有耦合的位置來驗證這個假設。此外，用步階式阻抗傳輸 線可以有效縮短開路傳輸線的長度，實驗也發現傳輸零點可以同時設計在輸入與 輸出端和耦合路徑上，得到理想的截止帶響應。由上述之設計，可得到以下的結 論：
(一) 傳輸零點和外部品質因素可以獨立設計：
分枝線共振器(圖 3-3)可以同時用來設計傳輸零點和外部品質因素。先決定傳輸 零點的位置，再調整傳輸線的特性阻抗和與其他共振器耦合的開路傳輸線長度 達到所需的外部品質因素。
(二) 耦合式濾波器所有的共振器皆可用來設計傳輸零點：
分枝線共振器模型可以分別運用在輸入與輸出共振器和耦合路徑上，所以可以 在所有的共振器上設計傳輸零點達到較好的截止帶響應，根據不同電路結構，
可以將分枝線共振器設計在方便設計的共振器上，提高傳輸零點設計的彈性和 自由度。
(三) 設計傳輸零點所使用的開路傳輸線不應位於與其它共振器耦合位置。在 4-2
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的實驗結果發現，設計傳輸零點所使用的開路傳輸線如果位於共振器與其他共 振器耦合的位置上，這個傳輸零點的位置將不容易預測。
(四) 對 耦 合 式 濾 波 器 而 言 ， 直 接 饋 入 (Tapping-line coupling) 較 耦 合 式 饋 入 (Coupling-line coupling)容易控制外部品質因素，這是由於耦合式饋入[22]-[23]
是靠饋入線與共振器之間的間距(耦合量)決定外部品質因素，耦合量越大，頻 寬越大，外部品質因素越小，但間距往往受到製程的限制，進而受限擬設計之 頻寬，而直接饋入耦合則較不會受限於製程，因此外部品質因素之設計彈性較 大。
(五) 電路結構簡單，容易運算：
單純改變共振器設計即可達到多傳輸零點，而且電路模型(圖 3-3 和圖 4-3)和設 計公式(3.2、3.3 和 4.1)都是簡單的傳輸線並聯，運用這個方法可以分別設計外 部品質因素和傳輸零點。
(六) 可以得到較好的截止帶響應：
藉由共振器的設計，傳輸零點可任意設計在所需之截止頻率上，因此截止帶也 會有較好的響應，另一方面，共振器經過設計之後會與其他二分之一波長共振 器不相似，因而倍頻壓制的效果也會更好。
本論文已經驗證了簡單的多傳輸零點帶通濾波器之設計方法，並且可運用到 所有的共振器設計上。依照這設計法則，更多傳輸零點、更好截止帶響應和倍頻 壓制的微波帶通濾波器應可被延伸實現的。
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