結論 - 以金屬波導分歧結構與基板整合波導Riblet短槽結構實現W頻段垂交混成器

本論文使用兩種不同的結構與不同的製程方式實現特高頻的垂交混成器，第一種是用矩形金屬波導製做分歧式的 3dB 耦合器，為使電路能有寬頻的效果，故將電路設計具有五個分支線，並且透過發展已十分成熟的四分之波長轉換器為其雛形，得到在某個頻寬互相對應下，分歧式方向耦合器各段主線與支線該有的阻抗值比。接著，透過數值矩陣分析法，得到此理想的分歧耦合器其頻率響應圖，

並且將矩陣分析法略為修改成適用於金屬波導的型式，快速的得到一個由於波導截止頻率以及 E-平面 T-接面造成頻率響應改變的模擬圖，此數值矩陣分析法與用全波模擬軟體 HFSS 模擬出的 S 參數響應相去不遠，故透過這種方式我們大幅縮減了在 3D 電磁模擬軟體上最佳化的時間，最後實作時對表面進行了三種不同的處理，分別是只有陽極氧化、表面鍍金、與表面鍍銀三種，如預期的表面鍍銀的電路其電路能量損耗最小，實作的結果與微調好 HFSS 的結果其反射增益差了約 2dB，振幅平衡差值約多了 0.3dB，相位差約差 1 到 2 度，誤差可能是來自此電路工作在特高頻頻段，故對其製成尺寸需要相當的精確度。

第二種是使用近期頗為熱門的基板整合波導，由於其是用整排貫孔以及上下層金屬覆蓋基板的形式來模仿矩形金屬波導的結構，故在適當貫孔設計下金屬波導該有的特性它都具有，不過因為基板整合波導電磁波是在介電常數比金屬波導還高的板材中傳遞能量，所以在相同架構的電路其電路尺寸比較小，又因為基板整合波導製成方便且方便與平面式電路，例如微帶線，共平面波導等電路整合在一起，這些原因使得基板整合波導的發展逐漸受到大家的重視。金屬波導用來作耦合器時常使用的有分歧式混成器或 Riblet 短槽式混成器，其中短槽式混成器為一個 H 平面的電路，相當適合應用在基板整合波導中。初始設計時，使用槽線來模擬金屬牆的特性得到了一個初步理想的基板整合波導響應，並且透過波導步階阻抗轉換來改善 S 參數響應，接著在槽線中各個具有形狀代表性的關鍵點打上

穿孔便可快速取得一個初步貫孔後的基板整合波導。由於特高頻的量測需要，我們也設計了一種適合用在特高頻 100m 探針量測所需要的轉換器，並且規劃了用兩埠網儀取得主電路頻率響應的方法，其模擬結果反射與隔離增益在 77~107GHz 都在 20dB 以下，振幅平衡在 0.5dB 左右，相位差在 5 度以內，但實作電路由於在特高頻頻段些許地組裝不當都會造成量測的失真，例如組裝陶瓷與 Duroid 兩個基板時沒有完善的貼齊，使得兩個板材微帶線的阻抗不匹配造成量測的反射增益只在 10dB 以下，且量測相位差時，若埠 2 與埠 3 兩種板材貼齊程度不同也會導致相位差的失真，同時特高頻電路其波長極小，量測其相位差時由於下探針位置些許的不同都會造成相位量測的不準。而導致量測失真的另一個組裝原因是塗抹在 Duroid 基板下多餘的銀膠溢入 Duroid 基板與陶瓷基板之間，導致兩個板材接合處有殘存的銀膠夾在其中而影響了阻抗的匹配，這方面的組裝還有待進一步的改善，由於製做一次 SIW 的 Duroid 基板與扇形轉換器的陶瓷基板以及將兩板材組裝起來相當耗時，加上量測電路大約要 5~6 個禮拜，故第二種的基板整合波導就先以這樣的量測結果進行比較與討論。

第一種的矩形金屬波導相較於第二種基板整合波導的優點是其電路能量損耗較少，且整體性能在整個 W 頻段中較佳，但缺點是製做矩形金屬波導整體花費高。而基板整合波導若沒有量測上的困難，其電路設計與製程會比基板整合波導簡易，同時其可直接與平面式電路整合不需像金屬波導還需另外製作 E-平面的轉換器才能整合到平面式印刷電路中。

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附錄(一)

Immittance of Branch-Line Couplers for n = 3, 4 and 5 Branches When wq=1.20

R K1 K2 H1 H2 H3

Reference [18]

Reference [11]

在文檔中以金屬波導分歧結構與基板整合波導Riblet短槽結構實現W頻段垂交混成器 (頁 85-92)