應用於毫米波頻段之基板合成波導濾波器及三工器設計

Abstract

本篇論文主要提出毫米波頻段上之濾波器及三工器的設計，並以基板合成波導的結構來實現。第一部分使用低溫共燒陶瓷技術，研製兩個二合一帶通濾波器的整合電路。第二部分則是在電路板上研製一個可實現於毫米波頻段、無匹配電路之三工器設計。 第一部分的設計概念是將兩個濾波器電路共用相同的共振腔，整合為單一個二合一帶通濾波器電路。利用基板合成波導所形成的共振腔中，各模態彼此之間場型的正交性，分別由不同模態控制不同路徑的濾波器響應。因此，共振腔之間在不同模態下的耦合係數可藉由選取適當的槽線位置去獨立控制。同時，藉由選擇適當的饋入位置，可以由不同的埠單獨激發出單一個模態。饋入開槽的選擇需確保模態維持其正交性，使兩模態所分別控制的濾波器響應之間能保有良好的隔離度，以便使該四埠整合電路具有兩路獨立的濾波器響應。二合一帶通濾波器相較於一般的濾波器電路，能利用相同數量的共振腔多設計出一組獨立的濾波器響應，在電路面積的微小化上可以縮小至原始大小的32.6 %。 第二部分則是針對毫米波頻段，提出一個可實現之三工器電路設計架構。其概念是將三個不同頻段之基板合成波導濾波器，分別以分佈式耦合技巧的方式將其分佈在饋入線上不同的位置。藉由在不同頻率下，饋入線上的磁場強度分佈不同，使各頻段之濾波器可以共用同一饋入線。如此，本三工器能省去額外的匹配電路設計，並達到良好的穿透損耗及24 dB以上的隔離度，且在通帶頻率的選擇上具有很高的自由度。

This thesis proposes new design concepts for millimeter-wave filters and triplexers based on SIW (substrate integrated waveguide) structures. The first part designs two variations of a two-in-one bandpass filter, implemented on LTCC (Low Temperature Co-fired Ceramics). The second part designs a triplexer without matching network that is realizable on millimeter-wave frequency, and is implemented on circuit boards. The design concept in the first part is to combine two filters using common resonators into a single two-in-one bandpass filter circuit. This part utilizes the concept of modal orthogonality in the SIW cavities by letting different modes control filter responses in different paths. Therefore, coupling coefficients of each mode between adjacent cavities may be controlled independently through proper locations of the coupling slots. Also, a port may only excite one of the modes with a proper feeding position. In order for the four port integrated circuit to have two independent filter response paths, good isolation between the filter responses must be maintained. Each response is controlled by one of the two orthogonal modes used, therefore, the position of the feeding slot is crucial in keeping the modes orthogonal. The two-in one bandpass filter achieves 32.6 % circuit area miniaturization by providing an additional filter response path using the same amount of cavities of a single bandpass filter. The second part proposes a triplexer design that is realizable in millimeter-wave frequency. The design concept is to use the distributed coupling technique to rearrange the three SIW filters along the feeding line. Each filter may share the common feeding line due to different magnitudes of the magnetic field at different frequencies, therefore the matching network is unnecessary for this design. This triplexer achieves good insertion loss, isolation greater than 24 dB, and has a high freedom in choosing passband frequencies.