毫米波多層基板合成波導帶通濾波器之研製

Abstract

本篇論文提出了兩種多層基板合成波導帶通濾波器的架構，並實現在低溫共燒陶瓷的多層技術上。選擇末端開路的微帶線來激發開槽的共振腔，可避免直流的功率損耗。 首先設計具有柴比雪夫響應的濾波器，共振腔之間是藉由槽線來耦合，將槽線放在能大量切割表面電流的位置以達成較有效率的耦合。在多層結構中，適當的排列每一個共振腔的位置，共振腔之間多了垂直方向的耦合，使得共振腔的佈局有了更大的彈性，縮減電路面積。 另一種設計為準橢圓函數濾波器，要實現準橢圓函數的響應，一般是需要以電場耦合作為交錯耦合的路徑。在此我們使用另一種以連通柱做為交錯耦合的新結構，使得共振腔之間可以互相推疊排列，達到縮減電路面積目的。 以上兩種濾波器的中心頻率分別為60.5GHz以及30GHz，有效比例頻寬分別為6%和10%，並且都實現在低溫共燒陶瓷的結構上。濾波器的穿透損耗皆小於3.4dB，反射損耗也都優於15dB。

This thesis proposed two types of multilayer substrate integrated waveguide (SIW) bandpass filter’s structures in a multilayer low-temperature co-fired ceramic (LTCC) structure. In the feeding structure, we use a λg/4 microstrip line open stub to excite the resonator through coupling slot etched in the top metal layer of the cavity. First we design waveguide filters with Chebyshev response. The direct coupling paths between vertically stacked cavities are achieved by narrow slots etched in the common metal layer. In order to efficiently couple two adjacent cavities, the position of the slot should largely interrupt surface current of the cavity. Compare with planar waveguide filters, the filters size can be reduced by appropriate arrangement of the vertically stacked cavitys. Another type of the waveguide filters with quasi-elliptical response is realized by cross couple path. In general, electric fields coupling is used for cross couple. Here we use transmission line couple structure for cross couple path. In the waveguide filters with quasi-elliptical response, vertically stacked cavities can be achieved by this kind of cross coupling structure . and the circuit area can be reduced to a single cavity size. The center frequency of the two filters are design at 60.5GHz and 30GHz with fractional bandwidth 6% and 10%. All the filters are fabricated by LTCC technology, and they exhibit an insertion loss better than 3.4dB at the center frequency and a rejection larger than 15dB over the pass band.