使用基板合成波導之60GHz雙模帶通濾波器研製

Abstract

本篇論文提出以存在雙模的矩形基板合成波導為基本架構，設計60GHz雙零點帶通濾波器，並實現在多層電路板技術上。矩形基板合成波導的結構是以連續的金屬連通柱取代連續金屬壁，因此可以容易得轉接到其他平面電路，然而此種結構之波導只能存在TEmnp (n = 0)模態。 首先設計的是串接兩個分別存在兩個不同模態的共振腔，以產生通帶兩側的零點，並以電場場形類似共振腔內電場場形的微帶線饋入，量測結果顯示濾波器最低之插入損失為1.15dB，反射損失低於12.6dB以及比例頻寬為5.65%。接著使用雙層RO5880基板，並將此兩共振腔堆疊，使面積縮小至一個共振腔的面積，因為堆疊後的共振腔輸入及輸出端分別在不同層，為了便於量測，於是設計了一個上下層轉接器，量測結果顯示濾波器最低之插入損失為3.32dB，反射損失低於17.2dB以及比例頻寬為4.63%。 另一設計為只使用一個製作於雙層RO5880基板上存在雙模的共振腔，使用微帶線經開槽激發的共振腔，為了實現通帶兩邊都有零點，利用輸出及輸入端在上層製造額外的耦合路徑，使得在通帶的另一側產生第二個零點，量測結果顯示帶通濾波器比例頻寬為4.13%，穿透損耗為2.66dB，而反射損失則低於4.45dB。 此三個帶通濾波器皆設計在V頻段，使用單層或雙層RO5880基板，且量測結果與模擬結果相當接近。

This thesis proposes two types of 60 GHz bandpass filters based on dual-mode existing in substrate integrated waveguide realized in multilayer technique. The structure of substrate integrated waveguide has two arrays of via-holes as the side walls of a conventional rectangular waveguide. Hence, using this structure, one can integrate with other active or passive planar circuits easily. However, this kind of waveguide can only exist TEmnp (n=0) mode. First type of bandpass filter is designed by cascading two cavities existing with dual-mode to give a transmission zero at each side of pass-band. The feeding circuit is a microstrip line because of the field in microstrip line is close to that in cavity. The lowest︱S21︳is -1.15 dB, the highest︱S11︳is -12.6 dB and bandwidth is 5.65%. Then two cavities are stacked by two layers of RO5880 to reduce the circuit area. However, because the locations of input and output ports are on the different layers, a transition is designed for easy measurement. The lowest︱S21︳is -3.32 dB, the highest︱S11︳is -17.2 dB and bandwidth is 4.63%. Another type of filter is designed based on single cavity implemented on two layers of RO5880 with a microstrip line to excite the resonator through a coupling slot etched at the top metal layer of the cavity. The second transmission zero is introduced through the coupling path at top layer between the input and output ports. The lowest︱S21︳is -2.66 dB, the highest︱S11︳is -4.45 dB and bandwidth is 4.13%. These three filters are designed in V-band and fabricated on single or two layer RO5880 substrate. Measurement results are shown in a good agreement with the simulation results.