W頻段基板整合波導帶通濾波器與基板整合波導頻率雙工器研製

Abstract

本論文在 W-頻段以基板整合波導完成帶通濾波器及雙工器的製作。基板整合波導帶通濾波器的設計是決定中心頻及頻寬後，將柴氏低通原型濾波器係數轉換至耦合係數，利用腔與腔間的耦合量設計完成。 論文中，基板整合波導雙工器分成四種種架構，前三種是T-形結耦合頻率雙工器，第四種是混成結耦合頻率雙工器。其中，第一、二種是以較長之 T-形結輸出臂結合基板整合波導帶通濾波器完成雙工器，其中T-形結分別用基板整合波導與傳統微帶線兩種形式來實現。第三 種是將微帶線 T-形結之長度儘量縮小完成的雙工器，其中基板整合波導帶通濾波器配合修改，取消了緩變線部分，以完成尺寸縮小的雙工器，以上三種雙工器的通帶分別是中心頻 81 GHz 頻寬 3%及 中心頻 96 GHz 頻寬 3%。第四種是垂交混成器所構成之雙工器，利用兩個基板整合波導垂交混成器器之垂交特性與兩個相同之基板整合波導帶通濾波器形成類似平衡式放大器之混成結濾波器結構，再將二個結構相同但頻率不同之混成結濾波器串接形成雙工器，此雙工器其通帶分別是中心頻 84 GHz 頻寬 5%及中心頻 93 GHz 頻寬 5%。 帶通濾波器及雙工器皆使用基板厚度 5mil，損耗較低的介電常數 2.2 的 Rogers RT-Duroud 5880TM 板材，並使用扇形轉換器進行特高頻探針的量測，扇形轉換器使用基板厚 度 5mil 介電常數 9.8 的陶瓷基板，完善的組裝兩種板材可得正確的量測結果。

In this thesis, we use W-band substrate integrated waveguide (SIW) to design and implement the bandpass filters and the diplexers. The design of SIW bandpass filter is firstly converting the Chebyshev low-pass prototype filter parameters to the coupling coefficients with respect to the passband centrer frequency and fractional bandwidth, and then obtaining the appropriate physical dimensions of the SIW structure corresponding to the specific coupling coefficient between resonators. The proposed diplexers involve two types, namely, the T-junction-coupled diplexer and the hybrid-coupled diplexer. The first three are the T-junction-coupled diplexers. The first and the second T-junction-coupled diplexers have long T-junction arms to match with two SIW bandpass filters where the T-junctions are much larger than a quarter wavelength. The T-junctions are realized by SIW and microstrip respectively. The third T-junction-coupled diplexer has very short microstrip T-Junction with modified SIW bandpass filter without the microstrip to SIW taper-line transition. The bandwidths and center frequencies of these three diplexers are 3%, 3% and 81GHz, 96GHz respectively. The fourth structure is the hybrid-coupled diplexer. This type of diplexer uses two SIW quardrature hybrids and two identical SIW filters to form a filter channel that is just like the conventional balanced amplifier. Cascading two of the filter channels forms the diplexer. The diplexer of this type is designed with the bandwidths of 5% and 5%, and a center frequency of 84 GHz and 93 GHz respectively. Both SIW bandpass filter and diplexer use the Rogers RT-Duroud 5880TM substrate with a thickness of 5mil, a dielectric constant of 2.2, and a dielectric loss tangent of 0.0021. A fan-shaped transition is used for probe measurement. The fan-shaped transition circuit is on the Al2O3 ceramic substrate with a thickness of 5mil, and a dielectric constant of 9.8. Precise assembly of transition and SIW circuit is essential for measurement accuracy and repeatability.