運作在W-band下的寬頻正交極化轉換器

Abstract

正交極化轉換器利用階梯狀的隔板，將兩個垂直的線性極化轉變為左旋及右旋極化。我們將以方型跟圓型兩種型式來設計W頻段的極化轉換器。現今的階梯狀極化轉換器由於隔板位置所造成的共振阻抗，頻寬最多只能到達17%。但我們的NTU-Array利用頻寬切割來避開阻抗，將頻寬加大到36.6% (78-113GHz)。我們以HFSS simulator來降低能量損失到20dB以下，同時也會注意它的相位損失，以達到極化器的最佳效能。我們將做出真實的正交極化轉換器和模擬結果做對比，希望能將之應用在位於夏威夷的NTU-Array計畫之中。

The septum OMT (orthomode transducer) is a three-port waveguide polarizer used to transform the orthogonal linear polarization into purely left and right hand circular polarization. In the design, we use the Ansoft HFSS (High Frequency Structure Simulator) to simulate this model. the W-band OMT will be produced and used in the NTU-Array project. We will discuss two kind of W-band OMT designs with square and circular cross-section. The extreme bandwidth of stepped septum OMT nowadays is about 17% because its resonance resulting from the septum. In our design, we make use the band division to avoid the resonance and increase the bandwidth to 36.6% (78-113GHz). We focus on the magnitude of two input polarization because of possible leakage from I to Q experiment. We do optimization to lower the return loss to -20dB, we also try to make the phase difference as close to as possible to preserve the quality of OMT polarizer.