Development of wideband circular polarizer in millimeter submillimeter wave band

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K03629
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 16010:Astronomy-related
• Research Institution: Osaka Metropolitan University (2022-2023); Osaka Prefecture University (2021)
• Principal Investigator: OGAWA Hideo 大阪公立大学, 大学院理学研究科, 客員教授 (20022717)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 円偏波 / 広帯域 / 電波天文学 / 導波管

Outline of Final Research Achievements

We have developed a wideband circular polarizer in the millimeter/submillimeter wave band. To realize a wideband circular polarizer, it was important to develop a wideband differential phase shifter that delays the phase difference between two orthogonal linearly polarized waves to 90 degrees. However, it is difficult for conventional circuits that use only a single type of phase shifter to obtain a constant 90 degrees phase difference because the frequency dependence of the phase difference is large. We designed and fabricated a differential phase shifter in 210-365 GHz band with a flat phase-difference characteristic by combining three different types of differential phase shifters to cancel out the frequency dependence of the phase difference. Measurement results has shown a tendency to match the design characteristics. We expect that this circular polarizer will contribute to future black hole observations.

Free Research Field

電波天文

Academic Significance and Societal Importance of the Research Achievements

本研究では、210-365 GHz帯における広帯域円偏波分離器の開発を行った。円偏波分離器を構成する位相遅延器と直交偏波分離器それぞれを広帯域に設計・測定し、それぞれを組み合わせた円偏波分離器として測定した。結果として、おおよそ設計と一致するような良好な結果が得られており、ブラックホール観測を含む次世代のミリ波サブミリ波帯の超長基線電波干渉法への応用が期待できる。