| 研究課題/領域番号 |
18K03708
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| 研究機関 | 国立天文台 |
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研究代表者 |
SHAN Wenlei 国立天文台, 先端技術センター, 准教授 (60792570)
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| 研究分担者 |
江崎 翔平 国立天文台, 先端技術センター, 技術員 (40794508)
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| 研究期間 (年度) |
2018-04-01 – 2021-03-31
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| キーワード | Multibeam SIS Receiver / Integrated Circuit / Membrane |
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| 研究実績の概要 |
The objective of this study is to explore a new approach with superconducting planar circuit to make essential breakthroughs in the techniques of constructing large-format and compact superconducting multibeam heterodyne receiver frontends. In 2018FY we completely settled the concept of the new approach, which is identified with following two distinctive features. (1) Silicon membranes with thickness of several micrometers are utilized to support waveguide probes that couple the signal and reference (usually called local oscillator, or LO); (2) The new coupling method utilizing membranes allows a two dimensional LO distribution, which is not possible in a conventional design. The combination of the two features enables a superconducting heterodyne receiver with large number of pixels. Based on this new concept, an experimental study was carried out at 2 millimeter wavelength. A single-pixel planar type superconducting receiver with dual-polarization and balanced circuit configuration was designed, fabricated and assessed. The measurement results show expected performance, which is comparable to the state-of-the-art performance that a conventional SIS mixer can reach. The positive results justify the new approach and suggest a bright prospect of the following study. This experiment is one of the four steps that we set in the research plan.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
1: 当初の計画以上に進展している
理由
The progress of 2018FY is smooth. The prototype planar superconducting SIS mixer circuit operating at 2 mm with dual polarization and balanced configuration has not been challenged with a monolithic planar circuit before because of its complexity. Our work is a pioneer work in this new approach. Our results not only proofed the feasibility of the concept by showing correct response of the receiver, they also demonstrated high quality of the performance. The receiver noise temperature is as low as about 40 K and show little frequency dependence. The noise rejection ratio (a figure-of-merit of balance circuit) is as high as 15 dB, and the cross polarization is lower than 20 dB. All of these performances are comparable to the best performance that a conventional SIS mixer can reach. This means that little penalty in performance has to paid to achieve the highly compact integration in the new approach.
The most important progress that allowed us to achieve good results lies in the building up of reliable fabrication process. To achieve high quality devices various new techniques were applied in the fabrication. Two of them deserve to be emphasized. Plasma-enhanced chemical vapor deposition (PECVD) is adopted rather than the more conventional magnetron sputtering for better side-wall coverage with insulator films. A machine-aligned via-hole etching process provides improved uniformity in the junction definition and therefore leads to good balance of the circuit.
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| 今後の研究の推進方策 |
In line with the defined research plan, in 2019FY following studies will be performed. (1) Demonstration of 4-beam dual-polarization balanced mixer and evaluation of the LO distribution approach. (2)Investigation of fabrication process of thin-film resistor, which is necessary to enable sideband separation (2SB) SIS mixer configuration. (3) With thin-film resistor process, design and fabricate single-pixel 2SB mixer circuit.
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