Dr. Takafumi Kojima Profile

Dr. Takafumi Kojima

at National Astronomical Observatory of Japan

SPIE Involvement:

Author

Publications (19)

Proceedings Article | 16 August 2024 Presentation + Paper

Presentation + Paper

ALMA Band 8 version2 receiver upgrade project

Takafumi Kojima, Tetsuhiro Minamidani, Ryo Sakai, Hiroaki Imada, Keiko Kaneko, Sho Masui, Kazunori Uemizu, Kazumasa Makise, Akihira Miyachi, Shohei Ezaki, Tomonori Tamura, Shun Ishii, Bunyo Hatsukade

Proceedings Volume 13102, 131020K (2024) https://doi.org/10.1117/12.3021139

KEYWORDS: Receivers, Design, Mirrors, Reflection, Waveguides, Double sideband modulation, Diagnostics, Radio frequency circuits, Polarization, Transformers

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Proceedings Article | 16 August 2024 Presentation + Paper

Presentation + Paper

Development of an SIS mixer-based amplifier for large-scale multipixel heterodyne receivers

Yoshinori Uzawa, Akira Kawakami, Takafumi Kojima, Kazumasa Makise, Sho Masui, Yosuke Murayama, Akihira Miyachi, Wenlei Shan

Proceedings Volume 13102, 131020L (2024) https://doi.org/10.1117/12.3020000

KEYWORDS: Oscillators, Superconductors, Heterodyning, Quantum noise, Amplifiers

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Proceedings Article | 16 August 2024 Presentation + Paper

Presentation + Paper

ALMA2030 Band-4+5 receiver front-end wideband sensitivity upgrade: first year initial development and future plan

Yuh-Jing Hwang, Bangwon Lee, MingJye Wang, Yu Chieh Huang, Chau-Ching Chiong, Yue-Fang Kuo, Chen Chien, Chin-Ting Ho, Tse-Jun Chen, Wei-Chun Lu, Yen-Pin Chang, Hsiao-Wen Chang, Chuang-Ping Chiu, Jia-Ruei Nian, Chao-Ching Wang, Fang-Yu Hsu, Pai-An Chen, Lou-Chien Lu, Patrick Koch, Takafumi Kojima, Alvaro Gonzalez

Proceedings Volume 13102, 131020M (2024) https://doi.org/10.1117/12.3017708

KEYWORDS: Receivers, Design, Waveguides, Cryogenics, Mirrors, Antennas, Quantum receivers, Field effect transistors, Transducers, Oscillators

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Proceedings Article | 16 August 2024 Presentation + Paper

Presentation + Paper

Development status of wideband millimeter-wave receivers for LMT-FINER

Haoran Kang, Takafumi Kojima, Takeshi Sakai, Yoichi Tamura, Airi Tetsuka, Sho Masui, Tatsuya Takekoshi

Proceedings Volume 13102, 131020J (2024) https://doi.org/10.1117/12.3018190

KEYWORDS: Waveguides, Radio astronomy, Terahertz technology

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Proceedings Article | 16 August 2024 Poster + Paper

Poster + Paper

Development of a wideband receiver for dual-band and dual-polarization observations in 230 and 345 GHz bands

Sho Masui, Sana Kawashita, Yasumasa Yamasaki, Yutaka Hasegawa, Takafumi Kojima, Takeru Matsumoto, Ikko Fujitomo, Yuma Nishikawa, Ryo Nakagawa, Hideo Ogawa, Toshikazu Onishi

Proceedings Volume 13102, 131022L (2024) https://doi.org/10.1117/12.3018561

KEYWORDS: Waveguides, Multiplexers, Phase shifts, Circular polarizers, Receivers, Polarization, Reflection, Prototyping, Telescopes, Phase measurement

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Proceedings Article | 16 August 2024 Presentation + Paper

Presentation + Paper

FINER: Far-Infrared Nebular Emission Receiver for the large millimeter telescope

Yoichi Tamura, Takeshi Sakai, Ryohei Kawabe, Takafumi Kojima, Akio Taniguchi, Tatsuya Takekoshi, Haoran Kang, Wenlei Shan, Masato Hagimoto, Norika Okauchi, Airi Tetsuka, Akio Inoue, Kotaro Kohno, Kunihiko Tanaka, Tom J. L. Bakx, Yoshinobu Fudamoto, Kazuyuki Fujita, Yuichi Harikane, Takuya Hashimoto, Bunyo Hatsukade, David Hughes, Takahiro Iino, Yuki Kimura, Hiroyuki Maezawa, Yuichi Matsuda, Ken Mawatari, Taku Nakajima, Shunichi Nakatsubo, Tai Oshima, Hideo Sagawa, F. Peter Schloerb, Shigeru Takahashi, Kotomi Taniguchi, Akiyoshi Tsujita, Hideki Umehata, Teppei Yonetsu, Min Yun

Proceedings Volume 13102, 131020G (2024) https://doi.org/10.1117/12.3017788

KEYWORDS: Galactic astronomy, Receivers, Telescopes, Spectrometers, Calibration, Mirrors, Spectroscopy, Spectral resolution

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SPIE Journal Paper | 23 June 2022

Digital calibration test results for Atacama Large Millimeter/submillimeter Array band 7+8 sideband separating receiver

Franco Curotto, Ricardo Finger, Takafumi Kojima, Kazunori Uemizu, Álvaro González, Yoshinori Uzawa, Leonardo Bronfman

JATIS, Vol. 8, Issue 02, 024004, (June 2022) https://doi.org/10.1117/12.10.1117/1.JATIS.8.2.024004

KEYWORDS: Calibration, Receivers, Field programmable gate arrays, Astronomy, Analog electronics, Signal processing, Phase measurement, Double sideband modulation, Dynamical systems, Waveguides

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Proceedings Article | 13 December 2020 Poster + Paper

Poster + Paper

Development of receiver optics for ALMA bands 1 and 2, and possible synergies with ngVLA

Álvaro González, Keiko Kaneko, Ryo Sakai, Takafumi Kojima, Yoshinori Uzawa

Proceedings Volume 11453, 114533S (2020) https://doi.org/10.1117/12.2561595

KEYWORDS: Receivers, Waveguides, Plastic lenses, Additive manufacturing, 3D printing, Astronomy, Observatories, Product engineering, Astronomical imaging, Optical fabrication equipment

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Proceedings Article | 13 December 2020 Poster + Paper

Poster + Paper

Development of a wideband waveguide diplexer for simultaneous observation at 210-375 GHz

Sho Masui, Taisei Minami, Masanari Okawa, Yasumasa Yamasaki, Koki Yokoyama, Shota Ueda, Yutaka Hasegawa, Atsushi Nishimura, Toshikazu Onishi, Hideo Ogawa, Takafumi Kojima, Alvaro Gonzalez

Proceedings Volume 11453, 114534F (2020) https://doi.org/10.1117/12.2561355

KEYWORDS: Waveguides, Telescopes, Receivers, Observatories, Clouds, Astronomy, Oscillators, Waveguide modes

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Proceedings Article | 13 December 2020 Poster + Paper

Poster + Paper

Optical design of the 1.85-m mm-submm telescope in 210–375 GHz band

Yasumasa Yamasaki, Sho Masui, Masanari Okawa, Koki Yokoyama, Taisei Minami, Shota Ueda, Yutaka Hasegawa, Atsushi Nishimura, Toshikazu Onishi, Hideo Ogawa, Nozomi Okada, Kimihiro Kimura, Alvaro Gonzalez, Takafumi Kojima, Keiko Kaneko, Ryo Sakai

Proceedings Volume 11453, 114534H (2020) https://doi.org/10.1117/12.2561955

KEYWORDS: Optical design, Telescopes, Receivers, Mirrors, Clouds, Reflectors, Antennas, Optical instrument design, Device simulation, Optical simulations

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Proceedings Article | 13 December 2020 Presentation + Paper

Presentation + Paper

An SIS-mixer-based amplifier for multi-pixel heterodyne receivers

Yoshinori Uzawa, Takafumi Kojima, Yuto Kozuki, Yasunori Fujii, Akihira Miyachi, Tomonori Tamura, Shohei Ezaki, Wenlei Shan

Proceedings Volume 11453, 114530Q (2020) https://doi.org/10.1117/12.2563183

KEYWORDS: Amplifiers, Heterodyning, Receivers, Microwave radiation, Cryogenics, Frequency conversion

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Proceedings Article | 13 December 2020 Poster + Paper

Poster + Paper

Status of the East Asia ALMA development program: Towards the implementation of the ALMA development roadmap

Álvaro González, Takafumi Kojima, Wenlei Shan, Hitoshi Kiuchi, Yoshinori Uzawa, Daisuke Iono, George Kosugi

Proceedings Volume 11445, 1144538 (2020) https://doi.org/10.1117/12.2561603

KEYWORDS: Receivers, Telescopes, Antennas, Spectroscopy, Calibration, Software development, Superconductors, Integrated circuit design, Integrated circuits

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Proceedings Article | 13 December 2020 Presentation + Paper

Presentation + Paper

Wideband technology development to increase the RF and instantaneous bandwidth of ALMA receivers

Takafumi Kojima, Kazunori Uemizu, Hitoshi Kiuchi, Tomonori Tamura, Keiko Kaneko, Ryo Sakai, Akihira Miyachi, Wenlei Shan, Yoshinori Uzawa, Alvaro Gonzalez, Matthias Kroug, Takeshi Sakai

Proceedings Volume 11453, 114530P (2020) https://doi.org/10.1117/12.2561240

KEYWORDS: Receivers, Radio frequency circuits, Astronomy, Observatories, Heterodyning, Waveguides

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Proceedings Article | 13 December 2020 Poster + Paper

Poster + Paper

Design of all-in-one 2SB mixer for ALMA band 10

Yasunori Fujii, Takafumi Kojima, Matthias Kroug, Yoshinori Uzawa

Proceedings Volume 11453, 114533Y (2020) https://doi.org/10.1117/12.2562032

KEYWORDS: Waveguides, Oscillators, Electromagnetic simulation, Interfaces

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Proceedings Article | 9 July 2018 Paper

Paper

Development of a low-power cryogenic MMIC HEMT amplifier for heterodyne array receiver application

J. Liu, W. Shan, T. Kojima, X. Zhang, Z. Li, Y. Chen

Proceedings Volume 10708, 107082X (2018) https://doi.org/10.1117/12.2314356

KEYWORDS: Cryogenics, Field effect transistors, Amplifiers, Gallium arsenide, Receivers, Capacitors, Astronomy, Transistors

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Proceedings Article | 9 July 2018 Paper

Paper

Overview of the East Asia ALMA development program

S. Asayama, A. Gonzalez, H. Kiuchi, T. Kojima, M. Kroug, W. Shan, G. Kosugi, D. Iono, S. Iguchi

Proceedings Volume 10708, 1070837 (2018) https://doi.org/10.1117/12.2313367

KEYWORDS: Receivers, Software development, Terahertz radiation, Spectroscopy, Observatories, Astronomy, Telescopes, Calibration, Data archive systems, Antennas

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Proceedings Article | 9 July 2018 Paper

Paper

Technical achievements of the ALMA future receiver development program at the National Astronomical Observatory of Japan

A. Gonzalez, T. Kojima, M. Kroug, W. Shan, S. Asayama, D. Iono, T. Noguchi, S. Iguchi

Proceedings Volume 10708, 1070812 (2018) https://doi.org/10.1117/12.2312969

KEYWORDS: Receivers, Waveguides, Superconductors, Telescopes, Heterodyning, Terahertz radiation, Antennas

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Proceedings Article | 6 July 2018 Paper

Paper

How do we design the interferometric system focused on the analog and digital backend and the correlator for scientifically valuable ALMA developments?

S. Iguchi, A. Gonzalez, T. Kojima, W. Shan, G. Kosugi, S. Asayama, D. Iono

Proceedings Volume 10700, 107002Y (2018) https://doi.org/10.1117/12.2312024

KEYWORDS: Data transmission, Analog electronics, Receivers, Interferometry, Antennas, Astronomy, Telescopes

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Proceedings Article | 23 July 2014 Paper

Paper

ALMA band 10 (787-950 GHz): summary of the production of 73 receivers and first light results

Alvaro Gonzalez, Yasunori Fujii, Keiko Kaneko, Matthias Kroug, Takafumi Kojima, Koichi Kuroiwa, Akihira Miyachi, Kazumasa Makise, Zhen Wang, Shin'ichiro Asayama, Yoshinori Uzawa

Proceedings Volume 9153, 91530N (2014) https://doi.org/10.1117/12.2055598

KEYWORDS: Receivers, Polarization, Tolerancing, Astronomy, Antennas, Mirrors, Optical testing, Terahertz radiation, Superconductors, Niobium

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Showing 5 of 19 publications

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