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Analysing the RF & IF bandwidth performances of ALMA Band-9 superconducting mixers for wideband sensitivity upgrade

Abstract:
The Atacama Large Millimetre/Sub-millimetre Array (ALMA) wideband sensitivity upgrade (WSU) project marks the next milestone in the development of millimetre (mm) and sub-mm astronomy. In this paper, we present the design, optimisation, and performance analysis of the ALMA Band-9 superconductor-insulator-superconductor (SIS) mixer for applications in the upcoming WSU programme, and other high-frequency astronomical observations. The mixers feature a niobium radial-rectangular probe antenna integrated with a silicon-on-insulator (SOI) substrate, which ensures minimal RF power leakage and optimised power coupling. We base our mixer design on conventional aluminium oxide (AlOx) tunnel junction technology, with a critical current density of about 10 kA cm−2. We explore the impact of different junction sizes on the radio frequency (RF) and intermediate frequency (IF) bandwidths. We demonstrate that the new mixer design is capable of meeting the more stringent sensitivity-bandwidth requirements of the ALMA-WSU programme over the original Band-9 frequency range (602–720 GHz), as the IF bandwidth performance reaches up to 20 GHz. The IF bandwidth improvement is approximately double that of the current existing ALMA Band-9 mixers. These results suggest that our mixer designs provide a promising solution for future ALMA upgrades and other high-frequency applications requiring broad RF and IF bandwidth.
Publication status:
Published
Peer review status:
Peer reviewed

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Publisher copy:
10.1088/1361-6668/adea63

Authors

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Institution:
University of Oxford
Division:
MPLS
Department:
Physics
Sub department:
Astrophysics
Role:
Author
ORCID:
0000-0002-6252-9351
More by this author
Institution:
University of Oxford
Division:
MPLS
Department:
Physics
Sub department:
Astrophysics
Role:
Author
More by this author
Role:
Author
ORCID:
0000-0002-7611-0148


More from this funder
Funder identifier:
https://ror.org/019w4f821
Grant:
803862
Programme:
Horizon 2020 research and innovation programme
More from this funder
Funder identifier:
https://ror.org/001aqnf71
Grant:
10079362
More from this funder
Funder identifier:
https://ror.org/057g20z61
Grant:
ST/Y002210/1
2888233
More from this funder
Funder identifier:
https://ror.org/00k4n6c32
Programme:
Horizon-Infra-2022-Tech-01 RadioBlock project
More from this funder
Funder identifier:
https://ror.org/052gg0110


Publisher:
IOP Publishing
Journal:
Superconductor Science and Technology More from this journal
Volume:
38
Issue:
8
Article number:
085001
Publication date:
2025-07-28
Acceptance date:
2025-06-30
DOI:
EISSN:
1361-6668
ISSN:
0953-2048

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