Superconductor Science and Technology

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

Boon-Kok Tan, J-H Kim, Christine Chaumont, Faouzi M. Boussaha, Andrey M. Baryshev

Published Jul 28, 2025• 0 citations

Abstract

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 (AlO x ) 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.

DOI: 10.1088/1361-6668/adea63

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