Investigating the theoretical noise-bandwidth limits of near-terahertz superconducting heterodyne mixers for up-coming far-infrared space satellite missions

Conference item

We present the design and performance analysis of waveguide-based superconductor–insulator–superconductor (SIS) mixers employing niobium titanium nitride (NbTiN) transmission lines and tunnel junctions comprising niobium/aluminium oxide (Nb/AlO_x/Nb) or niobium/aluminium nitride (Nb/AlN/Nb) topologies. These superconducting quantum devices are developed to enable wideband heterodyne operation for next-generation far-infrared (FIR) space missions in the sub-terahertz regime. The mixer circuits are optimised for simultaneous broadband radio-frequency (RF) and intermediate-frequency (IF) operation using microstrip architectures that incorporate end-stub, end-loaded, and twin-junction tuning networks. Threedimensional electromagnetic simulations, combined with quantum-mixing analyses, predict receiver noise temperatures approaching four times the quantum limit across 0.50–0.79 THz for the AlO_x-based design. The AlN-based variant further extends the RF coverage to 0.39–0.82 THz, satisfying the requirements of several proposed space missions while overlapping the Atacama Large Millimetre/sub-millimetre Array (ALMA) Bands 8 and extended Band 9. These simulated results demonstrate that NbTiN-based microstrip SIS mixers have the potential to deliver high sensitivity and wide instantaneous bandwidth at sub-terahertz frequencies, establishing them as strong candidates for next-generation space-borne and ground-based FIR observatories.

Authors: Tan, BK; Kim, J-H; Baryshev, A; Boussaha, F

• Publication status: Accepted
• Peer review status: Peer reviewed
• Acceptance date: 2026-04-19
• Event title: Progress In Electromagnetics Research Symposium (PIERS) 2026
• Event location: Suzhou, China
• Event website: https://suzhou2026.piers.org/
• Event start date: 2026-07-27
• Event end date: 2026-07-31
• Language: English