A 4-20 GHz Superconducting 90deg Hybrid Using Capacitively Loaded Coupled Lines for 2SB Heterodyne Receivers
Abstract
We report the design and cryogenic characterisation of a broadband superconducting 90deg intermediate-frequency (IF) hybrid covering 4 to 20 GHz for sideband-separating (2SB) heterodyne receivers. The hybrid is implemented in thin-film niobium using capacitively loaded edge coupled transmission lines, avoiding the air-bridge interconnections required in Lange-coupler layouts while retaining a compact superconducting implementation with low loss and good quadrature balance. Cryogenic measurements using Vector Network Analyser (VNA) show amplitude and phase imbalance better than 0.6 dB and 6deg, respectively, across the full band. When used in a 2SB receiver, this level of IF balance is consistent with the observed image-rejection performance in the 10-20 dB range, for the full receiver. The design supports the development of wide-instantaneous-bandwidth 2SB receivers for millimeter and submillimeter observatories, improving spectral grasp for broadband line surveys and high-redshift line searches.
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BibTeX
@misc{joint2026superconducting,
title = {{A 4-20 GHz Superconducting 90deg Hybrid Using Capacitively Loaded Coupled Lines for 2SB Heterodyne Receivers}},
author = {François Joint and Max Behrens and Denis Meledin and Cristian Lopez and Magnus Strandberg and Sven-Erik Ferm and Mathias Fredrixon and Leif Helldner and Alexei Pavolotsky and Erik Sundin and Igor Lapkin and Victor Belitsky and Vincent Desmaris},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.24859},
eprint = {2610.24859},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.24859},
}
RIS
TY - UNPB
TI - A 4-20 GHz Superconducting 90deg Hybrid Using Capacitively Loaded Coupled Lines for 2SB Heterodyne Receivers
AU - François Joint
AU - Max Behrens
AU - Denis Meledin
AU - Cristian Lopez
AU - Magnus Strandberg
AU - Sven-Erik Ferm
AU - Mathias Fredrixon
AU - Leif Helldner
AU - Alexei Pavolotsky
AU - Erik Sundin
AU - Igor Lapkin
AU - Victor Belitsky
AU - Vincent Desmaris
PY - 2026
DA - 2026/10/17
PB - arXiv
DO - 10.48550/arxiv.2610.24859
UR - https://arxiv.org/abs/2610.24859
AB - We report the design and cryogenic characterisation of a broadband superconducting 90deg intermediate-frequency (IF) hybrid covering 4 to 20 GHz for sideband-separating (2SB) heterodyne receivers. The hybrid is implemented in thin-film niobium using capacitively loaded edge coupled transmission lines, avoiding the air-bridge interconnections required in Lange-coupler layouts while retaining a compact superconducting implementation with low loss and good quadrature balance. Cryogenic measurements using Vector Network Analyser (VNA) show amplitude and phase imbalance better than 0.6 dB and 6deg, respectively, across the full band. When used in a 2SB receiver, this level of IF balance is consistent with the observed image-rejection performance in the 10-20 dB range, for the full receiver. The design supports the development of wide-instantaneous-bandwidth 2SB receivers for millimeter and submillimeter observatories, improving spectral grasp for broadband line surveys and high-redshift line searches.
ER -