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Updated: Sep 11, 2025

Fabrication and Characterization of Superconducting Resonators
Published on: May 21, 2016
Interpreting S-parameter spectra in coupled resonant systems: the role of probing configurations
Abstract:
The S-parameter S21 is widely used to characterize the resonant properties of various systems. However, we demonstrate that the reliability of S21 as a true indicator of system resonances depends heavily on the specific probing setup employed. While point-probe or weak probes preserve the integrity of the S21 spectrum and accurately reflect system resonances, multi-point and strong probes can introduce significant discrepancies. These discrepancies can manifest as misleading features such as repulsive level anti-crossing or attractive level crossing, even in fundamentally uncoupled systems. This highlights the critical importance of selecting appropriate probing techniques to ensure a precise evaluation of system resonances.
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