High-frequency crosstalk in superconducting microstrip waveguide interconnects

A low-temperature electro-optic sampling system was implemented to study the crosstalk of picosecond pulses between niobium microstrip interconnects. This system has been used to perform noninvasive, nodal testing on superconducting integrated circuits. We have characterized the crosstalk arising from the crossing of two microstrip waveguides. This is representative of high-speed interconnects in VLSI technology in which one signal line must cross above another. The measured crosstalk signal showed the capacitive nature of the coupling, thereby providing the material's dielectric permittivity at high frequencies. Our results have provided feedback for improving computer simulations of superconducting electronic circuits.