Fishbone Waveguide Resonator for Compact Superconducting Circuits
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Solution Overview
Problem
In superconducting circuits, constructing a resonator with a CPW requires a long and large chip shape, especially when multiple bends or parallel transmission lines are involved, leading to unintended resonance modes and design challenges. There is a demand for a smaller footprint in these circuits.
Innovation Solution
A resonator is designed using a fishbone-type waveguide coupled by a junction element, including a Josephson junction, which allows for a shorter waveguide length and reduced footprint. This configuration adjusts the characteristic impedance and phase velocity, increasing capacitance and inductance per unit length, effectively reducing the required waveguide length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a CPW with length equivalent to wavelength, half wavelength, or quarter wavelength is used to construct a resonator, then the resonance frequency requirement is met, but the chip shape becomes long and large
Solution Approach 1:
The patent transitions from a one-dimensional linear CPW structure to a two-dimensional fishbone-type structure with multiple branches extending perpendicular to the main transmission line. This dimensional change allows the resonator to achieve the required electrical length (wavelength, half-wavelength, or quarter-wavelength) while occupying significantly less chip area, as the signal path folds back on itself rather than extending in a straight line
2Adaptability or versatility
If a CPW is bent into meandering shape to increase degree of freedom in chip shape and pattern design, then design flexibility is improved, but unintended resonance modes appear making design difficult
Solution Approach 1:
The patent divides the transmission path into multiple segmented branches (first branch line, second branch line, third branch line, etc.) that extend perpendicular to the main transmission line. Each branch is carefully designed with specific lengths and spacing to maintain controlled impedance and avoid unintended resonances. This segmentation approach provides design flexibility while preventing the parasitic resonance modes that occur in continuous meandering structures
Solution Approach 2:
The fishbone-type waveguide employs asymmetric branch configurations where branches on opposite sides of the main transmission line may have different lengths or spacing. This asymmetric design allows optimization of the resonator's electrical characteristics and impedance matching while maintaining freedom in chip shape and pattern design, without introducing the symmetric parasitic resonances that plague conventional meandering structures
3Area of stationary object
If the waveguide length is shortened to reduce footprint, then the chip area is reduced, but the resonance frequency and impedance characteristics become difficult to control
Solution Approach 1:
The patent applies local quality changes by varying the impedance characteristics of different sections of the fishbone-type waveguide. Each branch line and section of the main transmission line can have different widths, spacing, or geometric configurations to locally adjust the electrical length and impedance. This allows the overall structure to be compact while maintaining precise control over resonance frequency and impedance matching through localized parameter optimization rather than requiring uniform dimensions throughout
Solution Approach 2:
The patent utilizes parameter changes in the geometric dimensions of the fishbone-type waveguide components (branch lengths, spacing between branches, width of transmission lines, distance from substrate) to control the effective electrical length and characteristic impedance. By carefully adjusting these parameters, the resonator achieves the desired resonance frequency and impedance characteristics in a compact footprint, as the electrical length is determined by the cumulative effect of multiple short sections rather than a single long continuous path
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The use of a fishbone-type waveguide in the resonator reduces the waveguide length required, thereby minimizing the footprint of the superconducting circuit while maintaining the intended resonance mode, thus addressing the design challenges associated with long CPWs.
Implementation Method 1
A single Josephson junction or a Superconducting Quantum Interference Device (SQUID) in which two or more Josephson junctions form a closed path is used as the nonlinear inductance
Data Source
AI summary
A resonator includes a junction element including a Josephson junction and a fishbone-type waveguide coupled by the junction element.