Whispering-Gallery-Mode Resonator Coupling Unit Design
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Solution Overview
Problem
Existing whispering-gallery-mode resonators face challenges in accurately measuring superconductor microwave surface impedance in millimeter and sub-millimeter wavelength ranges due to excessive resonant scattering and non-resonant radiation, leading to reduced signal-to-noise ratio and systematic measurement errors.
Innovation Solution
A novel coupling unit with a coaxial waveguide and m evenly spaced coupling holes on the endplate is introduced, reducing resonant scattering and enhancing the coupling coefficient, allowing for precise measurement of surface impedance by reflecting waves from the resonator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional coupling units are used in whispering-gallery-mode resonators, then the resonator can be excited, but excessive resonant scattering and non-resonant radiation occur, reducing signal-to-noise ratio and causing systematic measurement errors
Solution Approach 1:
The coupling unit is segmented into multiple discrete coupling holes (m holes) distributed around the resonator circumference, allowing controlled electromagnetic coupling while minimizing scattering. This segmentation enables precise control over the coupling coefficient and reduces harmful radiation effects compared to continuous or single-point coupling structures.
Solution Approach 2:
A dielectric waveguide serves as an intermediary structure between the feed line and the resonator, providing a controlled transition that reduces direct coupling between the feed line and resonator. This intermediary structure minimizes non-resonant radiation and scattering while maintaining effective energy transfer to the resonator modes.
2Measurement precision
If the coupling coefficient is increased to strengthen coupling with transmission feeder lines for measuring nonlinear properties, then measurement sensitivity improves, but resonant scattering and non-resonant radiation increase, degrading signal-to-noise ratio
Solution Approach 1:
The coupling holes are strategically positioned at specific locations around the resonator circumference where the electromagnetic field has optimal characteristics. This local optimization of coupling strength at specific positions allows maximum energy transfer to the resonator while minimizing overall scattering and radiation losses.
Solution Approach 2:
The coupling coefficient can be precisely controlled by adjusting parameters such as the number of coupling holes (m), their radial position, and their dimensions. By optimizing these parameters, the coupling strength can be tuned to achieve the desired balance between energy transfer efficiency and minimization of scattering and radiation losses.
3Measurement precision
If normal metals are completely excluded from the resonator to minimize energy losses, then measurement accuracy improves, but the device complexity increases due to the need for specialized materials and structures
Solution Approach 1:
The resonator employs composite material structures combining dielectric materials with controlled conductivity properties. The endplates and coupling structures use materials with optimized electrical characteristics that balance low loss requirements with manufacturing feasibility, avoiding the need for entirely exotic materials while maintaining high measurement accuracy.
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
This configuration significantly increases the signal-to-noise ratio, enabling accurate measurement of superconductor characteristics in short-wavelength ranges and reducing systematic errors by accounting for external resonator losses.
Implementation Method 1
the resonator is excited with higher modes, namely, whispering gallery modes
Implementation Method 2
coupling unit for coupling a measuring waveguide with the resonating body
Implementation Method 3
superconducting sample under test
Implementation Method 4
energy losses in superconductors compared with losses in normal metals
Implementation Method 5
allowing for precise measurement of surface impedance by reflecting waves from the resonator
Data Source
AI summary
A measuring whispering-gallery-mode resonator includes: a dielectric resonating body with a rotation axis, a superconducting sample under test mounted to the resonating body and a coupling unit for coupling a measuring waveguide with the resonating body. One side of the resonating body connected with the coupling unit has a first endplate, in which m coupling holes penetrate through the first endplate, and centers of the m coupling holes are arranged to be evenly spaced along a circle whose center is on the rotation axis. The coupling unit has a feeder line which is a coaxial waveguide, and an axis of the coaxial waveguide coincides with the rotation axis. One end surface of the coaxial waveguide, which is perpendicular to the rotation axis, abuts the first endplate; and the azimuth index of operated whispering gallery mode in the resonator is an integer multiple of the number m of the coupling holes.