Curved-Substrate Resonator Circuit for Spurious Mode Suppression
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Solution Overview
Problem
Electromechanical resonators suffer from spurious modes due to acoustic energy reflections at impedance mismatches, affecting stability and operation, especially when these modes occur near the resonant frequency or frequencies of nearby electrical signals.
Innovation Solution
Incorporating a curved surface on the substrate opposite the resonator, with curvature designed to introduce destructive interference and scattering of reflected acoustic energy, mitigating spurious modes by controlling signal reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If acoustic waves are generated and confined in the resonator to increase quality factor, then the quality factor is improved, but spurious modes are generated due to reflections at boundaries
Solution Approach 1:
The substrate surface is formed with a curved profile instead of a flat surface. The curvature radius is specifically designed to be between 0.5 mm and 2.0 mm to optimize the scattering of acoustic waves. This curved geometry causes reflected acoustic waves to scatter in multiple directions rather than forming coherent spurious modes, thereby maintaining high quality factor while eliminating harmful reflections
Solution Approach 2:
The invention converts the harmful reflected acoustic waves into beneficial scattered waves. By introducing the curved surface, the previously harmful reflections that caused spurious modes are transformed into scattered waves that do not interfere with the resonator operation. The curvature causes the acoustic energy to disperse constructively rather than form destructive interference patterns
2Object-generated harmful factors
If acoustic waves reflect at boundaries with acoustic impedance mismatch, then spurious modes are generated, but the resonator stability deteriorates
Solution Approach 1:
The curved surface with radius of curvature between 0.5 mm and 2.0 mm serves as an acoustic scattering structure. This curvature causes reflected waves to diverge and scatter rather than return to the resonator in a coherent manner. The scattering effect eliminates the formation of spurious modes and prevents frequency shifts, thereby maintaining resonator stability
3Object-generated harmful factors
If a curved surface is added to the substrate to reduce spurious modes, then spurious modes are reduced, but device complexity increases
Solution Approach 1:
The curved surface is formed by simple planarization processes such as chemical mechanical polishing (CMP) or spin-on-glass (SOG) techniques. The curvature radius is optimized between 0.5 mm and 2.0 mm to achieve effective scattering while maintaining manufacturability. This approach reduces spurious modes without requiring complex multi-layer structures or additional components
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 curved surface effectively reduces or eliminates spurious modes, enhancing the stability and performance of electromechanical resonators by minimizing interference and maintaining structural integrity.
Implementation Method 1
acoustic waves can escape from the resonator and become reflected at boundaries where there is an acoustic impedance mismatch
Implementation Method 2
curvature designed to introduce destructive interference and scattering of reflected acoustic energy
Implementation Method 3
curvature designed to introduce destructive interference and scattering of reflected acoustic energy
Data Source
AI summary
One example described herein includes an integrated circuit (IC). The IC includes a substrate having opposing first and second sides. The second side can include a curved surface. The IC also includes a resonator on the first side. A curvature of the curved surface can reflect a property of the resonator.