Bent Acoustic Wave Resonator for Transverse Mode Suppression
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Solution Overview
Problem
Transverse spurious modes in acoustic wave filters, particularly in temperature-compensated surface acoustic wave (TC-SAW) resonators, cause frequency ripples and increased noise figure, leading to performance degradation in radio frequency (RF) systems.
Innovation Solution
Implementing a bent acoustic wave resonator waveguide with a curvature and a piston mode structure to suppress transverse spurious modes by increasing radiation loss for higher modes while maintaining fundamental mode guidance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a straight waveguide structure is used in acoustic wave resonators, then the device is simpler to manufacture, but transverse spurious modes cause frequency ripples and increased noise figure
Solution Approach 1:
The waveguide structure is bent into a curved or arcuate shape rather than remaining straight. This curvature creates different acoustic path lengths for transverse spurious modes compared to the fundamental mode, causing the spurious modes to radiate away from the waveguide and be suppressed, while the fundamental mode remains guided and maintains its propagation
Solution Approach 2:
The waveguide is divided into multiple sections with different curvature radii. The first section has a larger curvature radius to guide the fundamental mode, while the second section has a smaller curvature radius to enhance suppression of transverse spurious modes through increased radiation loss
2Object-affected harmful factors
If a bent waveguide with small curvature radius is used to suppress transverse modes, then spurious mode suppression is improved, but insertion loss increases
Solution Approach 1:
The bent waveguide is divided into multiple sections with progressively varying curvature radii. This gradual transition allows the fundamental mode to adapt smoothly to the curvature changes, minimizing radiation loss, while the transverse spurious modes experience increasing mismatch and radiation loss throughout the structure
Solution Approach 2:
The curvature radius varies dynamically along the waveguide length rather than being uniform. This dynamic variation optimizes the balance between guiding the fundamental mode and suppressing transverse modes at different positions along the waveguide structure
3Object-affected harmful factors
If a bent waveguide structure is implemented, then transverse spurious modes are suppressed, but device complexity increases
Solution Approach 1:
The waveguide is formed with a simple arcuate or curved geometry that can be implemented using standard photolithography and deposition processes, avoiding the need for complex three-dimensional structures while still achieving effective spurious mode suppression through the curvature-induced radiation mechanism
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 bent resonator structure effectively suppresses transverse spurious modes, reducing frequency ripples and improving RF filter performance with minimal insertion loss and maintaining quality factor.
Implementation Method 1
A surface acoustic wave resonator can include an interdigital transductor electrode on a piezoelectric substrate. The surface acoustic wave resonator can generate a surface acoustic wave on a surface of the piezoelectric layer
Implementation Method 2
The bent section can have a bend angle in a range from 1° to 20°. The interdigital transducer electrode is configured to suppress a transverse spurious mode of the acoustic wave device
Data Source
AI summary
An acoustic wave device with a bent section is disclosed. The acoustic wave device includes a piezoelectric layer and an interdigital transducer electrode on the piezoelectric layer. The bent section is arranged to create a curvature in a waveguide of the acoustic wave device to suppress a transverse spurious mode of the acoustic wave device.