Electro acoustic resonator with suppressed transversal gap mode excitation and reduced transversal modes
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Solution Overview
Problem
Conventional electro acoustic resonators face challenges in suppressing transversal gap mode excitations and transversal modes, which adversely affect filter performance, especially in materials like TFSAW, leading to significant disturbances in passband performance and transition steepness between passband and stopband.
Innovation Solution
The introduction of a gap short structure with conductor strips that electrically short the transversal gaps, reducing electrical fields and modifying the acoustic velocity profile to suppress transversal gap mode excitations and reduce transversal modes, utilizing the same manufacturing steps as the electrode structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a transversal gap with higher wave velocity is used to reduce leakage of acoustic waves, then acoustic wave leakage is reduced, but transversal modes are excited due to wave diffraction
Solution Approach 1:
The patent converts the harmful effect of wave diffraction that excites transversal modes into a beneficial effect by intentionally designing velocity profiles that utilize diffraction to achieve desired acoustic field distribution while suppressing unwanted transversal modes through careful profile optimization
Solution Approach 2:
The patent applies parameter changes by adjusting the transversal acoustic velocity profile parameters to optimize the balance between reducing acoustic wave leakage and suppressing transversal mode excitation, achieving both goals through optimized velocity distribution
2Ease of manufacture
If conventional piston mode approach is used, then basic resonator function is achieved, but transversal gap modes are excited which disturb filter performance significantly
Solution Approach 1:
The patent applies local quality by implementing specific velocity profile characteristics in different regions of the resonator, particularly in the transversal gap regions, to locally suppress transversal gap modes while maintaining overall piston mode operation and conventional manufacturability
Solution Approach 2:
The patent modifies parameters of the velocity profile in specific regions to suppress transversal gap modes while maintaining compatibility with conventional manufacturing processes, achieving improved filter performance without increasing manufacturing complexity
3Object-generated harmful factors
If additional structures are added to suppress transversal modes, then transversal mode suppression is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent applies self-service by designing velocity profiles that automatically suppress transversal modes through their inherent acoustic field distribution characteristics, eliminating the need for additional suppression structures and maintaining simple resonator geometry
Solution Approach 2:
The patent uses parameter changes in the velocity profile to achieve transversal mode suppression without adding structural complexity, relying on optimized acoustic field distribution rather than additional physical structures
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 approach effectively suppresses transversal gap modes, improving filter performance by reducing disturbances, enhancing passband steepness, and minimizing losses, while maintaining manufacturability without increased complexity or cost.
Implementation Method 1
Electro acoustic resonators have an electrode structure and a piezoelectric material. Due to the piezoelectric effect an electro acoustic resonator converts between electromagnetic RF signals and acoustic RF signals.
Implementation Method 2
The gap short structure has conductor strips and is arranged inside the transversal gaps
Data Source
AI summary
An electro acoustic resonator is provided. The resonator has a gap short structure (GSS) to electrically short at least an area of the transversal gap to suppress transversal gap mode excitations. The gap short structure may be provided by a conductive stripe in the gap and parallel to or inclined with respect to the bus bar (BB) shorting adjacent IDT fingers. Additional connectors between the stripe and the bus bar may be provided. The connectors may have different pitch or metallization ratio with respect to the ID fingers. The connectors may be offset from the position of the fingers and my be inclined with respect to the bus bars. Multiple parallel stripes in the gap may provide a transversal reflector. By using a gap short structure a further improved transversal mode suppression of piston mode designs can be achieved.