BAW Resonator Annular Groove Structure for Parasitic Resonance
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Solution Overview
Problem
Bulk acoustic wave resonators in mobile terminals face challenges in achieving steep skirts and small insertion loss due to parasitic resonance, which affects their performance, and there is a need to reduce parasitic resonance while increasing the Q value.
Innovation Solution
A bulk acoustic wave resonance structure is designed with a substrate, a reflective structure, a first electrode layer, a piezoelectric layer with annular grooves, and a second electrode layer, where the grooves are located in the active area close to the edge to prevent transversal shear waves from propagating externally, thereby reducing energy leakage and increasing the Q value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the bulk acoustic wave resonator uses multiple frequency bands simultaneously, then the filter performance requires steeper skirts and smaller insertion loss, but parasitic resonance adversely affects the performance
Solution Approach 1:
The patent extracts and removes the harmful parasitic resonance from the system by introducing annular grooves that selectively eliminate transversal shear waves while preserving the desired longitudinal acoustic waves. This extraction principle allows the resonator to operate without the adverse effects of parasitic resonance.
Solution Approach 2:
The patent converts the harmful parasitic resonance into a beneficial effect by using the annular grooves to transform transversal shear waves into longitudinal waves through mode conversion. The grooves act as a mechanism that transforms the harmful wave type into the useful wave type, improving overall resonator performance.
2Reliability
If the Q value of the resonator is increased to achieve steep skirt and small insertion loss, then the filter performance improves, but parasitic resonance must be reduced simultaneously
Solution Approach 1:
The patent applies local quality by introducing annular grooves at specific locations (near the edge of the active area) with specific geometric characteristics. These localized structural modifications create different acoustic properties in different regions of the piezoelectric layer, enabling selective suppression of parasitic modes while maintaining desired resonance characteristics.
Solution Approach 2:
The patent segments the piezoelectric layer by introducing annular grooves that divide the continuous structure into distinct regions. This segmentation creates acoustic barriers that prevent the propagation of transversal shear waves while allowing longitudinal waves to maintain their energy, thereby increasing the Q value.
3Productivity
If transversal shear waves are allowed to propagate to the external region, then the resonator operates, but energy leakage occurs and reduces the Q value
Solution Approach 1:
The annular grooves serve as an intermediary structure between the internal resonator region and the external environment. They act as a mediator that selectively interacts with different wave types, allowing longitudinal waves to pass through while blocking transversal shear waves, thereby preventing energy leakage without stopping resonator operation.
Solution Approach 2:
The patent changes the acoustic parameters of the piezoelectric layer by introducing grooves with specific depth, width, and spacing parameters. These parameter changes create acoustic impedance variations that selectively affect different wave modes, enabling energy confinement for longitudinal waves while allowing suppression of transversal shear waves.
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 inclusion of annular grooves in the piezoelectric layer effectively reduces parasitic resonance and increases the Q value, leading to improved performance by concentrating energy on longitudinal waves within the active area.
Implementation Method 1
a piezoelectric layer, which is provided with at least one annular groove
Implementation Method 2
The groove can prevent transversal shear waves generated by a bulk acoustic wave resonator when stimulated by an electric field from propagating to the external region
Implementation Method 3
Bulk Acoustic Wave (BAW) resonators have advantages such as small size and high quality factor (Q)
Data Source
AI summary
A bulk acoustic wave resonant structure includes a substrate, and a reflection structure, a first electrode layer, a piezoelectric layer and a second electrode layer, which are sequentially stacked on the substrate, wherein ring-shaped grooves are provided in the piezoelectric layer; and the grooves are located in an active area and are close to an edge of the active area.