Acoustic Wave Resonator Cover Layout for Lower Wave Velocity
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Solution Overview
Problem
Acoustic wave filters in radio frequency electronic systems face challenges in compact design due to the propagation speed of acoustic waves, which is influenced by the thickness and density of components, making it difficult to integrate multiple resonators in a small area without impacting frequency response.
Innovation Solution
Incorporating a velocity reduction cover with increased thickness or density in edge regions over the interdigital transducer electrode and temperature compensation layer, allowing for slower acoustic wave propagation without modifying the IDT electrode design, enabling more compact resonator designs and shared manufacturing processes across filter components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the thickness and density of components are increased to slow acoustic wave propagation, then the acoustic wave velocity is reduced, but the device footprint and area increase
Solution Approach 1:
The patent applies local quality by placing velocity reduction covers with varying densities at specific locations - specifically at the edges of the interdigital transducer electrode rather than uniformly across the entire device. This localized approach reduces acoustic wave velocity where needed to improve frequency response while minimizing the overall area increase that would result from uniform thickening or densification of all components.
Solution Approach 2:
The patent employs composite materials by using velocity reduction covers made from materials with different densities than the substrate (such as tungsten, molybdenum, or other high-density materials) positioned strategically over the piezoelectric substrate. This allows selective modification of acoustic wave propagation characteristics without requiring the entire device to be made from low-velocity materials, thereby controlling the footprint.
2Area of moving object
If multiple resonators are integrated in a small area, then the device compactness is improved, but the frequency response is impacted
Solution Approach 1:
The velocity reduction covers are applied locally at the edges of each resonator's interdigital transducer electrode, creating localized modifications to acoustic wave propagation. This allows multiple resonators to be closely spaced (improving compactness) while each resonator maintains its proper frequency response characteristics through the localized velocity reduction, preventing unwanted interactions and frequency shifts.
3Speed
If the IDT electrode design is modified to reduce acoustic wave velocity, then the velocity control is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent segments the velocity control function from the IDT electrode design by using separate velocity reduction covers positioned over the substrate. This segmentation allows the IDT electrode to maintain its standard, easily-manufactured design while the velocity control is achieved through additional discrete layers that can be deposited independently, thus improving velocity control without increasing IDT manufacturing complexity.
Solution Approach 2:
The velocity reduction covers act as intermediary elements between the IDT electrode and the substrate, mediating the acoustic wave propagation characteristics. This intermediary approach allows velocity control to be achieved without directly modifying the IDT electrode structure, maintaining manufacturing simplicity while still achieving the desired velocity reduction effect.
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 allows for the creation of more compact acoustic wave resonators with improved frequency response and reduced footprint, enabling the integration of multiple resonators within a given area while maintaining performance, suitable for applications like mobile phone RF front ends.
Implementation Method 1
A surface acoustic wave resonator can generate a surface acoustic wave on a surface of the piezoelectric layer
Implementation Method 2
The velocity reduction cover is arranged to cause a velocity of an acoustic wave generated by the acoustic wave resonator to be reduced
Implementation Method 3
A surface acoustic wave resonator can include an interdigital transducer electrode on a piezoelectric substrate
Implementation Method 4
a temperature compensation layer positioned over the interdigital transducer electrode
Data Source
AI summary
An acoustic wave resonator is disclosed. The acoustic wave resonator can include a piezoelectric layer, an interdigital transducer electrode positioned over the piezoelectric layer, a temperature compensation layer positioned over the interdigital transducer electrode, and a velocity reduction cover that extends over at least a portion of a central region of the interdigital transducer electrode and over at least a portion of the temperature compensation layer. The velocity reduction cover is arranged to cause a velocity of an acoustic wave generated by the acoustic wave resonator to be reduced.