SAW Filter Velocity Regions for Low-Loss Frequency Response
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Solution Overview
Problem
Multimode surface acoustic wave (SAW) filters face challenges in reducing radiation losses and achieving desired frequency responses due to varying interdigital transducer (IDT) electrode pitches, which can lead to manufacturing difficulties and loss mechanisms that are hard to quantify and model.
Innovation Solution
Incorporating an acoustic velocity adjustment structure with high and low speed layers over specific regions of the SAW device, allowing for controlled acoustic wave propagation velocities without varying the IDT electrode pitch, thereby creating different velocity regions and reducing loss mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the IDT electrode pitch is varied to achieve desired frequency responses, then the frequency response is improved, but manufacturing precision deteriorates and radiation losses increase
Solution Approach 1:
The patent applies local quality by introducing an acoustic velocity adjustment structure with different material properties (first and second acoustic velocities) in specific regions of the SAW device. Instead of varying the IDT electrode pitch throughout the structure, the invention maintains uniform pitch while creating localized velocity adjustments through different acoustic media, thereby achieving desired frequency responses without compromising manufacturing precision.
Solution Approach 2:
The invention changes the acoustic velocity parameter in specific regions by introducing an acoustic velocity adjustment structure with different acoustic velocities (first acoustic velocity and second acoustic velocity). This parameter change allows frequency response optimization without altering the geometric pitch of the IDT electrodes, thus avoiding manufacturing precision issues associated with pitch variation.
2Measurement precision
If the IDT electrode pitch is varied to achieve desired frequency responses, then the frequency response is improved, but radiation losses increase and become hard to quantify and model
Solution Approach 1:
The patent applies local quality by introducing an acoustic velocity adjustment structure with different material properties (first and second acoustic velocities) in specific regions of the SAW device. Instead of varying the IDT electrode pitch throughout the structure, the invention maintains uniform pitch while creating localized velocity adjustments through different acoustic media, thereby achieving desired frequency responses without compromising manufacturing precision.
Solution Approach 2:
The invention changes the acoustic velocity parameter in specific regions by introducing an acoustic velocity adjustment structure with different acoustic velocities (first acoustic velocity and second acoustic velocity). This parameter change allows frequency response optimization without altering the geometric pitch of the IDT electrodes, thus avoiding manufacturing precision issues associated with pitch variation.
3Manufacturing precision
If uniform IDT electrode pitch is maintained, then manufacturing precision is improved, but achieving desired frequency responses becomes difficult
Solution Approach 1:
The patent applies local quality by introducing an acoustic velocity adjustment structure with different material properties (first and second acoustic velocities) in specific regions of the SAW device. Instead of varying the IDT electrode pitch throughout the structure, the invention maintains uniform pitch while creating localized velocity adjustments through different acoustic media, thereby achieving desired frequency responses without compromising manufacturing precision.
Solution Approach 2:
The invention changes the acoustic velocity parameter in specific regions by introducing an acoustic velocity adjustment structure with different acoustic velocities (first acoustic velocity and second acoustic velocity). This parameter change allows frequency response optimization without altering the geometric pitch of the IDT electrodes, thus avoiding manufacturing precision issues associated with pitch variation.
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 reduces radiation losses and achieves high quality factor and reduced bulk radiation, enabling the filtering of higher frequency signals with less pitch variation, thus improving the performance of SAW filters.
Implementation Method 1
The surface acoustic wave resonator can generate a surface acoustic wave on a surface of the piezoelectric layer on which the interdigital transductor electrode is disposed
Implementation Method 2
The acoustic velocity adjustment structure is arranged to increase an acoustic wave propagation velocity in a first region that includes the gap relative to a second region over at least a portion of the first interdigital transducer electrode
Implementation Method 3
A surface acoustic wave resonator can include an interdigital transductor electrode on a piezoelectric substrate
Data Source
AI summary
Aspects of this disclosure relate to a surface acoustic wave device with a vertical stack over a piezoelectric layer. The vertical stack can include a first acoustic reflector disposed on the piezoelectric layer, a second acoustic reflector disposed on the piezoelectric layer, and an interdigital transducer electrode disposed on the piezoelectric layer and positioned between the first acoustic reflector and the second acoustic reflector. The interdigital transducer electrode has a first side that is closer to the first acoustic reflector and a second side that is closer to the second acoustic reflector. A vertical arrangement of the vertical stack can be configured such that an acoustic wave propagation velocity of a first region between the first side and a first reflector is faster than an acoustic wave propagation velocity of a second region between the first side and the second side.