SAW Filter Acoustic Velocity Structure for Lower Radiation Loss
Find Innovative SolutionsGenerate Solutions
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
The implementation of an acoustic velocity adjustment structure, including high speed and low speed layers, is used to create different acoustic wave propagation velocity regions within the SAW device, reducing radiation losses and allowing for uniform or minimally varied IDT electrode pitches, thereby simplifying manufacturing and improving frequency response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If varying interdigital transducer electrode pitches are used to achieve desired frequency responses, then frequency response can be optimized, but radiation losses increase and manufacturing difficulty increases
Solution Approach 1:
The patent applies local quality by introducing an acoustic velocity adjustment structure with different velocity regions (first velocity region over the gap, second velocity region over the IDT electrodes) to create localized acoustic properties. This allows uniform IDT electrode pitches while achieving desired frequency responses through localized velocity modification, thereby reducing radiation losses associated with pitch variations.
Solution Approach 2:
The patent changes the acoustic velocity parameter by introducing materials with different acoustic velocities in specific regions. The acoustic velocity adjustment structure modifies the local acoustic velocity to compensate for the effects of varying pitch, enabling uniform electrode fabrication while maintaining optimized frequency response and reducing radiation losses.
2Measurement precision
If varying interdigital transducer electrode pitches are used to achieve desired frequency responses, then frequency response can be optimized, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies local quality by introducing an acoustic velocity adjustment structure with different velocity regions (first velocity region over the gap, second velocity region over the IDT electrodes) to create localized acoustic properties. This allows uniform IDT electrode pitches while achieving desired frequency responses through localized velocity modification, thereby reducing radiation losses associated with pitch variations.
Solution Approach 2:
The patent changes the acoustic velocity parameter by introducing materials with different acoustic velocities in specific regions. The acoustic velocity adjustment structure modifies the local acoustic velocity to compensate for the effects of varying pitch, enabling uniform electrode fabrication while maintaining optimized frequency response and reducing radiation losses.
3Reliability
If acoustic velocity adjustment structure is introduced to reduce radiation losses, then quality factor improves, but device complexity increases
Solution Approach 1:
The patent applies dimensionality change by transitioning from modifying electrode geometry (planar dimension) to introducing vertical layers with different acoustic velocities. The acoustic velocity adjustment structure is positioned above the IDT electrodes, utilizing the vertical dimension to achieve velocity modification without changing the horizontal electrode pitch, thereby simplifying manufacturing while improving quality factor.
Solution Approach 2:
The patent uses composite materials with different acoustic velocity properties to create the acoustic velocity adjustment structure. By combining materials with specific acoustic characteristics in layered configurations, the patent achieves precise control over acoustic wave propagation and radiation loss reduction without requiring complex electrode geometries.
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 enhances the quality factor of SAW filters, enabling them to filter higher frequency signals with reduced bulk radiation and manufacturing complexities, while maintaining a desirable frequency response.
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 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
The high speed layer can include a silicon nitride layer. The high speed layer can include an aluminum oxide layer
Data Source
AI summary
Aspects of this disclosure relate to a surface acoustic wave filter with an acoustic velocity adjustment structure. The surface acoustic wave filter can include a first interdigital transducer electrode disposed on a piezoelectric layer, an acoustic reflector disposed on the piezoelectric layer, and a second interdigital transducer electrode disposed on the piezoelectric layer. The second interdigital transducer electrode is longitudinally coupled to the first interdigital transducer electrode and positioned between the first interdigital transducer electrode and the acoustic reflector. The acoustic velocity adjustment structure can be positioned over at least a gap between the first interdigital transducer electrode and the second interdigital transducer electrode. The acoustic velocity adjustment structure can be 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.