SAW Filter Electrode Materials for Smaller Acoustic Wave Modules
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Solution Overview
Problem
Designing acoustic wave devices to meet performance and size specifications with low loss is challenging, particularly in reducing the size of acoustic wave filters while maintaining performance, as higher density materials used in transmit filters can complicate receive filter design and performance.
Innovation Solution
The use of high-density materials like tungsten in the interdigital transducer electrodes of transmit filters and lower density materials like molybdenum for at least a proportion of the receive filter electrodes, which reduces the overall size of the device and balances size and performance by optimizing reflection coefficients and acoustic wave velocities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If high-density materials are used in transmit filter electrodes, then the size of the transmit filter is reduced, but the receive filter design and performance becomes more complex
Solution Approach 1:
The patent applies different material densities to different functional sections: high-density materials (tungsten, platinum, gold) are used in transmit filter IDTs to reduce size, while low-density materials (molybdenum, aluminum, copper) are used in receive filter IDTs to maintain performance. This local differentiation resolves the contradiction by optimizing each section for its specific function rather than using a uniform material throughout the device.
2Volume of moving object
If high-density materials are used in transmit filter electrodes, then the size of the acoustic wave device is reduced, but the reflection coefficient characteristics deteriorate
Solution Approach 1:
The patent optimizes reflection coefficient characteristics by assigning low-density materials specifically to receive filter IDTs where good reflection characteristics are critical for signal reception. High-density materials are confined to transmit filter IDTs where size reduction is the primary goal. This local optimization ensures that each section's material properties serve its functional requirements.
Solution Approach 2:
The patent changes the density parameter of the electrode materials based on the functional requirements of different filter sections. By selecting materials with appropriate density values (high-density for transmit, low-density for receive), the patent simultaneously achieves size reduction in transmit filters and maintains reliable reflection coefficient characteristics in receive filters.
3Reliability
If low-density materials are used in receive filter electrodes, then the reflection coefficient characteristics improve, but the size of the device increases
Solution Approach 1:
The patent accepts the size increase in receive filters as necessary to achieve good reflection coefficient characteristics, while compensating for the overall device size through high-density material usage in transmit filters. This local optimization strategy allows each section to be sized appropriately for its function, with the transmit filter being compact and the receive filter being optimally sized for performance.
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 significantly reduces the size of acoustic wave devices while maintaining good electrical performance and improving reflection coefficient characteristics, particularly at the antenna port, making it suitable for filter ganging or banking.
Implementation Method 1
surface acoustic wave resonators
Implementation Method 2
surface acoustic wave (SAW) resonators
Data Source
AI summary
An acoustic wave device comprising a transmit filter including a plurality of surface acoustic wave resonators. Each surface acoustic wave resonator of the transmit filter including an interdigital transducer electrode comprising a first material. The acoustic wave device further comprising a receive filter including a plurality of surface acoustic wave resonators. At least a proportion of the plurality of surface acoustic wave resonators of the receive filter each including an interdigital transducer electrode comprising a second material. The density of the first material is greater than the density of the second material.