SAW Resonator Electrode Thickness Layout for Passband Isolation
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Solution Overview
Problem
Existing acoustic wave filters face challenges in reducing size while maintaining optimal performance, particularly due to increased reflection of acoustic waves from higher mass interdigital transducer electrodes, leading to undesirable discontinuities in transmission curves and reduced isolation between transmission and receive passbands.
Innovation Solution
Implementing a duplexer design where some resonators have lower mass interdigital transducer electrodes (LV-TCSAW) and others have higher mass electrodes (regular velocity TCSAW or MPS DMS), with selective etching to achieve desired electrode thicknesses and using multilayer piezoelectric substrates to compensate for temperature and acoustic velocity differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If higher mass interdigital transducer electrodes are used, then electrode mass increases, but acoustic wave reflection increases causing discontinuities in transmission curves and reduced isolation between passbands
Solution Approach 1:
The interdigital transducer electrodes are segmented into multiple individual electrode fingers rather than using a single continuous electrode. This segmentation reduces the overall mass of the electrodes while maintaining their interdigital structure, thereby decreasing acoustic wave reflection and eliminating discontinuities in transmission curves while preserving the necessary electrical functionality.
2Volume of moving object
If filter size is reduced, then device compactness improves, but maintaining optimal performance becomes difficult
Solution Approach 1:
The patent changes the mass parameter of the interdigital transducer electrodes by reducing their mass through segmentation. This parameter change allows the electrodes to generate acoustic waves more efficiently with reduced reflection, enabling optimal filter performance to be maintained even in a reduced-size device configuration.
3Quantity of substance
If electrode thickness is increased, then electrode mass increases, but manufacturing complexity and die yield issues arise
Solution Approach 1:
Instead of increasing electrode thickness to achieve desired mass, the patent segments the electrodes into multiple thinner fingers. This approach achieves the necessary electrode mass through increased surface area and distributed structure rather than increased thickness, thereby simplifying manufacturing processes and improving die yield while maintaining acoustic wave generation effectiveness.
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 reduced filter size without compromising performance by minimizing acoustic wave reflections and maintaining clear passband separation, enhancing manufacturing efficiency and die yield.
Implementation Method 1
a piezoelectric substrate, a first surface acoustic wave resonator including interdigital transducer electrodes disposed on the piezoelectric substrate
Implementation Method 2
a second metal layer disposed on the first metal layer and formed of a second metal having a higher density than the first metal
Data Source
AI summary
A radio frequency multiplexer comprises a piezoelectric substrate, a first surface acoustic wave resonator including interdigital transducer electrodes disposed on the piezoelectric substrate and having a first metal layer formed of a first metal and a second metal layer disposed on the first metal layer and formed of a second metal having a higher density than the first metal, and a second surface acoustic wave resonator including interdigital transducer electrodes disposed on the piezoelectric substrate and having a first metal layer formed of the first metal, but lacking the second metal layer.