XBAR Diaphragm Geometry for Spurious Mode Suppression
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Solution Overview
Problem
Existing RF filters using acoustic wave resonators are not well-suited for higher frequency communication bands above 3 GHz, as they struggle to maintain performance and efficiency at these frequencies.
Innovation Solution
The development of transversely-excited film bulk acoustic resonators (XBARs) with slanted and/or perforated membranes, which utilize a thin film conductor pattern on a piezoelectric plate to achieve improved performance at higher frequencies by suppressing spurious modes through asymmetric diaphragm shapes and oblique electric field excitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional acoustic wave resonators are used for RF filters, then they work well at lower frequencies, but they fail to maintain performance at higher frequencies above 3 GHz
Solution Approach 1:
The patent changes the physical parameters of the resonator by introducing a cavity structure beneath the piezoelectric plate and using specific electrode configurations. This modifies the acoustic wave propagation characteristics, enabling the resonator to maintain performance at higher frequencies above 3 GHz where conventional resonators fail.
Solution Approach 2:
The patent adds a vertical dimension by introducing a cavity structure beneath the piezoelectric plate. This three-dimensional configuration allows acoustic waves to propagate in multiple directions, creating resonant modes that are effective at higher frequencies and improving the overall frequency range coverage of the filter.
2Productivity
If wider communication channel bandwidths are achieved through higher frequency bands, then future wireless standards are supported, but existing RF filters cannot maintain performance and efficiency
Solution Approach 1:
The resonator design uses modified physical parameters including cavity depth, piezoelectric plate thickness, and electrode spacing to optimize performance for wider communication channels. These parameter adjustments enable the filter to maintain efficiency while supporting higher frequency bands required for increased bandwidth and future wireless standards.
3Reliability
If spurious modes are suppressed through asymmetric diaphragm shapes and oblique electric field excitation, then rejection and insertion loss characteristics improve, but device complexity increases
Solution Approach 1:
The patent employs asymmetric diaphragm shapes within the cavity structure to suppress spurious acoustic modes. The asymmetric geometry creates directional acoustic field distribution that enhances rejection characteristics and insertion loss performance while managing the increased structural complexity through systematic design.
Solution Approach 2:
The patent introduces oblique electric field excitation by orienting electrodes at specific angles relative to the piezoelectric plate. This angular configuration creates controlled acoustic wave propagation directions that suppress unwanted spurious modes, improving filter characteristics while the complexity is managed through precise geometric positioning.
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
XBARs demonstrate enhanced performance by achieving better rejection and insertion loss characteristics, allowing for the design of high-frequency RF filters with wider communication channel bandwidths, thus supporting future wireless communication standards.
Implementation Method 1
a piezoelectric plate to which a conductor pattern is attached
Implementation Method 2
transversely-excited film bulk acoustic resonators (XBARs)
Data Source
AI summary
Acoustic resonator devices, filter devices, and methods of fabrication are disclosed. An acoustic resonator includes a substrate having a surface and a single-crystal piezoelectric plate having front and back surfaces. The back surface is attached to the surface of the substrate except for a portion of the piezoelectric plate forming a diaphragm that spans a cavity in the substrate. An interdigital transducer (IDT) is formed on the front surface of the single-crystal piezoelectric plate such that interleaved fingers of the IDT are disposed on the diaphragm. The IDT is configured to excite a primary acoustic mode in the diaphragm in response to a radio frequency signal applied to the IDT. At least a portion of an edge of the diaphragm is at an oblique angle to the fingers.