XBAR IDT Thickness and Pitch Layout for Spurious Mode Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current RF filters, particularly those using acoustic wave resonators, are not well-suited for higher frequencies and wider bandwidths required in future communication networks, such as the 5G NR standard, which necessitates the development of more effective transversely-excited film bulk acoustic resonators (XBARs) capable of handling higher power and providing improved frequency selectivity and reduced spurious modes.
Innovation Solution
The design of XBARs involves optimizing the thickness and pitch of interdigital transducer (IDT) electrodes, using materials like lithium niobate, and incorporating features such as periodic etched holes and multi-mark IDTs to minimize spurious modes and enhance thermal conductivity, thereby improving the resonator's performance and power handling capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional acoustic wave resonators are used, then existing RF filter performance is maintained, but they are not suitable for higher frequencies and wider bandwidths required in 5G NR
Solution Approach 1:
The patent changes the fundamental operating parameters of the resonator by transitioning to a transverse excitation mode with specific electrode configurations. The IDT electrodes are designed with optimized pitch and mark dimensions, and the resonator operates at higher frequencies through controlled thickness and material selection (lithium niobate), enabling 5G NR compatibility
Solution Approach 2:
The patent employs composite material structures including lithium niobate piezoelectric material combined with metal electrodes of specific thickness ratios. The multi-layer construction with optimized material properties enables both high frequency operation and wide bandwidth performance required for 5G NR standards
2Power
If higher power handling is implemented, then power tolerance is improved, but spurious modes may increase
Solution Approach 1:
The patent applies local quality optimization by varying the electrode characteristics in different regions. The IDT electrodes have non-uniform pitch and mark dimensions across the aperture, creating localized acoustic field distributions that suppress spurious modes while maintaining high power handling capability in the primary resonance region
Solution Approach 2:
The resonator aperture is segmented into multiple regions with different electrode configurations. This segmentation allows independent optimization of power handling in the central region and spurious mode suppression in the peripheral regions, achieving both objectives simultaneously
3Manufacturing precision
If frequency selectivity is improved, then bandwidth performance is enhanced, but device complexity increases
Solution Approach 1:
The patent implements dynamic frequency selectivity through resonators that can be tuned via voltage application. The electric field distribution is dynamically adjusted by applying voltages to specific electrode regions, enabling frequency tuning and enhanced selectivity without requiring multiple fixed-frequency resonators, thus managing complexity
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
The optimized XBARs demonstrate enhanced frequency selectivity, reduced spurious modes, and improved power handling, making them suitable for high-frequency applications like 5G NR, with the ability to tolerate higher RF power inputs and maintain performance across broader bandwidths.
Implementation Method 1
transversely-excited film bulk acoustic resonators (XBARs)
Implementation Method 2
acoustic wave resonators
Data Source
AI summary
Acoustic resonators and filter devices. An acoustic resonator includes a piezoelectric plate having front and back surfaces, a portion of the piezoelectric plate forming a diaphragm, and a conductor pattern on the front surface, the conductor pattern including an interdigital transducer (IDT), fingers of the IDT on the diaphragm. A thickness of the interleaved fingers is greater than or equal to 0.85 times a thickness of the piezoelectric plate and less than or equal to 2.5 times the thickness of the piezoelectric plate. The IDT comprises a first portion having a first pitch and a first mark and a second portion having a second pitch and a second mark not equal to the first pitch and first mark.