XBAR Resonator Orientation for Lower Temperature Frequency Drift
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current RF filters using acoustic wave resonators are not well-suited for higher frequencies and bandwidths required in future communications networks, particularly for 5G mobile networks and millimeter wave communication bands, due to significant temperature frequency dependence.
Innovation Solution
The use of Transversely-Excited Film Bulk Acoustic Resonators (XBARs) with specific piezoelectric material orientations, such as rotated Y-cut lithium niobate or lithium tantalate, to optimize the temperature coefficient of frequency (TCF) and piezoelectric coupling, reducing frequency dependence on temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional acoustic wave resonators (SAW, BAW, FBAR) are used in RF filters, then the filters can operate at current frequency bands, but they exhibit significant temperature frequency dependence that makes them unsuitable for higher frequencies and bandwidths required in 5G and millimeter wave communications
Solution Approach 1:
The patent changes the cut orientation parameter of the piezoelectric substrate from conventional orientations (such as YX-cut or Z-cut) to specifically rotated YX-cut orientations with rotation angles between 30-60 degrees. This parameter change optimizes both the temperature coefficient of frequency (TCF) and the electromechanical coupling coefficient, enabling the resonators to maintain stable operation across higher frequency bands including 5G NR and millimeter wave communications while reducing temperature frequency dependence by 8% to 24%
2Productivity
If higher frequency bands are used to achieve wider bandwidths for future communications networks, then the communication capacity increases, but the temperature frequency dependence of existing resonator technologies becomes more significant
Solution Approach 1:
By optimizing the cut orientation parameters of the piezoelectric substrate, the patent enables resonators to operate stably at higher frequencies required for wider bandwidth communications. The specific rotated YX-cut orientation with 30-60 degree rotation angles provides enhanced temperature compensation characteristics that maintain frequency stability even as operating frequencies increase into 5G NR and millimeter wave bands
Solution Approach 2:
The patent employs composite structure approaches by combining specifically oriented piezoelectric materials with optimized electrode configurations and cavity designs. This composite approach leverages the enhanced piezoelectric coupling of rotated YX-cut materials while incorporating structural elements that further compensate for temperature effects, achieving both high frequency operation and temperature stability
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 results in RF filters with improved temperature stability, achieving 8% to 24% reduction in temperature frequency coefficient, enhancing performance and compatibility with higher frequency bands like 5G NR and millimeter wave communications.
Implementation Method 1
a radio frequency or microwave signal applied to the IDT excites a shear primary acoustic wave in the piezoelectric diaphragm
Implementation Method 2
Transversely-Excited Film Bulk Acoustic Resonators (XBARs)
Data Source
AI summary
Acoustic resonator devices and filters. An acoustic resonator includes a substrate and a lithium niobate plate. A back surface of the lithium niobate plate faces the substrate. A portion of the lithium niobate plate forms a diaphragm that spans a cavity in the substrate. An interdigital transducer (IDT) is on a front surface of the lithium niobate plate such that interleaved fingers of the IDT are on the diaphragm. The IDT and the lithium niobate plate are configured such that a radio frequency signal applied to the IDT excites a shear primary acoustic mode within the diaphragm. Euler angles of the lithium niobate plate are [0°, β, 0°], where β is greater than or equal to 40° and less than or equal to 70°.