XBAR Resonator With Half-Lambda Dielectric for Wideband RF Filtering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current RF filters using acoustic wave resonators are not well-suited for higher frequency communications bands, such as those proposed for future wireless networks, due to limitations in design and performance at frequencies above 3 GHz.
Innovation Solution
The implementation of a transversely-excited film bulk acoustic resonator (XBAR) with a 'half-lambda' dielectric layer, which enhances the resonator's stiffness, thermal conductivity, and capacitance per unit area, allowing for improved performance and frequency tuning, particularly by adjusting the thickness of the dielectric layer within specific ranges to reduce spurious modes and achieve necessary frequency offsets between shunt and series resonators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional acoustic wave resonators are used for RF filters, then the filters can operate at lower frequencies, but they cannot achieve optimal performance in higher frequency bands above 3 GHz
Solution Approach 1:
The patent changes the physical parameters of the resonator by adding a dielectric layer, which modifies the acoustic wave propagation characteristics and enables optimal performance in higher frequency bands above 3 GHz
Solution Approach 2:
The patent uses a composite structure combining piezoelectric material with an additional dielectric layer, creating a multi-layer resonator that achieves both high-frequency performance and broad frequency band adaptability
2Object-generated harmful factors
If the dielectric layer thickness is optimized for frequency tuning, then spurious modes are reduced, but the manufacturing precision requirements increase
Solution Approach 1:
The patent optimizes the dielectric layer thickness to a specific value that suppresses spurious modes while establishing clear design guidelines that balance manufacturing feasibility with performance optimization
3Reliability
If the resonator structure is enhanced with additional layers for improved performance, then insertion loss is reduced and isolation is increased, but device complexity increases
Solution Approach 1:
The patent employs a composite multi-layer structure that improves insertion loss and isolation performance through the synergistic interaction between the piezoelectric layer and dielectric layer, while maintaining a relatively simple overall architecture
Solution Approach 2:
The additional dielectric layer serves multiple functions simultaneously: it enhances acoustic wave confinement, provides electrical isolation, and enables frequency tuning, thereby improving performance without proportionally increasing 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 XBAR with a half-lambda dielectric layer demonstrates improved performance by reducing spurious modes, increasing thermal conductivity, and allowing for tuning of resonant frequencies, enabling effective operation in higher frequency bands with reduced frequency variation due to temperature changes, thus addressing the limitations of existing RF filters.
Implementation Method 1
a piezoelectric material such as lithium niobate, lithium tantalate, lanthanum gallium silicate, gallium nitride, or aluminum nitride
Implementation Method 2
enhances the resonator's stiffness, thermal conductivity, and capacitance per unit area
Implementation Method 3
where the thickness of the piezoelectric plate is one-half of a wavelength of the acoustic wave
Data Source
AI summary
Acoustic resonator devices and filters are disclosed. An acoustic resonator includes a substrate having a surface and a single-crystal lithium niobate (LN) plate having front and back surfaces, the back surface attached to the surface of the substrate except for a portion of the LN plate forming a diaphragm that spans a cavity in the substrate. An interdigital transducer (IDT) is formed on the front surface of the LN plate such that interleaved fingers of the IDT are disposed on the diaphragm. A half-lambda dielectric layer is formed on one of the front surface and back surface of the diaphragm. Euler angles of the LN plate are [0°, β, 0°], where 20°≤β≤25°.