Decoupled XBAR Resonator Structure for Wider 5G Filter Bandwidth
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current RF filters using acoustic wave resonators, such as SAW and BAW resonators, are not well-suited for the higher frequencies and wider bandwidths required by future communication networks, particularly for 5G NR standards like band n77 and n79, which demand improved performance in terms of frequency handling and bandwidth.
Innovation Solution
The development of a decoupled transversely-excited film bulk acoustic resonator (XBAR) with a dielectric layer between the IDT fingers and the piezoelectric diaphragm to reduce electromechanical coupling, allowing for tailored frequency response and improved bandwidth capabilities, specifically using rotated Y-cut lithium niobate with a decoupling dielectric layer to adjust the resonance and anti-resonance frequency difference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a dielectric layer is added between the IDT fingers and the piezoelectric diaphragm to reduce electromechanical coupling, then the bandwidth capability and frequency tuning flexibility are improved, but the device complexity and manufacturing steps increase
Solution Approach 1:
A dielectric layer is introduced as an intermediary element between the IDT fingers and the piezoelectric diaphragm. This intermediate layer modifies the electromechanical coupling by controlling the acoustic wave propagation, thereby enabling tailored frequency response and improved bandwidth capabilities without fundamentally changing the resonator structure
Solution Approach 2:
The electromechanical coupling parameter is adjusted by changing the dielectric layer properties (material, thickness, position). By modifying these parameters, the resonance and anti-resonance frequency difference can be controlled to achieve desired bandwidth and frequency tuning characteristics
2Adaptability or versatility
If the difference between resonance and anti-resonance frequencies is reduced to enable wider bandwidth filters, then the bandwidth capability is improved, but the insertion loss performance may deteriorate
Solution Approach 1:
The electromechanical coupling coefficient is adjusted by modifying the dielectric layer configuration, which directly controls the separation between resonance and anti-resonance frequencies. By optimizing this parameter, wider bandwidth can be achieved while managing the trade-off with insertion loss through careful design of the coupling reduction degree
3Reliability
If conventional acoustic wave resonators are used for higher frequency applications, then the existing technology is maintained, but the performance requirements for 5G NR bands cannot be met
Solution Approach 1:
The resonator is designed with modified electromechanical coupling parameters through the dielectric layer, enabling operation at higher frequencies (3.3-5.0 GHz for 5G NR bands) with improved bandwidth handling capability while maintaining reliable filter performance
Solution Approach 2:
The dielectric layer acts as a mediator that enables the resonator to achieve the higher frequency response and wider bandwidth required for 5G NR applications, bridging the gap between conventional resonator design and next-generation communication requirements
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 enables the design of RF filters with wider bandwidths and more flexible frequency tuning, suitable for high-frequency applications like 5G NR band N79, by reducing the difference between resonance and anti-resonance frequencies, thus enhancing the performance of RF filters in communication systems.
Implementation Method 1
a decoupled transversely-excited film bulk acoustic resonator (XBAR) with a dielectric layer between the IDT fingers and the piezoelectric diaphragm to reduce electromechanical coupling
Implementation Method 2
an interdigital transducer (IDT) formed on a thin floating layer, or diaphragm, of a single-crystal piezoelectric material. A microwave signal applied to the IDT excites a shear primary acoustic wave in the piezoelectric diaphragm
Data Source
AI summary
Acoustic resonator devices and filters are disclosed. An acoustic resonator includes a substrate and a piezoelectric plate having front and back surfaces, the back surface attached to the substrate. A decoupling dielectric layer is on the front surface of the piezoelectric plate. An interdigital transducer (IDT) is formed over the decoupling dielectric layer such that interleaved fingers of the IDT are over a portion of the piezoelectric plate suspended across a cavity formed in the substrate. A thickness of the interleaved fingers is greater than or equal to 1.17 times a thickness of the piezoelectric plate and less than or equal to 1.7 times the thickness of the piezoelectric plate.