XBAR Resonator Front-Side Dielectric Layout for Spurious Mode Suppression
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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 includes bands like n77 and n79, and WiFi frequencies, due to limitations in power handling and spurious mode suppression.
Innovation Solution
The development of transversely-excited film bulk acoustic resonators (XBARs) with optimized electrode thickness, pitch, and dielectric layer thickness, along with interdigital transducers with varied mark and pitch, and the use of piezoelectric materials like lithium niobate, to enhance frequency capability, power handling, and reduce spurious modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional acoustic wave resonators are used, then existing filter designs can be maintained, but power handling capability and frequency capability for 5G NR bands are insufficient
Solution Approach 1:
The patent changes the fundamental operating parameters of the resonator by transitioning to transverse excitation mode and using varied mark and pitch IDT designs, enabling the resonator to operate effectively at higher frequencies (5G NR bands) and power levels required for modern communication standards
Solution Approach 2:
The patent employs composite structures including piezoelectric materials with specific crystal orientations, metal electrodes with optimized thicknesses, and dielectric layers with tailored properties to achieve the required power handling and frequency performance for 5G applications
2Ease of manufacture
If uniform mark and pitch IDT design is used, then manufacturing is simplified, but spurious modes are not sufficiently suppressed
Solution Approach 1:
The patent applies local quality by implementing varied mark and pitch patterns in specific regions of the IDT structure, creating localized variations that suppress spurious modes while maintaining overall manufacturing feasibility through systematic design approaches
Solution Approach 2:
The patent introduces asymmetry in the IDT design through non-uniform mark and pitch configurations, which disrupts the symmetry that typically generates spurious modes, thereby reducing harmful oscillations while maintaining a structured fabrication process
3Reliability
If optimized electrode thickness and dielectric layer thickness are implemented, then electromechanical coupling is enhanced, but manufacturing precision requirements increase
Solution Approach 1:
The patent optimizes specific parameter ranges for electrode thickness and dielectric layer thickness to achieve enhanced electromechanical coupling, balancing performance improvement with manufacturability by identifying practical thickness ranges that deliver high coupling without excessive precision requirements
4Adaptability or versatility
If wider bandwidth filters are designed, then 5G NR band coverage is improved, but spurious modes and power handling challenges increase
Solution Approach 1:
The patent utilizes varied mark and pitch IDT designs to broaden the operational bandwidth of the resonator, enabling coverage of 5G NR bands while the transverse excitation mode and optimized structure suppress spurious modes that would otherwise be amplified in wider bandwidth designs
Solution Approach 2:
The patent employs composite material structures with carefully selected piezoelectric, metallic, and dielectric layers to achieve wide bandwidth operation with controlled spurious mode generation, allowing simultaneous improvement in bandwidth coverage and spurious mode suppression
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 provide high electromechanical coupling and improved frequency selectivity, enabling the design of filters that can handle higher power levels and wider bandwidths while minimizing spurious modes, thus meeting the requirements of advanced communication standards.
Implementation Method 1
transversely-excited film bulk acoustic resonators (XBARs) with optimized electrode thickness, pitch, and dielectric layer thickness, along with interdigital transducers with varied mark and pitch, and the use of piezoelectric materials like lithium niobate
Implementation Method 2
transversely-excited film bulk acoustic resonators (XBARs) provide high electromechanical coupling and improved frequency selectivity
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, a conductor pattern on the front surface, the conductor pattern including an interdigital transducer (IDT), fingers of the IDT on the diaphragm, and a front-side dielectric layer on the front surface of the piezoelectric plate between the interleaved fingers. A resonant frequency is determined, in part, by a thickness of the front-side dielectric layer. A ratio of a mark of the interleaved fingers to a pitch of the interleaved fingers is greater than or equal to 0.12 and less than or equal to 0.3.