XBAR Fast-Region Structures for Acoustic Leakage Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current RF filters using acoustic wave resonators are not well-suited for higher frequencies and wider bandwidths required in future communication networks, such as those defined in the 5G NR standard, leading to challenges in achieving optimal performance in terms of insertion loss, rejection, isolation, power handling, linearity, size, and cost.
Innovation Solution
The use of Transversely-Excited Film Bulk Acoustic Resonators (XBARs) with specific structural modifications, including a piston mode design and the incorporation of dummy electrodes, to reduce acoustic energy leakage and improve waveguiding, thereby enhancing the frequency response and reducing spurious modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional acoustic wave resonators are used, then existing technology is available, but they are not well-suited for higher frequencies and wider bandwidths required in future communication networks
Solution Approach 1:
The patent changes the operating parameters by transitioning from conventional SAW/BAW resonators to XBAR resonators that operate in the piston mode at higher frequencies (3-300 GHz range). This parameter change enables the resonators to be well-suited for future communication networks requiring higher frequencies and wider bandwidths while maintaining reliable performance across multiple parameters including insertion loss, rejection, isolation, power handling, and linearity
Solution Approach 2:
The patent employs composite material structures in the XBAR resonator design, combining piezoelectric materials with specific crystal orientations (Z-cut, rotated Y-cut, rotated Z-cut) and metal electrode configurations. This composite approach enables the device to achieve both high frequency operation and wide bandwidth while maintaining reliable performance characteristics
2Speed
If XBAR resonators are used for higher frequencies, then frequency capability is improved, but acoustic energy leakage occurs at the ends of the interdigital transducer fingers
Solution Approach 1:
The patent extracts or removes the source of acoustic energy leakage by eliminating the traditional interdigital transducer finger structure that causes leakage at its ends. Instead, it uses a planar electrode configuration that does not have protruding fingers, thereby removing the leakage problem while maintaining high frequency capability
Solution Approach 2:
The patent introduces an intermediary structure (the specific electrode configuration and piezoelectric material arrangement) that mediates between the electrical input and acoustic wave generation. This intermediary structure enables high frequency operation while preventing acoustic energy leakage by controlling the acoustic wave generation mechanism
3Adaptability or versatility
If wider bandwidths are implemented, then communication channel capacity is improved, but filter design complexity increases to maintain performance parameters
Solution Approach 1:
The patent creates a universal XBAR resonator design that can operate across a wide frequency range (3-300 GHz) and be adapted for different bandwidth requirements. The same basic structure can be configured for various filter types (band-pass, band-reject, low-pass, high-pass) and communication standards (5G NR bands n77, n79, WiFi 5GHz and 6GHz, millimeter wave), reducing design complexity through multi-functionality
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 modified XBARs demonstrate improved frequency selectivity and reduced energy leakage, leading to more effective filtering performance across higher frequency ranges, particularly in the 5G NR bands, with reduced spurious modes and lower loss, thus addressing the limitations of existing technologies.
Implementation Method 1
comprises 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.
Implementation Method 2
A microwave signal applied to the IDT excites a shear primary acoustic wave in the piezoelectric diaphragm. The IDT is positioned on the piezoelectric plate such that at least the fingers of the IDT are disposed on the diaphragm that spans, or is suspended over, a cavity in the substrate.
Implementation Method 3
The IDT is positioned on the piezoelectric plate such that at least the fingers of the IDT are disposed on the diaphragm that spans, or is suspended over, a cavity in the substrate.
Data Source
AI summary
Acoustic resonators, acoustic filter devices and methods of making the same. An acoustic resonator device includes a piezoelectric plate having front and back surfaces, and an interdigital transducer (IDT) on the front surface including interleaved fingers. An overlapping distance of the interleaved fingers defines an aperture of the acoustic resonator device. The device further includes a fast region between the aperture and a busbar of the IDT. The piezoelectric plate and the IDT are configured such that a radio frequency signal applied to the IDT excites a primary shear acoustic mode having a first frequency in the piezoelectric plate within a central portion of the aperture and a primary shear acoustic mode having a second frequency in the fast region. The second frequency is higher than the first frequency.