Transverse XBAR Structure With Thick IDT Fingers for 5G Power Handling
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Solution Overview
Problem
Current radio frequency (RF) filters, particularly those using acoustic wave resonators, are not well-suited for higher frequency communications networks such as 5G, which require bandpass filters capable of handling higher transmit power and wider communication channel bandwidths.
Innovation Solution
The development of transversely-excited film bulk acoustic resonators (XBARs) with specific geometries and materials, including piezoelectric plates and interdigital transducers, which enable high power handling and wide bandwidth capabilities by utilizing shear acoustic modes and optimizing IDT finger geometry to minimize losses and maximize heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional acoustic wave resonators are used, then existing filter designs can be maintained, but they cannot handle higher transmit power and wider bandwidths required for 5G frequencies
Solution Approach 1:
The patent changes the excitation mode parameter from longitudinal to transverse, and selects specific piezoelectric material parameters (lithium tantalate with particular crystal orientation) to enable higher power handling capability in XBAR resonators for 5G applications
Solution Approach 2:
The patent employs composite structure combining piezoelectric material (lithium tantalate) with metal interdigital transducer electrodes, where the piezoelectric layer thickness and material properties are optimized to achieve both high power handling and wide bandwidth performance
2Loss of energy
If conventional resonator geometries are used, then manufacturing processes remain simple, but insertion loss increases and bandwidth is limited
Solution Approach 1:
The patent applies local quality optimization by varying the interdigital transducer finger dimensions (width, length, spacing) in specific regions to minimize insertion loss at critical frequency points while maintaining overall device functionality
Solution Approach 2:
The patent transitions from two-dimensional surface acoustic waves to three-dimensional bulk acoustic waves with transverse excitation, enabling better control of energy propagation paths and reduced insertion loss through optimized wave trajectories
3Adaptability or versatility
If existing resonator designs are used, then current filter architectures work, but spurious resonances occur and bandwidth is constrained
Solution Approach 1:
The patent introduces dynamic control of acoustic wave propagation through transverse excitation mechanisms that allow adaptive manipulation of wave paths, enabling suppression of spurious resonances and enhancement of desired frequency responses across wide bandwidths
Solution Approach 2:
The patent uses the piezoelectric material as an intermediary that converts electrical signals to transverse acoustic waves and back, with the material's specific properties filtering out spurious modes while transmitting desired frequency components across wide bandwidths
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 improved performance in RF filters by achieving high power handling and wide bandwidth capabilities, addressing the limitations of existing technologies in 5G frequency ranges while minimizing insertion loss and spurious resonances.
Implementation Method 1
An interdigital transducer (IDT) is formed on the front side of the piezoelectric plate
Implementation Method 2
utilizing shear acoustic modes and optimizing IDT finger geometry to minimize losses and maximize heat dissipation
Implementation Method 3
optimizing IDT finger geometry to minimize losses and maximize heat dissipation
Data Source
AI summary
There is disclosed acoustic resonators and filter devices. An acoustic resonator includes a substrate having a surface and a single-crystal piezoelectric plate having parallel front and back surfaces, the back surface attached to the surface of the substrate except for a portion of the piezoelectric plate forming a diaphragm that spans a cavity in the substrate. An interdigital transducer (IDT) is formed on the front surface of the single-crystal piezoelectric plate such that interleaved fingers of the IDT are disposed on the diaphragm. The IDT is configured to excite a primary acoustic mode in the diaphragm in response to a radio frequency signal applied to the IDT. A thickness of the interleaved fingers of the IDT is greater than or equal to 0.85 times a thickness of the piezoelectric plate.