Series XBAR Sub-Resonator Layout for Lower Parasitic Capacitance
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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 the 5G NR standard, which necessitates improved filter designs to handle frequencies above 3 GHz and provide enhanced performance in communication systems.
Innovation Solution
The improved layout of Transversely-Excited Film Bulk Acoustic Resonators (XBARs) with sub-resonators in series, featuring a conductor configuration that minimizes interconnect capacitance to ground, reducing parasitic effects and optimizing filter performance for higher frequency bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional RF filter designs are used, then existing technologies can be maintained, but they are not well-suited for higher frequencies and wider bandwidths required in future communication networks
Solution Approach 1:
The resonator is divided into multiple sub-resonators connected in series, each with optimized dimensions and spacing. This segmentation allows the filter to be designed for higher frequency bands while maintaining controllability over the frequency response and reducing parasitic effects that limit conventional designs.
Solution Approach 2:
Different portions of the resonator structure are given different properties through varying the number, dimensions, and spacing of sub-resonators. This allows optimization of specific frequency responses for different communication bands, enabling the same basic structure to serve multiple frequency ranges effectively.
2Ease of manufacture
If standard conductor configurations are used in XBAR layouts, then manufacturing is simplified, but parasitic effects and spurs increase, degrading filter performance
Solution Approach 1:
The harmful interconnect capacitance to ground is minimized by extracting or removing the problematic conductor connections. The patent uses floating busbars and optimized conductor routing that eliminates direct ground connections, thereby reducing parasitic capacitance and associated spurs while maintaining manufacturing feasibility.
Solution Approach 2:
The design converts the potential harm of conductor interconnects into a benefit by using floating busbars that eliminate ground connections. This approach transforms what would normally be parasitic capacitance sources into a feature that reduces spurs and improves frequency response, while still allowing standard manufacturing processes to be used.
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 configuration enhances the performance of RF filters by reducing spurs and improving frequency response, enabling effective operation in higher frequency bands and wider bandwidths, thus addressing the limitations of existing technologies.
Implementation Method 1
A microwave signal applied to the IDT excites a shear primary acoustic wave in the piezoelectric diaphragm
Implementation Method 2
High performance RF filters for present communication systems commonly incorporate acoustic wave resonators including surface acoustic wave (SAW) resonators, bulk acoustic wave (BAW) resonators
Data Source
AI summary
An acoustic filter device includes a transversely-excited film bulk acoustic resonator (XBAR) including a plurality of sub-resonators, and conductors connecting the plurality of sub-resonators in series between a first node and a second node. At least one of the conductors connects two of the plurality of sub-resonators and has a shape that minimizes an area of the at least one conductor.