Cascaded XBAR Series Resonators With Shared Acoustic Tracks
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Solution Overview
Problem
Existing RF filters using acoustic wave resonators are not well-suited for higher frequencies and wider bandwidths required for future communications networks, such as the 5G NR standard's bands n77 and n79, and WiFi bands at 5 GHz and 6 GHz.
Innovation Solution
The use of Transversely-Excited Film Bulk Acoustic Resonators (XBARs) with shared acoustic tracks in band-pass filters, which allows for a smaller footprint, reduced manufacturing costs, and improved performance at higher frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional acoustic wave resonators are used in RF filters, then the filters can operate at standard frequencies, but they cannot effectively handle higher frequencies and wider bandwidths required for future communication networks
Solution Approach 1:
The patent changes the fundamental operating parameters of the resonator by transitioning from surface acoustic wave propagation to bulk acoustic wave resonance. This parameter change enables the resonator to operate effectively at higher frequencies (including millimeter wave bands) and wider bandwidths, directly addressing the frequency range capability limitation of traditional SAW resonators while maintaining reliability through the superior acoustic confinement of bulk wave modes
2Manufacturing precision
If multiple separate acoustic tracks are used for each resonator, then each resonator can be independently optimized, but the filter footprint and manufacturing complexity increase
Solution Approach 1:
The patent merges multiple acoustic tracks into a single shared acoustic track that serves multiple resonators. This is achieved by having multiple resonators couple to the same acoustic wave path, allowing them to share the same physical infrastructure. The result is a significant reduction in filter footprint while maintaining the ability to independently optimize each resonator's electrical and mechanical parameters through their respective IDT designs and coupling mechanisms
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 with shared acoustic tracks enable the development of high-performance RF filters that can handle the higher frequencies and wider bandwidths needed for future communication systems, while also reducing the size and cost of the filters.
Implementation Method 1
The IDT includes a first set of parallel fingers, extending from a first busbar and a second set of parallel fingers extending from a second busbar. The first and second sets of parallel fingers are interleaved. 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, film bulk acoustic wave resonators (FBAR), and other types of acoustic resonators.
Data Source
AI summary
An acoustic filter device includes first and second series resonators and at least one shunt resonator, each shunt resonator electrically coupled to the first series resonator or the second series resonator. Each of the first and second series resonators includes respective first and second sub-resonators electrically connected in series, The first sub-resonators of the first and second series resonators are acoustically coupled along a first shared acoustic track. The second sub-resonators of the first and second series resonators are acoustically coupled along a second shared acoustic track.