XBAR Resonator Package With Suspended Plates for 3 GHz RF Filters
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Solution Overview
Problem
Current RF filters using acoustic wave resonators are not well-suited for higher frequency communications networks, particularly those proposed for 5G cellular service and WiFi frequencies above 3 GHz, due to limitations in bandwidth and frequency range.
Innovation Solution
The development of transversely-excited film bulk acoustic resonators (XBARs) that utilize a thin film conductor pattern on a piezoelectric plate, with a cavity formed in the substrate to suspend the piezoelectric plate, enabling efficient operation at higher frequencies and wider bandwidths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional acoustic wave resonators are used, then device structure is simple, but frequency range and bandwidth are limited below 3 GHz
Solution Approach 1:
The resonator is segmented into multiple functional layers: piezoelectric substrate, thin film conductor pattern, and suspended cavity structure. This segmentation enables higher frequency operation by creating distinct functional zones that optimize acoustic wave propagation at frequencies above 3 GHz
Solution Approach 2:
The invention transitions from planar resonator structures to three-dimensional suspended cavity structures. By creating vertical cavities and suspending the piezoelectric plate, the design adds a vertical dimension that enables higher frequency resonance modes and wider bandwidth operation
2Adaptability or versatility
If RF filters are designed for wider bandwidth, then frequency range improves, but insertion loss and rejection performance deteriorate
Solution Approach 1:
The invention changes key physical parameters including piezoelectric material composition, thin film conductor pattern geometry, and cavity dimensions to optimize the balance between bandwidth and insertion loss. By adjusting these parameters, the resonator achieves wide bandwidth operation while maintaining low insertion loss through enhanced acoustic coupling and reduced energy dissipation
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 achieve improved performance by allowing for wider bandwidth filters capable of operating at frequencies above 3 GHz, addressing the limitations of existing technologies and enabling more efficient communication systems.
Implementation Method 1
a piezoelectric plate, with a conductor pattern formed on a surface of the piezoelectric plate
Data Source
AI summary
A radio frequency filter includes bulk acoustic resonator chips that each include a substrate; a piezoelectric plate that includes multiple separate plates; and a conductor pattern on the piezoelectric layer and including an interdigitated transducer (IDT) with interleaved fingers on the piezoelectric layer opposite the substrate. The filter further includes an interposer having a surface facing the piezoelectric layer of each of the plurality of bulk acoustic resonator chips; a conductor pattern on the surface of the interposer; a conductive metal bump between the piezoelectric layer and the interposer that electrically connects the plurality of bulk acoustic resonator chips to the interposer; and a cover bonded to the substrates of the plurality of bulk acoustic resonator chips and to the interposer, wherein the cover seals an interior of the plurality bulk acoustic resonator chips.