XBAR Multi-Port Filter With Multi-Thickness Diaphragms for 5G Bands
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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 includes bands like n77, n79, and millimeter wave frequencies, due to limitations in design and manufacturing methods.
Innovation Solution
The development of transversely-excited film bulk acoustic resonators (XBARs) with multiple diaphragm thicknesses and dielectric layer configurations, allowing for frequency separation between shunt and series resonators, enabling the design of high-frequency band-pass filters and multiplexers that can handle increased bandwidths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional acoustic wave resonators are used, then existing filter designs can be maintained, but they cannot achieve the 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 longitudinal to transverse excitation mode, enabling operation at higher frequencies (above 3 GHz) and wider bandwidths suitable for 5G NR bands. This parameter change allows the resonator to achieve the required adaptability for future communication networks while maintaining reliable performance through optimized piezoelectric coupling.
Solution Approach 2:
The patent introduces a new dimension of design by implementing multiple diaphragm thicknesses within a single resonator structure. This dimensional variation enables frequency separation between shunt and series resonators, creating a multi-functional device that can handle multiple frequency bands and wider bandwidths, thereby improving adaptability without sacrificing reliability.
2Adaptability or versatility
If single diaphragm thickness resonators are used, then manufacturing is simpler, but frequency separation between shunt and series resonators cannot be achieved
Solution Approach 1:
The patent applies local quality by creating regions with different diaphragm thicknesses within the same resonator structure. Specific areas have thinned diaphragms while other areas maintain original thickness, allowing frequency separation between shunt and series resonators. This localized variation enables multi-frequency operation while managing device complexity through targeted modifications rather than complete structural redesign.
3Productivity
If existing resonator designs are used, then current manufacturing methods can be maintained, but they are not suited for higher frequencies above 3 GHz
Solution Approach 1:
The patent implements preliminary action by incorporating multiple diaphragm thicknesses and optimized transverse excitation structures during the initial manufacturing process. This upfront design consideration enables the resonator to be manufactured using existing methods while being pre-configured for high-frequency operation above 3 GHz, thereby maintaining manufacturing efficiency while achieving the required adaptability for 5G NR bands.
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 by achieving high piezoelectric coupling and enabling the design of filters with appreciable bandwidth, suitable for frequencies above 3 GHz, addressing the limitations of existing technologies in handling higher frequencies and wider bandwidths.
Implementation Method 1
an interdigital transducer (IDT) configured to convert the radio frequency signal to a transverse acoustic wave in the piezoelectric plate
Implementation Method 2
exciting transverse acoustic waves in the piezoelectric plate
Data Source
AI summary
Filter devices and methods are disclosed. A single-crystal piezoelectric plate is attached to substrate, portions of the piezoelectric plate forming a plurality of diaphragms spanning respective cavities in the substrate. A conductor pattern formed on the piezoelectric plate defines a low band filter including low band shunt resonators and low band series resonators and a high band filter including high band shunt resonators and high band series resonators. Interleaved fingers of interdigital transducers (IDTs) of the low band shunt resonators are disposed on respective diaphragms having a first thickness, interleaved fingers of IDTs of the high band series resonators are disposed on respective diaphragms having a second thickness less than the first thickness, and interleaved fingers of IDTs of the low band series resonators and the high band shunt resonators are disposed on respective diaphragms having thicknesses intermediate the first thickness and the second thickness.