XBAR Acoustic Filter Pitch Layout for Resonator Frequency Separation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current RF filters using acoustic wave resonators are not well-suited for higher frequency communications bands, such as those proposed for future wireless networks, which require improved performance and frequency separation capabilities.
Innovation Solution
The development of transversely-excited film bulk acoustic resonators (XBARs) with a uniform-thickness dielectric overlayer, which utilize a piezoelectric plate and interdigital transducers to achieve high-frequency separation and efficient acoustic energy propagation, enabling the design of filters suitable for frequencies above 3 GHz.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional acoustic wave resonators are used for RF filters, then the filters can operate at lower frequencies, but they cannot achieve the required performance and frequency separation for higher frequency communications bands
Solution Approach 1:
The patent changes the operating parameters of the resonator by using transversely-excited film bulk acoustic resonators (XBARs) with specific pitch dimensions and uniform-thickness dielectric overlayers, enabling the filter to achieve the required frequency separation and performance for higher frequency bands (above 3 GHz) while maintaining reliability
Solution Approach 2:
The patent employs composite material structures including piezoelectric plates with uniform-thickness dielectric overlayers and specifically engineered pitch configurations, creating a composite resonator system that simultaneously achieves high-frequency operation and improved frequency separation capability
2Reliability
If the pitch between resonators is increased to achieve frequency separation, then frequency separation improves, but the device size increases
Solution Approach 1:
The patent optimizes the pitch parameter to a specific optimized value that simultaneously achieves the required frequency separation and minimizes the overall filter size, rather than simply increasing pitch to its maximum value
Solution Approach 2:
The patent applies uniform-thickness dielectric overlayers with specifically engineered local properties at critical locations within the resonator structure, enabling enhanced frequency separation without requiring increased overall device dimensions
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 enhanced performance and frequency separation, enabling the creation of high-frequency filters with improved bandwidth, reduced spurious modes, and increased piezoelectric coupling, suitable for millimeter-wave communications.
Implementation Method 1
transversely-excited film bulk acoustic resonators (XBARs) with a uniform-thickness dielectric overlayer, which utilize a piezoelectric plate and interdigital transducers
Implementation Method 2
efficient acoustic energy propagation
Implementation Method 3
achieve high-frequency separation and efficient acoustic energy propagation
Data Source
AI summary
Acoustic filters are disclosed. An acoustic filter device includes a substrate having a surface and a single-crystal piezoelectric plate having front and back surfaces and a thickness ts, the back surface attached to the surface of the substrate except for portions of the piezoelectric plate forming a plurality of diaphragms that span respective cavities in the substrate. A conductor pattern is formed on the front surface of the piezoelectric plate, the conductor pattern comprising a plurality of interdigital transducers (IDTs) of a plurality of acoustic resonators, interleaved fingers of each IDT of the plurality of IDTs disposed on a respective diaphragm of the plurality of diaphragms. The interleaved fingers of all of the plurality of IDTs are substantially aluminum with a common thickness tm, where 0.12 ts≤tm≤0.32 ts.