XBAR Ladder Filter Using LiNbO3 and LiTaO3 for Wideband RF Stability
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Solution Overview
Problem
Existing RF filters using acoustic wave resonators are not well-suited for higher frequency communication bands proposed for future wireless communications networks.
Innovation Solution
The use of transversely-excited film bulk acoustic resonators (XBARs) made from lithium niobate and lithium tantalate, which are integrated into filters to provide improved performance at higher frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional acoustic wave resonators (SAW, BAW, FBAR) are used, then filter performance is adequate for current communication systems, but the filters are not suitable for higher frequency bands (millimeter wave up to 28 GHz)
Solution Approach 1:
The patent changes the material parameters by using lithium niobate and lithium tantalate instead of conventional piezoelectric materials, and modifies the resonator structure to transverse excitation mode. These parameter changes enable the filter to operate at millimeter wave frequencies (up to 28 GHz) while maintaining performance reliability, resolving the contradiction between frequency range adaptability and performance reliability.
2Speed
If wider communication channel bandwidths are implemented, then future communication capabilities are enhanced, but existing resonator technologies cannot support the required higher frequencies
Solution Approach 1:
The patent employs composite material structures combining lithium niobate and lithium tantalate layers with specific piezoelectric properties. This composite approach enables the resonator to achieve both high frequency operation (supporting wider bandwidths) and sufficient adaptability, as the composite structure can be tailored for different frequency requirements while maintaining compatibility with existing filter architectures.
3Productivity
If lithium niobate XBARs are used for wide bandwidth, then bandwidth performance is improved, but temperature coefficient of frequency (TCF) variations increase
Solution Approach 1:
The patent merges lithium niobate XBARs (providing wide bandwidth) with lithium tantalate XBARs (providing low TCF) into a single filter system. The lithium niobate resonators contribute to wide bandwidth performance while the lithium tantalate resonators compensate for temperature coefficient variations, achieving both wide bandwidth and frequency stability simultaneously.
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
These XBARs enable the design of RF filters with wider bandwidths and reduced temperature coefficient of frequency (TCF) variations, enhancing the performance and reliability of filters in future wireless communication systems.
Implementation Method 1
transversely-excited film bulk acoustic resonators (XBARs) made from lithium niobate and lithium tantalate
Implementation Method 2
film bulk acoustic resonators (FBAR), and other types of acoustic resonators
Data Source
AI summary
Acoustic filters are disclosed. A bandpass filter has a passband between a lower band edge and an upper band edge. The bandpass filter includes a plurality of transversely-excited film bulk acoustic resonators (XBARs) connected in a ladder filter circuit. The plurality of XBARs includes at least one lithium tantalate XBAR and at least one lithium niobate XBAR.