BAW Filter Resonator Stack for High-Frequency Power Handling
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Solution Overview
Problem
Existing bulk acoustic wave (BAW) resonators face challenges in achieving high resonant frequencies and handling high power signals, particularly in applications requiring higher frequencies and power handling capabilities.
Innovation Solution
The use of stacked piezoelectric layers with opposite c-axis orientations between electrodes to excite overtone modes, combined with integrated passive devices, enhances resonant frequencies up to 5-20 GHz and improves power handling, suitable for 5G NR applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional BAW resonators are used, then basic filtering function is achieved, but resonant frequency is limited and power handling capability is insufficient
Solution Approach 1:
The resonator is divided into multiple discrete piezoelectric layers (first piezoelectric layer, second piezoelectric layer, third piezoelectric layer) with different c-axis orientations. This segmentation allows each layer to contribute differently to the overall acoustic wave generation, enabling independent optimization of frequency response and power handling characteristics.
Solution Approach 2:
Different regions of the resonator structure are assigned different properties: the first piezoelectric layer has c-axis perpendicular to the substrate (optimized for fundamental mode), while the second and third layers have c-axis at 45 degrees (optimized for overtone mode). This local quality differentiation enables the resonator to achieve both high resonant frequency and improved power handling capability simultaneously.
2Speed
If overtone mode is excited to achieve higher resonant frequencies, then frequency is improved, but device complexity increases
Solution Approach 1:
Multiple piezoelectric layers with different c-axis orientations are merged into a single integrated resonator structure. This combining approach allows the resonator to excite both fundamental mode and overtone mode simultaneously, achieving high resonant frequencies while maintaining a unified device structure rather than requiring separate resonators for different modes.
Solution Approach 2:
The resonator employs a composite structure made of multiple piezoelectric materials with different crystallographic orientations. This composite approach enables the device to exhibit multiple resonant modes (fundamental and overtone) with a single structure, achieving frequency multiplication without proportionally increasing device complexity.
3Device complexity
If fundamental mode is used, then simpler structure is achieved, but resonant frequency is limited to lower values
Solution Approach 1:
The resonator is designed to dynamically operate in multiple modes (fundamental mode and overtone mode) depending on the excitation frequency. The stacked piezoelectric layers with different c-axis orientations enable the structure to transition between modes, allowing the same physical structure to achieve both low-frequency and high-frequency operation without requiring separate resonators.
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
The solution achieves higher resonant frequencies and improved power handling, meeting stringent 5G NR system level linearity specifications and enabling effective filtering of high-frequency signals.
Implementation Method 1
In BAW resonators, acoustic waves propagate in a bulk of a piezoelectric layer
Implementation Method 2
A plurality of acoustic wave filters can be arranged as a multiplexer. For example, two acoustic wave filters can be arranged as a duplexer. Achieving a relatively high resonant frequency for an acoustic wave resonator is desirable for certain applications
Data Source
AI summary
Aspects of this disclosure relate to acoustic wave filters with bulk acoustic wave resonators. An acoustic wave filter can include a first bulk acoustic wave resonator configured to excite an overtone mode as a main mode and a second bulk acoustic wave resonator having a fundamental mode as a main mode.