BAW Filter Layout Using High-Aspect-Ratio Series Resonators
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Solution Overview
Problem
Existing radio frequency filters face challenges in achieving improved performance factors such as lower insertion loss, increased quality factor, reduced interference, and decreased form factor, particularly in the context of 5G NR frequency bands and carrier aggregation technologies, while maintaining efficient power handling and minimizing spurious acoustic waves.
Innovation Solution
The use of bulk acoustic wave resonators with high aspect ratios, specifically in series arm resonators, is implemented to enhance the quality factor, reduce insertion loss, and improve power handling by strategically positioning electrical connections and incorporating recessed and raised frame regions to suppress transverse acoustic waves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high aspect ratio resonators are used in series arm positions, then quality factor and power handling are improved, but device complexity increases due to non-uniform resonator design
Solution Approach 1:
The patent applies local quality by differentiating resonator aspect ratios based on their circuit position. Series arm resonators use high aspect ratios (e.g., 3:1 or 4:1) to maximize quality factor and power handling, while shunt resonators use lower aspect ratios (e.g., 1:1 or 2:1) for stability. This localized optimization allows each resonator type to be tuned for its specific functional requirements without unnecessarily complicating the entire device.
Solution Approach 2:
The filter design segments resonators into distinct categories based on their circuit function (series arm vs. shunt). This segmentation allows independent optimization of each group's geometric parameters. The series arm resonators are specifically designed with high aspect ratios to handle power and maintain quality factor, while shunt resonators are designed differently for their stabilizing function, resolving the complexity issue through functional segmentation.
2Loss of energy
If high aspect ratio resonators are used, then insertion loss is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent changes the geometric parameters of resonators by implementing high aspect ratios (length-to-width ratios of 3:1 or 4:1) for series arm resonators. This parameter change reduces insertion loss by minimizing edge effects and improving acoustic wave propagation. The standardized high aspect ratio design provides clear manufacturing targets, actually simplifying the precision requirements compared to optimizing each resonator individually.
3Power
If series arm resonators have greater aspect ratio than shunt resonators, then power handling is enhanced, but device area increases
Solution Approach 1:
The patent introduces asymmetry in resonator design by making series arm resonators significantly longer than shunt resonators. The series arm resonators have aspect ratios of 3:1 or 4:1, while shunt resonators maintain aspect ratios of 1:1 or 2:1. This asymmetric design concentrates the power handling function in the series arm positions where long resonators are electrically necessary, while keeping shunt resonators compact for stability, thus optimizing power handling without excessive area increase.
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 high aspect ratio resonators significantly increase the quality factor and reduce insertion loss, enhance power handling, and minimize spurious acoustic wave interference, thereby improving filter performance in multi-frequency band operations.
Implementation Method 1
A radio frequency filter can include a plurality of series arm bulk acoustic wave resonators connected in series
Implementation Method 2
acoustic wave filters can filter radio frequency signals
Data Source
AI summary
Aspects and embodiments disclosed herein include a radio frequency filter comprising a plurality of series arm bulk acoustic wave resonators connected in series between an input and an output of the filter, and a plurality of shunt bulk acoustic wave resonators connected between nodes between adjacent series arm bulk acoustic wave resonators and ground. At least one of the plurality of series arm bulk acoustic wave resonators has a greater aspect ratio than at least one of the plurality of shunt bulk acoustic wave resonators.