BAW Resonator Frequency Detuning for Steeper Filter Roll-Off
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Solution Overview
Problem
Bulk acoustic wave (BAW) filters face limitations in roll-off behavior, particularly in PCS duplexers, where the steepness of the filter skirt is critical, and existing technologies struggle to optimize roll-off performance independently of other filter parameters like insertion loss and temperature coefficient of frequency (TCF), leading to production yield issues.
Innovation Solution
The proposed solution involves detuning the resonance frequencies of BAW resonators by shifting their individual resonance frequencies, allowing for a minimized roll-off at the filter passband edges, achieved by modifying layer thicknesses in the resonator stacks, which provides additional degrees of freedom for roll-off optimization without affecting resonator performance or requiring additional passive components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If additional passive components are added to optimize roll-off, then the roll-off behavior is improved, but the device complexity increases
Solution Approach 1:
The invention extracts the roll-off optimization function from external passive components and integrates it directly into the BAW resonator structure itself. By modifying the layer thicknesses of the resonators to achieve frequency detuning, the patent eliminates the need for additional passive components while maintaining improved roll-off behavior, thereby reducing device complexity.
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
This approach improves the roll-off behavior of BAW filters, enhancing the duplexer's performance and production yield by achieving a steeper filter skirt, specifically improving the roll-off at both the upper and lower passband edges, while maintaining control over other critical filter parameters.
Implementation Method 1
The present invention relates to the field of bulk acoustic wave filters (Bulk Acoustic Wave=BAW)
Implementation Method 2
a first piezoelectric layer 212, which is arranged between the first and second electrodes 214, 216
Data Source
AI summary
A bulk acoustic wave (BAW) filter device includes at least one first serial BAW resonator, at least one first shunt BAW resonator, at least one second serial BAW resonator or at least one second shunt BAW resonator. The resonance frequencies of the first and the second serial BAW resonators or the resonance frequencies of the first and the second shunt BAW resonators are detuned with respect to each other.