BAW Filter Resonator Layout for Steep Skirts and Power Handling
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Solution Overview
Problem
Existing acoustic wave filters with steep band edges face challenges in maintaining high power handling capabilities near the band edge, which is crucial for efficient radio frequency operations.
Innovation Solution
Incorporating a shunt bulk acoustic wave resonator with a higher resonant frequency and smaller size in parallel with series resonators to create a steep skirt and enhance power ruggedness, while providing temperature compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If acoustic wave filters are designed with steep band edges, then filter selectivity is improved, but power handling capability near the band edge deteriorates
Solution Approach 1:
The filter is segmented into multiple resonators with different functions: series resonators (first, second, third) for creating the steep band edge and a shunt resonator for power handling. Each resonator is designed with specific parameters to optimize its contribution to either selectivity or power handling, allowing the system to achieve both goals simultaneously through functional division
Solution Approach 2:
Different regions of the filter have specialized characteristics: the series resonators are optimized for steepness with specific resonant frequencies and coupling coefficients, while the shunt resonator is optimized for power handling with higher resonant frequency and different quality factor. This local optimization allows each component to excel at its specific function while contributing to overall system performance
2Volume of moving object
If the resonator size is reduced to achieve higher resonant frequency, then filter compactness is improved, but power handling capability deteriorates
Solution Approach 1:
The filter uses multiple resonators with different sizes and frequencies: smaller resonators (second series resonator, shunt resonator) for high frequency operation and compactness, and larger resonators (first series resonator, third series resonator) for power handling. This segmentation allows the system to achieve high resonant frequencies without requiring all resonators to be small, as power handling is distributed to larger resonators
Solution Approach 2:
The resonators are designed with asymmetric parameters: the shunt resonator has higher resonant frequency and smaller size for compactness, while the series resonators have lower resonant frequencies and larger sizes for power handling. This asymmetric design breaks the traditional uniform resonator approach, allowing simultaneous optimization of size and power handling across different resonators
3Measurement precision
If series resonators are used to create steep skirt, then filter selectivity is improved, but frequency response variation with temperature increases
Solution Approach 1:
The shunt resonator acts as an intermediary element that stabilizes the frequency response. It has higher resonant frequency that places it outside the passband, allowing it to provide temperature compensation without interfering with the steep skirt formation. The shunt resonator compensates for temperature-induced frequency shifts in the series resonators, maintaining stable filter characteristics across temperature variations
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 maintains a steep skirt with improved power handling and reduced frequency response variation due to temperature changes, enhancing the performance of acoustic wave filters in radio frequency systems.
Implementation Method 1
In BAW resonators, acoustic waves propagate in a bulk of a piezoelectric layer
Implementation Method 2
acoustic waves propagate in a bulk of a piezoelectric layer
Implementation Method 3
A plurality of acoustic wave resonators and a plurality of shunt acoustic wave resonators can be arranged to form a bandpass filter with a passband
Data Source
AI summary
Aspects of this disclosure relate to an acoustic wave filter with series bulk acoustic wave resonators. In some embodiments, the acoustic wave filter is a band pass filter having a pass band. One of the series bulk acoustic wave resonators can contribute to forming a lower edge of the pass band. That series bulk acoustic wave resonator can be smaller than another series bulk acoustic wave resonator of the acoustic wave filter.