Ladder Acoustic Wave Filter Using Split Piezoelectric Substrates
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Solution Overview
Problem
Existing acoustic wave filter devices face challenges in achieving a wide pass band while maintaining desired filter characteristics due to the sharing of piezoelectric substrates by series and parallel arm resonators, which complicates the suppression of filter degradation.
Innovation Solution
The filter device incorporates series and parallel arm resonators with separate piezoelectric substrates, allowing for independent adjustment of electrode pitches and frequencies, thereby enhancing the pass bandwidth and preventing degradation of filter characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If series arm resonators and parallel arm resonators share a piezoelectric substrate, then device complexity is reduced, but filter characteristics degradation occurs
Solution Approach 1:
The piezoelectric substrate is divided into multiple separate substrates, with each acoustic wave resonator (series arm and parallel arm) using its own dedicated piezoelectric substrate. This segmentation prevents mutual interference between resonators while maintaining individual optimization of each resonator's filter characteristics, thereby resolving the contradiction between device complexity and filter characteristics reliability.
2Length of moving object
If a wide pass band is achieved through inductor coupling, then bandwidth is expanded, but filter characteristics stability deteriorates
Solution Approach 1:
By separating each acoustic wave resonator onto its own piezoelectric substrate, the design enables independent optimization of each resonator's electrode pitch and frequency characteristics. This segmentation allows the ladder filter to achieve wide pass bandwidth through inductor coupling while maintaining stable filter characteristics, as each resonator can be precisely controlled without interference from others.
Solution Approach 2:
Each piezoelectric substrate is optimized with local quality variations, allowing different electrode pitches and resonant frequencies for series and parallel arm resonators. This local optimization enables the overall filter to achieve wide bandwidth while maintaining characteristic stability through precise local control of each resonator's properties.
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 configuration enables a wide pass band with improved filter characteristics by allowing individual adjustment of electrode pitches, reducing variations and maintaining stability across individual products.
Implementation Method 1
The series arm resonator includes a first piezoelectric substrate. The parallel arm resonator includes a second piezoelectric substrate different from the first piezoelectric substrate.
Data Source
AI summary
A filter device includes a filter substrate and a ladder filter at the filter substrate. The ladder filter includes at least one inductor and acoustic wave resonators including a series arm resonator and a parallel arm resonator. The at least one inductor is coupled to the acoustic wave resonators. A pass bandwidth of the ladder filter is larger than a resonance bandwidth of at least one of the acoustic wave resonators. The series arm resonator includes a first piezoelectric substrate. The parallel arm resonator includes a second piezoelectric substrate that is different from the first piezoelectric substrate.