Stepped SAW Reflectors for Shear Horizontal Spurious Suppression
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Solution Overview
Problem
Multi-mode surface acoustic wave filters face challenges in suppressing spurious responses due to the shear horizontal mode, which can lead to insertion loss degradation, and existing designs struggle to achieve this without degrading electrical performance.
Innovation Solution
The implementation of multi-mode surface acoustic wave filters with stepped acoustic reflector finger lengths and slanted pitches, where the acoustic reflectors on opposing sides have different spacings and pitches, effectively suppresses the spurious response due to the shear horizontal mode without compromising electrical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If acoustic reflectors with uniform pitch are used, then the filter structure is simple, but spurious responses due to shear horizontal mode cannot be suppressed
Solution Approach 1:
The patent applies asymmetry by configuring acoustic reflectors with non-uniform pitch distributions, where different regions of the reflector have different spacing between fingers. This asymmetric pitch configuration disrupts the symmetry of shear horizontal mode propagation, effectively suppressing spurious responses while maintaining filter functionality
Solution Approach 2:
The acoustic reflectors are segmented into multiple sections with different pitch values. Each segment has a specific pitch range that targets different spatial frequencies of the acoustic wave, allowing selective suppression of spurious modes while maintaining the main filter response
2Object-generated harmful factors
If stepped acoustic reflector finger lengths are implemented, then spurious response is suppressed, but manufacturing complexity increases
Solution Approach 1:
The reflector fingers are divided into multiple groups with different lengths, where each group corresponds to a specific pitch section. This segmentation allows standardized manufacturing processes to be applied to each group independently, reducing overall manufacturing complexity despite the varied finger lengths
Solution Approach 2:
Different regions of the reflector have locally optimized finger lengths tailored to their specific pitch requirements. The local quality of each finger group is optimized for its function, with longer fingers in regions requiring stronger reflection and shorter fingers in regions targeting different spatial frequencies
3Object-generated harmful factors
If acoustic reflectors with different pitches on opposing sides are used, then shear horizontal mode suppression is improved, but device complexity increases
Solution Approach 1:
The patent deliberately introduces asymmetry between opposing reflectors by configuring them with different pitch distributions. This asymmetric configuration creates unequal path lengths for shear horizontal mode waves traveling in opposite directions, effectively suppressing spurious responses that would otherwise propagate symmetrically
Solution Approach 2:
The pitch parameters of the acoustic reflectors are varied between opposing sides to optimize spurious response suppression. By changing the pitch distribution parameters of each reflector group, the system achieves better control over shear horizontal mode propagation while maintaining overall filter performance
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 design significantly reduces spurious responses while maintaining low loss and good out-of-band rejection, enhancing the overall performance of the multi-mode surface acoustic wave filters.
Implementation Method 1
surface acoustic wave (SAW) filters
Implementation Method 2
acoustic reflectors on opposing sides of the plurality of interdigital transducer electrodes
Data Source
AI summary
Multi-mode surface acoustic wave filters are disclosed. A multi-mode surface acoustic wave filter can include a plurality of interdigital transducer electrodes that are longitudinally coupled to each other and stepped acoustic reflectors on opposing sides of the plurality of interdigital transducer electrodes. The acoustic reflectors include acoustic reflector fingers with stepped lengths.