Multi-Mode SAW Filter Reflector Layout for Shear-Mode Spurious Control
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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 acoustic reflectors having stepped lengths and slanted pitches, which are arranged to suppress spurious responses by varying the reflector finger lengths and pitches, thereby reducing the spurious response without affecting the electrical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If acoustic reflectors with uniform lengths and pitches are used, then the filter structure is simple, but spurious responses due to shear horizontal mode cannot be suppressed
Solution Approach 1:
The acoustic reflectors are segmented into multiple sections along the propagation direction, with each section having different finger lengths. This segmentation allows different portions of the reflector to suppress spurious responses at different frequency ranges, effectively reducing overall spurious responses while maintaining a relatively simple structure.
Solution Approach 2:
Different sections of the acoustic reflector are designed with locally optimized finger lengths and pitches tailored to suppress spurious responses in specific frequency bands. This local quality variation enables targeted suppression of shear horizontal mode spurious responses without affecting the main filter performance.
2Object-generated harmful factors
If acoustic reflectors with stepped lengths are implemented, then spurious responses are suppressed, but the reflector structure becomes more complex
Solution Approach 1:
The reflector is divided into a limited number of discrete sections with stepped finger lengths, rather than continuous variation. This segmentation achieves spurious response suppression while keeping the manufacturing complexity manageable through discrete, standardized length steps.
Solution Approach 2:
The finger length parameter is systematically varied across different sections of the reflector according to a stepped pattern. This parameter change strategy provides effective spurious response suppression while maintaining design simplicity through regular, predictable variations rather than complex irregular patterns.
3Object-generated harmful factors
If acoustic reflectors with modulated pitches are used, then spurious responses are reduced, but manufacturing precision requirements increase
Solution Approach 1:
The pitch modulation is implemented in discrete segments rather than continuous variation, reducing the precision requirements for pitch control while maintaining effectiveness in suppressing spurious responses across different frequency ranges.
Solution Approach 2:
The pitch parameter is modified in distinct steps corresponding to the segmented structure, making the pitch control more manageable for manufacturing while still achieving the desired spurious response suppression through systematic parameter variation.
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 proposed solution effectively suppresses spurious responses due to the shear horizontal mode, improving the filter's performance by reducing insertion loss and maintaining good electrical characteristics.
Implementation Method 1
Multi-mode surface acoustic wave filters face challenges in suppressing spurious responses due to the shear horizontal mode
Implementation Method 2
acoustic reflectors having stepped lengths and slanted pitches, which are arranged to suppress spurious responses by varying the reflector finger lengths and pitches
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.