Slanted Acoustic Reflectors for SAW Filter 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 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

VSEngineering 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

Engineering Contradiction:

Improveacoustic reflector structure simplicityVSAvoidspurious response

Core Design Contradiction:

Ease of manufactureVSObject-generated harmful factors

Solution Approach 1:

The acoustic reflectors are divided 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.

Inventive Principle:

Principle #1Segmentation

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.

Inventive Principle:

Principle #3Local quality

2Object-generated harmful factors

If acoustic reflectors with stepped lengths are used, then spurious responses are suppressed, but the filter structure becomes more complex

Engineering Contradiction:

Improvespurious responseVSAvoidacoustic reflector structure

Core Design Contradiction:

Object-generated harmful factorsVSDevice complexity

Solution Approach 1:

The reflector is segmented into discrete sections with stepped finger lengths, where each section corresponds to a specific frequency range. This segmentation achieves spurious response suppression through a systematic design that limits complexity to manageable discrete variations rather than continuous complexity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The finger length parameter is changed in discrete steps across different sections of the reflector, creating a stepped structure that suppresses spurious responses. This parameter variation is implemented in a controlled manner that balances effectiveness with structural simplicity.

Inventive Principle:

Principle #35Parameter changes

3Object-generated harmful factors

If acoustic reflectors with slanted pitches are used, then spurious responses are reduced, but manufacturing precision requirements increase

Engineering Contradiction:

Improvespurious responseVSAvoidreflector finger pitch

Core Design Contradiction:

Object-generated harmful factorsVSManufacturing precision

Solution Approach 1:

The reflector pitch is segmented into discrete zones with different pitch values, where each zone is optimized for specific frequency suppression. This segmentation allows manufacturing to focus on achieving precision within each discrete zone rather than requiring continuous precision across the entire reflector, reducing overall manufacturing difficulty.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different pitch values are applied locally to different sections of the reflector, with each local pitch optimized for suppressing spurious responses in its corresponding frequency range. This local optimization approach allows standard manufacturing tolerances to be sufficient for each local section.

Inventive Principle:

Principle #3Local quality

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 effectively suppresses spurious responses due to the shear horizontal mode, improving the filter's performance by reducing insertion loss and maintaining good out-of-band rejection and low loss within the desired frequency range.

Implementation Method 1

acoustic reflectors having stepped lengths and slanted pitches, which are arranged to suppress spurious responses by varying the reflector finger lengths and pitches

Methodology Applied

Scientific EffectAcoustic wave reflection: Reflection

Implementation Method 2

suppress spurious responses due to the shear horizontal mode

Methodology Applied

Scientific EffectShear horizontal mode:

Implementation Method 3

A SAW resonator of a SAW filter typically includes an interdigital transductor electrode on a piezoelectric substrate. A SAW resonator is arranged to generate a surface acoustic wave

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS11545960B2Multi-mode surface acoustic wave filter with slanted acoustic reflectors

Publication Date: 2023.01.03 SKYWORKS SOLUTIONS INC

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 slanted acoustic reflectors on opposing sides of the plurality of interdigital transducer electrodes. The acoustic reflectors include acoustic reflector fingers with slanted pitches.