SAW Resonator Pitch Modulation for Wide Rejection and High Q
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Solution Overview
Problem
Existing surface acoustic wave (SAW) filters struggle to achieve a wide frequency range rejection with minimal degradation of the quality factor and passband performance.
Innovation Solution
The implementation of a surface acoustic wave resonator with multiple resonant frequencies, featuring an interdigital transducer electrode with a specific pitch and paired with reflectors of varying pitches, compensates for pitch-related degradations and enhances frequency rejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the interdigital transducer electrode uses a larger pitch to achieve wider frequency range, then the frequency rejection improves, but the quality factor degrades
Solution Approach 1:
The reflectors are designed with different pitches than the interdigital transducer electrode, creating local structural variations. Specifically, the reflectors have a first pitch while the IDT electrode has a second pitch (1.05 to 1.2 times the first pitch), allowing each component to optimize its local function: the IDT for broad frequency response and the reflectors for maintaining quality factor through compensated acoustic wave reflection
Solution Approach 2:
The patent changes the pitch parameter between different components of the resonator system. By setting the IDT electrode pitch to be 1.05 to 1.2 times the reflector pitch, the system achieves parameter differentiation that enables both wide frequency range operation and maintained quality factor, resolving the contradiction between these two performance metrics
2Object-affected harmful factors
If multiple resonators are used to meet rejection specifications, then the out-of-band rejection improves, but the device complexity increases
Solution Approach 1:
The surface acoustic wave resonator is designed to perform multiple functions simultaneously: it provides both the primary resonance function and the frequency rejection function through its modulated pitch structure. The reflectors with different pitches enable the single resonator to achieve wide frequency range rejection without requiring additional resonator elements, thus reducing device complexity while maintaining effective rejection 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 configuration achieves improved out-of-band rejection and maintains a high quality factor, allowing for stringent rejection specifications to be met with fewer resonators, thus optimizing filter performance.
Implementation Method 1
The surface acoustic wave resonator can include an interdigital transductor electrode on a piezoelectric substrate. The surface acoustic wave resonator can generate a surface acoustic wave on a surface of the piezoelectric layer on which the interdigital transductor electrode is disposed.
Implementation Method 2
The set of reflectors can include a number of reflectors having a second pitch. The first pitch is greater than the second pitch. The number of reflectors are configured to compensate for degradation of a quality factor of the surface acoustic wave resonator due to having the first pitch greater than the second pitch.
Data Source
AI summary
A surface acoustic wave resonator that has at least a first resonant frequency and a second resonant frequency is disclosed. The surface acoustic wave resonator can include an interdigital transducer electrode over a piezoelectric layer. The interdigital transducer electrode includes fingers having a first pitch. The surface acoustic wave resonator can also include a set of reflectors that is positioned over the piezoelectric layer. The set of reflectors includes a number of reflectors having a second pitch. The first pitch is greater than the second pitch. The number of reflectors is configured so as to compensate for degradation of a quality factor of the surface acoustic wave resonator due to having the first pitch greater than the second pitch.