Elastic Wave Resonator Layout to Suppress Parasitic Tuning Modes
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Solution Overview
Problem
Existing elastic wave resonators have limited adjustable resonance frequency ranges and are prone to parasitic resonances due to increased numbers of interdigitated electrodes, complicating radio communication frequency management.
Innovation Solution
The resonator design incorporates multiple interfacing and tuning transducers with interdigitated electrodes alternating along the propagation path, connected by meticulous electrical tracks on the piezoelectric support to distribute electrode control and minimize parasitic resonances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of fingers in interdigitated electrodes is increased to achieve wider frequency adjustment range, then the adjustable resonance frequency range is improved, but parasitic resonant modes are generated due to increased reflection coefficients
Solution Approach 1:
The resonator is divided into multiple sections, each containing a subset of interdigitated electrode fingers. Instead of using one large electrode structure, the fingers are segmented into groups that can be independently controlled. This segmentation reduces the reflection coefficient of each individual electrode group, thereby suppressing parasitic resonant modes while maintaining the overall frequency adjustment capability through coordinated control of multiple segments.
2Adaptability or versatility
If a single interfacing transducer is used, then the device structure is simple, but the adjustable frequency range is limited and impedance matching is poor
Solution Approach 1:
Multiple interfacing transducers are combined within the resonator structure, each contributing to the overall frequency adjustment capability. These transducers work cooperatively to provide broader frequency coverage and improved impedance matching. The merging of multiple transducer functions enables extended adjustable frequency range while distributing the complexity across multiple manageable components.
3Ease of operation
If interdigitated electrodes are used for frequency tuning, then electrical control of resonance frequency is achieved, but parasitic resonant modes localize due to high reflection coefficients
Solution Approach 1:
Different sections of the resonator are assigned different electrode configurations and control characteristics. Each local section has optimized electrode finger arrangements tailored to its specific function, creating local quality variations that prevent uniform parasitic resonance localization. This allows electrical frequency control to be maintained while distributing resonance modes more evenly across the resonator structure.
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 a wide adjustable resonance frequency range with reduced parasitic modes, maintaining high impedance and electromechanical coupling, suitable for complex radio communication applications.
Implementation Method 1
a piezoelectric support delimited by a surface, or by two surfaces parallel to each other
Implementation Method 2
Two reflectors, reflective for these surface waves and located facing one another, are then made on the surface of the substrate
Implementation Method 3
Two reflectors, reflective for these surface waves and located facing one another, are then made on the surface of the substrate in order to form an elastic surface wave resonator
Implementation Method 4
An electric resonance, associated with an elastic wave resonance in the resonator, is then obtained between these two terminals
Data Source
AI summary
An electromechanical device includes a piezoelectric support delimited by a surface, or by two surfaces parallel to each other, and, on this support, a resonator for elastic waves propagating parallel to the surface or surfaces, the resonator including two reflectors that delimit the resonator and which are reflective for the waves, several interfacing transducers, to generate the waves from an electrical signal, and several transducers for controlling the resonance frequency, each transducer including a first electrode and a second electrode that are interdigitated, the transducers being arranged along the propagation path followed by the waves in the resonator, with, along the path, an alternation between interfacing transducer and tuning transducer.