Upper-Stopband SAW Resonator Layout for Spurious Mode Suppression
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Solution Overview
Problem
Current surface acoustic wave (SAW) resonators often have resonance frequencies at the lower stopband edge, which limits their miniaturization and efficiency in wireless communication devices, as they require larger chip sizes and are prone to spurious modes that existing design techniques struggle to suppress effectively.
Innovation Solution
The design of a SAW resonator with a resonance frequency located at the upper stopband edge, utilizing a Rayleigh wave as the main propagating wave and optimizing the pitch ratio and slope in the transition region between the interdigital transducer (IDT) and reflectors to suppress longitudinal spurious modes, thereby achieving a smaller device size and improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If SAW resonators are designed with resonance frequency at the lower stopband edge, then the device can be manufactured with conventional design techniques, but the device size is large and spurious modes are difficult to suppress
Solution Approach 1:
The patent inverts the conventional design approach by positioning the resonance frequency at the upper stopband edge instead of the lower stopband edge. This inversion enables the use of pitch reduction techniques that effectively suppress longitudinal spurious modes while achieving device miniaturization, resolving the contradiction between conventional manufacturability and size reduction.
Solution Approach 2:
The patent changes the pitch parameter in the transition region between the IDT and reflectors, using a pitch ratio and slope optimization to suppress longitudinal spurious modes. This parameter change enables smaller device size while maintaining manufacturability through controlled pitch variations in specific regions.
2Ease of manufacture
If SAW resonators are designed with resonance frequency at the lower stopband edge, then conventional design techniques can be used, but spurious modes are prone to occur and are difficult to suppress
Solution Approach 1:
The patent inverts the conventional design approach by positioning the resonance frequency at the upper stopband edge instead of the lower stopband edge. This inversion fundamentally changes the spurious mode behavior, enabling effective suppression through pitch optimization techniques that are not available in conventional lower stopband edge designs.
Solution Approach 2:
The patent applies different pitch characteristics to different regions of the resonator. The transition region between the IDT and reflectors uses a specific pitch ratio and slope to suppress longitudinal spurious modes locally, while other regions maintain appropriate pitch characteristics for overall device operation, achieving reliable spurious mode suppression.
3Reliability
If the pitch of IDT electrode fingers is increased in the transition region, then longitudinal spurious modes are suppressed, but the device complexity increases
Solution Approach 1:
The patent applies pitch optimization specifically to the transition region between the IDT and reflectors, rather than uniformly across the entire device. By localizing the pitch ratio and slope optimization to this specific region, the patent achieves effective spurious mode suppression while minimizing the overall device complexity.
Solution Approach 2:
The patent divides the resonator into distinct regions (IDT region, transition region, reflector region) with different pitch characteristics. This segmentation allows independent optimization of each region, enabling effective spurious mode suppression in the transition region without unnecessarily complicating the overall device design.
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 approach results in a spurious-free, miniaturized SAW resonator with a high electromechanical coupling coefficient and low temperature coefficient of frequency, suitable for various frequency bands, while effectively managing spurious modes, thus enhancing the performance and efficiency of wireless communication devices.
Implementation Method 1
Using a piezoelectric material as a vibrating medium, acoustic resonators operate by transforming an electrical signal wave, that is propagating along an electrical conductor, into an acoustic wave that is propagating via the piezoelectric material.
Implementation Method 2
The acoustic wave propagates at a velocity having a magnitude that is significantly less than that of the propagation velocity of the electromagnetic wave.
Implementation Method 3
a first reflector positioned at the surface of the piezoelectric material, the first reflector comprising first reflector electrode fingers and having a first reflector region; a second reflector positioned at the surface of the piezoelectric material
Implementation Method 4
utilizing a Rayleigh wave as the main propagating wave
Data Source
AI summary
Aspects of the disclosure relate to devices, wireless communication apparatuses, methods, and circuitry implementing a SAW resonator with a resonance frequency located at the upper stopband edge. One aspect is an apparatus including an electrode structure with an interdigital transducer (IDT) having a center IDT region, a first IDT region, and a second IDT region. The center IDT region has a first pitch level, and the center IDT region has a first pitch level, and, reflectors comprising a first reflector region and a second reflector region, the first reflector region and the second reflector region each comprise a third pitch level lower than the first pitch level and the second pitch level.