Surface Acoustic Wave Resonator Layout for Compact Differential Sensing
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Solution Overview
Problem
Existing acoustic wave sensors face challenges in achieving high signal-to-noise ratio and reliable measurement results due to bulky configurations, high spatial demands, production tolerances, and environmental influences affecting RF links, leading to unreliable differential measurements.
Innovation Solution
The acoustic wave sensor device incorporates modified resonance cavities with differing physical and/or chemical treatments, such as metalization or passivation layers, and reflection structures like Bragg mirrors, to enhance propagation characteristics and sensitivity, allowing for a compact design and improved differential sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional acoustic wave sensors are designed with multiple resonators and differential measurement structures, then measurement reliability and signal-to-noise ratio improve, but device size and spatial requirements increase
Solution Approach 1:
The patent combines multiple resonators (first and second resonators with different resonance frequencies) into a single integrated device structure. The resonators share common components including the piezoelectric substrate, interdigitated transducer, and reflection structures, allowing differential measurements to be performed within a compact footprint rather than requiring separate sensor devices.
Solution Approach 2:
The patent utilizes the frequency domain as an additional dimension to differentiate between multiple sensing elements. By operating resonators at different resonance frequencies (first resonance frequency and second resonance frequency), the system can perform differential measurements without requiring spatial separation, effectively using frequency multiplexing to reduce spatial requirements.
2Reliability
If acoustic wave sensors use unmodified resonance cavities, then device complexity is reduced, but signal-to-noise ratio and measurement sensitivity deteriorate
Solution Approach 1:
The patent applies different physical and chemical modifications to different regions of the resonance cavities. Specifically, metalization layers are deposited on certain cavity surfaces while passivation layers are applied to other surfaces. This creates local variations in acoustic wave propagation characteristics, enhancing the sensitivity to specific measurands while maintaining overall device functionality.
Solution Approach 2:
The patent modifies the physical and chemical parameters of the resonance cavity surfaces through metalization and passivation treatments. These parameter changes alter the acoustic wave propagation characteristics, quality factor, and sensitivity of the resonators, thereby improving signal-to-noise ratio without requiring fundamental redesign of the device architecture.
3Ease of manufacture
If resonance cavities are left with exposed surfaces, then manufacturing process is simpler, but environmental influences and interference patterns increase
Solution Approach 1:
The patent applies passivation layers selectively to specific surfaces of the resonance cavities that are most susceptible to environmental influences. This localized protection approach prevents harmful effects such as oxidation, contamination, and moisture absorption while maintaining manufacturing simplicity by not requiring complete encapsulation of the entire device.
Solution Approach 2:
The patent controls the metalization ratio (a/p) of the interdigitated transducer electrodes to optimize acoustic wave generation while managing the potential for interference patterns. By carefully designing the electrode geometry and metalization ratio, the system converts what could be harmful interference into controlled acoustic field distribution that enhances measurement capability.
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 solution provides a compact sensor with enhanced signal-to-noise ratio and reliable measurement sensitivity, achieving sensitivity of over 1 ppm/K for temperature measurements and reduced environmental interference.
Implementation Method 1
Acoustic wave sensors utilize the piezoelectric effect to transduce an electrical signal into a mechanical/acoustic wave
Implementation Method 2
The acoustic wave travels across the surface (or bulk) of a device substrate via the so-called delay line
Implementation Method 3
The surface acoustic wave resonator comprises an electroacoustic interdigitated transducer IDT with interdigitated comb electrodes C and C′ arranged between Bragg mirrors M
Data Source
AI summary
An acoustic wave sensor device comprises a first interdigitated transducer, a first reflection structure, a second reflection structure, a first resonance cavity comprising a first upper surface and formed between the first interdigitated transducer and the first reflection structure, and a second resonance cavity comprising a second upper surface and formed between the first interdigitated transducer and the second reflection structure. At least one of the first and second upper surfaces is covered at least partly by a metalization layer or a passivation layer. The present invention relates also to an acoustic wave sensor assembly.