Tunable Helmholtz Resonator for MUT Frequency Control
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Solution Overview
Problem
Conventional micro-machined ultrasonic transducers (MUTs) face challenges in maintaining consistent resonance frequencies, especially when multiple transducers are used cooperatively, due to process tolerances that result in variations in membrane element properties, leading to increased production costs with existing laser trimming techniques.
Innovation Solution
A micro-machined ultrasonic transducer design incorporating a cap structure that acts as a tunable Helmholtz resonator, allowing the resonance frequency to be adjusted by varying the volume of a cavity above the membrane element through a biasing electric signal, enabling precise tuning of the resonance frequency without the need for costly laser trimming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If laser trimming techniques are used to adjust resonance frequency, then manufacturing precision is improved, but production cost increases significantly
Solution Approach 1:
The patent applies parameter changes by modifying the physical dimensions of the membrane element (area, thickness) and cavity volume through standard micromachining processes. By varying these geometric parameters during fabrication, the resonance frequency can be adjusted without requiring post-manufacturing laser trimming, thus achieving frequency precision while maintaining low production costs.
Solution Approach 2:
The patent implements preliminary action by pre-configuring the membrane element and cavity dimensions during the manufacturing process to achieve the desired resonance frequency. This upfront design approach eliminates the need for subsequent laser trimming operations, resolving the contradiction between precision and manufacturing ease.
2Reliability
If process tolerances are reduced to ensure uniform resonance frequency, then reliability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent uses parameter changes to compensate for process tolerances. By designing the membrane area, thickness, and cavity volume with appropriate margins and relationships, the system achieves uniform resonance frequency across multiple transducers without requiring extremely tight manufacturing tolerances or complex additional processes.
Solution Approach 2:
The patent applies universality by using the same micromachining processes for both structural fabrication and resonance frequency tuning. The cavity structure serves both as a mechanical support and as a resonant element whose volume directly controls frequency, eliminating the need for separate tuning mechanisms and reducing overall device complexity.
3Measurement precision
If membrane element properties are tightly controlled, then measurement precision is improved, but ease of manufacture deteriorates
Solution Approach 1:
The patent applies parameter changes by controlling the relationship between membrane area, thickness, and cavity volume rather than strictly controlling each parameter independently. This approach allows for broader manufacturing tolerances on individual parameters while maintaining consistent resonance frequency, thereby improving ease of manufacture without sacrificing measurement precision.
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 solution effectively adjusts the resonance frequency of the transducer, compensating for process tolerances and ensuring uniformity across multiple transducers, thereby reducing production costs and improving cooperative operation without the use of expensive finishing techniques.
Implementation Method 1
the cap structure and the membrane element, by acting as a Helmholtz resonator, allow adjusting the resonance frequency at which the membrane element oscillates
Implementation Method 2
the membrane element oscillates (or vibrates) about an equilibrium position thereof in response to the application of an electric signal in alternating current (AC), thereby generating ultrasonic waves
Implementation Method 3
the membrane element oscillates (or vibrates) about its equilibrium position as a consequence of an ultrasonic wave incident thereon, corresponding electric signals (for example, current and/or voltage electric signals) are generated
Data Source
AI summary
A micro-machined ultrasonic transducer is proposed. The micro-machined ultrasonic transducer includes a membrane element for transmitting/receiving ultrasonic waves, during the transmission/reception of ultrasonic waves the membrane element oscillating, about an equilibrium position, at a respective resonance frequency. The equilibrium position of the membrane element is variable according to a biasing electric signal applied to the membrane element. The micro-machined ultrasonic transducer further comprises a cap structure extending above the membrane element; the cap structure identifies, between it and the membrane element, a cavity whose volume is variable according to the equilibrium position of the membrane element. The cap structure comprises an opening for inputting/outputting the ultrasonic waves into/from the cavity. The cap structure and the membrane element act as tunable Helmholtz resonator, whereby the resonance frequency is variable according to the volume of the cavity.