Curved Back Cavity for MUT Acoustic Resonance Control
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Solution Overview
Problem
Traditional packaging designs for micromachined ultrasonic transducers (MUTs) with rectangular back-cavities generate multiple acoustic resonance modes, leading to reduced output pressure and bandwidth due to standing waves, making it challenging to ensure consistent performance across frequencies and temperatures.
Innovation Solution
The use of curved geometries, such as hemispherical or cylindrical shapes, in the back cavity of the transducer package reduces the number and adjusts the frequency of resonant acoustic modes, minimizing interference with the transducer's operating frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a traditional rectangular cavity is used in the transducer package, then the packaging structure is simple and easy to manufacture, but multiple acoustic resonance modes are generated that reduce output pressure and bandwidth
Solution Approach 1:
The patent applies curvature by replacing the traditional rectangular back-cavity with a hemispherical geometry. This curved surface design reduces the number of acoustic resonance modes from multiple (in rectangular) to a single mode, thereby eliminating standing wave interference and improving transducer performance consistency across frequencies and temperatures.
2Device complexity
If a rectangular back-cavity is used, then the package dimensions are easy to define, but standing waves are generated that significantly reduce output pressure and bandwidth
Solution Approach 1:
The hemispherical back-cavity geometry is implemented to eliminate standing wave patterns that occur in rectangular cavities. This curved design reduces acoustic resonance from multiple modes to a single mode, significantly improving output pressure and bandwidth by preventing destructive interference of acoustic waves.
3Volume of stationary object
If traditional packaging dimensions are used, then the package size is compact, but acoustic resonance modes at incorrect frequencies reduce transducer performance
Solution Approach 1:
The hemispherical back-cavity design maintains compact packaging dimensions while fundamentally changing the acoustic resonance characteristics. By curving the cavity surfaces, the design reduces resonance modes from multiple to one, allowing consistent transducer performance across a range of frequencies and temperatures.
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 significantly reduces the number of acoustic resonances and flattens the frequency response, allowing for improved transducer performance by shifting resonant modes outside the operating frequency band, thereby enhancing output pressure and bandwidth consistency.
Implementation Method 1
the design of the back-cavity on the enclosed side of the membrane has a strong effect on transducer performance, particularly the output pressure and bandwidth. Because typical packaging dimensions for MUTs are on the order of a wavelength for transducers operating at ultrasonic frequencies, standing waves are generated in the package back-cavity giving rise to acoustic resonant modes
Implementation Method 2
standing waves are generated in the package back-cavity giving rise to acoustic resonant modes
Data Source
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AI summary
A package design for a micromachined ultrasound transducer (MUT) utilizing curved geometry to control the presence and frequency of acoustic resonant modes is described. The approach consists of reducing in number and curving the reflecting surfaces present in the package cavity to adjust the acoustic resonant frequencies to locations outside the band of interest. The design includes a cavity characterized by a curved geometry and a MUT mounted to a side of a substrate facing the cavity with a sound emitting portion of the MUT facing an opening in the substrate. The substrate is disposed over an opening of the cavity with the substrate oriented such that the MUT located within the cavity.