PMAUT Resonator Damping for Long-Range High-Resolution Imaging
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Solution Overview
Problem
Microelectromechanical systems (MEMS) resonators, particularly piezoelectric microelectromechanical acoustic and ultrasonic transducers (MAUTs), face challenges in achieving high-resolution and long-range imaging due to limitations in resonant frequency reproducibility and quality factor, which affects their performance in applications like distance sensing and medical imaging.
Innovation Solution
The integration of electromechanical actuators within the design of MAUTs allows for selective control of the quality factor, and a conformal layer deposition method is used to tune the resonant frequency of MEMS resonators, addressing issues of process variations and improving inter-chip reproducibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high-Q transducers are used to provide higher acoustic power output, then imaging range is improved, but pixel depth resolution deteriorates due to increased pulse duration from ringing
Solution Approach 1:
The patent applies dynamic quality factor control by enabling the transducer to operate with high Q-factor during transmission to maximize acoustic power output, then rapidly switching to low Q-factor mode after transmission to quickly dampen residual vibrations. This temporal dynamic adjustment allows the system to achieve both high imaging range (during transmission) and high pixel depth resolution (during reception), resolving the fundamental trade-off between these two parameters.
2Measurement precision
If low-Q transducers are used to minimize ringing and reduce pulse duration, then pixel depth resolution is improved, but imaging range deteriorates due to reduced acoustic power output
Solution Approach 1:
The patent implements dynamic Q-factor control that switches the transducer between high-Q and low-Q states based on operational phase. During the transmission phase, the transducer operates in high-Q mode to maximize acoustic power output and extend imaging range. Immediately after transmission, it switches to low-Q mode to rapidly dampen residual vibrations and minimize pulse duration, thereby achieving high pixel depth resolution. This temporal separation of Q-factor requirements resolves the contradiction between power output and resolution.
3Manufacturing precision
If conformal layer deposition is used to tune resonant frequency, then inter-chip reproducibility is improved, but device complexity increases
Solution Approach 1:
The patent employs conformal layer deposition to precisely adjust the resonant frequency of each transducer element. By controlling the thickness and material properties of the deposited conformal layer, the resonant frequency can be tuned to a target value, compensating for variations introduced during fabrication. This parameter adjustment approach significantly improves inter-chip reproducibility while adding minimal complexity to the overall fabrication process, as it builds upon existing semiconductor manufacturing capabilities.
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 enables the use of high-Q transducers for long-range and high-resolution imaging while reducing pulse duration, maintaining acoustic power transmission efficiency, and achieving precise frequency tuning across multiple resonators.
Implementation Method 1
a piezoelectric actuator is provided. The piezoelectric actuator is configured to generate a mechanical force in response to an applied voltage
Implementation Method 2
a MEMS resonator for generating an acoustic signal... the MEMS resonator has a first resonance frequency of a predetermined mode of the MEMS resonator
Data Source
AI summary
Micro-machined acoustic and ultrasonic transducer (MAUT), particularly piezoelectric MAUT (PMAUT), performance tradeoffs have meant reasonable pixel depth resolution necessitated low quality factor (Q) transducers with power distributed over a large bandwidth yielding modest imaging ranges whilst high-Q transducers providing higher acoustic power output for longer imaging ranges exhibit extended ringing limiting pixel depth information. Accordingly, the inventors have established MAUTs supporting high-Q transducers for long-range high-resolution imaging by integrating electromechanical actuators (dampers) which can be selectively engaged to mechanically damped the MAUT. In several applications PMAUT arrays are required where all transducer elements should have almost identical resonant frequencies. However, prior art fabrication processes have tended to produce PMAUTs with large inter-chip and inter-wafer variances. Prior art methodologies to reduce inter-wafer process variations do not address intra-wafer or inter-chip process variations and accordingly the inventors have established manufacturing methodologies and design solutions to address these for the PMAUT resonant frequency.