cMUT Mixed-Bias Grouping for Wider Fractional Bandwidth
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Solution Overview
Problem
Existing MEMS ultrasound devices face challenges in achieving high fractional bandwidth for higher frequency applications due to the constraint of sub-micron membrane thickness, which affects structural reliability and wafer level device scalability, limiting their use in diverse frequency applications.
Innovation Solution
A method involving a mixed-bias strategy is applied to capacitive micromachined ultrasound transducers (cMUTs) by dividing them into groups and applying different DC bias voltages to induce different resonance frequencies, leveraging constructive interference to increase the fractional bandwidth without relying on thinner membranes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If sub-micron membranes are used to increase fractional bandwidth for high frequency applications, then bandwidth is improved, but structural reliability deteriorates and manufacturing cost increases
Solution Approach 1:
The patent divides the cMUT array into multiple groups, where each group is assigned a different DC bias voltage. This segmentation allows each group to operate at a different resonance frequency, collectively covering a wider bandwidth without requiring sub-micron membranes. The groups are spatially separated and controlled independently through separate bias voltage lines.
Solution Approach 2:
The patent changes the DC bias voltage parameter for different groups of cMUTs to shift their resonance frequencies. By applying different bias voltages (e.g., 70V to one group, 80V to another), the resonance frequencies are tuned to different values, enabling bandwidth expansion through parameter variation rather than membrane thickness reduction.
2Adaptability or versatility
If sub-micron membranes are used to increase fractional bandwidth, then bandwidth is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent segments the cMUT array into multiple independently biased groups, allowing standard-thickness membranes to be used while achieving wide bandwidth through electrical control. This avoids the need for complex sub-micron membrane fabrication processes.
Solution Approach 2:
The patent makes a single cMUT array capable of operating across multiple frequency bands by applying different DC bias voltages to different groups. This multi-functionality is achieved through electrical reconfiguration rather than physical membrane modification, simplifying manufacturing.
3Adaptability or versatility
If multiple geometric configurations are used to address different bandwidth targets, then bandwidth adaptability is improved, but device complexity increases
Solution Approach 1:
The patent divides the cMUT array into multiple groups that can be independently controlled through different DC bias voltages. This segmentation allows a single geometric configuration to achieve multiple bandwidth targets by electrical reconfiguration, avoiding the need for multiple physical geometries.
Solution Approach 2:
The patent introduces dynamic control of resonance frequencies through variable DC bias voltages. The system can adapt its frequency response in real-time by changing bias voltages, providing bandwidth adaptability without requiring multiple static geometric configurations.
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 allows a single ultrasound device to be used across a range of frequencies, reducing costs and enhancing workflow efficiency by enabling operation at both lower and higher frequencies without membrane thickness constraints.
Implementation Method 1
causing membranes of the first portion of cMUTs to vibrate at a first resonance frequency defined by the first DC bias voltage; applying the AC drive signal to the second portion of cMUTs to generate a second acoustic signal based on a second combination of the second DC bias voltage and the AC drive signal, the second combination causing membranes of the second portion of cMUTs to vibrate at a second resonance frequency defined by the second DC bias voltage
Implementation Method 2
combining the first acoustic signal and the second acoustic signal to generate a higher-bandwidth signal, the higher-bandwidth signal based on constructive interference between a first transmit transfer function of the first portion of cMUTs and a second transmit transfer function of the second portion of cMUTs
Implementation Method 3
The MEMS device may rely on vibration of a membrane with a first electrode to receive and transmit signals. For some types of MEMS devices used as a transmit transducer and/or a receive transducer, such as a capacitive micromachined ultrasound transducer (cMUT), the cMUT may include a top electrode and a bottom electrode. The top electrode may move upon receiving electrical signals to generate sound waves
Data Source
AI summary
Various methods and systems are provided for increasing a fractional bandwidth of an ultrasound device, for use in both low and high frequency applications. In one example, where a transducer array includes one or more transducer elements comprising a plurality of capacitive micromachined ultrasound transducers (cMUT), the fractional bandwidth may be advantageously increased by applying different bias voltages to different groupings of cMUTs within each transducer element. A ratio between the different bias voltages may be optimized to maximize the fractional bandwidth. In another example, the different bias voltages may be configured to operate a first grouping of cMUTs in a transmit mode, and a second grouping of cMUTs in a receive mode.