Faraday-Caged CMUT Array for Electrical Crosstalk Isolation
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Solution Overview
Problem
Existing capacitive micromachined ultrasonic transducer (CMUT) arrays suffer from significant electrical crosstalk and parasitic capacitance, which degrade performance by increasing noise and reducing sensitivity, particularly in medical ultrasound applications.
Innovation Solution
The introduction of an individual Faraday cage with a diamond emitter lightning rod structure for each CMUT array element, allowing the shield to be electrically controlled between grounded and floating states, provides a safe discharge path and reduces parasitic and cross-coupling capacitance, thereby enhancing receive sensitivity and minimizing electrical crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of elements in a CMUT array is increased to improve imaging quality and reduce noise, then image quality improves, but electrical crosstalk between adjacent elements increases
Solution Approach 1:
A ground electrode is introduced as an intermediary element positioned between adjacent CMUT elements. This ground electrode acts as an electrical shield that redirects capacitive coupling paths, preventing direct crosstalk between neighboring elements while maintaining the benefits of having multiple elements for improved imaging quality.
Solution Approach 2:
The patent segments the electrical coupling path by introducing ground electrodes that divide the continuous capacitive field into isolated segments. This segmentation prevents electrical signals from propagating directly between adjacent CMUT elements, thereby reducing crosstalk while preserving the array's imaging capabilities.
2Measurement precision
If pitch between CMUT elements is reduced to improve image quality, then imaging resolution improves, but mechanical stability of the array decreases
Solution Approach 1:
Adjacent CMUT elements are merged into a common capacitive structure that shares a ground electrode. This merging approach allows elements to be positioned closer together (reducing pitch) while the shared ground structure provides mechanical support and electrical stability, preventing the degradation of mechanical stability that would normally occur with reduced spacing.
3Measurement precision
If pitch between CMUT elements is reduced to improve image quality, then imaging resolution improves, but electrical crosstalk increases
Solution Approach 1:
Ground electrodes serve as intermediary shielding elements positioned between closely-spaced CMUT elements. These ground electrodes intercept and redirect capacitive coupling fields, preventing direct electrical interaction between adjacent elements even when the pitch between elements is reduced for improved imaging resolution.
4Measurement precision
If CMUT elements are made smaller to increase array density, then imaging resolution improves, but manufacturing precision requirements increase
Solution Approach 1:
Multiple small CMUT elements are merged into a common capacitive structure with shared ground electrodes. This merging approach allows the array to achieve high imaging resolution through increased element density while the larger common structure and ground electrodes remain within manufacturable size ranges, reducing the precision requirements for fabricating individual small elements.
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 effectively reduces parasitic capacitance by up to 51.4% and electrical crosstalk by 97.72 dB, improving the overall performance and reliability of CMUT arrays by maintaining the Faraday cage in a stable floating state without dielectric breakdown.
Implementation Method 1
electrical crosstalk or capacitive coupling between adjacent elements
Data Source
Figure 1(a)~1(c)
Figure 2~4
Figure 5(a)~5(d)
AI summary
This invention introduces a novel capacitive micromachined ultrasonic transducer (CMUT) array employing an additional electrically-addressable conductive shield that isolates each array element individually, hence the novel array is coined as Faraday Caged CMUT array. The state of this conductive shield corresponding to each array element can be set as floating for reduced parasitic and cross-coupling capacitance or grounded for reduced electrical crosstalk. Perpetual, reliable operation in floating state without the risk of catastrophic dielectric electric field breakdown event is enabled by the self-discharging mechanism through diamond emitters featuring high field emission efficiency and acting as lightning rods in a cavity. The lightning rod structure features a movable diamond membrane, which deflects towards the diamond emitter due to electrostatic force (acting as a charge-controlled capacitive device) closing the gap to facilitate the safe intermittent discharging.