Piezoelectric Ultrasonic Probe Electrode Segmentation for Stray Capacitance Reduction
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Solution Overview
Problem
Existing piezoelectric devices face a reduction in signal voltage due to the influence of stray capacitance in receiving circuits, which affects the accuracy of ultrasonic imaging and diagnostics.
Innovation Solution
A piezoelectric device design featuring a vibrating film with a piezoelectric film, first and second electrodes, and a third electrode, where the third electrode is strategically positioned to maximize strain and reduce stray capacitance, allowing for increased signal voltage detection by optimizing electrode placement and configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the distance between electrodes is increased to generate higher voltage, then the signal voltage increases, but the stray capacitance of the receiving circuit increases causing signal voltage to decrease
Solution Approach 1:
The patent divides the electrode structure into first and second electrodes on the piezoelectric film and a third electrode on the vibrating film. This segmentation allows the piezoelectric film to be strained effectively while positioning the third electrode at the maximum strain location, optimizing voltage generation without excessive capacitance
Solution Approach 2:
The patent positions electrodes in three-dimensional space with specific spacing relationships. The first and second electrodes are disposed at positions away from each other on the piezoelectric film, while the third electrode is positioned away from both on the vibrating film, creating optimal electric field paths that maximize voltage while minimizing stray capacitance effects
2Measurement precision
If the area of electrode opposite surfaces is increased to form larger electrostatic capacitance, then the electrostatic capacitance increases, but the stray capacitance of the receiving circuit increases reducing signal voltage
Solution Approach 1:
The patent creates different functional zones: the third electrode is positioned where strain is maximized on the vibrating film, while the first and second electrodes are positioned on the piezoelectric film to capture the strain-induced charge. This local optimization ensures maximum signal generation without requiring large overall electrode areas that would increase stray capacitance
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 design effectively reduces the impact of stray capacitance, leading to an increased measured signal voltage and improved sensitivity in ultrasonic imaging and diagnostics.
Implementation Method 1
If the vibrating film performs ultrasonic vibration, the piezoelectric film is strained in response to the deformation of the vibrating film. Surface charges are generated according to the strain ε of the piezoelectric film.
Implementation Method 2
The electrostatic capacitance is formed between the end portion of the first electrode and the side portion of the third electrode, and the electrostatic capacitance is formed between the end portion of the second electrode and the side portion of the third electrode. The electrostatic capacitance increases with an increase in the area of the opposite surfaces of each of the first and second electrodes and the third electrode.
Data Source
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AI summary
A piezoelectric device includes: a piezoelectric film (51) having a first surface in contact with a vibrating film (48) and a second surface on the opposite side to the first surface; first (52) and second electrodes (53) that are provided on the second surface of the piezoelectric film (51) and that are disposed at positions away from each other and are short-circuited to each other at a position away from the piezoelectric film (51); and a third electrode (54) that is provided between the first (52) and second electrodes (53) on the second surface of the piezoelectric film (51) and is disposed at a position away from the first (52) and second electrodes (53). At least parts of the contours of end portions of the first (52) and second electrodes (53) are defined in parallel to side portions of the third electrode (54).