Electrostatic Capacitance Transducer Harmonic Cancellation
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Solution Overview
Problem
Electrostatic capacitance type transducers face challenges in separating harmonic waves generated during transmission due to variations in device characteristics and electrical components, leading to difficulties in visualization techniques like harmonic imaging, as existing methods require time-consuming and costly adjustments for each transducer and cannot handle characteristic distributions among elements.
Innovation Solution
A drive method for electrostatic capacitance type transducers involves setting a phase difference of approximately 90 degrees between alternating current voltage waveforms applied to different elements, which cancels out second harmonic waves by making their phases nearly opposite, allowing for uniform application across transducers regardless of manufacturing variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a large amplitude voltage is applied to generate high transmission sound pressure, then the output sound pressure increases, but harmonic waves are generated due to distance variation between electrodes
Solution Approach 1:
The patent applies preliminary anti-action by generating a second harmonic wave with opposite phase in advance to cancel the harmonic waves produced during ultrasonic transmission. A second harmonic wave generation unit creates a voltage signal at twice the fundamental frequency with 180-degree phase shift, which is then applied to the transducer to destructively interfere with and cancel the harmonically distorted waves generated by large amplitude vibrations.
Solution Approach 2:
The patent employs parameter changes by dynamically adjusting the phase and amplitude of the second harmonic wave based on the operating conditions. The control unit modifies the phase difference and voltage amplitude of the compensation signal to optimize harmonic cancellation across different transmission power levels and frequency conditions, adapting the cancellation parameters to match the actual harmonic generation characteristics.
2Object-generated harmful factors
If waveform adjustment is performed for each transducer to cancel harmonic waves, then harmonic wave cancellation improves, but time and cost increase due to individual measurement and adjustment
Solution Approach 1:
The patent implements universality by designing a standardized second harmonic wave generation and control system that can be applied across multiple transducers without individual calibration. The control unit generates phase-inverted second harmonic waves using a unified algorithm that works effectively for transducers with similar characteristics, eliminating the need for time-consuming individual measurement and adjustment of each element while maintaining harmonic cancellation performance.
3Power
If the distance between upper and lower electrodes varies with time to produce ultrasonic waves, then acoustic wave transmission improves, but harmonic waves are generated due to nonlinearity
Solution Approach 1:
The patent converts the harmful effect of electrode distance variation into a beneficial cancellation mechanism. The same nonlinearity that generates unwanted harmonic waves during large amplitude vibration is exploited to generate a phase-inverted second harmonic wave that actively cancels the distortion. The control system uses the fundamental frequency components from the electrode vibration to synthesize a compensation signal that transforms the harmful nonlinearity into a useful harmonic cancellation effect.
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 reduces second harmonic waves, enabling high-contrast ultrasonic wave imaging by suppressing harmonic interference, thus providing clear information from both the transmission source and the medium or living body tissue, with minimal impact on the dynamic range of ultrasonic wave imaging.
Implementation Method 1
electrostatic capacitance type transducer including a plurality of elements, each of the plurality of elements including at least one cell, the cell having a first electrode and a second electrode separated from the first electrode
Implementation Method 2
setting a phase difference between the alternating current voltage applied to the first element and the alternating current voltage applied to the second element to be equal to approximately 90 degrees
Data Source
AI summary
A drive method for an electrostatic capacitance type transducer is provided. The electrostatic capacitance type transducer includes a plurality of elements, the element including one or more cells, the cell having a first electrode and a second electrode separated from the first electrode by a gap, the first electrode or the second electrode in the plurality of elements being applied with an alternating current voltage. The plurality of elements includes a first element and a second element. A waveform of an alternating current voltage applied to the first element is set the similar as a waveform of an alternating current voltage applied to the second element. A phase difference between the alternating current voltage applied to the first element and the alternating current voltage applied to the second element is set equal to approximately 90 degrees.