• The Journal of the Acoustical Society of Korea
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• v.39 no.2
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• pp.87-97
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• 2020

In this paper, the design of piezoelectric Micro-machined Ultrasonic Transducer (pMUT) for wideband ultrasonic radiation in air was investigated. One of the methods to achieve wide frequency bandwidth in single device is modeling the transducer to multi-resonance system. The new pMUT was designed as a multi-resonance system with the addition of a suitable acoustic structure to the front and back of a thin film structure. A new pMUT consisting of thin film parts, radiation parts, and packaging parts is designed with a Lumped Parameter Model (L.P.M). Finally, it was validated as a Finite Element Method (FEM) simulation. The final designed pMUT achieved a frequency band of 102 kHz ~ 132 kHz (-3 dB).

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.3
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• pp.383-390
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• 2018

Piezoelectric micro-machined ultrasonic transducers for highly directional speaker need DC bias voltage. Most existing power amplifiers are not suitable for use in highly directional transducers because they are based on AC. In addition, since the piezoelectric micro-machined ultrasonic transducer has a large capacitive reactance, the power efficiency of the power amplifier is very low. Thus this paper proposes a new high efficiency power amplifier with DC bias voltage. In addition, by designing a matching circuit to compensate the capacitive reactance of the micro-machined ultrasonic transducer, the power efficiency of the power amplifier increases. The operating characteristics of the proposed power amplifier was verified by an experimental prototype. The proposed power amplifier is expected to be widely used in designing and implementing other related power amplifiers.

• Journal of Sensor Science and Technology
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• v.29 no.1
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• pp.33-39
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• 2020

Typically, photoacoustic images are obtained in water or gelatin because the impedance of these mediums is similar to that of the human body. However, these acoustic mediums can have an additional mass effect that changes the resonance frequency of the transducer. The acoustic radiation impedance in air is negligible because it is very small compared to that of the transducer. However, the high acoustic impedance of mediums such as the human body and water is quite large compared to that of air, making it difficult to ignore. Specifically, in a case where the equivalent mass is very small, such as with a micro-machined ultrasound transducer, the additional mass effects of the acoustic medium should be considered for an accurate resonance frequency design. In this study, a piezoelectric micro-machined ultrasonic transducer (pMUT) was designed to have a resonance frequency of 10 MHz in the acoustic medium of water, which has similar impedance as the human body. At that time, the resonance frequency of the pMUT in air was calculated at 15.2 MHz. When measuring the center displacement of the manufactured pMUT using a laser vibrometer, the resonance frequencies were measured as 14.3-15.1 MHz, which is consistent with the finite element method (FEM) simulation results. Finally, photoacoustic images of human hair samples were successfully obtained using the fabricated pMUT.

• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.149-150
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• 2015

압전 마이크로머신 초음파 트랜스듀서(Piezoelectric micro-machined ultrasonic transducers)는 DC 바이어스 전압을 인가해야 구동되는 특성을 가지고 있다. 따라서 초음파 트랜스 듀서를 구동하기 위한 전력증폭기는 DC 바이어스 전압이 요구되므로 기존의 전력증폭기에 비해 효율이 매우 낮아지게 된다. 이를 해결하기 위해 본 논문에서는 압전 마이크로머신 초음파 트랜스듀서를 구동하기 위한 고효율 전력증폭기를 제안한다. 전력증폭기는 AMP부와 전원부로 나뉘며, AMP부는 Class B Amp를 사용하여 높은 증폭 선형성을 갖는다. 전원부는 Amp를 구동하기위한 DC-DC converter가 에너지 회수 동작을 하므로 전력증폭기의 효율을 높일 수 있다. 본 연구에서는 압전 마이크로머신 초음파 트랜스듀서를 구동하기 위한 전력증폭기 회로를 제시하고 시뮬레이션과 실험을 통해 동작 특성을 검증한다.