• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.1
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• pp.137-146
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• 2019

The ultrasonic phased arrays are used for treating tumors in the human body by the focus control of the acoustic pressure at the desired position. The magnitude and phase of the surface acoustic pressure in each ultrasonic transducer is controlled by the magnitude and phase of the applied voltage to it. In this paper, the relationship between the applied voltage and the surface acoustic pressure of the ultrasound transducer is modelled, and the desired voltage is realized by PWM technique. The validity of the proposed method is verified by computer simulation of the focus control of a ultrasonic phased array composed of 61 ultrasonic transducers.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.353-356
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• 2002

심근 경색 및 뇌졸중 등 혈관과 관련된 질환들의 진단 및 치료의 목적으로 미세 크기의 원형 배열 초음파 트랜스듀서가 사용되고 있다. 원형 배열 초음파 트랜스듀서는 종래의 선형 배열 트랜스듀서에 비해 반경 방향의 입체적 진단을 가능케 하고 높은 감도 및 해상도를 구현할 수 있는 장점을 가진다. 본 연구에서는 이러한 원형 배열 초음파 트랜스듀서의 개발을 위하여, 유한요소법 및 이론적인 해석으로 트랜스 eb서의 방사특성을 분석함으로써 무지향성을 이루기 위한 트랜스듀서 내 진동자의 최적 규격을 설정하였다. 나아가 해석 결과에 따라 직경이 약 10mm정도가 되는 알루미나 $Al_2O_3$ 튜브에 32개의 진동자가 원형으로 배열된 트랜스 듀서 시작품의 제작 및 방사특성 측정 실험을 수행함으로써 설계 결과의 타당성을 검증하였다.

• The Journal of the Acoustical Society of Korea
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• v.35 no.6
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• pp.466-472
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• 2016

In this work, a medical linear array ultrasonic transducer working in the range of 20 MHz has been developed for high-resolution ultrasonic imaging. After devising the structure of the transducer suitable for the transmission of high-frequency waves, we optimized the dimension of constituent components. Then, the process to fabricate the transducer was developed to realize the designed structure, and a prototype of the transducer was fabricated and characterized. The center frequency of the fabricated transducer was measured to be 19 MHz, and the fractional bandwidth to be 84.5 %, and the standard deviation of the sensitivity over the entire channels to be 0.74 dB. These measurement results showed good agreement with design data, which confirmed the validity of the high frequency ultrasonic transducer structure developed in this work. It was confirmed that the developed transducer with new structure had wider frequency bandwidth and uniform sensitivity than a conventional 20 MHz transducer.

• The Journal of the Acoustical Society of Korea
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• v.22 no.8
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• pp.629-636
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• 2003

It will be very convenient if the directivity characteristics of ultrasonic transducer array are controllable by the purpose of use in the fields of sonar system or ultrasonic diagnostic system, In this paper, a control method of the directivity characteristics was suggested. The transducer array was consisted of two-layered piezoelectric vibrators. Efficiency of each vibrator is controlled in 2nd harmonic mode by electrical capacitance. Therefore, the beam width of the transducer array can be controlled by changing the capacitance. The directivity characteristics of the array were analyzed experimentally and theoretically. As the results, it is confirmed that -3 dB beam width of main lobe can be controlled in the range of 7.6°∼16.2°.

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.1
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• pp.27-34
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• 2016

The type of ultrasound transducer used influences the quality of a reconstructed ultrasound image. This study analyzed the effect of transducer type on ultrasound computed tomography (UCT) image quality. The UCT was modeled in an ultrasound simulator by using a 5 cm anatomy model and a ring-shape 5 MHz 128 transducer array, which considered attenuation, refraction, and reflection. Speed-of-sound images were reconstructed by the Radon transform as the UCT image modality. Acoustic impedance images were also reconstructed by the delay-and-sum (DAS) method, which considered the speed of sound information. To determine the optimal combination of transducers in observation, point-source, flat, and focused transducers were tested in combination as trasmitters and receivers; UCT images were constructed from each combination. The combination of point-source/flat transducer as transmitting and receiving devices presented the best reconstructed image quality. In UCT implementation, the combination of a flat transducer for transmitting and a point transducer for receiving permitted acceptable image quality.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.445-446
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• 2016

초음파 트랜스듀서는 다양한 산업 분야에 응용되고 있다. 초음파 트랜스듀서는 압전 소자에서 발생하는 초음파를 이용하는데, 본 논문은 알루미늄 용탕 처리에 적용하였다. 알루미늄 용탕 처리용 초음파 트랜스듀서는 고주파인 공진주파수를 이용하여 동작하게 된다. 초음파 트랜스듀서는 압전 소자의 온도 및 부하에 따라 공진 주파수가 이동하게 되는 문제점을 가지고 있다. 본 논문은 알루미늄 용탕을 처리할 때 발생하는 문제점을 해결하기 위하여 LLCC 공진형 컨버터를 이용하여 공진주파수를 추적 및 일정한 전력을 공급하는 제어 방식을 제안한다.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.5
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• pp.585-596
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• 2012

PVDF(poly vinylidene fluoride) and P(VDF-TrFE)(poly vinylidene fluoride-tetrafluoroethylene) are the typical piezoelectric polymers with unique properties. Even they are inferior to conventional piezoelectric ceramics PZT in electromechanical conversion efficiency and interior loss, though they are superior in receiving sensitivity and frequency bandwidth. Their acoustic impedances are relatively close to water or biological tissue and it is easier to make thin film than other piezoelectric materials. Futhermore, the film is so flexible that it is easy to attach on a complex surface. Those properties are suitable for the ultrasound transducers which are useful for medical and biological application, so that various types of polymer transducers have been developed. In this paper, several important considerations for design and fabrication of piezoelectric polymer transducers were described and their effect on the transducer performance were demonstrated through the KLM model analysis. Then, it was briefly reviewed about the structures of the polymer transducers developed for obtaining images as well as the characteristics of the images in several important medical and biological application fields.

• The Journal of the Acoustical Society of Korea
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• v.32 no.6
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• pp.502-508
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• 2013

In this paper, 2D array transducers using a conductive backer similar to 1-3 composites have been designed, fabricated, and evaluated. The conductive backer was based on well known manufacturing process of 1-3 composites with affordable ingredients. The 2D array transducer had 4,096 elements designed to have 3.5 MHz center frequency and a fractional bandwidth over 60 %. Fabricated prototype of the transducer satisfied the specifications in the center frequency and bandwidth. Performance over the entire elements was so uniform that the standard deviation was less than 0.81 dB. Thus applicability of the conductive backer proposed in this work to 2D array transducers was verified.

• The Journal of the Acoustical Society of Korea
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• v.22 no.8
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• pp.622-628
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• 2003

Recently, ultrasound transducers in several tens MHz band, which can give the spatial resolution higher than several tens micrometers, have been intensively studying for applying to medical diagnostic fields of ophthalmology and dermatology. In this paper, the background of the studies, structures and characteristics of the transducers, and images obtained by the transducers are briefly reviewed.

• 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.