• The Journal of the Acoustical Society of Korea
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• v.20 no.5
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• pp.69-75
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• 2001

In this paper, a fast and easy impedance matching method, which could give the impedance matching component for the general 1 or 2-port network was introduced. First, the entire network structure was defined which consists of the network part to be matched and the impedance matching part composed of inductors and capacitors. Next, the transmission matrix and input and output impedances of the entire network from the terminal impedance conditions were calculated, then the exact solutions for the matching components were obtained. To verify the efficiency of this method, this method was applied to the CDMA If band withdrawal weighted SAW transversal filter, and investigated the effects of the impedance matching before and after, through the simulation and experiment. As the result, the performance of a fractional bandwidth of 1.2%, insertion loss of 29 dB, and VSWR of 80 have improved to a factional bandwidth of 1.8％, insertion loss of 9 dB, VSWR of 3 at 85.38 MHz center frequency. The result shows that this impedance matching method could be used in the SAW devices and other types of 1 or 2-port network.

• Journal of Biosystems Engineering
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• v.32 no.4
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• pp.269-275
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• 2007

In this study, ultrasonic transducers for non-destructive contact measurement of whole fruits were developed. The design parameters for ultrasonic transducer such as acoustical impedance of fruits, kinds of piezoelectric materials, ultrasonic wave frequency, and transducer diameter were investigated. In order to match the acoustical impedance between piezoelectric material and fruit, various materials were fabricated and evaluated. Also to control the sensitivity and bandwidth of the ultrasonic transducer, various backing materials were fabricated and evaluated. Especially, the wear plate of the ultrasonic transducer was designed and fabricated considering the curvature of fruit. The central frequencies of two developed ultrasonic transducers were about 100 kHz and 200 kHz, respectively. With the developed ultrasonic transducers, non-destructive evaluation of the fruit will be possible.

• The Journal of the Acoustical Society of Korea
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• v.28 no.6
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• pp.491-498
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• 2009

This paper presents the design method of an impedance matching network using an isolation transformer and the Chebyshev filter function for the high efficiency and the flat power driving of an underwater acoustic piezoelectric transducer. The proposed impedance matching network is designed for minimizing the reactance component of transducer and having the flat power response in the wide frequency range. We design a low pass filter with ladder-type circuit using the Chebyshev function as standard prototype filter function. In addition, we design the impedance matching network which is suitable for the equivalent circuit of transducer and the turn ratio of transformer through the bandpass frequency transformation. The proposed method is applied to the simulated dummy load of the tonpilz-type transducer operating in the middle frequency range. The simulation results are compared with the measured characteristics and the validity of the proposed method is verified.

• The Journal of the Acoustical Society of Korea
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• v.33 no.6
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• pp.366-374
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• 2014

With the advent of submarine detection technology using low-frequency active sonar there is a call for a new submarine stealth device that can replace the existing passive anechoic tiles. Proposed in this study is a low-frequency echo reduction technique based on active impedance matching, which employs a tile projector designed to cover a wide area such as the surface of a ship. To judge the feasibility of the active impedance matching technique finite-element simulations of low-frequency echo reduction are performed. Based on the analysis, a tile projector is designed, fabricated, and tested in an acoustic tank for its low-frequency echo reduction performance.

• The Journal of the Acoustical Society of Korea
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• v.17 no.2
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• pp.25-31
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• 1998

본 연구에서는 자동차 유리판에 초음파 대역 진동을 효율적으로 발생시킬 수 있는 압전 액츄에이터를 개발하고자 하였다. 자동차 유리판을 단순지지 평판으로 가정하였으며, 액츄에이터로는 PZT 진동자를 사용하였다. 유한 요소법(Finite Element Method)을 통하여 유리판의 최적 공진 주파수와 유리판에 부착할 압전 진동자의 구조 조건인 최적 위치와 개 수를 결정하였다. 설계 결과에 따라 자동차 유리판에 압전 진동자를 부착하여 임펄스 응답 해석(impulse response analysis)과 임피던스 해석(impedance analysis)을 수행하여 구동 주 파수를 확인하였다. 그 결과, 이 주파수로 가진하여 유리판 전면에 걸쳐 고른 초음파 진동이 분포함을 확인하였으며, 나아가 전기적 임피던스 매칭(impedance matching)을 통해 더 큰 효율의 진동을 발생시킬 수 있었다.

• The Journal of the Acoustical Society of Korea
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• v.31 no.7
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• pp.480-486
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• 2012

In the design of electro acoustic transducer, power factor improvement circuit is more required rather than impedance matching if the driving power amplifier has little inner resistance. Many research results have been focused on the power matching circuit designing for transferring maximum power in the wideband. There are few results in the designing study on the power factor improvement for the wide band electro acoustic transducer. In this paper, we propose a new design method on the power factor improvement for the wide band electro acoustic transducer. The proposed method consists of two steps, the chebyschev matching method and the constrained optimization, respectively.

• Journal of Biosystems Engineering
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• v.35 no.3
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• pp.189-196
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• 2010

This study was conducted to develop an non-contact ultrasonic transducer for measurement of fruit firmness. The center frequency of non-contact ultrasonic transducer was 500 kHz. As an active element of non-contact ultrasonic transducer, the 1-3 piezoelectric composite material was selected. That material has high piezoelectric properties such as electro-mechanical coupling factor, $k_t$ and piezoelectric voltage constant, $d_{33}$ and also that material has low acoustical impedance which enables to matching the acoustical impedances between piezoelectric material and air. As a front matching material between 1-3 piezoelectric composite material and air, various kinds of paper with different thickness were tested. To control the dead-zone of the fabricated non-contact ultrasonic transducer, the backing material composed of epoxy resin and tungsten powder were made and evaluated. The fabricated non-contact ultrasonic transducer for fruit showed that the cneter frequency, bandwidth and beamwidth were approximately 480 kHz, 30 % and 12 mm, respectively. It was concluded that non-contact measurement of apple firmness would be possible by using the fabricated non-contact ultrasonic transducer.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.519-522
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• 2004

수중 음향 탐지 시스템에서 빔 형성 기법은 탐지 성능에 큰 영향을 미치기 때문에 최적의 빔 설계는 오랫동안 많은 연구자들에 의해 연구되어 왔다. 실제로 최적의 빔 형성기를 구현할 때에는 각각의 센서에 대한 특성 고려와 파워를 효율적으로 전달하기 위한 정합회로의 설계가 필수적이다. 이전의 논문에서는 BeamCAD Tool을 이용한 최적 가중치의 계산, 센서 임피던스 측정 데이터와 Sensor Modeling Tool을 이용한 등가회로 모델링 그리고 Impedance Matching Tool을 이용한 정합회로 설계 기법에 대해서 소개하였다. 본 논문에서는 이러한 기법들과 함께 ABCD 전송 파라메터를 이용한 센서 가중치 보정 기법을 소개한다. 그리고 이러한 여러 기법들을 이용하여 최적빔 설계를 위한 가중회로를 구성하는 방법에 대해서 논의한다.

• The Journal of the Acoustical Society of Korea
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• v.41 no.5
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• pp.481-491
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• 2022

The active sonar transmission system consists of a transmitter that outputs an electrical signal and an underwater acoustic transducer that converts the amplified electrical signal into an acoustic signal. In general, the transmitter output characteristics are dependent on load impedance, and an underwater acoustic transducer, which is a transmitter load, has a characteristic that the electrical impedance varies largely according to frequency when driven. In such a variable impedance condition, the output of the active sonar transmission system may become unstable. Hence, this paper proposes a design and control technique of a sonar transmitter for transmitting a stable transmission signal even under variable impedance conditions of an underwater acoustic transducer in an active sonar transmission system. The electrical impedance characteristics of the underwater acoustic transducer are experimentally analyzed, and the sonar transmitter is composed of a single-phase full-bridge inverter, an LC filter, and a matching circuit. In this paper, the design and output control method of the sonar transmitter is proposed to protect the transmitter and transducer. It can secure stable output voltage characteristics even if it transmits the Linear Frequency Modulation (LFM) signal. The validity is verified through the simulation and the experiment.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.389-392
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• 2000

본 연구에서는 1, 2단자쌍 회로망의 임피던스 정합회로를 간단하고 빠르게 구할 수 있는 방안을 개발하였다. 우선 회로망의 전체 전달함수를 F 행열로 부터 계산하고, 이를 이용하여 양단의 부하저항 및 정합회로가 포함된 각각의 단자의 입출력 임피던스를 구하였으며, 이 식으로부터 정합용 소자의 정확한 값을 계산하였다. 본 연구의 타당성을 검증하기 위해 CDMA용 소자로 널리 사용되는 중간주파수 대역 withdrawal 가중형 SAW 필터에 본 연구의 결과를 적용하여 임피던스 정합 전후의 특성변화를 시뮬레이션과 실험을 통하여 동시에 확인하였다 그 결과 85.38 MHz의 중심주파수에서 비대역폭이 $1.2\%$, 삽입손실이 29dB, VSWR이 80인 필터를 본 연구방법을 이용하여 정합 한 경우, 각각 $1.8\%$, 9dB, 3으로 향상됨을 시뮬레이션과 실험을 통해 확인하였다. 본 연구결과는 SAW 디바이스의 정합에 매우 용이하게 이용될 수 있을 뿐만 아니라 일반적인 1, 2단자쌍 회로망의 임피던스 정합에도 널리 사용될 수 있다