• 전력전자학회논문지
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• 제19권6호
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• pp.522-529
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• 2014

This study proposes an isolation amplifier circuit for the sensing and feedback of inverter DC-link voltage, which is inevitable for the precise control of inverter output voltage. The isolation amplifier consists of a pulse-width modulator and a pulse transformer with dual secondary windings. The accuracy of the proposed circuit depends on the precise matching of filter parameters in dual secondary circuits. The influences of parameter inaccuracy on the amplifier performances are analyzed. A modified circuit is proposed to reduce the dependency on filter parameters. The validity of the proposed method is verified through simulation and experiment.

• ETRI Journal
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• 제35권4호
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• pp.718-721
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• 2013

This letter proposes a novel calibration method for a multiport amplifier (MPA) to achieve optimum port-to-port isolation by correcting both the amplitude and phase of the calibration signals. The proposed architecture allows for the detection of the phase error and amplitude error in each RF signal path simultaneously and can enhance the calibrated resolution by controlling the analog phase shifters and attenuators. The designed $2{\times}2$ and $4{\times}4$ MPAs show isolation characteristics of 30 dB and 27 dB over a frequency range of 19.5 GHz to 22.5 GHz, respectively.

• 대한전기학회논문지:시스템및제어부문D
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• 제50권11호
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• pp.550-556
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• 2001

The computerized cardiac analysis system, which acquires and analyzes the electrical activation signal propagating along the surface of the heart, is indispensible equipment for the open heart surgery and electrical cardiac study. In this paper, the design requirement and the electrical circuit analysis are performed to construct the multi-channel cardiac activation pre-amplifier necessary for a signal conditioning circuit. The general 64 channel configuration is expanded into 128 channels to enhance the spatial resolution on the mapped surface of the heart. The 128 channels pre-amplifier consists of input circuit, differential amplifier, right leg driven circuit and isolation part. It has distinct features; high voltage protection, leakage current limitation, isolation and the maximization of common mode rejection ratio with respect to the half-cell potential difference due to different electrode materials. The final pre-amplifier circuit is assembled with 8 boards, each of which composing of 16 channels.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1995년도 춘계학술대회
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• pp.68-70
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• 1995

A low-noise pre-amplifier is developed for use in Topographic Brain Mapping system. It consists of signal generator, signal amplifier with a impedance converter, shield driver, body driver, differential amplifier, and isolation amplifier. Pre-amplifier circuit is designed with the concept of isolation and active body and shield driver. This amplifier shows the good noise behavior, high CMRR, high input impedance, low leakage current and high IMRR.

• 전기학회논문지
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• 제56권12호
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• pp.2240-2246
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• 2007

Optically coupled linear isolation amplifier requires special care to avoid oscillation in actual applications. In this paper methods to analyze the frequency characteristics of the amplifier are proposed to reveal the cause of oscillation and to provide design guidelines. The loop gain of the amplifier obtained through the equivalent circuit model shows that the phase margin is too small to ensure stable operations. Methods to get non-oscillatory response are proposed and the resulting frequency responses are analyzed. The common method adding a small capacitor to the amplifier is shown to degrade the frequency bandwidth. The frequency response of output voltage explains the need of filter capacitor in output stage. The usefulness of the method is verified through experiments.

• 대한의용생체공학회:의공학회지
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• 제16권3호
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• pp.301-308
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• 1995

A high-precision pre-amplifier is designed for general use in EEG measurement system. It consists of signal generator, signal amplifier with a impedance converter, shield driver, body driver, differential amplifier, and isolation amplifier. The combination of minimum use of inaccurate passive components and the appropriate matching of each monolithic amplifiers results in good noise behavior, low leakage current, high CMRR, high input impedance, and high IMRR. The performance of EEG pre-amplifier has been verified by showing the typical EEG pattevn of a nomad person through the clinical experiments.

• 한국전자파학회논문지
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• 제13권1호
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• pp.19-25
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• 2002

본 논문에서는 전력증폭기를 슬롯이 적재된 삼각형 마이크로스트립 패치 안테나와 동일 평면의 기판에 집적화하여 전력증폭기 출력단의 제 3 고조파 튜닝을 안테나가 수행함으로써 전력효율을 향상시키는 효과와, 실제 집적화에 따른 송.수신 신호의 분리 문제를 위해 이중공진, 이중급전을 이용한 능동 집적 안테나의 특성을 고찰하였다. 제 3 고조파에서 방사를 억제 구조로서 안테나에 슬롯을 적재시킨 능동 집적 안테나를 설계, 제작하여 측정한 결과, B급 전력증폭기와 안테나를 각각 제작하여 결합한 형태보다 약 5 %의 전력효율 개선 효과를 얻을 수 있었다. 또한, 송.수신 분리에 대하여서도 IMT-2000주파수 대역의 수신 port에서 송신 주파수의 신호를 -35 dB 이하로 격리시키는 특성을 나타냄을 관찰할 수 있었다.

• 전기학회논문지
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• 제68권1호
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• pp.140-144
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• 2019

This paper proposes an approach for measuring voltage of high voltage(HV) battery of plug-in hybrid electric vehicle(PHEV) and battery electric vehicle(BEV). The proposed methods use isolation resistor and isolation amplifier in order to measure high voltage which should be electrically separated from measuring circuit. In terms of practical applications their advantages and disadvantage are discussed and key design points are addressed by simulations. More importantly, the proposed methods are applicable to various applications such as on-board charger, inverter and battery management system (BMS) which are directly connected to HV battery in PHEV and BEV.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2005년도 추계종합학술대회
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• pp.921-924
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• 2005

We report low conversion loss and high LO to RF isolation 94 GHz MMIC resistive mixers based on 0.1 ${\mu}m$ InGaAs/InAlAs/GaAs metamorphic HEMT technology. The fabricated resistive mixers applied a one-stage amplifier on RF port of the mixer. By using the one-stage amplifier, we obtained the decrement of conversion loss and the increment of LO to RF isolation. So, we can obtain higher performances than conventional resistive mixers. The modified mixer shows excellent conversion loss of 6.7 dB at a LO power of 10 dBm. We also observed an extremely high isolation characteristic from the MMICs exhibiting the LO-RF isolation of 21 ${\pm}$ 0.5dB in a frequency range of 93.7${\sim}$ 94.3 GHz. The low conversion loss and high LO-RF isolation characteristics of the MMIC modified resistive mixers are mainly attributed to the performance of the MHEMTs exhibiting a maximum transconductance of 654 mS/mm, a current gain cut-off frequency of 173 GHz and a maximum oscillation frequency of 271 GHz.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 추계학술대회 논문집
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• pp.409-412
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• 2000

A high performance EEG signal measurement system is fabricated. It consists of high precision pre-amplifier and auto identification bandwidth unit. High precision pre-amplifier is composed of signal generator, signal amplifier with a impedance converter, body driver and isolation amplifier. The pre-amplifier is designed for low noise characteristics, high CMRR, high input impedance, high IMRR and safety, Auto identification bandwidth unit is composed of AD-converter and PIC micro-controller for real time processing EEG signal. The performance of EEG signal measurement system has been shown the classified bandwidth through the clinical demonstrations.