• 한국전자파학회논문지
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• 제29권12호
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• pp.986-991
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• 2018

본 논문은 광대역 디지털 수신기의 동적 범위 개선을 위한 A/D 변환 모듈을 설계 및 제작하였다. 동적 범위 확장을 위한 A/D 변환 모듈은 입력신호 레벨에 따라 정상 경로와 증폭 경로로 신호를 분기하여 디지털 신호로 변환하는 방식이다. 제작 및 측정 결과, A/D 변환 모듈의 정상 경로는 입력 레벨 -57 dBm~-12 dBm 신호를 디지털 신호로 변환하고, 증폭 경로는 입력 레벨 -30 dBm~+12 dBm 신호를 왜곡 없이 디지털 신호로 변환하여 69 dB의 입력 동적 범위 특성을 나타내었다. 또한 순시 대역폭 100 MHz에서 일정한 출력 특성을 나타내고 있음을 확인하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.25-27
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• 2003

In this paper the instantaneous thrust of a linear induction motor(LIM) with cage-type secondary is estimated by the line voltages and phase currents measurement when the LIM is fed by PWM inverter. The estimated thrust values according to various input frequencies are compared with the measured ones.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 B
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• pp.996-998
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• 2001

This paper presents an approach based on knowledge models to detect and isolate faults in a voltage source inverter. These faults do not affect the existing system protections. A diagnosis system which uses only the input variables of the drive is presented. It is based on the analysis of the current-vector trajectory and of the instantaneous frequency in faulty mode. These two methods have been verified in simulation results.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.1033-1034
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• 2006

The paper demonstrates OFDM with LDPC and adaptive modulation applied to Multiple-Input Multiple-Output (MIMO) system. An optimization algorithm to obtain a bit and power allocation for each subcarrier assuming instantaneous channel knowledge is used. The experimental results are shown the potential of our proposed system.

• Journal of Communications and Networks
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• 제16권1호
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• pp.26-35
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• 2014

We consider multiple-input multiple-output decode-and-forward relay systems in Rayleigh fading channels under the partial channel state information (CSI) that the channel statistics of the source-relay (SR) link and the instantaneous CSI of the source-destination and relay-destination links are known at the destination. In this paper, we propose a new near maximum likelihood (near-ML) decoder with two-level pairwise error probability (near-ML-2PEP) which uses the average PEP instead of the exact PEP. Then, we theoretically prove that the near-ML and near-ML-2PEP decoders achieve the maximum diversity, which is confirmed by Monte Carlo simulations. Moreover, we show that the near-ML-2PEP decoder can also achieve the maximum diversity by substituting the average PEP with the values that represent the error performance of the SR link.

• 전력전자학회논문지
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• 제4권2호
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• pp.175-183
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• 1999

PWM 컨버터에서 직류출력전압의 빠른 응답을 위해 입력 및 출력의 전력평형개념을 시스템 모델링에 도입하는 것이 바람직하다. 이 경우 시스템은 비선형이 되며 제어기 설계가 용이하지 않다. 본 논문에서는 입출력 궤환선형화 기법을 응용하여 시스템의 비선형성을 제거하였으며 그 결과 빠른 전압응답특성을 얻을 수 있었다. 또한 작은 용량의 전해커패시터를 사용하더라도 부하변동에 대해 직류출력전압을 일정하게 유지하는 것이 가능함을 보였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2012년도 추계학술대회 논문집
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• pp.137-138
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• 2012

In this paper, three-port flyback inverter with Active Power Decoupling(APD) circuit is analyzed. Conventional flyback inverter with passive power decoupling circuit needs the electrolytic capacitor with large capacitance for decoupling between constant DC power and instantaneous AC power. However the electrolytic capacitor has low lifespan about 50000 to 100000 hours. So the active power decoupling techniques are applied to reduce input capacitance of flyback inverter. Thus the overall system can achieve smaller size and longer lifespan. Proposed three-port flyback inverter is verified by design optimization, simulation and experimental result.

• Journal of Communications and Networks
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• 제10권2호
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• pp.163-174
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• 2008

Performance of downlink transmission strategies exploiting cooperative transmit diversity is investigated for distributed multiple-input single-output (MISO) systems, for which geographically distributed remote antennas (RA) in a cell can either communicate with distinct mobile stations (MS) or cooperate for a common MS. Statistical characteristics in terms of the signal-to-interference-plus-noise ratio (SINR) and the achievable capacity are analyzed for both cooperative and non-cooperative transmission schemes, and the preferred mode of operation for given channel conditions is presented using the analysis result. In particular, we determine an exact amount of the maximum achievable gain in capacity when RAs for signal transmission are selected based on the instantaneous channel condition, by deriving a general expression for the SINR of such antenna selection based transmission. For important special cases of selecting a single RA for non-cooperative transmission and selecting two RAs for cooperative transmission among three RAs surrounding the MS, closed-form formulas are presented for the SINR and capacity distributions.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.181-183
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• 2004

Conventional VVVF control voltage-fed inverter of blower induction motor has advantage that very speedy response characteristics for air-harmonic. But there have bad power factor on input orient have its large volume and high error ratio over 80%. And there are very expensive by reason of using the capacitor input rectifier. In this paper, It could make the smoothing capacitor-less inverter for air-blower motor by using the instantaneous compensation PWM controller. This inverter system has small volume and value compare with the conventional VVVF control inverter for blower induction motor for air-harmonic equipment.

• Journal of Power Electronics
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• 제8권4호
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• pp.345-353
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• 2008

In this paper, a novel loss minimization of an induction generator in wind energy generation systems is presented. The proposed algorithm is based on the flux level reduction, for which the generator d-axis current reference is estimated using support vector regression (SVR). Wind speed is employed as an input of the SVR and the samples of the generator d-axis current reference are used as output to train the SVR algorithm off-line. Data samples for wind speed and d-axis current are collected for the training process, which plots a relation of input and output. The predicted off-line function and the instantaneous wind speed are then used to determine the d-axis current reference. It is shown that the effect of loss minimization is more significant at low wind speed and the loss reduction is about to 40% at 4[m/s] wind speed. The validity of the proposed scheme has been verified by experimental results.