• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1991년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 22-24 Oct. 1991
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• pp.1219-1219
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• 1991

This paper proposes the model order reduction with pass band error reduction in the frequency domain of discrete time linear systems. The algorithm is the new method of reduced order model which reduces passband error by changing controllability and observability gramian used with weighted functions. A numerical example shows that this algorithm has lower passband error than balanced w&l and weighted function characteristics in frequency domain.

• 한국정밀공학회지
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• 제14권9호
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• pp.52-60
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• 1997

This paper proposes the effective method of the software based motion control by using lenear, exponential and bell type discrete filters for acceleration and deceleration of servo motors. Recursive filters are designed in discrete time domain which can reduce computation time and vibration of motors due to load disturbance. Also it deals with the method which decides the time constants of filters when a machine tool is driven at rapid, cutting and jog feedrate. Validity of the proposed method is verified by corner cutting experiments.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 추계종합학술대회 논문집(1)
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• pp.489-492
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• 2000

Film Bulk Acoustic Wave Resonator(FBAR) used in microwave region was analyzed with Finite Difference Time-Domain Methods(FDTD) in this paper. FBAR have been analyzed with one dimensional Mason model analysis or Finite Element methods(FEM), but the first couldn't analyze effect of area variation and spurious characteristics, the second had difficulty in element separation because of thin electrode. So in this paper FBAR was analyzed by Finite Difference Time-Domain Methods and it's results were transformed to frequency domain using Discrete Fourier Transform.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 하계종합학술대회 논문집
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• pp.69-72
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• 1999

In this paper, an efficient time domain equalization algorithm for discrete wavelet multitone(DWMT) data transmission is developed. In this algorithm, the time domain equalizer(TEQ) consists of two stages, i.e., the channel impulse response shortening equalizer(TEQ-S) in the first stage and the channel frequency flattening equalizer(TEQ-F) in the second stage. TEQ-S reduces the length of transmission channel impulse response to decrease intersymbol interference(ISI) followed by TEQ-F that enhances the channel frequency response characteristics to the level of an ideal channel, hence diminishes the bit error rate. TEQ-S is implemented using the least-squares(LS) method, while TEQ-F is designed by using the least mean-square(LMS) algorithm. Since DWMT system also requires of the frequency domain equalizer in order to further reduce ICI and ISI the hardware complexity is an another concern. However, by adopting an well designed and trained TEQ, the hardware complexity of the whole DWMT system can be greatly reduced.

• ETRI Journal
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• 제37권1호
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• pp.32-42
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• 2015

Orthogonal frequency-division multiplexing (OFDM) suffers from spectral nulls of frequency-selective fading channels. Linear precoded (LP-) OFDM is an effective method that guarantees symbol detectability by spreading the frequency-domain symbols over the whole spectrum. This paper proposes a computationally efficient and low-cost implementation for discrete Hartley transform (DHT) precoded OFDM systems. Compared to conventional DHT-OFDM systems, at the transmitter, both the DHT and the inverse discrete Fourier transform are replaced by a one-level butterfly structure that involves only one addition per symbol to generate the time-domain DHT-OFDM signal. At the receiver, only the DHT is required to recover the distorted signal with a single-tap equalizer in contrast to both the DHT and the DFT in the conventional DHT-OFDM. Theoretical analysis of DHT-OFDM with linear equalizers is presented and confirmed by numerical simulation. It is shown that the proposed DHT-OFDM system achieves similar performance when compared to other LP-OFDMs but exhibits a lower implementation complexity and peak-to-average power ratio.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2013년도 추계학술대회 논문집
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• pp.63-64
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• 2013

Induction motors' faults detection is almost a popular topic among researchers. Monitoring the output of motors is a key factor in detecting these faults. (Short-time) Fourier, (continuous, discrete) wavelet, and extended Park vector transformations are among the methods for fault detection. One major deficiency of these methods is not being able to detect the severity of faults that carry low energy information, e.g. in ball bearing system failure, there is absolutely no way to detect the severity of fault using Fourier or wavelet transformations. In this paper, the authors have applied the Discrete Wavelet Transform (DWT) frequency-domain analysis to detect bearing faults in an induction motor. In other words, in discrete transform which the output signal is decomposed in several steps and frequency resolution increases considerably, the frequency-band analysis is performed and it will be verified that first of all, fault sidebands become more recognizable for detection in higher levels of decomposition, and secondly, the inner race bearing faults turn out easier in these levels; and all these matter because of eliminating the not-required high energy components in lower levels of decomposing.

• 한국정보통신학회논문지
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• 제11권3호
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• pp.600-607
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• 2007

차세대 이동 멀티미디어 통신에서는 전송지연을 줄이고 버스트 시변채널의 시간변화를 제한하기 위해 버스트 전송이 많이 사용된다. 그러나 채널적응을 위한 훈련 심볼은 짧은 길이의 버스트 데이터에 대해 심각한 문제를 야기할 수 있다. 따라서 심볼에 대한 적응 등화기의 설계에 있어서 짧은 길이의 훈련 심볼과 빠른 수렴을 갖는 적응 알고리즘이 필요로 된다. 본 논문에서는 DMWT (discrete multi-wavelet transform)과 LMS(least mean square) adaptation 을 갖는 적응 등화기를 제안한다. 제안된 등화기는 복잡성의 증가를 최소화하면서도 현재의 transform-domain equalizer보다 빠른 수렴을 갖는다.

• 한국통신학회논문지
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• 제25권4B호
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• pp.629-634
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• 2000

본 논문에서는 VSDL 시스템을 위한 discrete wavelet multitone (DWMT) 송수신기의 구조에 대해 기술한다. DWMT 송수신기는 코사인 변조 필터 뱅크를 사용한 트랜스 멀티플렉서, 전송 채널의 영향을 최소화하기 위한 시간 영역 등화기 및 주파수 영역 등화기 등으로 구성된다. 주파수 영역 등화기를 위해 기존의 1차원 선형 등화기법을 시간 및 부채널 축의 2차원으로 확장하여 2차원 LMS 방법으로 구현하였다. 등화기 평가 계수를 DWMT 기반 VDSL 송수신기에 적용하여 ANSI T1E1.4의 VDSL 전송 시험 선로 규격을 사용한 모의실험을 통해 성능을 확인하였다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권11호
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• pp.551-558
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• 2002

A time-domain combined field integral equation (CFIE) is presented to obtain the transient scattering response from arbitrarily shaped three-dimensional conducting bodies. This formulation is based on a linear combination of the time-domain electric field integral equation (EFIE) with the magnetic field integral equation (MFIE). The time derivative of the magnetic vector potential in EFIE is approximated using a central finite difference approximation and the scalar potential is averaged over time. The time-domain CFIE approach produces results that are accurate and stable when solving for transient scattering responses from conducting objects. The incident spectrum of the field may contain frequency components, which correspond to the internal resonance of the structure. For the numerical solution, we consider both the explicit and implicit scheme and use two different kinds of Gaussian pulses, which may contain frequencies corresponding to the internal resonance. Numerical results for the EFIE, MFIE, and CFIE are presented and compared with those obtained from the inverse discrete Fourier transform (IDFT) of the frequency-domain CFIE solution.

• 전기학회논문지
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• 제63권7호
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• pp.1001-1007
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• 2014

This paper proposes a method to reduce operation time using discrete cosine transform and to improve image quality by the DC gain correction. Conventional filtered back projection (FBP) filtering in the frequency domain using Fourier transform, but the filtering process uses complex number operations. To simplify the filtering process, we propose a filtering process using discrete cosine transform. In addition, the image quality of reconstructed images are improved by correcting DC gain of sinograms. To correct the DC gain, we propose to find an optimum DC weight is defined as the ratio of sinogram DC and optimum DC. Experimental results show that the proposed method gets better performance than the conventional method for phantom and clinical CT images.