• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.2
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• pp.253-260
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• 2009

This paper, mathematically analyzes the performance of newly proposed TR-UWB system which the frequency components of a UWB pulse were processed so that the system could be implemented with ADCs of a few MHz sampling rate, and presents the comparison with an existing frequency-domain based TR-UWB system. The comparison is mainly based on the SNR ratio which depends on the mean and the variance of the frequency components. We also shows that the simulation results to support the theoretical analysis where the comparison is made under the IEEE 802.15.3a channel model as well as AWGN channel.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.5
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• pp.479-485
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• 2011

To acquire images in a thermionic-scanning electron-beam system, a scanning unit is needed to control the electron beam emitted from the tungsten filament source. In scanning the electron beam on the solid surface, the signalto-noise ratio depends on the scanning frequency. We used a digital filter to reduce noise by analyzing the real-time frequency of a secondary electron signal. The noise and the true image signal were well separated. We designed the digital filter via a DSP floating-point operation, and the noise elimination resulted in enhanced image quality in a highresolution mode.

• Journal of the Korean Institute of Intelligent Systems
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• v.20 no.3
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• pp.380-387
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• 2010

For the fault diagnosis of three-phase induction motors, we propose a diagnosis algorithm based on mutual information and linear discriminant analysis (LDA). The experimental unit consists of machinery module for induction motor drive and data acquisition module to obtain the fault signal. As the first step for diagnosis procedure, DFT is performed to transform the acquired current signal into frequency domain. And then, frequency components are selected according to discriminate order calculated by mutual information As the next step, feature extraction is performed by LDA, and then diagnosis is evaluated by k-NN classifier. The results to verify the usability of the proposed algorithm showed better performance than various conventional methods.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.105-106
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• 2004

음성인식, 합성 및 분석과 같은 음성신호처리 분야에 있어서 피치검출이나 포만트검출은 매우 중요하다. 주파수 영역의 스펙트럼 신호는 잡음이 부가되는 경우에도 고조파정보와 포만트 포락선 정보를 유지하기 때문에 음성신호처리분야에서 매우 유용하다고 할 수 있다. 고조파 정보나 포만트 포락선 정보는 피치검출과 포만트 주파수 검출에 직접 이용된다 하지만 두 성분을 분리하는 방법에 따라 피치검출이나 포만트 주파수 검출에 영향을 미칠 수 있으므로 기존의 방법보다 두 성분을 더 잘 분리할 수 있는 방법이 필요한 것이다. 본 논문에서는 스펙트럼 신호를 최대한 평탄화시킴으로써 포만트의 영향을 제거하고 고조파 성분을 분리해 내어 이를 피치검출에 사용한다. LSP를 이용하여 적응적 밴드에서 평탄화를 시도하고 이를 피치 검출에 이용하였다.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.1
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• pp.152-157
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• 2014

Digital still camera generally uses optical low-pass filter(OLPF) to enhance its image quality because it removes high spatial frequencies causing aliasing. However, the use of OLPF causes some loss of detail. On the other hand, when image are captured by using no OLPF, the moir$\acute{e}$ is generally existed in high spatial frequency region of an image. Therefore, in this paper, moir$\acute{e}$ reduction method in case of using no OLPF is suggested. To detect the moir$\acute{e}$, spatial frequency response(SFR) of camera was firstly analyzed by using ISO 12233 resolution chart. Then, moir$\acute{e}$ region is detected by using the patterns that are related to the SFR of camera. next, this region is analysed in the frequency domain. Then, the moir$\acute{e}$ is reduced by removing its frequency component, which represents inflection point between high frequency and DC components. Through the experimental results, it is shown that the proposed method can achieve moir$\acute{e}$ reduction with preserving the detail.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.728-732
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• 2008

일반적으로 유역의 유출량을 모의하는 경우 강우-유출모형을 구축한 후 해당 모형에서 제공하는 유출결과를 활용하고 있다. 그러나 모형에 의한 유출결과는 단편적인 유출총량에 대해서만 검증된 결과이기 때문에 기저 및 직접유출성분 각각의 적정에 대한 신뢰성 문제가 야기될 수 있다. 본 연구에서는 금강유역을 대상으로 SSARR모형을 적용하고 단순 유출결과 뿐만 아니라 유출성분별로 결과값을 도출하고, 이를 검증하기 위해 분리주파수 기법을 활용하여 관측값의 유출성분을 분리하고, 모의결과와 서로 비교하였다. 이와같이 적용 검증된 모형을 토대로 유출성분 뿐만 아니라 소유역별 습윤상황과 용수이용정보 등 유출지표를 산정하여 효율적 유출관리 지원을 위한 기초 수문정보를 제공하고자 하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.10a
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• pp.76-78
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• 1993

간접적인 방법으로 가공중(In process)공구상태를 감시하기 위해, 센서신호를 분석하는 방법으로 시간영역 (Time Domain) 해석과 주파수 영역(Frequency Domain)해석이 주로 이용되어 왔다. 시간영역해석의 경우 RMS,PEak Value, 평균/분산을 이용한 정적분석과 AR 모델, ARMA 모델, Kalman Filter등 동적 시계열 모델이 연구되어 왔다. 주파수영역해석의 경우 푸리에 변환 (Fourier Transform)에 의한 신호해석 기술이 주로 이용되고 있다. 그러나 푸리에 변환된 결과에는 시간정보가 포함되어 있지 않고, 국부적인 변환결과가 전체를 대표하는 성질을 가지고 있다. 이에 비해 웨이브렛(Wavelet) 변환은 고주파성분에 대해서는 시간분해능이 높고, 저주파 성분에 대해서는 주파수분해능이 높은 다중해상도 해석기술로서 국소적인 변동점을 민검하게 검지하는 것이 가능하다. 본연구에서는 엔드밀 가공중 발생하는 공구의 파손을 검출하기 위해, 전류센서로 부터 얻은 이송축 부하 전류의 변화에 웨이브렛 변환을 통해 공구의 파손을 검출하는 방법에 대한 연구결과를 소개한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.3A
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• pp.225-234
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• 2008

Orthogonal Frequency Division Multiplexing (OFDM) systems utilizing direct conversion receiver suffer from frequency selective (FS) and frequency independent (FI) phase and gain imbalances caused by imperfect local oscillator and low pass filter. In this paper, we analyze the impacts of the transmit/receive IQ imbalances on the system and propose the estimation and compensation schemes for those imbalances. The preamble signals coded by Alamouti scheme in the frequency domain could be used in the estimation of relatively large IQ imbalances with FS and FI characteristics and the estimation results are used for the compensation of distortions caused by the FI and FS IQ imbalances. The optimal maximum likelihood (ML) receiver or suboptimal ordered successive interference cancallation (OSIC) receiver utilizing the estimation results show symbol error rate (SER) performance improvement compared to zero-forcing (ZF) technique due to diversity gain inherent in the frequency domain IQ imbalances combined with the frequency selective channels.

• The Journal of the Acoustical Society of Korea
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• v.35 no.2
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• pp.110-117
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• 2016

Passive sonar systems detect and classify the target by analyzing the radiated noises from vessels. If multiple noise sources exist within the sonar detection range, it gets difficult to classify each noise source because mixture of noise sources are observed. To overcome this problem, a beamforming technique is used to separate noise sources spatially though it has various limitations. In this paper, we propose a new method that uses a FDICA (Frequency Domain Independent Component Analysis) to separate noise sources from the mixture. For experiments, each noise source signal was synthesized by considering the features such as machinery tonal components and propeller tonal components. And the results of before and after separation were compared by using LOFAR (Low Frequency Analysis and Recording), DEMON (Detection Envelope Modulation On Noise) analysis.

• Tunnel and Underground Space
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• v.15 no.4 s.57
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• pp.316-323
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• 2005

As a result of waveform analysis, the separation of waveform found that high frequency well accomplishes but low frequency doesn't accomplish that. The data which measured less than 60 Hz and more than 60 Hz was analysed to examine the relation between cooperating charge and frequency. The measured data of more than 70 Hz was also analysed to consider the characteristics of high frequency.