• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.192-195
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• 2003

본 논문에서는 FFT(Fast Fourier Transform)를 수행하며 이를 원격지에 전송할 수 있는 원격 모니터링 시스템을 위한 FFT서버 시스템 구축에 대하여 기술하고자 한다. 실시간으로 얻어지는 데이터를 동시에 FFT분석을 하여 이를 원격지에 전송할 수 있다. 그리고 방대한 양의 데이터의 처리와 전송과정에서 발생하는 시간적, 자원적 손실을 줄일 수 있도록 데이터를 선별하여 분석한다. 제안된 시스템은 실시간 계측 데이터에서 의미있는 데이터를 추출하고, FFT를 통해 1차 처리 후 네트워크를 통해 이를 목적지에 전달한다. 이로 인해 네트워크 자원의 보다 효율적인 사용과 감시 대상의 다양한 각도에서의 분석에 도움이 될 것으로 기대한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2008.05a
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• pp.1029-1030
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• 2008

FFT(Fast Fourier Transform)는 디지털신호처리에 폭넓게 사용되며 특히 여러 OFDM 시스템에 FFT 처리 과정은 꼭 필요한 부분이다. 본 논문에서는 802.11a W-LAN 에 사용되는 64-point FFT 프로세서를 설계하였다. 설계된 FFT 프로세서는 Radix-$2^3$ 알고리즘을 사용하였으며 저면적복소곱셈기를 사용하여 FFT 프로세서의 면적을 줄이는 방법을 제안한다. 기존의 방식에서 네 개의 실수 곱셈기와 두 개의 덧셈기로 구성되는 복소 곱셈기를 두 개의 실수 곱셈기와 한 개의 덧셈기가 수행하도록 설계하였다. 제안한 FFT 프로세서는 VHDL 로 구현되었고 Quartus 4.2 에서 합성되었다. 합성결과 기존 방식에 비해 약 21%의 면적효율이 발생하였다.

• Journal of Positioning, Navigation, and Timing
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• v.11 no.1
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• pp.11-21
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• 2022

Fast Fourier transform (FFT)-based parallel acquisition techniques with reduced computational complexity have been widely used for the acquisition of binary phase shift keying (BPSK) global positioning system (GPS) signals. In this paper, we propose a low computational FFT-based fine acquisition technique, for binary offset carrier (BOC) modulated BPSK signals, that depending on the subcarrier-to-code chip rate ratio (SCR) selectively utilizes the computationally efficient frequency-domain realization of the BPSK-like technique and two-dimensional compressed correlator (BOC-TDCC) technique in the first stage in order to achieve a fast coarse acquisition and accomplishes a fine acquisition in the second stage. It is analyzed and demonstrated that the proposed technique requires much smaller mean fine acquisition computation (MFAC) than the conventional FFT-based BOC acquisition techniques. The proposed technique is one of the first techniques that achieves a fast FFT-based fine acquisition of BOC signals with a slight loss of detection probability. Therefore, the proposed technique is beneficial for the receivers to make a quick position fix when there are plenty of strong (i.e., line-of-sight) GNSS satellites to be searched.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2001.05a
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• pp.109-112
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• 2001

Recently, the subject of \"wavelet analysis\" has drawn much attention from both mathematical and engineering application fields such as Signal Processing, Compression/Decomposition, Statistics and ets. Analogous to Fourier analysis, wavelets is a versatile tool with very rich mathematical content and great potential for applications. Specially, wavelet transform uses localizable various mother wavelet functions in time-frequency domain. In this paper, discrimination analyses of acquired electrical current signals for each and mixed loads were tried by using Morlet wavelet transform. Their representative loads were classified as TV, DRY(Dryer), REF(Refrigerate), and FL(Fluorescent Lamp).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.169-172
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• 1999

Recently, the wavelet transform has been a new and powerful tool for signal processing. It is more suitable specially for the feature extraction and detection of non-stationary signals than traditional methods such as, the Fourier Transform(FT), the Fast Fourier Transform(FFT) and the Least Square Method etc. because of the characteristic of the multi-scale analysis and time-frequency domain localization. The wavelet transform has been developed for the analysis of PD pulse signal to raise in the progress of insulation degradation. In this paper, the wavelet transform was applied to one foundational method for feature extraction. For the obtain experimental data, a computer-aided partial discharge measurement system with a single acoustic sensor was used. If we are applying to the neural network method the accumulated data through the extracted feature, it is expected that we can detect the PD pulse signal in the insulation materials on the on-line.

• Proceedings of the Korea Multimedia Society Conference
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• 2004.05a
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• pp.179-182
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• 2004

무선통신분야에서 LMS5(Least Mean Square) 알고리즘은 식이 간단하고 계산량이 비교적 적기 때문에 널리 사용되고 있다. 그러나 시간영역에서 처리할 경우 입력신호의 고유치 변동폭이 넓게 분포되어 수렴속도가 저하하는 문제점이 있다. 이를 해결하기 위하여 신호를 FFT(Fast Fourier Trasnform)나 DCT(Discrete Cosine Transform)로 변환하여 신호간의 상관도를 제거함으로써 시간영역에서 LMS알고리즘을 적용할 때 보다 수렴속도를 크게 향강시킬 수 있다. 본 논문에서는 수렴속도 향상을 위해 시간영역의 적응 알고리즘을 직교변환인 고속웨이브렛(wavelet)변환을 이용하여 변환영역에서 수행하며, 짧은 필터계수를 가지는 DWT(Discrete Wavelet Transform)특성에 맞는 Fast running FIR 알고리즘을 이용하여 WTLMS(Wavelet Transform LMS)적응알고리즘을 통신시스템에 적용한다. 적응 알고리즘의 성능향상을 위하여 시간에 따라 적응상수의 크기를 가변시켜 수렴 초기에는 큰 적응상수로 따른 수렴이 가능하도록 하고 점차 적응상수의 크기를 줄여서 misadjustment도 줄이는 방법의 적응 알고리즘을 제안하였다. 제안한 알고리즘을 실제로 적응잡음제거기(adaptive noise canceler)에 적용하여 컴퓨터 시뮬레이션을 하였으며, 각 알고리즘들의 계산량, 수렴속도를 이용하여 각각 비교, 분서하여 그 성능이 우수함을 입증하였다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.1
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• pp.67-74
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• 2004

The dynamic instability for snapping phenomena has been studied by many researchers. Few paper deal with the dynamic buckling under the load with periodic characteristics, and the behavior under periodic excitation is expected the different behavior against STEP excitation. We investigate the fundamental mechanisms of the dynamic instability when the sinusoidal shaped arch structures are subjected to sinusoidal harmonic excitation with pin-ends. By using Newmark- β method, we can get the nonlinear displacement response, and using this analyze characteristics of the dynamic instability through the running response spectrum by FFT(Fast Fourier Transform).

• Asian Journal of Atmospheric Environment
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• v.5 no.2
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• pp.105-112
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• 2011

In order to investigate the effects of local and synoptic meteorological conditions on urban scale particulate air pollutants observed over the Busan coastal area, power spectrum analysis was applied to observed particulate matter with an aerodynamic diameter $\leq10\;{\mu}m$ ($PM_{10}$) for the period from 1 October, 1993 to 31 December, 2004. Fast Fourier Transform (FFT) analysis was used to obtain the hourly mean observed $PM_{10}$ concentrations to identify different periodicity scales of $PM_{10}$ concentrations. The results showed that, aside from the typical and well-known periodicities such as diurnal and annual variations caused by anthropogenic influences, three other significant power spectral density peaks were identified: 7-day, 21-day and 2.25-year periodicities. Cospectrum analysis indicated that the seven-day variations were closely related to the synoptic meteorological conditions such as weak wind speed, which are relevant to the stagnant high pressure system slowly passing through the Korean Peninsula. The intra-seasonal 21-day variation was negatively correlated with wind speed but was consistently positively correlated with relative humidity, which is related to aerosol formation that can be achieved as a result of the hygroscopic characteristics of aerosols. However, the quasibiennial 2.25-year variation was correlated with the frequency of Asian dust occurrence, the periodicities of which have been recorded inter-annually over the Korean Peninsula.

• Journal of Korean Association for Spatial Structures
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• v.4 no.2 s.12
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• pp.81-88
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• 2004

The dynamic instability of snapping phenomena has been studied by many researchers. Few papers deal with dynamic buckling under loads with periodic characteristics, and the behavior under periodic excitations is expected to be different from behavior under STEP excitations. We investigate the fundamental mechanisms of the dynamic instability when the sinusoidally shaped arch structures are subjected to sinusoidally distributed excitations with pin-ends. The mechanisms of dynamic indirect snapping of shallow arches are especially investigated under not only STEP function excitations but also under sinusoidal harmonic excitations, applied i the up-and-down direction. The dynamic nonlinear responses are obtained by the numerical integration of the geometrically nonlinear equation of motion. And using this analyze characteristics of the dynamic instability through the running response spectrum by FFT(Fast Fourier Transform).

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.5
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• pp.1076-1082
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• 2013

The frequency bands were discovered which maximize the slopes of autocovariances of speech signals in frequency domain to increase the possibility of segregation between speech signals and background noise signal. A speech signal is divided into blocks which include multiples of sampled data, then those blocks are transformed to frequency domain using Fast Fourier Transform(FFT). To find linear equation by Linear Regression, the coefficients of autocovariance within blocks of some frequency band are used. The slope of the linear equation which is called the slope of autocovariance is varied from band to band according to the characteristics of the speech signal. Using speech signals of a man which consist of 200 files, the coefficients of the slopes of autocovariances are analyzed and compared from band to band.