• 한국정보보호학회:학술대회논문집
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• 한국정보보호학회 2001년도 종합학술발표회논문집
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• pp.464-468
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• 2001

In this paper, we propose a robust watermarking technique that accepts time scaling, pitch shift, add noise and a lot of lossy compression such as MP3, AAC, WMA. The technique is developed based on digital filtering. Being designed according to critical band of HAS (human auditory system), the digital filters nearly affect audio quality. Furthermore, before implementing digital filtering, wavelet transform decomposes the audio signal into several signals that is composed of specific frequencies. Designed digital filters scan the decomposed signal. The designed digital filter, band-stop filter, distorts and eliminates specific frequencies of audio signals. Watermarking detection can be accomplished by FFT (Fast Fourier Transform). Firstly, segments of audio signal are transformed by FFT. Then, the obtained amplitude spectrum by FFT is summed repeatedly. Finally the watermark detector can find filters used to watermark encoding based on eliminating frequencies. The suggested technique can embed 4bits/s in a robust manner.

• 센서학회지
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• 제5권4호
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• pp.81-87
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• 1996

이 논문은 임의의 주파수 특성을 갖는 표면음파 필터의 최적화 설계 방법에 관한 연구이다. 임의의 주파수 특성을 갖는 표면음파 필터를 설계하기 위하여 비제한 비선형 최적화 방법과 FFT 알고리즘을 이용한 설계 프로그램을 개발하였다. 설계의 예로서 비대칭 진폭과 비선형 위상 주파수 특성을 갖는 표면음파 TV IF 필터를 설계하였다.

• 전기학회논문지
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• 제57권7호
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• pp.1295-1297
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• 2008

Large-sized flat-panel displays are widely used for PC monitors and TV displays. In this paper, frequency domain pre-filter algorithms are presented for detection of defects in large-sized Thin Film Transistor-Liquid Crystal Display(TFT-LCD) panel surfaces. Frequency analysis with 1-D, 2-D FFT methods for extract the periodic patterns of lattice structures in TFT-LCD is performed. To remove this patterns, frequency domain band-stop filters were used for eliminating specific frequency components. In order to acquire only defected images, 2-D inverse FFT methods to inverse transform of frequency domain images were used.

• Journal of Electrical Engineering and Technology
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• 제8권6호
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• pp.1380-1388
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• 2013

The conventional graphical representation of the instantaneous compensation power flow for single-phase active power filters(APFs) simply represents the active power flow and the reactive power flow which flowing between the power source and the active filter / the load. But, this method does not provide the information about the rectification mode and the compensation mode of APFs, especially, the loss for each mode was not considered at all. This is very important to understand the compensation operation characteristics of APFs. Therefore, this paper proposes the graphical representation of the instantaneous compensation power flow for single-phase APFs considering the instantaneous rectification mode and the instantaneous inversion mode. Three cases are verified in this paper - without compensation, with compensation of the active power 'p' and the fundamental reactive power 'q', and with compensation of only the distorted power 'h'. To ensure the validity of the proposed approach, PSIM simulation is achieved. As a result, we could confirm that the proposed approach was easy to explain the instantaneous compensation power flow considering the instantaneous rectification mode and the instantaneous inversion mode of APFs, also, Total Harmonic Distortion(THD)/Power Factor (P.F) and Fast Fourier Transform(FFT) analysis were compared for each case.

• Journal of Power Electronics
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• 제12권3호
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• pp.509-517
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• 2012

This paper presents control strategies for cascaded H-bridge multilevel active power filters (APFs). A current loop controller is implemented using a proportional-resonant (PR) regulator, which achieves zero steady-state error at target frequencies. The power balancing mechanism for the dc-link capacitor voltages is analyzed and a voltage balancing controller is presented. To mitigate the picket-fence effect of the conventional FFT algorithm under asynchronous sampling conditions, the Hanning Windowed-FFT algorithm is proposed for reference current generation (RCG). This calculates the frequency, amplitude and phase of individual harmonic components accurately and as a result, selective harmonic compensation (SHC) is achieved. Simulation and experimental results are presented, which verify the validity and effectiveness of the devised control algorithms.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.2283-2286
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• 2003

This paper presents conservation of electrical energy in building with harmonics analysis and compensation which occur in electrical system. We use load controlling and management system in order to adjust load factor of system.The maximum demand limiting and controlling are used ,then the system can acquire the prediction and compare it to the maximum demand set point.The electrical signal analysis based on FFT technique. The harmonics are compensated by using harmonic filters.This system consists computer which works as controller, processor , analysis and database unit together with digital power meter in form of multidrop network through serial communication via RS-485.The load control system uses PLC to control load via serial communication RS-485. The A/D converter is used for sampling the electrical signals via parallel port of computer.The harmonic filters are controlled by a computer.The data of measurement such as voltage, current, power, power factor, total harmonic distortion, energy, etc., can be saved as database and analysis. The load factor is adjusted by limiting and controlling maximum demand. The load factor adjustment can reduce the cost of electric consumption and energy generation together with harmonics compensation in order to increase high efficiency of electrical system.

• 한국통신학회논문지
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• 제25권5A호
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• pp.618-633
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• 2000

본 논문은 COFDM 시스템에 대해 기존의 선형 보간 필터에 비해 보다 정확한 추정을 위해 가우시안 보건 필터와 입방 원형자 보간 필터가 제시되었다. 또한 보간 필터에 의한 채널 추정치의 잡음 성분을 제거하기 위해 IFFT와 FFT를 이용한 저역 통과 필터를 제시하였다. 보간 필터와 저역 통과 필터를 결합한 채널 추정치는 보간 필터만을 사용한 것에 비해 에러 바닥을 낮출 수 있다. 제시된 채널 추정 기법을 시변 다중 경로 페이딩 채널의 COFDM 시스템에 적용시켜 컴퓨터 모의 시험한 결과, 기존의 선형 보간 필터에 비해 성능이 향상됨을 보였으며, 저역 통과 필터를 결합한 경우에는 완벽한 채널 추정과 비교시 BER이 10-4일 때 Eb/No가 0.1∼0.2dB 정도 차이만이 존재한다.

• 전자공학회논문지B
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• 제30B권9호
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• pp.27-35
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• 1993

In this paper, a new algorithm for high level security and quality of speech is proposed. The algorithm is based on the rearrangement of the fast fourier transform (FFT) coefficients with pre and post filter process, hamming window and adaptive pseudo spectrum insertion. Then, the pre and post filters are used for the whitening of speech spectrum and the adaptive pseudo spectrum is inserted for the unclassification of silence/speech. Also, the hamming window technique is applied for the robustness to the syncronization error in the telephone line. According to the simulation results, it can be seen that the security of scrambled signal and the quality of descrambled signal have been improved fairly in both subjective and objective performance test and the new FFT scrambler is robust to the synchronization error.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1864-1865
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• 2007

In this paper, we proposed pre-filter algorithms which using frequency domain analysis method, for the detections of defects in large-sized Thin Film Transistor-Liquid Crystal Display(TFT-LCD) panel surfaces. We performed frequency analysis with 1-D, 2-D FFT methods for extract periodic patterns of lattice structures in TFT-LCDs. To remove this patterns, band-stop filters were used for eliminating specific frequency components. In order to acquire only defected images, we used 2-D inverse FFT methods which can be reverts images that remains defects.

• Journal of the Korean Wood Science and Technology
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• 제41권5호
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• pp.399-405
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• 2013

This study demonstrates the utilization of light microscopy and Fast Fourier Transform-Peak Finding (FPF) method for microfibril angle (MFA) measurement from unstained sections of red pine (Pinus densiflora). To obtain an image with optimal contrast and resolution for MFA measurement, effects of numerical aperture (NA) of condenser lens and color filters were investigated. About 60% of NA of the maximum condenser NA produced an image with optimal contrast, but a color filter with short wavelength range (DAPI) created images with improved resolution. Manual angle measurement and the FPF method were applied to the image with optimal contrast for MFA measurement. The experimental results from the FPF method were considered to be more repeatable and less subjective than those from the manual angle measurement.