• 제목/요약/키워드: Wigner-Ville Distribution(WVD)

검색결과 13건 처리시간 0.02초

이동 표적에 의한 도플러 신호의 시간-주파수 분석 (Time-Frequency Analysis of the Doppler Signals by Moving Targets)

  • 손중탁;이승훈;박길흠
    • 한국군사과학기술학회지
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    • 제8권2호
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    • pp.38-48
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    • 2005
  • Instantaneous frequency of doppler signals is used to get the information of the relative velocity and the miss distance between a missile and a corresponding target. In this paper, we have performed time-frequency analysis and instantaneous frequency estimation with Short Time Fourier Transform(STFT), Wigner Ville Distribution(WVD) and Continuous Wavelet Transform(CWT) about the doppler signals generated by moving targets. Performance evaluation was performed using simulated doppler signals generated by a single moving target and two moving targets. From the results of the time-frequency analysis, we found that WVD method was the most efficient instantaneous frequency estimator among the three methods. But in case of two moving targets, WVD method got cross talks and CWT method got oscillation when two doppler frequencies were close to each other.

시간-주파수 변환에 요동보상을 적용한 UWB 레이다 바이스테틱 ISAR 이미징 (Bistatic ISAR Imaging with UWB Radar Employing Motion Compensation for Time-Frequency Transform)

  • 장문광;조춘식
    • 한국전자파학회논문지
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    • 제26권7호
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    • pp.656-665
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    • 2015
  • 본 논문에서는 시간-주파수 변환에 요동보상을 적용한 UWB 레이다 Bistatic ISAR (Bistatic Inverse Synthetic Aperture Radar: B-ISAR) 이미징에 적용하여 레이다 이미징의 선명도와 품질을 개선하였다. UWB 레이다를 사용하여 제안하는 시간-주파수 알고리즘을 검증하였으며, 이를 위하여 B-ISAR 알고리즘 절차, 시간-주파수 변환과 요동보상 개선 등 필요한 이론적 근거를 제시하였다. B-ISAR 이미징 알고리즘으로 이미지를 생성하였으며, UWB 바이스테틱 ISAR 이미징 생성시 요동보상을 적용한 시간-주파수 변환 기법인 STFT(Short-Time Fourier Transform), GWT(Gabor Wavelet Transform), WVD(Wigner-Ville distribution) 방식을 차례대로 구현하였다. 그리고 STFT, GWT와 WVD 알고리즘을 이용하여 B-ISAR 이미징 알고리즘의 성능을 비교하였으며, 그 결과 WVD가 다른 방식들에 비하여 영상이 선명하고, 퍼짐 현상이 줄어듦을 알 수 있었다.

열화된 SUS 316강의 시간-주파수 해석에 의한 비파괴평가 (Nondestructive Evaluation by Joint Time-Frequency Analysis of Degraded SUS 316 Steel)

  • 이건찬;오정환;남기우;이주석
    • 비파괴검사학회지
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    • 제19권4호
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    • pp.270-276
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    • 1999
  • 지금까지 퓨리에 변환이 신호처리법으로 가장 널리 사용되고 있다. 그러나, 이 방법은 신호의 주파수성분이 시간에 대하여 어떻게 변화하는지를 표현하지 못한다. 따라서, 최근 이와 같이 비정상신호를 표현하지 못하는 퓨리에 변환의 단점을 보완하여, 신호의 시간과 주파수에 대한 정보를 동시에 표현할 수 있는 시간-주파수 해석법들이 개발되기 시작하였다. 본 연구에서는 인공열화된 SUS 316강의 초음파신호를 시간-주파수 해석법으로 분석하였다. 특히, 단시간 퓨리에 변화법과 위그너 빌 분포법을 이용하여 초음파 신호의 주파수 성분과 특성을 분석하였다.

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시간 주파수 분석을 이용한 충격발생 위치 추정 (Source Localization of an Impact on a Plate using Time-Frequency Analysis)

  • 박진호;최영철;이정한
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2005년도 추계학술대회논문집
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    • pp.107-111
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    • 2005
  • It has been reviewed whether it would be suitable that the application of the time-frequency signal analysis techniques to estimate the location of the impact source in plate structure. The STFT(Short Time Fourier Transform), WVD(Wigner-Ville distribution) and CWT(Continuous Wavelet Transform) methods are introduced and the advantages and disadvantages of those methods are described by using a simulated signal component. The essential of the above proposed techniques is to separate the traveling waves in both time and frequency domains using the dispersion characteristics of the structural waves. These time-frequency methods are expected to be more useful than the conventional time domain analyses fer the impact localization problem on a plate type structure. Also it has been concluded that the smoothed WVD can give more reliable means than the other methodologies for the location estimation in a noisy environment.

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위그너-빌 분포함수의 계산시 창문함수의 적용에 의한 바이어스 오차 (The Bias Error due to Windows for the Wigner-Ville Distribution Estimation)

  • 박연규;김양한
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 1995년도 추계학술대회논문집; 한국종합전시장, 24 Nov. 1995
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    • pp.80-85
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    • 1995
  • Too see the effects of finite record on the estimation of WVD in practice, a window which has time varying length is examined. Its length increases linearly with time in the first half of the record, and decreases from the center of the record. The bias error due to this window decreases inversely proportionally to the window length as time increases in the first half. In the second half, the bias error increases and the resolution decreases as time increases. The bias error due to the smoothing of WVD, which is obtained by two-dimensional convolution of the true WVD and the smoothing window, which has fixed lengths along time and frequency axes, is derived for arbitrary smoothing window function. In the case of using a Gaussian window as a smoothing window, the bias error is found to be expressed as an infinite summation of differential operators. It is demonstrated that the derived formula is well applicable to the continuous WVD, but when WVD has some discontinuities, it shows the trend of the error. This is a consequence of the assumption of the derivation, that is the continuity of WVD. For windows other than Gaussian window, the derived equation is shown to be well applicable for the prediction of the bias error.

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재배치 시간-주파수 해석을 이용한 슬라이더 공기베어링의 비정상 거동 연구 (Study on the Nonstationary Behavior of Slider Air Bearing Using Reassigned Time -frequency Analysis)

  • 정태건
    • 한국소음진동공학회논문집
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    • 제16권3호
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    • pp.255-262
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    • 2006
  • Frequency spectrum using the conventional Fourier analysis gives adequate information about the dynamic characteristics of the slider air bearing for the linear and stationary cases. The intermittent contacts for the extremely low flying height, however, generate nonlinear and nonstationary vibration at the instant of contact. Nonlinear dynamic model should be developed to simulate the impulse response of the air bearing during slider-disk contact. Time-frequency analysis is widely used to investigate the nonstationary signal. Several time-frequency analysis methods are employed and compared for the slider vibration signal caused by the impact against an artificially induced scratch on the disk. The representative Wigner-Ville distribution leads to the severe interference problem by cross terms even though it gives good resolution both in time and frequency. The smoothing process improves the interference problem at the expense of resolution. In order to get the results with good resolution and little interference, the reassignment method is proposed. Among others the reassigned Gabor spectrogram shows the best resolution and readability with negligible interference.

Nondestructive Evaluation for Artificial Degraded Stainless 316 Steel by Time-Frequency Analysis Method

  • Nam, Ki-Woo;Kim, Young-Un
    • 한국해양공학회지
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    • 제15권3호
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    • pp.87-92
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    • 2001
  • In this studies, joint time-frequency analysis techniques were applied to analyze ultrasonic signals in the degraded austenitic 316 stainless steels, to study the evolution of damage in these materials. It was demonstrated that the nonstationary characteristics of ultrasonic signals could be analyzed effectively by these methods. The WVD was more effective for analyzing the attenuation and frequency characteristics of the degraded materials through ultrasonic. It is indicated that the joint time-frequency analysis, WVD method, should also be useful in evaluating various damages and defects in structural members.

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시주파수 표현에 의한 시변파워스펙트럼 추정 알고리즘에 관한 연구 (A STUDY ON THE TIME-VARYING POWER SPECTRUM ESTIMATION ALGORITHM USING TIME-FREQUENCY REPRESENTATION)

  • 이정환;이준영;이동준;김한수;전우철;이명호
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 1999년도 하계학술대회 논문집 B
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    • pp.991-993
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    • 1999
  • This study proposed a new algorithm to assess autonomic function activity using Time-Frequency Representation(TFR). TFR is a way of describing the time-valiant energy of a signal. A discrete Wigner representation that is capable of filtering out any cross terms occuring in the Wigner-Ville Distribution(WVD) is used for time-variant energy distribution of heart rate variability(HRV) signals. And the marginal condition are evaluated to estimate power spectrum of HRV signals. The proposed algorithm showed that estimated power spectrum of HRV signals well describe the autonomic nerve system function and also showed the dynamics of autonomic nervous system response.

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시간-주파수 해석법에 의한 5083 알루미늄의 피로균열 진전에 의할 음향방출 신호의 주파수특성 (Frequency Characteristics of Acoustic Emission Signal from Fatigue Crack Propagation in 5083 Aluminum by Joint Time-Frequency Analysis Method)

  • 남기우;이건찬
    • 한국해양공학회지
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    • 제17권3호
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    • pp.46-51
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    • 2003
  • Acoustic emission (AE) signals, emanated during local failure of aluminum alloys, have been the subject of numerous investigations. It is well known that the characteristics of AE are strongly influenced by the previous thermal and mechanical treatment of the sample. Possible sources of AE during deformation have been suggested as the avalanche motion of dislocations, fracture of brittle particles, and debonding of these particles from the alloy matrix. The goal of the present study is to determine if AE occurring as the result of fatigue crack propagation could be evaluated by the joint time-frequency analysis method, short time Fourier transform (STFT), and Wigner-Ville distribution (WVD). The time-frequency analysis methods can be used to analyze non-stationary AE more effectively than conventional techniques. STFT is more effective than WVD in analyzing AE signals. Noise and frequency characteristics of crack openings and closures could be separated using STFT. The influence of various fatigue parameters on the frequency characteristics of AE signals was investigated.

시간-주파수 기법을 이용한 금속파편 질량 추정 (Mass estimation using time-frequency analysis)

  • 최영철;박진호;윤두병;박근배
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2006년도 춘계학술대회논문집
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    • pp.1129-1134
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    • 2006
  • Mass estimation was derived as functions of acceleration magnitude and primary frequency. The conventional method of mass estimation used frequency data directly in the frequency domain. The signals that can be obtained sensor contained noise as well as impact signal. Therefore, how well we can detect the frequency data in noise directly determines the quality of mass estimation. To find exact frequency data, we used time-frequency analysis. The time frequency method are expected to be more useful than the conventional frequency domain analyses for the mass estimation problem on a plate type structure. Also it has been concluded that the smoothed WVD can give more reliable means than the other methodologies for the mass estimation in a noisy environment.

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