• Title, Summary, Keyword: Frequency Domain

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An Effect of Sampling Rate to the Time and Frequency Domain Analysis of Pulse Rate Variability (샘플링율이 맥박변이도 시간 및 주파수 영역 분석에 미치는 영향)

  • Yang, Yoon La;Shin, Hangsik
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.65 no.7
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    • pp.1247-1251
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    • 2016
  • This study aims to investigate the effect of sampling frequency to the time domain and frequency domain analysis of pulse rate variability (PRV). Typical time domain variables - AVNN, SDNN, SDSD, RMSSD, NN50 count and pNN50 - and frequency domain variables - VLF, LF, HF, LF/HF, Total Power, nLF and nHF - were derived from 7 down-sampled (250 Hz, 100 Hz, 50 Hz, 25 Hz, 20 Hz, 15 Hz, 10 Hz) PRVs and compared with the result of heart rate variability of 10 kHz-sampled electrocardiogram. Result showed that every variable of time domain analysis of PRV was significant at 25 Hz or higher sampling frequency. Also, in frequency domain analysis, every variable of PRV was significant at 15 Hz or higher sampling frequency.

Estimation of Fault Location on a Transmission Line via Time-Frequency Domain Reflectometry (시간-주파수 반사파 계측 방법을 이용한 전송선로의 결함 위치 추정)

  • Choe TokSon;Kwak Ki-Seok;Yoon Tae Sung;Park Jin Bae
    • The Transactions of the Korean Institute of Electrical Engineers D
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    • v.54 no.9
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    • pp.521-530
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    • 2005
  • In this paper, a new high resolution reflectometry scheme, time-frequency domain reflectometry(TFDR), isproposed to detect and estimate a fault in a transmission line. Traditional reflectometry methodologies have been achieved either in the time domain or in the frequency domain only. However, the TFDR can jump over the performance limits of the traditional reflectometry methodologies because the acquired signal is analyzed in time and frequency domain simultaneously. In the TFDR, the new reference signal and the novel TFDR algorithm are proposed for analyzing the acquired signal in the time-frequency domain. Because the reference signal of Gaussian envelop chirp signal is localized in the time and frequency domain simultaneously, it is suitable to the analysis in the time-frequency domain. In the proposed TFDR algorithm, the time-frequency distribution function and the normalized time-frequency cross correlation function are used to detect and estimate a fault in a transmission line. That algorithm is verified for real-world coaxial cables which are typical transmission line with different types of faults by the TFDR system composed of real instruments. The performance of the TFDR methodology is compared with that o( the commercial time domain reflectomeoy(TDR) experiments, so that concludes the TFDR methodology can detect and estimate the fault with smaller error than TDR methodology.

Experimental identification of nonlinear model parameter by frequency domain method (주파수영역방법에 의한 비선형 모델변수의 실험적 규명)

  • Kim, Won-Jin
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.22 no.2
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    • pp.458-466
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    • 1998
  • In this work, a frequency domain method is tested numerically and experimentally to improve nonlinear model parameters using the frequency response function at the nonlinear element connected point of structure. This method extends the force-state mapping technique, which fits the nonlinear element forces with time domain response data, into frequency domain manipulations. The force-state mapping method in the time domain has limitations when applying to complex real structures because it needd a time domain lumped parameter model. On the other hand, the frequency domain method is relatively easily applicable to a complex real structure having nonlinear elements since it uses the frequency response function of each substurcture. Since this mehtod is performed in frequency domain, the number of equations required to identify the unknown parameters can be easily increased as many as it needed, just by not only varying excitation amplitude bot also selecting excitation frequency domain method has some advantages over the classical force-state mapping technique in the number of data points needed in curve fit and the sensitivity to response noise.

Frequency-Domain Adaptive Noise Canceller and Its Algorithm with Adaptive Compensator (적응보상기를 채용한 주파수영역 적응 잡음제거 시스템 및 알고리즘)

  • 손경식;김수중
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.27 no.9
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    • pp.1456-1467
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    • 1990
  • The time domain adaptive noise canceller (time domain ANC) with the adaptive compensator and its algorithm, so called compensated least mean squares(CLMS) algorithm, had been introduced to improve the performance of ANC[1]. In this paper the time domain ANC with the adaptive compensator is transformed into the frequency domain ANC with the adaptive ocmpensator. An compensated frequency-domain least mean squares(CFLMS) algorithm that can adapt the proposed frequency domain ANC is presented.

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ERROR ESTIMATIES FOR A FREQUENCY-DOMAIN FINITE ELEMENT METHOD FOR PARABOLIC PROBLEMS WITH A NEUMANN BOUNDARY CONDITION

  • Lee, Jong-Woo
    • Bulletin of the Korean Mathematical Society
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    • v.35 no.2
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    • pp.345-362
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    • 1998
  • We introduce and anlyze a naturally parallelizable frequency-domain method for parabolic problems with a Neumann boundary condition. After taking the Fourier transformation of given equations in the space-time domain into the space-frequency domain, we solve an indefinite, complex elliptic problem for each frequency. Fourier inversion will then recover the solution of the original problem in the space-time domain. Existence and uniqueness of a solution of the transformed problem corresponding to each frequency is established. Fourier invertibility of the solution in the frequency-domain is also examined. Error estimates for a finite element approximation to solutions fo transformed problems and full error estimates for solving the given problem using a discrete Fourier inverse transform are given.

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A Study on Frequency and Time Domain Interpretation for Safety Evaluation of old Concrete Structure (노후된 콘크리트 구조물의 안전도 평가를 위한 초음파기법의 주파수 및 시간영역 해석에 관한 연구)

  • Suh Backsoo;Sohn Kwon-Ik
    • Tunnel and Underground Space
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    • v.15 no.5
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    • pp.352-358
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    • 2005
  • For non-destructive testing of concrete structures, time and frequency domain method were applied to detect cavity in underground model and pier model. To interpret the measured data, time domain method made use of tomography which was completed with first arrivaltime and inversion method. In this steady, frequency domain method using Fourier transform was tried. Maximum frequency in the frequency domain was analyzed to calculate location of cavity.

Principal component analysis in the frequency domain: a review and their application to climate data (주파수공간에서의 주성분분석: 리뷰와 기상자료에의 적용)

  • Jo, You-Jung;Oh, Hee-Seok;Lim, Yaeji
    • The Korean Journal of Applied Statistics
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    • v.30 no.3
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    • pp.441-451
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    • 2017
  • In this paper, we review principal component analysis (PCA) procedures in the frequency domain and apply them to analyze sea surface temperature data. The classical PCA defined in the time domain is a popular dimension reduction technique. Extending the conventional PCA to the frequency domain makes it possible to define PCA in the frequency domain, which is useful for dimension reduction as well as a feature extraction of multiple time series. We focus on two PCA methods in the frequency domain, Hilbert PCA (HPCA) and frequency domain PCA (FDPCA). We review these two PCAs in order for potential readers to easily understand insights as well as perform a numerical study for comparison with conventional PCA. Furthermore, we apply PCA methods in the frequency domain to sea surface temperature data on the tropical Pacific Ocean. Results from numerical experiments demonstrate that PCA in the frequency domain is effective for the analysis of time series data.

Detection and Estimation of a Faults on Coaxial Cable with TFDR Algorithm (Time Frequency Domain Reflectometry 기법을 이용한 Coaxial Cable에서의 결함 감지 및 추정)

  • Song, Eun-Seok;Shin, Yong-June;Choe, Tok-Son;Yook, Jong-Gwan;Park, Jin-Bae;Powers, Edward J.
    • The Journal of Advanced Navigation Technology
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    • v.7 no.1
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    • pp.38-50
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    • 2003
  • In this paper, a new high resolution reflectometry scheme, time-frequency domain reflectometry (TFDR), is proposed to detect and locate fault in wiring. Traditional reflectometry methods have been achieved in either the time domain or frequency domain only. However, time-frequency domain reflectometry utilizes time and frequency information of a transient signal to detect and locate the fault. The time-frequency domain reflectometry approach described in this paper is characterized by time-frequency reference signal design and post-processing of the reference and reflected signals to detect and locate the fault. Design of the reference signal in time-frequency domain reflectometry is based on the determination of the frequency bandwidth of the physical properties of cable under test. The detection and estimation of the fault on the time-frequency domain reflectometry relies on the time-frequency domain reflectometry is compared with commercial time domain reflectomtery (TDR) instrument. In these experiments provided in this paper, TFDR locates the fault with smaller error than TDR. Knowledge of time and frequency localized information for the reference and reflected signal gained via time-frequency analysis, allows one to detect the fault and estimate the location accurately.

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Frequency Domain Processing Techniques for Pulse Shape Modulated Ultra Wideband Systems

  • Gordillo, Alex Cartagena;Kohno, Ryuji
    • Journal of Communications and Networks
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    • v.9 no.4
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    • pp.482-489
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    • 2007
  • In this paper, two frequency domain signal processing techniques for pulse shape modulation(PSM) ultra wideband(UWB) systems are presented. Firstly, orthogonal detection of UWB PSM Hermite pulses in frequency domain is addressed. It is important because time domain detection by correlation-based receivers is severely degraded by many sources of distortion. Pulse-shape, the information conveying signal characteristic, is deformed by AWGN and shape-destructive addition of multiple paths from the propagation channel. Additionally, because of the short nature of UWB pulses, timing mismatches and synchronism degrade the performance of PSM UWB communication systems. In this paper, frequency domain orthogonality of the Hermite pulses is exploited to propose an alternative detection method, which makes possible efficient detection of PSM in dense multipath channel environments. Secondly, a ranging method employing the Cepstrum algorithm is proposed. This method is partly processed in the frequency domain and can be implemented without additional hardware complexity in the terminal.

On Estimating Magnitude-Squared Coherence Functions Using Frequency-Domain Adaptive Digital Filters (주파수 영역 적응 디지탈 필터를 이용한 Magnitude-Squared Coherence 함수 추정)

  • Kim, D.N.;Cha, I.W.;Youn, D.H.
    • The Journal of the Acoustical Society of Korea
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    • v.7 no.2
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    • pp.39-50
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    • 1988
  • It is proposed to use a pair of frequency-domain adaptive digital filters to estimate the magnitude squared coherence (MSC) functions of two signals. Such a method requires less computations than the LMS-MSC algorithm in which the least mean square (LMS) algorithm is applied in the time domain to compute the coefficients of a pair of adaptive digital filters. The frequency-domain adaptive digital filtering algorithms considered in this paper include the constrained frequency domain LMS (CFLMS) and the unconstrained frequency domain LMS (UFLMS) algorithms. The performance of the proposed methods are compared with those of the LMS-MSC algorithm.

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