• Title/Summary/Keyword: Power spectrum

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Improvement of Power Spectrum in Ultrashort Pulse Reflectometry Signals Using Three Chirp Configuration

  • Roh, Young-Su
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.28 no.3
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    • pp.51-56
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    • 2014
  • The flat power spectrum of the transmitter output signal for the desired frequency range is ideal to achieve the best performance of ultrashort pulse reflectometry. However, the power spectrum of a typical pulse generator decreases significantly as frequency increases. A configuration of three chirped waveforms was employed to improve the power spectrum of the transmitter signal at higher frequencies. To determine the amplification gain required for higher frequency components, three chirped waveforms were theoretically generated and their power spectra were measured using numerical band-pass filters. Based on the results of numerical computations, the three chirp configuration was successfully applied to the design of the transmitter for a broadband system.

Efficient Method for Recovering Spectral Reflectance Using Spectrum Characteristic Matrix (스펙트럼 특성행렬을 이용한 효율적인 반사 스펙트럼 복원 방법)

  • Sim, Kyudong;Park, Jong-Il
    • Journal of Korea Multimedia Society
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    • v.18 no.12
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    • pp.1439-1444
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    • 2015
  • Measuring spectral reflectance can be regarded as obtaining inherent color parameters, and spectral reflectance has been used in image processing. Model-based spectrum recovering, one of the method for obtaining spectral reflectance, uses ordinary camera with multiple illuminations. Conventional model-based methods allow to recover spectral reflectance efficiently by using only a few parameters, however it requires some parameters such as power spectrum of illuminations and spectrum sensitivity of camera. In this paper, we propose an enhanced model-based spectrum recovering method without pre-measured parameters: power spectrum of illuminations and spectrum sensitivity of camera. Instead of measuring each parameters, spectral reflectance can be efficiently recovered by estimating and using the spectrum characteristic matrix which contains spectrum parameters: basis function, power spectrum of illumination, and spectrum sensitivity of camera. The spectrum characteristic matrix can be easily estimated using captured images from scenes with color checker under multiple illuminations. Additionally, we suggest fast recovering method preserving positive constraint of spectrum by nonnegative basis function of spectral reflectance. Results of our method showed accurately reconstructed spectral reflectance and fast constrained estimation with unmeasured camera and illumination. As our method could be conducted conveniently, measuring spectral reflectance is expected to be widely used.

False Alarm Probability of the Spectrum Sensing Scheme Using the Maximum of Power Spectrum (전력 스펙트럼의 최대값을 사용한 스펙트럼 감지 방식의 오경보 확률)

  • Lim, Chang Heon
    • Journal of the Institute of Electronics and Information Engineers
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    • v.51 no.1
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    • pp.37-41
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    • 2014
  • Recently, a lot of research efforts has been directed toward spectrum sensing techniques exploiting the some characteristics of power spectrum. Among them, a sensing technique employing the maximum of power spectrum as a test statistic has appeared in the literature and its false alarm probability was also derived under the assumption that the test statistic follows the Gaussian distribution. This paper provides an exact form of the false alarm probability without using the assumption and compares it with the previous work.

CONVERGENCE AND POWER SPECTRUM DENSITY OF ARIMA MODEL AND BINARY SIGNAL

  • Kim, Joo-Mok
    • Korean Journal of Mathematics
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    • v.17 no.4
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    • pp.399-409
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    • 2009
  • We study the weak convergence of various models to Fractional Brownian motion. First, we consider arima process and ON/OFF source model which allows for long packet trains and long inter-train distances. Finally, we figure out power spectrum density as a Fourier transform of autocorrelation function of arima model and binary signal model.

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Spread Spectrum Method based Power Line Communication for Plant Monitoring and Control System (전력선 통신을 이용한 plant 감시 제어 시스템)

  • 서민상;성석경;안병규
    • Proceedings of the KIPE Conference
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    • 1997.07a
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    • pp.211-215
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    • 1997
  • Localized communication networks for office automation, security monitoring, environmental management of buildings, computer communications, and other applications enjoy every increasing demand. This paper proposes a direct sequence spread spectrum communication system for use in power line data transmission. Advantages of power distribution circuits include reasonably universal coverage and easy access vis a standard wall plug. Disadvantages include limited communication bandwidth, relatively high noise levels, and varying levels of impedance, noise, and attenuation. Spread spectrum signalling provides immunity to narrow-band signal impairments and multiplexing capability. Our prototype power line communication module supports completely physical and data link layers based on the international standard ISO 10368 for reliable high-speed power line communication system. Moreover it provides useful functions to compose a plant monitoring and control system. All the circuits of the communication module are included in one compact circuit. Thus a functional communication system for the power line plant monitoring and control is implemented.

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Vocal Tract Normalization Using The Power Spectrum Warping (파워 스펙트럼 warping을 이용한 성도 정규화)

  • Yu, Il-Su;Kim, Dong-Ju;No, Yong-Wan;Hong, Gwang-Seok
    • Proceedings of the KIEE Conference
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    • 2003.11b
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    • pp.215-218
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    • 2003
  • The method of vocal tract normalization has been known as a successful method for improving the accuracy of speech recognition. A frequency warping procedure based low complexity and maximum likelihood has been generally applied for vocal tract normalization. In this paper, we propose a new power spectrum warping procedure that can be improve on vocal tract normalization performance than a frequency warping procedure. A mechanism for implementing this method can be simply achieved by modifying the power spectrum of filter bank in Mel-frequency cepstrum feature(MFCC) analysis. Experimental study compared our Proposal method with the well-known frequency warping method. The results have shown that the power spectrum warping is better 50% about the recognition performance than the frequency warping.

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Noise Power Spectrum of Radiography Detectors: II. Measurement Based on the Spectrum Averaging (방사선 디텍터의 Noise Power Spectrum : II. Spectrum의 평균을 통한 측정)

  • Lee, Eunae;Kim, Dong Sik
    • Journal of the Institute of Electronics and Information Engineers
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    • v.54 no.3
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    • pp.63-69
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    • 2017
  • In order to observe the noise property of the flat-panel digital radiography detector, measuring the normalized noise power spectrum (NNPS) from acquired x-ray images is conducted. However, the conventional NNPS measurement has an unstable property depending on the acquired image. Averaging the sample periodograms of the input image is usually performed to estimate the NNPS values and increasing the number of samples can provide a reliable NNPS measurement. In this paper, for a finite number of images, two measurement methods, which are based on averaging spectra, such as the image periodogram, are proposed and their performances are analyzed. Using x-ray images acquired from two types of radiography detectors, the two spectrum averaging methods are compared and it is shown that averaging spectra based on the maximal number of combinations of the image pairs provides the best performance in measuring NNPS.

Two-Tier Interference Elimination for Femtocells Based on Cognitive Radio Centralized Spectrum Management

  • Yi, Leng-Gan;Lu, Yi-Min
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.8 no.5
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    • pp.1514-1531
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    • 2014
  • Femtocell provides better coverage and higher spectrum efficiency in areas rarely covered by macrocells. However, serious two-tier interference emerging from randomly deploying femtocells may create dead zones where the service is unavailable for macro-users. In this paper, we present adopting cognitive radio spectrum overlay to avoid intra-tier interference and incorporating spectrum underlay and overlay to coordinate cross-tier interference. It is a novel centralized control strategy appropriate for both uplink and downlink transmission. We introduce the application of proper spectrum sharing strategy plus optimal power allocation to address the issue of OFDM-based femtocells interference-limited downlink transmission, along with, a low-complexity suboptimal solution proposed. Simulation results illustrate the proposed optimal scheme achieves the highest transmission rate on successfully avoiding two-tier interference, and outperforms the traditional spectrum underlay or spectrum overlay, via maximizing the opportunity to transmit. Moreover, the strength of our proposed schemes is further demonstrated by comparison with previous classic power allocation methods, in terms of transmission rate, computational complexity and signal peak-to-average power ratio.

Power Spectrum of Jittered Random Pulse Train (불규칙 Pulse 신호의 전력 Spectrum)

  • 최양희;김재경
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.17 no.1
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    • pp.10-13
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    • 1980
  • The power spectrum of jittered pulse train is derived for the independent stationary pulse sequence with a stationary Gaussian phase jitter. For the unipolar pulse train signal, it is shown that as the phase jitter increases, the continuous Part of the power spectrum increases chile the discrete part decreases.

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Computation of Uniform Hazard Spectrum for Wolsong Nuclear Power Plants. (월성 원전 부지의 등재해도 스펙트럼 계산)

  • 신진수
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 1998.10a
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    • pp.297-303
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    • 1998
  • The uniform hazard spectrum of Wolsong Nuclear Power plant Site is computed in order to estimate probabilistically the characteristics of spectral ground response. The spectral hazard values calculated from the seismic zoning maps proposed by eight seismologist are combined with equal weight to produce a uniform hazard spectrum. The uniform hazardd spectra corresponding to reference probabilities of 1.0 $\times$10-4/year and 1.0$\times$10-5/year are presented, which largely depend on the spectral attenuation relation. The computational results of this study contribute to verify the conservatism of the design ground spectrum of Wolsong Nuclear Power Plant.

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