• 전기학회논문지P
• /
• 제66권4호
• /
• pp.247-251
• /
• 2017

This paper proposes a low power transmission technique for single-carrier modulation with frequency domain equalization. As time domain signals and frequency domain signals have unique corresponding functions, inserting zeros after each symbol causes a repetition in other domain, so maximal ratio combining technique using repetitive transmission can be applied in the frequency domain. In this paper, we configure transmit signals to insert zeros after each symbols for single-carrier modulation with frequency domain equalization and maximal ratio receive combining block in the receiver structures, propose a structure for transmitter and receiver and show that its performance is better than the traditional algorithm by simulations.

• 한국소음진동공학회논문집
• /
• 제26권7호
• /
• pp.844-850
• /
• 2016

This study pertains to the extraction of the road noise component of signals from a vehicle's interior noise via the traditional frequency domain and time domain system identification methods. For road noise extraction based on the frequency domain system identification method, the appropriate matrix inversion strategy is investigated and causal and non-causal impulse response filters are compared. Furthermore, appropriate data lengths for the frequency domain system identification method are investigated. In addition to the traditional road noise extraction methods based on frequency domain system identification, a new approach to extract road noise via the time domain system identification method based on a parametric input-output model is proposed and investigated in the present study. In this approach, instead of constructing a higher order model for the full-band road noise, input and output signals are processed in the subband domain and lower order parametric models optimal to each subband are determined. These parametric models are used to extract road noises in each subband; the full band road noise is then reconstructed from the subband road noises. This study shows that both the methods in the frequency domain and the time domain successfully extract the road noise from the vehicle's interior noise.

• 대한음성학회지:말소리
• /
• 제47호
• /
• pp.85-96
• /
• 2003

It is difficult to implement sound field effect on real time using linear convolution in time domain because linear convolution needs much multiply operations. In this paper three ways is introduced to reduce multiplication operations. Firstly, linear convolution in time domain is replaced with circular convolution in frequency domain. It means that it operates multiplication in place of convolution. Secondly, one frame will be divided into several frames. It will reduce the multiplication operation in processing that transforms time domain into frequency domain. Finally, QFT will be used in place of FFT. Three ways result much reduction in multiplication operations. The reduction of the multiplication operation makes the real time implementation possible.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2006년도 심포지엄 논문집 정보 및 제어부문
• /
• pp.336-338
• /
• 2006

One of the important topics concerning the safety of electrical and electronic system is the reliability of the wiring system. The Time-Frequency Domain Reflectometry(TFDR) is a state-of-the-art system for detection and estimation of the fault on a wiring/cable. The purpose of this paper is to implement a Labview based TFDR Real Time system though the instruments of PCI extensions for Instrumentation(PXI). The TFDR Real Time system consists of the five parts: Reference signal design, signal generation, signal acquisition, algorithm execution, results diplay part. In the signal generation and acquisition parts we adopt the Arbitrary Waveform Generator(AWG) and Digital Storage Oscilloscope(DSO) PXI modules which offer commonality, compatibility and easy integration at low cost. And execution of the PXI modules not only is controlled by the Labview programing but also the total system process is executed by the Labview application software.

• 한국지진공학회논문집
• /
• 제24권2호
• /
• pp.103-110
• /
• 2020

Seismic qualification of instruments and devices mounted on electrical cabinets in a nuclear power plant is performed in this study by means of the in-cabinet response spectrum (ICRS). A simple method and two rigorous methods are proposed in the EPRI NP-7146-SL guidelines for generating the ICRS. The simple method of EPRI can give unrealistic spectra that are excessively conservative in many cases. In the past, the time domain analysis (TDA) methods have been mostly used to analyze a structure. However, the TDA requires the generation of an artificial earthquake input motion compatible to the target response spectrum. The process of generating an artificial earthquake may involve a great deal of uncertainty. In addition, many time history analyses should be performed to increase the accuracy of the results. This study developed a numerical analysis program for generating the ICRS by frequency domain analysis (FDA) method. The developed program was validated by the numerical study. The ICRS calculated by FDA thoroughly matched with those obtained from TDA. This study then confirms that the method it proposes can simply and efficiently generate the ICRS compared to the time domain method.

• International Journal of Automotive Technology
• /
• 제3권3호
• /
• pp.101-109
• /
• 2002

A time domain method for solving nonstationary random vibration caused by vehicle acceleration is first proposed in which a time changing model is established for representing nonstationary excitation of a rough road. Furthermore a novel frequency domain method called the transient power spectral density with spatial frequency (TPSD) is presented to obtain a response of vehicle system in frequency domain. This method has been proved to be valid by comparing numerical results with the exact solution.

• East Asian Economic Review
• /
• 제19권2호
• /
• pp.189-220
• /
• 2015

Multi-scale representations are effective in characterising the time-frequency characteristics of financial return series. They have the capability to reveal the properties not evident with typical time domain analysis. Given the aforesaid, this study derives crucial insights from multi scale analysis to investigate the co-movements between Indian and emerging Asian equity markets using wavelet correlation and wavelet coherence measures. It is reported that the Indian equity market is strongly integrated with Asian equity markets at lower frequency scales and relatively less blended at higher frequencies. On the other hand the results from cross correlations suggest that the lead-lag relationship becomes substantial as we turn to lower frequency scales and finally, wavelet coherence demonstrates that this correlation eventually grows strong in the interim of the crises period at lower frequency scales. Overall the findings are relevant and have strong policy and practical implications.

• 한국통신학회논문지
• /
• 제12권4호
• /
• pp.365-372
• /
• 1987

본 논문에서는 시간영역(time domain)에서 주파수안정도의 정밀정확한 측정방법중의 하나인 비트주파수방법을 이용한 주파수 안정도 측정시스템의 기본이론과 구성에 관한 사항을 다루었으며 실제 구성한 시스템의 특성을 조사하고 분석하였다.

• 한국지반환경공학회 논문집
• /
• 제15권5호
• /
• pp.31-37
• /
• 2014

탄성파는 지반 및 지반환경 관련 과업에서 다양한 형태로 활용되어 왔다. 일반적으로는 현장에서 탄성파 탐사를 수행하여 시추조사와 더불어 지반의 물성값을 평가하는 목적으로 사용되고 있으며, 지하공동의 위치파악 등에도 사용되고 있다. 환경복원이 필요한 버려진 부지에 매립된 유류 저장시설의 위치 파악 등 지반환경공학과 관련하여서도 탄성파의 활용은 활발히 이루어지고 있다. 또한 지반의 미소변형률 구간에서의 지반 거동 분석에도 탄성파를 활용하고 있다. 탄성파의 매질 내 이동속도가 주요 인자로서 활용되고 있는데, 이는 시간 영역과 주파수 영역에서 산정할 수 있다. 시간 영역에서의 탄성파의 이동속도 평가방법은 동일 위상을 갖는 특정한 점들의 시간차이를 분석하는 방법, 상호상관법을 활용한 방법으로 나뉠 수 있다. 주파수 영역에서의 탄성파의 이동속도는 진원과 수신점에서의 입력 파형과 수신파형의 위상 차이를 분석하여 산정할 수 있다. 본 연구에서는 시카고 지역에서 채취한 불교란 빙하퇴적 점성토 시료에 벤더 엘리먼트를 이용한 탄성파 시험을 실시, 동일한 탄성파에 대해 여러 가지 산정 방법을 적용하여 탄성파의 이동속도를 분석하였다. 시간영역에서 탄성파의 이동속도를 분석한 결과 데이터로거의 표본화 주파수에 영향을 크게 받는 것으로 분석되었으며, 신호에 포함되어있는 노이즈 및 수신파형의 요철 특성으로 인하여 같은 위상을 갖는 점을 정확히 찾는 것은 불가능하였다. 상호상관법으로 분석한 경우도 입력 파형과 수신파형의 주기의 차이로 인해 탄성파의 정확한 이동속도를 산정하는 것은 불가능하였다. 주파수 영역에서의 이동속도 산정의 경우 영채우기를 통해 주파수 분해능을 개선시킬 수 있어 데이터로거의 표본화 주파수에 영향을 받지 않았다. 과도파 사용으로 인한 지배주파수가 유일 값이 아닌 범위로 나타나는 단점이 있었으나, 지배주파수 범위 내의 탄성파의 이동속도의 범위는 시간 영역에서 산정한 값보다 정밀한 것으로 나타났다.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2006년도 춘계학술대회논문집
• /
• pp.1129-1134
• /
• 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.