• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.969-974
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• 2004

Although guided-waves are very efficient for long-range nondestructive damage inspection, it is not easy to extract meaningful pulses of small magnitude out of noisy signals. The ultimate goal of this research is to develop an efficient signal processing technique for the current guided-wave technology. The specific contribution of this investigation towards achieving this goal, a two-stage Gabor pulse-based matching pursuit algorithm is proposed : rough approximations with a set for predetermined parameters characterizing the Gabor pulse and fine adjustments of the parameters by optimization. The parameters estimated from the measured signal are then used to assess not only the location but also the size of a crack existing in a rod. To validate the effectiveness of the proposed method, the longitudinal wave-based damage detection in rods is considered. To estimate the crack size, Love's theory for the dispersion of longitudinal waves is employed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.9C
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• pp.905-913
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• 2006

In the impulse radio ultra-wideband communication systems, the residual timing offset exists when the acquisition and tracking of the timing synchronization is well done. And the offset affects the performance of the system dramatically. In order to compensate the offset, we present the digital phase-locked loop that uses the reference signal in the correlation detection receiver. First, we show the degradation of BER performance that is caused by the offset, and then compensation process of the timing tracker and performance improvement. In this paper, the timing detector in the tracker operates at the sampling period of frame level uses the correlation between received and reference signal. Also, we present the performance comparison by using the computer simulation results for different Gaussian monocycle pulses.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.3
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• pp.3-8
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• 2002

본 논문에서는 수 GHz 대역폭에 이르는 매우 짧은 펄스를 이용하여 신호를 고속으로 전송할 수 있는 초광대역 통신 시스템(Ultra Wide Band system : UWB)의 특성에 대해 분석하고자 한다. UWB 시스템은 기존 시스템보다 더 낮은 비용과 전력 소비로 훨씬 넓은 주파수 대역을 이용하여, 기존 협대역 시스템과의 공유를 가능하게 하며, IEEE 802.11나 Bluetooth에 비해 월등히 높은 bits/sec/squaremeter로 정의되는 spatial capacity를 제공할 수 있어 최근 활발히 개발되고 있는 근거리 무선 통신망에 매우 적합하다. 특히 UWB 시스템은 짧은 펄스를 이용한 매우 정교한 시간 분해능을 이용한 Cm단위 위치 추적이라는 UWB만의 고유 기능도 제공할 수 있다.

• Current Industrial and Technological Trends in Aerospace
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• v.7 no.1
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• pp.113-118
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• 2009

In this paper, we described the model of noise, target for tracking radar and range tracking, angle tracking, and Doppler frequency tracking for target acquisition and tracking. Target signal as well as the noise signal is modeled as random process varying with elapsed time. This paper addresses three areas of radar target tracking: range tracking, angle tracking, and Doppler frequency tracking. In general, range tracking is prerequisite to and inherent in both angle and Doppler frequency tracking systems. First, we introduced the several range tracking and described techniques for achieving range tracking. Second, we described the radar angle tracking techniques including conical scan, sequential lobing, and monopulse. Finally, we presented concepts and techniques for Doppler frequency tracking for several radar types.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.6
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• pp.572-580
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• 2015

RF skin tracking of instrumentation RADAR cannot acquire stable track data, because of effect of multipath interference especially elevation direction. In this paper, low altitude target tracking method using laser tracking system is suggested to overcome this restriction. The effect of multipath can be reduced by increasing angle resolution with laser characteristics of very short pulse and narrow beamwidth. RF skin track, beacon track and laser track data for the integrated calibration target on the ground and target ship on the sea are gathered. And they are compared and analyzed to confirm the performance of laser tracking system. As a result, it shows that the suggested laser track method has better performance than RF skin track under multipath conditions.

• Journal of Advanced Navigation Technology
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• v.27 no.5
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• pp.568-573
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• 2023

Range resolution is the ability to distinguish different targets placed in same angular direction but at different distances from the radar. Normally, Range resolution requirement is defined as the width of transmitting pulse. The width of transmitting pulse does not mean the ability to distinguish two different targets. Range resolution performance to detect and track targets separately depends on the signal processing and tracking algorithm not only the width of transmitting pulse. This paper analyzes the processing steps in algorithms to affect the range resolution performance and verifies the results by roof-lab ground test using beacon signal. As a result, to track targets with the same angular position separately, it is desirable to have larger range difference than plot-track association test gate.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.9
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• pp.2139-2144
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• 2013

This paper has analyzed the possibility about implementation of the low-cost, high-efficiency tracking antenna using flat panel antenna. Tracking antenna is consisted of four flat-antenna, comparators, tracking receiver, controller. We analyzed input signal of antenna array about the magnitude and phase of radio wave. In addition, We suggested the available tracking range through the analysis of output signal. We have minimized the error rate that happened on two path through design two path of the azimuth and elevation. Analysis results has a tracking range of ${\pm}3$ degrees, it is possible to implement.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.5
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• pp.528-536
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• 2010

A monopulse feeder gives the most important impact upon the radiation pattern characteristics of a multi-function radar or a tracking radar which uses the space feed. It is described that the triple-mode type monopulse feeder which possesses the optimum aperture illumination for three monopulse channels is designed and measured in this paper. The measured results show that the designed feeder has not only the characteristics of the optimum aperture illimination in each channel and also very low return loss over the 10 % of fractional bandwidth at X-band. This means that the feeder provides the antenna system with low sidelobe level and high monopulse slope characteristics.

• Proceedings of the KSEG Conference
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• 2003.04a
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• pp.139-145
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• 2003

본 연구는 화강암 분포지역의 150m 심도에 분포하는 소규모 국지 단열대에 대한 추적자 시험 결과이다. 해수를 사용하여 관측공에서 측정한 지하수의 전기전도도 변화를 $Cl^{-}$ 농도로 계산하였고, 모멘트해석법과 준해석해를 이용한 해로 단열대에 대한 수리파라메터를 추정하였다. 그 결과를 펄스시험에서 얻은 수리전도도와 비교하였으며, 계산된 수리파라메터를 사용하여 시험구간 내의 유효단열간극의 크기를 구하였다.

• Journal of the Korean Vacuum Society
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• v.4 no.4
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• pp.425-430
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• 1995

본 연구에서는 Marx Generator와 펄스 형성라인을 결합시켜 만든 VEBA(Versatile Electron Beam Accelerator)장치를 사용하여 아르곤 이온의 에너지를 식각 추적 방법을 써서 측정하였다. 이 장치에서 240kV, 30kA, 60ns의 전자빔이 발생되었다. 이 전자빔이 이극관을 통과하면서 이 때 주입된 아르곤 기체가 이온화되어 아르곤 이온이 얻어진다. 이렇게 형성된 이온은 가상적 음극에 의해 진공 전파관 속으로 가속되고 이를 전자빔과 분리한 후 알루미늄 박막으로 만든 식각 추적판을 때리도록 장치하였다. 이때 아르곤 이온이 뚫고 들어간 알루미늄 박막의 수로부터 이온의 에너지를 구하였다. 이렇게 얻어진 실험값은 이론값과 잘 일치하였다.