• Title/Summary/Keyword: Reflected Signal

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Optical Resonance-based Three Dimensional Sensing Device and its Signal Processing (광공진 현상을 이용한 입체 영상센서 및 신호처리 기법)

  • Park, Yong-Hwa;You, Jang-Woo;Park, Chang-Young;Yoon, Heesun
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2013.10a
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    • pp.763-764
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    • 2013
  • A three-dimensional image capturing device and its signal processing algorithm and apparatus are presented. Three dimensional information is one of emerging differentiators that provides consumers with more realistic and immersive experiences in user interface, game, 3D-virtual reality, and 3D display. It has the depth information of a scene together with conventional color image so that full-information of real life that human eyes experience can be captured, recorded and reproduced. 20 Mega-Hertz-switching high speed image shutter device for 3D image capturing and its application to system prototype are presented[1,2]. For 3D image capturing, the system utilizes Time-of-Flight (TOF) principle by means of 20MHz high-speed micro-optical image modulator, so called 'optical resonator'. The high speed image modulation is obtained using the electro-optic operation of the multi-layer stacked structure having diffractive mirrors and optical resonance cavity which maximizes the magnitude of optical modulation[3,4]. The optical resonator is specially designed and fabricated realizing low resistance-capacitance cell structures having small RC-time constant. The optical shutter is positioned in front of a standard high resolution CMOS image sensor and modulates the IR image reflected from the object to capture a depth image (Figure 1). Suggested novel optical resonator enables capturing of a full HD depth image with depth accuracy of mm-scale, which is the largest depth image resolution among the-state-of-the-arts, which have been limited up to VGA. The 3D camera prototype realizes color/depth concurrent sensing optical architecture to capture 14Mp color and full HD depth images, simultaneously (Figure 2,3). The resulting high definition color/depth image and its capturing device have crucial impact on 3D business eco-system in IT industry especially as 3D image sensing means in the fields of 3D camera, gesture recognition, user interface, and 3D display. This paper presents MEMS-based optical resonator design, fabrication, 3D camera system prototype and signal processing algorithms.

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Radio Path Loss and Angle of Arrival Measurements to the Radio Environments at 60GHz (60GHz 대역에서의 전파 환경별 경로손실 및 도래각 측정)

  • Song, Ki-Hong
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.11 no.12
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    • pp.2233-2240
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    • 2007
  • This paper presents the measured path loss exponents and standard deviations using measured data at 60GHz to analyze the propagation characteristics of millimeter wave bands having great demand for picocellular communications. In addition the angle of arrival(AOA) were measured to analyze the arrival direction of muitipath waves affecting the received signal strength. As results of analysis, the pathloss exponents in each environment are found to be lower than 2 for free space pathloss exponent. They were determined with the qualities of bottom materials affecting signal strength. The angles of arrival by multipath waves were different with the circumference structures between transmitter and receiver. That is, the multipath waves excluding direct and ground reflected wave were difficult to find in wide space such a gymnasium and playground, however the wall multipath waves were found to arrive at receiver in the corridor. The multipath waves at 60GHz can be known to hardly affect to the received signal strength because of weak signals compared with direct wave.

Study on Depth Estimation and Characteristic Analysis of Underwater Source Based on Deep-Sea Broadband Signal Modeling (심해역 광대역 신호 모델링 기반 수중 음원의 심도 추정 및 특성 분석 연구)

  • Sunhyo Kim;Hansoo Kim;Donhyug Kang;Sungho Cho
    • Journal of the Korea Institute of Military Science and Technology
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    • v.27 no.5
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    • pp.535-543
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    • 2024
  • Studies on estimating the underwater sound source localization using acoustic signal characteristics have mainly been conducted in shallow waters. Recently, technologies for stably and efficiently estimating the underwater sound sources localization using the underwater sound propagation characteristics of the Reliable Acoustic Path(RAP) in deep water areas are being studied. Underwater surveillance technology in deep sea areas is known to have the advantage of having low detection performance variability due to time-varying underwater environments and having a small shadow zone, making it easy to stably detect underwater sound sources and estimate location even from relatively long distance. In this study, we analyzed the sound propagation characteristics based on the actual marine environment in the deep sea of the Korean Peninsula and conducted a study to analyze the estimation performance of sound source depth using the broadband interference pattern of direct wave and sea surface reflected waves radiating from underwater sound sources.

Effects of External PIM Sources on Antenna PIM Measurements

  • Kim, Jin-Tae;Cho, In-Kui;Jeong, Myung-Yung;Choy, Tae-Goo
    • ETRI Journal
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    • v.24 no.6
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    • pp.435-442
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    • 2002
  • Antenna Passive Intermodulation (PIM) level measurement results are rarely credited to be due to external signal receiving characteristics of the antennas or serious effects from external PIM sources, such as the anechoic chamber absorber and antenna tower. This paper presents an antenna PIM model for a reflected PIM measurement method. Based on the findings of null point generation and the behavior of the third order PIM values obtained by theoretical predictions and experimental results, we concluded that the results of the antenna PIM level test were influenced by the external PIM sources generated by the anechoic chamber absorber and the path differences of PIM signals coming into the antenna.

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Improvement of a Pound-Drever-Hall Technique to Measure Precisely the Free Spectral Range of a Fabry-Perot Etalon

  • Seo, Dong-Sun;Park, Chongdae;Leaird, Daniel E.;Weiner, Andrew M.
    • Journal of the Optical Society of Korea
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    • v.19 no.4
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    • pp.357-362
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    • 2015
  • We examine the principle of a modified Pound-Drever-Hall (PDH) technique to measure the free spectral range of a Fabry-Perot etalon (FPE). The FPE's periodic transmission of phase-modulated light allows us to adopt a sampling theorem to develop a new relationship for the PDH error signal. This leads us to find the key parameters governing the measurement accuracy: the phase modulation index ${\beta}$ and the FPE finesse. Without any additional complexity for background noise reduction, we achieve a measurement accuracy of 0.5 ppm. The improvement is mainly attributed to the wide-band phase modulation approaching ${\beta}=10$, and partly to the use of both reflected and transmitted light from the FPE and good FPE finesse.

Stereo Sound Image Expansion Using Phase Shifting and Precedence Effect in Television (위상 처리 방식과 선착 효과를 이용한 텔레비전에서의 스테레오 음상 확대)

  • 오제화;이종철
    • Proceedings of the IEEK Conference
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    • 1998.10a
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    • pp.1239-1242
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    • 1998
  • In television stereo system, to produce a realistic sound effect is very difficult because the distance between stereo speakers is very narrow. Many signal processing methods of widening the sound image for spatial impression have been studied. One of the methods of widening the sound image is using the Precedence Effect by reflected sound. However, this method does not work effectively in lower frequencies because of directivity of a speaker. In this paper, we propose an effective method of expanding stereo image using Precedence Effect and Phase Shifting method to produce a whole band frequency sound expansion. In experiments, we confirm the usefulness of the proposed stereo sound image expansion system.

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Optical Autofocus System for Wafer Steppers using PSD as the Position Sensor (PSD를 이용한 광학적 자동 촛점장치)

  • 박기수
    • Korean Journal of Optics and Photonics
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    • v.4 no.2
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    • pp.157-161
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    • 1993
  • An optical autofocus system for a DUV KrF excimer laser wafer stepper was developed by using the PSD (Position Sensitive Detector) as the position sensor. The laser beam was incident on the surface of wafer and the reflected beam was magnified optically by a lens. And the beam was directed onto the surface of PSD by a mirror system. The spatial resolution of the autofocus system was found to be $0.03{\mu}m$.

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Measurement of the acoustic impedance by using beamforming method in a free-field (자유 음장에서 빔형성 방법을 이용한 음향 임피던스 측정)

  • Sun, Jong-Cheon;Shin, Chang-Woo;Baek, Sun-Gwon;Kang, Yeon-June
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2007.11a
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    • pp.969-974
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    • 2007
  • In this paper, a beamforming technique is introduced to measure the acoustic impedance at both normal and oblique incidence in a free field. The acoustic impedance is obtained by separating incident and reflected signals using the adaptive nulling method which is one of the various beamforming algorithms. To obtain better results, pressure vector commonly used in array signal processing is replaced with the transfer function vector between each microphone and the white Gaussian noise is suppressed by a wavelet shrinkage technique. The experiments conducted in a semi-anechoic room show that the proposed method is efficient and accurate in measuring the acoustic impedance of sound absorbing materials under a free field condition.

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Characterization of Pipe Defects in Torsional Guided Waves Using Chirplet Transform (첩릿변환을 이용한 배관 결함 특성 규명)

  • Kim, Chung-Youb;Park, Kyung-Jo
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.24 no.8
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    • pp.636-642
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    • 2014
  • The sensor configuration of the magnetostrictive guided wave system can be described as a single continuous transducing element which makes it difficult to separate the individual modes from the reflected signal. In this work we develop the mode decomposition technique employing chirplet transform, which is able to separate the individual modes from dispersive and multimodal waveform measured with the magnetostrictive sensor, and to estimate the time-frequency centers and individual energies of the reflection, which would be used to locate and characterize defects. The reflection coefficients are calculated using the modal energies of the separated mode. Results from experimental results on a carbon steel pipe are presented, which show that the accurate and quantitative defect characterization could become enabled using the proposed technique.

Detection of Axial Defects in Pipes Using Chirplet Transform (첩릿변환을 이용한 배관 축방향 결함검출)

  • Kim, Young-Wann;Park, Kyung-Jo
    • Journal of Power System Engineering
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    • v.20 no.4
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    • pp.26-31
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    • 2016
  • The implementation of chirplet transform to locate axially aligned defects in pipes has been investigated. The results are obtained from experiments performed on a carbon steel pipe using magnetostrictive sensors. Chirplet transform is applied to the reflected signal to separate the individual modes from dispersive and multimodal waveform. The separated modes are used to calculate reflection coefficients which would be used to characterize defects. It is found that the reflection from a defect consists of the wave pulses with gradually decaying amplitudes. Also the results show that the reflection coefficient initially increases with the crack length but finally reaches an oscillating regime.