• Title/Summary/Keyword: doppler measurements

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Ranging Data Accuracy in K13 S-Band Antenna

  • Ahn Sang-il;Park Dong-Chul
    • Proceedings of the KSRS Conference
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    • 2004.10a
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    • pp.464-466
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    • 2004
  • Ranging and 2-way Doppler measurements are very essential source for orbit determination in LEOP (Launch and Early Operation). This paper shows ranging system features of 13M TT &C antenna and test results recently acquired with KOMPSAT-l. Ranging and 2-way Doppler measurements were compared with KOMPSAT-I GPS telemetry data. Through comparison, it was found that constant and accurate ranging measurements are available with 13M antenna system. Ranging and Doppler measurement function is expected to be used for KOMPSAT-1 and KOMPSAT-2.

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A Study on Precise Positioning with Doppler Measurements for Ground Transportation System (도플러 측정치를 이용한 육상교통 환경에 적합한 정밀 측위 기법 연구)

  • Lee, Byung-Hyun;Jee, Gyu-In
    • Journal of Advanced Navigation Technology
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    • v.14 no.5
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    • pp.632-639
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    • 2010
  • Ground Transportation is one of the most required field that users need positioning information Especially, more precise position can make smart traffic management possible and bring convenience to users. By advanced wireless network, cars can receive the GPS information of reference station in any tim e and any where. Thus land vehicles are possible to process precise positioning. In general, for precise positioning code and phase measurements are used. But receivers provide not only code and phase measurements but also doppler measurements and Doppler is direct measurement of velocity. In this paper, because velocity is very important information required in Ground Transportation, precise positioning for Ground Transportation is studied. For precise positioning RTK(Real-Time Kinematic) was used and double differenced doppler measurements were added, As a Result, positioning error by multipath and cycle slip was soften. However there still remained Positioning error. Thus smoothing technique using doppler measurement in position domain is used for softening positioning error.

GNSS Precise Positioning Design for Intelligent Transportation System (지능형 교통시스템에 적합한 위성항법 기반의 정밀측위 구조 설계)

  • Lee, Byung-Hyun;Im, Sung-Hyuck;Heo, Moon-Beom;Jee, Gyu-In
    • Journal of Institute of Control, Robotics and Systems
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    • v.18 no.11
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    • pp.1034-1039
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    • 2012
  • In this paper, a structure of precise positioning based on satellite navigation system is proposed. The proposed system is consisted with three parts, range domain filter, navigation filter and position domain filter. The range domain filter generates carrier phase-smoothed-Doppler and Doppler-smoothed-code measurements. And the navigation filter calculates position and velocity using double-differenced code/carrier phase/Doppler measurements. Finally, position domain filter smooth position error, and it means enhancement of positioning performance. The proposed positioning method is evaluated by trajectory analysis using precise map date. As a result, the position error occurred by multipath or cycle slip was reduced and the calculated trajectory was in true lane.

Assessment of a Phase Doppler Anemometry Technique in Dense Droplet Laden Jet

  • Koo, Ja-Ye;Kim, Jong-Hyun
    • Journal of Mechanical Science and Technology
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    • v.17 no.7
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    • pp.1083-1094
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    • 2003
  • This study represents an assessment of the phase-Doppler technique to the measurements of dense droplet laden jet. High-pressure injection fuel sprays have been investigated to evaluate the use of the Phase-Doppler anemometry (PDA) technique. The critical issue is the stability of the phase-Doppler anemometry technique for dense droplet laden jet such as Diesel fuel spray in order to insure the results from the drop size and velocity measurements are repeatable, consistent, and physically realistic because the validation rate of experimental data is very low due to the thick optical density. The effect of shift frequency is minor, however, the photomultiplier tube (PMT) voltage setting is very sensitive to the data acquisition and noise in dense droplet laden jet. The optimum PMT voltage and shift frequency should be chosen so that the data such as volume flux and drop diameter do not change rapidly.

The Technique and Normal Values of Transcranial Doppler Ultrasonography(TCD) (Transcranial Doppler Ultrasonography (TCD)의 시행 방법 및 정상치)

  • Sohn, Young Ho
    • Annals of Clinical Neurophysiology
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    • v.1 no.1
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    • pp.39-46
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    • 1999
  • Transcranial doppler ultrasonography (TCD) is a new, non-invasive and easily applicable method to evaluate cerebral hemodynamics. Last 10 years, its use in Korea has been dramatically expanded, but the qualification of TCD laboratory has yet to be settled. Since duplex sonography is seldom used in Korea, we have to depend totally on TCD to evaluate cerebral hemodynamic changes. Thus, all of the available data from every detectabler cerebral arteries has to be obtained for accurate interpretation of TCD measurements. Moreover, flow direction and wave form should be concerned in addition to the flow velocity. In this article, I present technique to measure the anterior, meddle and posterior cerebral arteries, the internal carotid artery siphon and at cervical level, and the vertebral and the basilar artery, and normal values for these measurements which is essential for the adequate interpretation.

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Multi-Target Position Estimation Technique Using Micro Doppler in FMCW Radar System (FMCW 레이다 시스템에서 마이크로 도플러를 이용한 다중 목표물 위치 추정 기법)

  • Yoo, Kyungwoo;Chun, Joohwan;Ryu, Chung-Ho
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.27 no.11
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    • pp.996-1003
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    • 2016
  • Trilateration technique using time of arrival(TOA) is generally used for single target position estimation in radar system. However, trilateration technique has limitation in case of multiple targets, since it is difficult to distinguish the measurements corresponding to the respective targets. In this study, to eliminate ambiguity of relation between measurements and targets, micromotion of each target is measured by micro Doppler which is actively studied in radar industry nowadays and these information are used to distinguish measurements used at trilateration technique. Resultingly, the trilateration technique is applied successfully for each target. The targets are considered as multiple submissiles separated from the missile. Simulation results shows the performance of the proposed algorithm.

Development of Dual Beam High Speed Doppler OFDI

  • Kim, SunHee;Park, TaeJin;Oh, Wang-Yuhl
    • Journal of the Korean Society for Nondestructive Testing
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    • v.33 no.3
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    • pp.283-288
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    • 2013
  • This paper describes development of a high speed Doppler OFDI system for non-invasive vascular imaging. Doppler OFDI (optical frequency domain imaging) is one of the phase-resolved second generation OCT (optical coherence tomography) techniques for high resolution imaging of moving elements in biological tissues. To achieve a phase-resolved imaging, two temporally separated measurements are required. In a conventional Doppler OCT, a pair of massively oversampled successive A-lines is used to minimize de-correlation noise at the expense of significant imaging speed reduction. To minimize a de-correlation noise between targeted two measurements without suffering from significant imaging speed reduction, several methods have been developed such as an optimized scanning pattern and polarization multiplexed dual beam scanning. This research represent novel imaging technique using frequency multiplexed dual beam illumination to measure exactly same position with aimed time interval. Developed system has been verified using a tissue phantom and mouse vessel imaging.

Velocity measurements in complex flows of non-Newtonian fluids

  • Muller, Susan J.
    • Korea-Australia Rheology Journal
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    • v.14 no.3
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    • pp.93-105
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    • 2002
  • Experimental methods for making quantitative measurements of velocity fields in non-Newtonian fluids are reviewed. Techniques based on light scattering spectroscopy - laser Doppler velocimetry and homodyne light scattering spectroscopy, techniques based on imaging the displacement of markers - including particle image velocimetry and molecular tagging velocimetry, and techniques based on nuclear magnetic resonance imaging are discussed. The special advantages and disadvantages of each method are summarized, and their applications to non-Newtonian flows are briefly reviewed. Example data from each technique are also included.

Ocean Surface Current Retrieval Using Doppler Centroid of ERS-1 Raw SAR Data

  • Kim Ji-Eun;Kim Duk-jin;Moon Wooil M.
    • Proceedings of the KSRS Conference
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    • 2004.10a
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    • pp.590-593
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    • 2004
  • Extraction of ocean surface current velocity offers important physical oceanographic parameters especially on understanding ocean environment. Although Remote Sensing techniques were highly developed, the investigation of ocean surface current using Synthetic Aperture Radar (SAR) is not an easy task. This paper presents the results of ocean surface current observation using Doppler Centroid of ERS-1 SAR data obtained off the coast of Korea peninsula. We employed the concept, in which Doppler frequency shift and the ocean surface current are closely related, to evaluate ocean surface current. Moving targets cause Doppler frequency shift of the back scattered radar waves of SAR, thus the line-of-sight velocity component of the scatters can be evaluated. The Doppler frequency shift can be measured by estimating the difference between Doppler Centroid of raw SAR data and reference Doppler Centroid. Theoretically, the Doppler Centroid is zero; however, squinted antenna which is affected by several physical factors causes Doppler Centroid to be nonzero. The reference Doppler Centroid can be obtained from measurements of sensor trajectory, attitude and Earth model. The estimated Doppler Centroid was compensated by considering the accurate attitude estimation of ERS-1 SAR. We could verify the correspondence between the estimated ocean surface current and observed in-situ data in the error bound.

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Accuracy of Pulsed Doppler Ultrasound Velocity Measurements : In Vitro Flow Phantom Study (Pulsed Doppler 초음파속도측정의 정확도 판정 : 유동 phantom 연구)

  • Kim, Young-Ho;Min, Byung-Goo
    • Proceedings of the KOSOMBE Conference
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    • v.1994 no.12
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    • pp.153-156
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    • 1994
  • An in vitro steady flow experiment was performed in order to test the accuracy of velocity measurement obtained through a pulsed Doppler echocardiography. A flow phantom was designed for the use in a wide velocity range at a given flow rate. The results showed that the pulsed Doppler velocity measurement obtained in this flow phantom is accurate at low flow rates. However, ultrasound velocity measurement should be performed under a careful considerations of PRF and Doppler gain settings, especially at higher flow rates.

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