• Title, Summary, Keyword: field measurement

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Study on Sound Field Analysis in Near-Field using Boundary Collocation Method; Decision of Optimum Points of Measurement for Line Array Sound Source with Weighting Value (경계배치법에 의한 근거리 음장 해석 기법 연구; 가중치를 갖는 선배열 음원의 최적 측정점 개수의 결정)

  • Kim, Won-Ho
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.1752-1761
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    • 2000
  • This paper describes the far-field estimation using the near-field measurement data. Measurement in far-field region gives us the acoustical characteristics of the source but in general measurement is made in near-field such as acoustic water tank or anechoic chamber, so far-field acoustical characteristics of the source should be predicted from near-field data. In this case, the number of measurement points in the near field which relates to the accuracy of the predicted field and the amount of data processing, should be optimized. Existing papers say that measurement points is proportional to kL and depends on geometry and directivity of the source. But they do not give us any definite criterion for the required number of measurement points. Boundary Collocation Method which is one of the far-field prediction methods, is analyzed based on Helmholtz integral equation and Green function and it has been found that the number of measurement points is optimized as 0.54kL which is about one half of the existing results.

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Antenna Measurement on Cylindrical Surface in Fresnel Region Using Direct Far-Field Measurement System

  • Oh, Soon-Soo;Kim, Joung-Myoun;Yun, Jae-Hoon
    • ETRI Journal
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    • v.29 no.2
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    • pp.135-142
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    • 2007
  • The small anechoic chambers built by many small-/medium-sized companies and universities present difficulties in testing electrically large antennas because the chamber size cannot satisfy the far-field criterion of large antennas. In this paper, a method for Fresnel-region measurement on a cylindrical surface with variation of the measurement height is proposed and verified by both calculations and experiments. We implement the proposed method using a direct far-field measurement system by adding a few supporting structures. The results show good accuracy.

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Planar near-field antenna measurement method based on symplectic relation and reaction concept

  • Cho, Yong-Heui
    • International Journal of Contents
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    • v.6 no.2
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    • pp.6-9
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    • 2010
  • Using symplectic relation and reaction concept, we propose a planar near-field antenna measurement method. A generalized probe compensation equation is deduced to obtain the probe correction formulation. To verify our approach, a reflector antenna with $1{\times}2$ horn array is fabricated and measured in the near-field measurement facility. The near-field measurement results are compared with the physical optics (PO) simulation. The results of measurement and simulation agree very well near to the mainbeam.

Far-Field Sound Field Estimation from Near-Field Sound Field Data Using Boundary Collocation Method ; Decision of Optimum Points of Measurement (경계 배치법(Boundary Collocation Method)에 의한 근거리 음장 자료로부터 원거리 음장의 예측 ; 최적 측정점 개수의 결정)

  • 김원호;윤종락
    • The Journal of the Acoustical Society of Korea
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    • v.18 no.6
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    • pp.31-37
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    • 1999
  • This paper describes the far-field estimation using the near-field measurement data. Measurement in far-field region gives us the acoustical characteristics of the source but in general measurement is made in near-field such as acoustic water tank or anechoic chamber, so far-field acoustical characteristics of the source should be predicted from near-field data. In this case, the number of measurement points in the near field which relates to the accuracy of the predicted field and the amount of data processing, should be optimized. Existing papers say that measurement points is proportional to kL and depends on geometry and directivity of the source. But they do not give us any definite criterion for the required number of measurement points. Boundary Collocation Method which is one of the far-field prediction methods, is analyzed based on Helmholtz integral equation and Green function and it has been found that the number of measurement points is optimized as 0.54kL which is about one half of the existing results.

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Measurement uncertainty in heavy-weight floor impact sounds (측정 불확도에 따른 중량충격음 측정편차에 관한 연구)

  • Yoo, Seung-Yup;Kim, Yong-Hee;Sim, Myoung-Hee;Jeon, Jin-Yong
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.826-829
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    • 2008
  • In a field measurement, measurement errors are produced by measuring environments and systematic errors in the measurement procedure. Measurement errors can be expressed as a measurement uncertainty. In this study, the measurement uncertainty and various measuring factors are investigated in heavy-weight impact sounds. According to KS 2810-2, the model functions, which is the estimation of the maximum SPL measurement in each octave band frequency, are determined. From this estimation model, 3.53dB is shown in 63Hz. This level is caused by the sound field of the receiving room, which does not meet the diffusing field.

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Transmit-Beam Pattern Measurement of the Active Phased-Array Antenna Using Near-Field Measurement Facility (근접 전계 시험 시설을 이용한 능동 위상 배열 안테나 송신 빔 패턴 측정)

  • Chae, Hee-Duck;Kim, Han-Saeng;Lee, Dong-Kook;Jeong, Myung-Deuk;Park, Jong-Kuk
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.22 no.12
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    • pp.1155-1164
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    • 2011
  • In this paper, we proposed the transmit beam measurement method of active phased array antenna, which is installed in Korea's first developed naval medium range radar, using near-field measurement facility. The pulse-mode high power characteristics of active phased array antenna's trasmit-beam make it difficult to measure with general near-field measurement facilities where low power continuous RF signals are used. Thus, in this paper, the measurement method of active phased array antenna's transmit beam in conjunction with the near-field measurement facility, which is suitable for the high-power transmit beam measurement, and PNA-X network analyzer(Agilent Technologies), which can support pulse-mode measurement, was proposed and measured by near-field measurement techniques. And the EIRP(Effective Isotropic Radiated Power), the transmit characteristic of active phased array antenna, was measured by the near field measurement techniques and compared to numerical estimation which was nearly equal with small difference of 0.1 dB.

A remote long-term and high-frequency wind measurement system: design, comparison and field testing

  • Zhao, Ning;Huang, Guoqing;Liu, Ruili;Peng, Liuliu
    • Wind and Structures
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    • v.31 no.1
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    • pp.21-29
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    • 2020
  • The wind field measurement of severe winds such as hurricanes (or typhoons), thunderstorm downbursts and other gales is important issue in wind engineering community, both for the construction and health monitoring of the wind-sensitive structures. Although several wireless data transmission systems have been available for the wind field measurement, most of them are not specially designed for the wind data measurement in structural wind engineering. Therefore, the field collection is still dominant in the field of structural wind engineering at present, especially for the measurement of the long-term and high-frequency wind speed data. In this study, for remote wind field measurement, a novel wireless long-term and high-frequency wind data acquisition system with the functions such as remote control and data compression is developed. The system structure and the collector are firstly presented. Subsequently, main functions of the collector are introduced. Also novel functions of the system and the comparison with existing systems are presented. Furthermore, the performance of this system is evaluated. In addition to as the wireless transmission for wind data and hardware integration for the collector, the developed system possesses a few novel features, such as the modification of wind data collection parameters by the remote control, the remarkable data compression before the data wireless transmission and monitoring the data collection by the cell phone application. It can be expected that this system would have wide applications in wind, meteorological and other communities.

ZOOMING FUNCTIONAL METHOD FOR POSITION MEASUREMENT IN ENCLOSING SIGNAL FIELD BASED N CONCEPT OF PROGRESSIVE LEARNING MEASUREMENT SYSTEM

  • Ohyama, Shinji;Cao, Li;Kobayashi, Akira
    • 제어로봇시스템학회:학술대회논문집
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    • pp.1318-1321
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    • 1997
  • A method for two-dimensional position measurement using an enclosing field has been studied and reported. The feature of this mehtod is zooming functional measurement by operating both the initial phase shift and the brightness ratio of the lighting function. An experimental system was developed and the experimental results on zooming effects are shown in this paper. This system is also an example of a "progressive learning measurement system".tem".uot;.

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Measurement Guideline of Fresnel-Field Antenna Measurement Method

  • Oh, Soon-Soo;Moon, Jung-Ick
    • ETRI Journal
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    • v.31 no.1
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    • pp.68-70
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    • 2009
  • In this letter, a parametric analysis of the Fresnel-field antenna measurement method is performed for a square aperture. As a result, the optimum number of Fresnel fields for one far-field point is guided as $M_{opt}=N_{opt}=D^2/{\lambda}R+5$, where D is the antenna diameter, ${\lambda}$ is the wavelength, and R is the distance between the source antenna and the antenna under test. For the aperture size 5 ${\leq}$ $L_x/{\lambda}$ ${\leq}$ 20, the tolerable distances for gain errors of 0.5 dB and 0.2 dB can be guided as $R_{0.5\;dB}$ ${\approx}$ $1.2Lx/{\lambda}$ and $R_{0.2\;dB}$ ${\approx}$ $2.0L_x/{\lambda}$, where $L_x$ is the lateral length of the square aperture. The tolerable distances for 20 ${\leq}$ $L_x/{\lambda}$ ${\leq}$ 200 are also proposed. This measurement guideline can be fully utilized when performing the Fresnel-field antenna measurement method.

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Effect of sensor positioning error on the accuracy of magnetic field mapping result for NMR/MRI

  • Huang, Li;Lee, Sangjin
    • Progress in Superconductivity and Cryogenics
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    • v.17 no.3
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    • pp.28-32
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    • 2015
  • Nowadays the magnetic field mapping is widely used in the design and analysis of the NMR/MRI magnet system, and the accuracy of mapping result has become more and more important. There are several factors affecting the accuracy of the mapping such as the mapping method, the precision of the sensor, the position of the measurement points, the calculation accuracy, and so on. In this paper the error due to the misalignment of the measurement points was discussed. The magnetic field in the central volume was mapped using an indirect method in an MRI magnet system and the magnetic field was fitted to a polynomial. Considering the misalignment between the original measurement points and the practical measurement points, there must be some errors in the mapping calculation and we called it positioning error. Several comparisons of the positioning error have been presented through the theoretical estimates and the exact magnetic field values. Finally, the allowable positioning errors were suggested to guarantee the accuracy of the magnetic field mapping within a certain degree for an example case.