• Title/Summary/Keyword: Near Field Interference

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Study on Minimizing Electromagnetic Interference to Capture Vortex Structures in Turbulent Boundary Layer (경계층 유속 정밀도 증가를 위한 전자파 간섭 최소화 연구)

  • Dong-Hoon Kang;Yong Duck Kang
    • Journal of the Institute of Convergence Signal Processing
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    • v.25 no.2
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    • pp.52-57
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    • 2024
  • To measure the vortex structures within the turbulent boundary layer, a hot-wire sensor was mounted on a stepper motor controller and moved to the designated measurement points. Near the surface within the flow field, the velocity is relatively slow, making the measurements highly sensitive to electromagnetic interference (EMI) during signal processing. This EMI primarily originates from the power supplies of computers and other electronic equipment. In our experimental setup, EMI was introduced into BNC cables connected to the hot-wire sensor from the powered stepper motor. When power was supplied to the motor controller to move the hot-wire sensor, EMI appeared on the oscilloscope screen. Consequently, unexpected noise was present in the data measured by the hot-wire sensor. To mitigate this and enhance the signal-to-noise ratio (SNR) during measurements, the connecting cables were shielded, and an old computer without EMI shielding was replaced.

The theory of non-Markovian optical gain in excited semiconductors

  • Ahn, Doyeol
    • Proceedings of the Optical Society of Korea Conference
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    • 1995.06a
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    • pp.138-148
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    • 1995
  • A reduced description of the dynamics of carriers in excited semiconductors is presented. Fristly, a time-convolutionless equation of motion for the reduced density operator is derved from the microscopic Liouville wquation operator method. Secondly, the quantum kinetic equations for intercting electron-hole parirs near band-edge in semiconductors under an extermal optical field are obtained from the equation of motion for the reduced density operator. The non-Markovian optical gain of a driven semiconductor is derived including the many-body effects. plasma screening and excitinic effects are taken into account using as effective Hamiltonian in the time-dependent Hartree-Fock approximation. it is shown that the line shape of optical-gain spectra gain is enhanced by the exicitonic effects caused by the attrative electron-hole Coulomb interaction and the interference effects (renormalized memory effects) between the extermal driving filed and the intermal driving Filed and the stochastic reservoir of the system.

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Design of Power Plane for Suppressing Spurious Resonances in High Speed PCBs

  • Oh Seung-Seok;Kim Jung-Min;Yook Jong-Gwan
    • Journal of electromagnetic engineering and science
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    • v.6 no.1
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    • pp.62-70
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    • 2006
  • This paper presents a new power plane design method incorporating a single geometry derived from a unit cell of photonic bandgap(PBG) structure. This method yields constantly wide suppression of parallel plate resonances from 0.9 GHz to 4.2 GHz and is very efficient to eliminate PCB resonances in a specified frequency region to provide effective suppression of simultaneous switching noise(SSN). It is shown that with only two cells the propagation of unwanted high frequency signals is effectively suppressed, while it could provide continuous return signal path. The measured results agree very well with theoretically predicted ones, and confirm that proposed method is effective for reducing EMI, with measured near-field distribution. The proposed topology is suitable for design of high speed digital system.

Environmental Effect Analysis of Electromagnetic Induction in Express Electric Railway (고속 전철구간에서의 전력유도 환경 영향 분석)

  • Lee, Sang-Mu;Choi, Mun-Hwan;Cho, Pyung-Dong
    • Journal of The Institute of Information and Telecommunication Facilities Engineering
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    • v.9 no.1
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    • pp.19-23
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    • 2010
  • The Electromagnetic Interference could occur due to power line on the telecommunication service. The Countermeasure is practised by legal law. Various affecting factors are described in the law. In this paper, an effect by pipeline especially in the ground, power feeding plant, and curved railway sector is analyzed as environmental factors which are not included in the law. By the practical measurement, it appears that the measured voltages on the spots with underground pipeline are grouped into lower voltage level, induced voltage tends to be high near power feeding plant, and also in the curved railway line. These analytical results can be meaningly considered in the application of countermeasure.

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Acousto-optic generation of orbital angular momentum states of light in a tapered optical fiber

  • Song, Changkeun;Park, Hee Su;Song, Kwang Yong;Kim, Byoung Yoon
    • Current Applied Physics
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    • v.18 no.11
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    • pp.1441-1446
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    • 2018
  • We demonstrate an acousto-optic mode converter based on a tapered optical fiber to efficiently generate orbital angular momentum states of light. In our scheme an acoustic wave is deployed to the waist of tapered optical fiber where two degenerate $HE_{21}$ modes leading to +1 and -1 orbital angular momentum eigen-modes are resonantly excited. The excitation of $TM_{01}$ and $TE_{01}$ modes is suppressed by enlarging the intermodal index difference between near-degenerate spatial modes. Numerical calculation for optimization of the taper diameter is provided. The experimental characterization of generated states is performed by analyzing the output far-field pattern and the spatial interference fringes with a uniform reference beam.

A Study on the Radiated Noise from Power Line during EFT Immunity Test (EFT(Electrical Fast Transient)내성 시험시 발생되는 전원선 복사 잡음에 관한 연구)

  • 정삼영;이중근
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.11 no.2
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    • pp.234-241
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    • 2000
  • During the EFT immunity test, the fast transient voltage is injected to the power or signal line. The radiated noise from these lines influences the near-by EUT, and consequently, the reliability of the test result can be jeopardized. The measured data of the field strength and wave shape of the noise were compared with the result of the mathematical analysis using transmission line model. When the tests were performed by the conditions the same as stated in IEC 61000-4-4, the results showed that the magnitude of the radiated electric field strength was about 2.4KV/m, and it can cause severe interference to the intended operation of EUT.

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Low-Frequency Electromagnetic Leakage Signal Analysis According to Fundamental Operations of Smartphones (스마트폰 기본 동작 모드에 따른 저주파 대역 누설 전자파 신호 특성 분석)

  • Lee, Young-Jun;Park, Heesun;Kwon, YoungHyoun;Lee, Jaeki;Choi, Ji-Eun;Cho, Sangwoo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.41 no.9
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    • pp.1108-1119
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    • 2016
  • This paper presents the spectral analysis and radiation pattern of low-frequency electromagnetic(EM) leakage signals according to the fundamental operations of smartphones. The EM leakage signals generated by the activation of four I/O sensor modules such as a touch-screen, a camera, a microphone and a speaker are captured by the commercial near-field magnetic probe with 1cm spatial resolution. The analysis results show that the leakage of the EM wave occurs strongly around the activated I/O sensor modules, AP(Application Processor) and memory modules. Also, the distinguishable frequency characteristic is shown in each spectrum of EM leakage signals.

Application of the CS-based Sparse Volterra Filter to the Super-RENS Disc Channel Modeling (Super-RENS 디스크 채널 모델링에서 CS-기반 Sparse Volterra 필터의 적용)

  • Moon, Woo-Sik;Park, Se-Hwang;Im, Sung-Bin
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.49 no.5
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    • pp.59-65
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    • 2012
  • In this paper, we investigate the compressed sensing (CS) algorithms for modeling a super-resolution near-field structure (super-RENS) disc system with a sparse Volterra filter. It is well known that the super-RENS disc system has severe nonlinear inter-symbol interference (ISI). A nonlinear system with memory can be well described with the Volterra series. Furthermore, CS can restore sparse or compressed signals from measurements. For these reasons, we employ the CS algorithms to estimate a sparse super-RENS read-out channel. The evaluation results show that the CS algorithms can efficiently construct a sparse Volterra model for the super-RENS read-out channel.

Design of EMI Reduction of SMPS Using MLCC Filters (MLCC를 이용한 SMPS의 EMI 저감 설계)

  • Choi, Byeong-In;Choa, Sung-Hoon
    • Journal of the Microelectronics and Packaging Society
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    • v.27 no.4
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    • pp.97-105
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    • 2020
  • Recently, as the data speed and operating frequencies of Ethernet keeps increasing, electro magnetic interference (EMI) also becomes increasing. The generation of such EMI will cause malfunction of near electronic devices. In this study, EMI filters were applied to reduce the EMI generated by DC-DC SMPS (switching mode power supply), which is the main cause of EMI generation of Ethernet switch. As the EMI filter, MLCCs with excellent withstanding voltage characteristics were used, which had advantages in miniaturization and mass production. Two types of EMI MLCC filters were used, which are X-capacitor and X, Y-capacitor. X-capacitor was composed of 2 MLCCs with 10 nF and 100 nF capacity and 1 Mylar capacitor. Y-capacitor was consisted of 6 MLCCs with a capacity of 27 nF. When only X-capacitor was applied as EMI filter, the conductive EMI field strength exceeded the allowable limit in frequency range of 150 kHz ~ 30 MHz. The radiative EMI also showed high EMI strength and very small allowable margin at the specific frequencies. When the X and Y-capacitors were applied, the conductive EMI was greatly reduced, and the radiation EMI was also found to have sufficient margin. In addition, X, Y-capacitors showed very high insulation resistance and withstanding resistance performances. In conclusion, EMI X, Y-capacitors using MLCCs reduced the EMI noise effectively and showed excellent electrical reliability.

Evaluation of Stiffness Profile for a Subgrade Cross-Section by the CAP(Common-Array-Profiling)-SASW Technique (CAP SASW 기법에 의한 지반단면의 전단강성구조 평가)

  • Joh Sung-Ho;Jang Dae-Woo;Kang Tae-Ho;Lee Il-Wha
    • Journal of the Korean Geotechnical Society
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    • v.21 no.4
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    • pp.71-81
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    • 2005
  • Surface wave techniques were initially based on 2-D plane waves and were later improved to the techniques based the 3-D based cylindrical waves. However, body-wave interference, near-field effect and limited technology in surface wave measurements restricted the use of 3-D cylindrical waves to the 1-D evaluation of subgrade stiffness. In this study, by the numerical simulation of SASW measurements, the dispersion properties of surface waves including vertical, horizontal Rayleigh waves and Love waves were thoroughly investigated in the 3-D domain, and a new filter criteria to minimize the near-field effect was established, which led to CAP (common-array-profiling)-SASW technique. The CAP-SASW technique enabled the evaluation of subgrade stiffness fur a specific subgrade segment, not for a whole section of measurement array. Therefore, a contour plot of subgrade stiffness with a ground-truth quality can be obtained by the CAP-SASW technique. The procedure proposed in this study was verified by comparing the shear-wave velocity profiles with the shear-wave velocity profiles of downhole testing at two geotechnical sites.