• Journal of electromagnetic engineering and science
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• v.4 no.2
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• pp.79-86
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• 2004

In this paper, the uncertainty in the calibration of coaxial thermal noise sources using a noise figure measuring (NFM) equipment is evaluated. Contributions to the uncertainty such as the calibration uncertainty of the standard noise source, mismatch, measurement of adapter efficiency, ambient temperature variation, and repeatability are evaluated in the frequency range of 10 MHz to 18 ㎓. Results show that the expanded uncertainty(k=2) is 0.23 ㏈ for the noise sources of 5 ㏈ and 15 ㏈ ENR, and 0.27 ㏈ for those of 21 ㏈.

• Journal of information and communication convergence engineering
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• v.15 no.4
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• pp.237-243
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• 2017

This paper presents an analysis of the electromagnetic interference of a heterogeneous power bus where electromagnetic bandgap (EBG) cells are irregularly arranged. To mitigate electrical-noise coupling between high-speed circuits, the EBG structure is placed between parallel plate waveguide (PPW)-based power buses on which the noise source and victim circuits are mounted. We examine a noise suppression characteristic of the heterogeneous power bus in terms of scattering parameters. The characteristics of the dispersion and scattering parameters are compared in the sensitivity analysis of the EBG structure. Electric field distributions at significant frequencies are thoroughly examined using electromagnetic simulation based on a finite element method (FEM). The noise suppression characteristics of the heterogeneous power bus are demonstrated experimentally. The heterogeneous power bus achieves significant reduction of electrical-noise coupling compared to the homogeneous power buses that are adopted in conventional high-speed circuit design. In addition, the measurements show good agreement with the FEM simulation results.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.2
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• pp.154-158
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• 2013

Reduction of electromagnetic vibration and acoustic noise from three-phase squirrel-cage induction motors (IMs) is very important, particularly from the standpoint of environmental considerations. Although the electromagnetic vibration of IMs has been studied for several years, the relationships between the radial distribution of the electromagnetic vibration and noise and the electromagnetic forces responsible for them have not yet been analyzed in sufficient detail. In the present study, we investigated this relationship experimentally for a small IM under different load conditions. Our results clearly show that the radial distributions of the dominant electromagnetic vibration and noise components match the mode shape of the dominant electromagnetic force producing these components.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.1
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• pp.3-9
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• 2009

This paper presents the reduction of acoustic noise generated by electromagnetic force in an induction motor of the electrical forklift. After summarizing the electromagnetic excitation forces due to the interaction between the stator/rotor slot permeance and the stator winding magnetomotive force, the effects of the electromagnetic force on the noise and vibration of an induction motor are analyzed. In order to experimentally identify the noise sources of the motor, the signal analyses for noise and vibration are performed by using waterfall plots of noise and vibration spectrums. It is found that severe noise and vibration are caused by the electromagnetic force when the mode number of the excitation shape for a stator is low. Furthermore, it is verified that the motor noise is amplified if the excitation frequency of the electromagnetic force coincides with one of the natural frequencies of the stator. It is experimentally demonstrated that this severe noise can be considerably reduced by structure modifications. Finally, some design guidelines are suggested to develop an induction motor with a low level of noise.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.5
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• pp.439-446
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• 2009

Noise sources in electric machines are broadly categorized as magnetic, mechanical, electronic and aerodynamic. Especially, there are several kinds of noise sources due to the change of reluctance by rotor position in IPM motor. To separate acoustic noise by mechanical structure and electromagnetic sources, resonance frequency and the effect of vibration and acoustic noise by electromagnetic sources are analyzed. And then, the structural and electromagnetic designs to reduce acoustic noise are performed. The relevance about the study on noise reduction of IPM motor is verified by noise experiment, noise and vibration analysis.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.206-211
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• 2008

Noise sources in electric machines are broadly categorized as magnetic, mechanical, electronic and aerodynamic. Especially, there are several kinds of noise sources due to the change of reluctance by rotor position in IPM motor. To separate acoustic noise by mechanical structure and electromagnetic sources, resonance frequency and the effect of vibration and acoustic noise by electromagnetic sources are analyzed. And then, the structural and electromagnetic designs to reduce acoustic noise are performed. The relevance about the study on noise reduction of IPM motor is verified by noise experiment, noise and vibration analysis.

• Journal of KSNVE
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• v.7 no.4
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• pp.663-668
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• 1997

In general, the noise of alternator is generated by structure of attachment and structural characteristics of alternator itself. In this paper, general phenomena and causes of alternator noise have been considered. Especially, electromagnetic noise source of alternator has been discussed by consideration about the vibration of stator teeth. Also experimental method and simulation method have been used for the proof.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.7
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• pp.1115-1121
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• 2001

In this paper, we analyzed the performance of GFSK system that presence fading effect in indoor radio communication environments and impulsive electromagnetic noise from electronic equipments then we applied the Truncated Type- II Hybrid ARQ scheme to make satisfied in data transmission service. As a result, the system was influenced by fading and impulsive electromagnetic noise. Especially, the system was much degraded by high occurrence frequency and amplitude of impulsive electromagnetic noise than fading which has direct frequency. By adopting the Truncated Type-II hybrid ARQ technique we can also obtained the performance improvement in the low signal power(20 dB) arid over 24 dB in strong impulsive electromagnetic noise environment which is occurred error floor and terribly influenced by the system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.5
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• pp.492-498
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• 2015

As the integration of circuit components increases steadily, various EMS(Electromagnetic Susceptibility) problems have emerged from integrated circuits and electrical systems. The electromagnetic susceptibility of VCOs(Voltage Controlled Oscillator) is especially critical in RF systems. Therefore, in this paper, through the phase noise theory that models electrical oscillators as linear time variant systems, the EMS characteristics of representative VCO -ring VCO and LC VCO- with 1.2 GHz of reference oscillating frequency are analyzed under the existence of the electromagnetic noise coupled in power supply. An simulation algorithm is developed to extract impulse response function based on the phase noise theory. When there is no supply noise, the magnitude of the jitter of two oscillators were similar to around 2.1 ps, but in presence of supply noise, the jitter was significantly lower in LC VCOs than ring VCOs.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.4
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• pp.552-559
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• 1998

Conducted noise in power line contains both the common mode(CM) and differential mode(DM) noise. These two modes of noise are caused by different noise sources and paths. Therefore, CM/DM noise must be deal with individually in EMI filter. In this paper the technique to separate power line noise is presented, which can be used to measure both the CM and the DM noise from total generated noise. Also, noise-separator is designed and experimental results showed 30 dB above of separation performance in 10 kHz~10 MHz.