• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.4
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• pp.56-62
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• 1994

Far-zone electric fields radiated by a coaxial cable through an aperture in a perfectly conducting ground plane are calculated utilizing the dyadic Green's function and vector wave functions. In this paper the outer radius $\alpha$ is assumed to be less than 0.02 so that the aperture fields is well approximated by the dominant TEM mode in the coaxial cable. The result of present approach is compared with the readily obtained solution. The present solution is valid outside of the spherical regions with radius `$\alpha$' from the center of coaxial cable.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.2
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• pp.259-267
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• 2000

This paper presents the method for an estimation of discharge current waveshapes in short gap discharge by radiated electromagnetic fields. The method of current waveform estimation described is using the one antenna method(single field method) and two antennal method(complex field method) with a measured electric or magnetic fields at given field point by a time domain antenna. In order to verify the availability of the estimation theory, the discharge current waveshape estimation was performed by one and two antenna methods using the measured electric fields of Wilson & Ma and compared with experiments.

• Proceedings of the KIEE Conference
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• 1998.07e
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• pp.1656-1658
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• 1998

This paper deals with a measurement system of a distance between lightning strokes and observatory station and spectrum analysis of electric fields radiated from lightning discharges. The distance measurement system, which consists of a loop type magnetic field sensor, a microphone and one chip microprocessor, is connected to a personal computer through RS232 port to acquire and process the data. This system is to use a difference of propagation velocity between an electromagnetic wave and a sonic wave produced by lightning discharge. Also, an electric field waveform and a frequency spectrum were investigated by an electric field measurement system with a hemisphere antenna and a spectrum analyzer with a biconical antenna and a log-periodic antenna, respectively. The results would be used as a basic reference to protect the power systems and electric circuits from lightning overvoltages.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.10
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• pp.492-499
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• 2002

This paper presents the method for an estimation of discharge current waveform in short gap discharge by radiated electromagnetic fields. The method of current waveform estimation is to use the one antenna method (single field method) with a measured electric or magnetic field at given field point by a time domain antenna. In order to verify the availability of the estimation theory, the discharge current waveform estimation was performed by one antenna methods using the measured electric fields of Wilson & Ma and compared with experiments. In addition diagnosis technique for power equipments is able to prevent from large accidents by finding signs of tile accidents before they happen. From the results of the estimation of discharge current, we have a possibility for the application of insulation diagnosis technique for power equipments using S$F_6$ gas. From this point of view, this paper simulated discharge progress and partial discharge by using needle-plan electrodes system in S$F_6$, studied the distribution of frequency spectrum of the radiated electromagnetic waves using a biconical antenna and a spectrum analyzer. From the experimental results of this study, according to the consideration of the mutual relation between frequency spectrum of the radiated electromagnetic waves and discharge progress, it was confirmed that detecting Partial discharge and estimating discharge progress in S$F_6$ could be Possible.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.12
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• pp.1-7
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• 1997

Serious troubles may occur in electromagnetic equipments due to electrostatic discharge (ESD). The number of the damaging incidents are significantly increasing with the increased use of integrated semiconductor elements with loer operation pwoer. In order to examine the phenomena theoretically, this paper anlyzes properties of the transient electromagnetic fields rdiated by ESD. A new model is presented using the Rompe-weizel formula for the spark resistance. The numerical results of ESD fields are compared with the experimental data that were given by wilson-Ma.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.5
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• pp.57-63
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• 2006

This paper deals with the physical properties and statistical analysis of waveform parameters of electric and magnetic folds radiated from lightning return strokes. The lightning electric and magnetic fields were detected by an plate-type electric field sensor and a loop-type magnetic field sensor respectively, and they were recorded by a data acquisition system having a resolution of 12bits, a sampling rate of 10[MS/s] and recording length of 10[ms]. As a result, a little difference between the parameters of electric and magnetic fields for positive and negative polarities was observed. The rise times of electric and magnetic fields were within the range of less than $13[{\mu}s]$ and the average values for positive and negative polarities were $4.1[{\mu}s]\;and\;4.2[{\mu}s]$, respectively. The average values of the zero-to zero crossing times were $65.2[{\mu}s]\;and\;67.0[{\mu}s]$, and the average depths of the dip to opposite polarity were 38.0[%] and 40.3[%], for positive and negative polarities, respectively.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.447-450
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• 2002

In the surrounding of the electric machinery and equipments occurring of using the electromagnetic fields, other electric machinery or equipments are induced the malfunctions by the radiated and leaked electromagnetic fields. And the human hazardous problems by that effect are being discussed frequently. So efficiently shielding technique of injurious electromagnetic field for high frequency welder is discussed in this paper.

• Journal of Advanced Navigation Technology
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• v.28 no.2
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• pp.225-231
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• 2024

In this article, a new approach is presented to improve the unchangeable function of a ready-made millimeter-wave antenna system. By designing a metamaterial surface appropriate for the given geometry and fixed electrical characteristics of the device, the properties of the radiated fields of the RF product are changed to have directivity and higher antenna gain. Unlike other designs using periodic metamaterials for a single patch, an aperiodic metasurface is developed to handle two patches. For a higher received signal strength and a longer RF path in the 24 GHz-radio link, an aperiodic metasurface enhances the radiated fields by 10 dB.

• Journal of electromagnetic engineering and science
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• v.7 no.1
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• pp.7-11
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• 2007

PCB Power-Bus (comprising power/ground planes) impedance and fields are evaluated by an efficient series expansion method that is suggested in this paper. It is used to investigate the structure's radiated emission(RE) levels and find acceptable ways of loading the power/ground planes such as decoupling capcitor(DeCap)s, balanced feeding and slits, in order to reduce the interferences. Also, the calculations and measurements of a proposed geometry are verified by vector fitting as a analysis model to check the behavior of the slit.

• Journal of KSNVE
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• v.6 no.6
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• pp.781-790
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• 1996

The goal of current research is to suppress the acoustic noise radiated from vibration of composite plate structure. The induced noise can be reduced through the control of the corresponding structural vibration modes by using the piezoelectric materials as actuator. The acoustic fields are to be analyzed through the boundary element method (BEM) based on the Rayleigh intergral equation and structural system through the finite element method (FEM). The suppression of rediated sound is studied by adaping the piezoelectric material as the distributed actuator. Numerical results are presented on the sound radiation from composite plate of arbitrary boundary conditions, the noise reduction adapting the piezoelectric materials as distributed actuator. The results show the effectiveness and possibility of piezoelectric actuator in the control of sound radiation from composite structure.