• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2001.11a
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• pp.34-38
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• 2001

This paper proposes a CP-OFDM(Orthogonal Frequency Division Multiplexing using Circular Polarization) system for improving the system performance. The circular polarization has a characteristic that it cannot receive the reflected waves which are reflected by odd times. By reducing the influences of the reflected waves, the circular polarization can reduce the time delay spread and the inter-channel interference. The guard interval needed for the OFDM frame can be minimized and the orthogonality between subchannels can be improved by using circular polarization. Therefore the proposed CP-OFDM system can improve the system performance as well as the spectrum efficiency. Both theoretical analysis and system simulation results are described.

• Electronics and Telecommunications Trends
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• v.33 no.3
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• pp.41-50
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• 2018

In order to ensure the electromagnetic safety of a complex facility equipped with a variety of electric and electronic equipment, the European Union (EU) has enacted and applied the Electromagnetic Compatibility Directive (EMC Directive 2004/108/EC) to a fixed installation. This paper introduces the regulations and techniques related with electromagnetic compatibility (EMC) engineering applied to a fixed installation, which is used to prevent a malfunction of critical equipment and systems caused by unwanted electromagnetic waves and to operate the facilities with stability.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.5
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• pp.13-18
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• 2008

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.1174-1180
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• 2015

We investigate in this paper the radiated electromagnetic waves together with the discharge characteristics of Trichel pulse of negative DC corona discharge in air in pin-to-plate and wire-to-plate configurations. The feature of the current pulse and the frequency spectrum of the electromagnetic radiations were measured under various pressures and gas gaps. The results show that the repetition frequency and the amplitude of Trichel pulse current depend on the discharge conditions, but the rising time of the pulse relates only to the radius of needle or wire and keeps constant even if the other conditions (including the discharge current, the gas gap and the gas pressure) change. There exists the characterized spectrum of electromagnetic waves from negative corona discharge in Trichel pulse regime. These characterized radiations do not change their frequency at a given cathode geometry even if the averaged current, the gas gap or the air pressure changes, but the amplitude of radiations changes accordingly. The characterized electromagnetic radiations from Trichel pulse corona relate to the formation or the rising edge of current pulse. It confirms that the characterized radiations from Trichel pulse supply information of discharge system and provide a potential method for detecting charged targets.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1862-1864
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• 2000

Recently diagnostic techniques have been investigated to detect a partial discharge(PD) associated with a dielectric material defect in a high-voltage electrical apparatus. Among the PD measuring method, detecting electromagnetic wave generated by PD is one of the most effective method because PD radiates wide frequency of electromagnetic wave up to UHF. From the above points of view, we have investigated the polarization and distance characteristics of electromagnetic wave radiated by an insertion of solid insulators between needle-plane electrodes in the air. According to the magnitude of applied voltage, the frequency spectrum of radiated electromagnetic waves were increased about under 100(MHz), compared with background noise. The electromagnetic wave magnitude is attenuated about 4$\sim$7.6[dB] at the point 3[m] away from PD.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.1 s.116
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• pp.76-81
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• 2007

In this paper, we analyzed the vulnerability of information leakage due to the leakage electromagnetic waves of a PC keyboard. First, we reviewed the keyboard protocol and hardware structure, we analyzed the correlation between the data signal, which is transmitted from the keyboard to the main body, and the leakage signal on the power cable. With the result, we grasped the cause of the Conducted Emission of a PC keyboard. Also, we compared the limit level of the CISPR 22 standard with the amplitude of the keyboard leakage electromagnetic waves we calculated. By analyzing the signal on the power cable of the PC main body through the simple experiment, we show that it is possible to extract the contents of the PC key. Therefore it is verified that the secret information of the PC user could leak out.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.10a
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• pp.57-58
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• 2017

In this paper, we have studied electromagnetic susceptibility tests of the battery protection circuit module of a lithium ion battery. Electromagnetic susceptibility tests can be divided into conducted susceptibility for electromagnetic waves flowing through power lines, input / output lines, antenna ports, and radiated susceptibility for spatially radiated electromagnetic waves. A lithium ion battery of S company was used as an experimental sample, and conducted susceptibility tests were conducted on Surge (IEC 61000-4-5), Ring wave (IEC 61000-4-12), and Damped oscillatory wave(IEC 61000-4-18). Radiated susceptibility tests were performed according to IEC 61000-4-3.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.1
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• pp.1-5
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• 2018

This study analyzed the change of electrical characteristics of a photocoupler when a narrow-band electromagnetic wave was combined with the photocoupler. A magnetron (3 kW, 2.45 GHz) was used as the narrow-band electromagnetic source. The EUT was Photocoupler (6N139) and the input signal was divided into two types: a square pulse and the second signal is 0 V. The malfunction of the photocoupler was confirmed by monitoring the variation in the output voltage of the photocoupler. As a result of the experiment, changes in the malfunctioning was observed as the electric field was increased. There are three types of malfunction modes: delay, output voltage off, and fluctuation. Bit errors were analyzed to verify the electrical characteristics of the photocoupler by narrow-band electromagnetic waves. The result of this study can be used as basic data for the effect analysis of photocoupler protection and impact analysis of high-power electromagnetic waves.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.12
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• pp.49-55
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• 2020

In order to improve the electromagnetic shielding rate of Carbon Fiber (CF), it was produced using the nickel nano-powder impregnating method. Using two types of nickel powder having thicknesses of 50 ㎛ and 100 ㎛, and a thermoplastic elastomer resin, a compound containing 10-20% nickel content was mixed and then manufactured through an extruder. The CF coated with the compound was woven and manufactured using a 1-ply specimen. The final nickel content of the specimen was verified using TGA and the distribution of nickel powder on the CF surface was verified using SEM. The metal shows a high shielding rate in the low-frequency band, but the shielding rate decreases at higher-frequency bands. The CF improves at the higher frequency band, and metals reflect electromagnetic waves while carbon absorbs electromagnetic waves. The study of shielding materials, which are stronger and lighter than metal, by using CF lighter than metal and enabling the shielding rate from low-frequency band to high-frequency band, confirmed that the larger the area coated with nickel nano-powder, the better the electromagnetic shielding performance. In particular, CF coated with a thickness of 100 ㎛ has a shielding rate similar to that of copper and can also be used for EV/HEV automotive cables and other applications in the future.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.15 no.4
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• pp.43-50
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• 2001

In this paper, the discharge phenomena and electromagnetic waves caused by discharge with insertion of a solid insulator and flame between sphere-sphere electrodes in air ware investigated. The surface discharge light and patterns of flame generated on a solid insulator surface were observed by using a CCD(Charged Coupled Device) camera. Also, the radiated electromagnetic waves were measured by using a biconical antenna and a spectrum analyzer. The surface discharge light generated on the solid insulator surface was larger and the size of flame was smaller by increasing allied voltages. Also, voltage distortion by voltage drop was strongly revealed when a insulator surface was polluted. When a solid insulator surface was not polluted, the electric field stength of electromagnetic waves was 10∼17[dBuV/m] higher than a polluted solide insulator, and 5∼9[dBuV/m] higher than a polluted solide insulator and flame.