• The Transactions of the Korean Institute of Electrical Engineers D
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• v.55 no.12
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• pp.511-517
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• 2006

The key issues in high power, high energy applications such as electromagnetic launchers include safety, reliability, flexibility, efficiency, compactness, and cost. To explore some of the issues, a control scheme for a large current wave-forming was designed, built and experimentally verified using a 2.4MJ pulse power system (PPS). The PPS was made up of eight capacitors bank unit, each containing six capacitors connected in parallel. Therefore there were 48 capacitors in total, with ratings of 22kV and 50kJ each. Each unit is charged through a charging switch that is operated by air pressure. For discharging each unit has a triggered vacuum switch (TVS) with ratings of 200kA and 250kV. Hence, flexibility of a large current wave-forming can be obtained by controlling the charging voltage and the discharging times. The whole control system includes a personal computer(PC), RS232 and RS485 pseudo converter, electric/optical signal converters and eight 80C196KC micro-controller based capacitor-bank module(CBM) controllers. Hence, the PC based controller can set the capacitor charging voltages and the TVS trigger timings of each CBM controller for the current wave-forming. It also monitors and records the system status data. We illustrated that our control scheme was able to generate the large current pulse flexibly and safely by experiments. The our control scheme minimize the use of optical cables without reducing EMI noise immunity and reliability, this is resulting in cost reduction. Also, the reliability was increased by isolating ground doubly, it reduced drastically the interference of the large voltage pulse induced by the large current pulse. This paper contains the complete control scheme and details of each subsystem unit.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.10
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• pp.97-104
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• 2003

This paper addresses EMC test results for the EQM Communications & Broadcasting Satellite(CBS) Ka-band Payload System. The aim of the EMC test is to verify that the payload system has no effect on the other system and is not affected by the external field. The compliance of EMC system requirements was verified by the analysis and measurement of the emission level from the payload system. The variation of performance by noise injection was measured to inspect the susceptibility of the payload system. The analysis and test results also showed that the electromagnetic interference has no serious effect on the overall payload system performance. It is confirmed that the EQM CBS Ka-band payload system can be operable in the space environment from the EMC performance's viewpoint. It is also obtained that better performance can be acquired by improving waveguide design and integration method.

• Bulletin of the Korean Space Science Society
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• 2004.10b
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• pp.231-234
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• 2004

Electrical grounding is defined as referencing an electrical circuit or a common reference plane for preventing shock hazards and for enhancing operability of the circuit and EMI control. In order to realize the best electrical grounding system of korean space launch vehicle, we should design the electrical grounding architecture of korean space launch vehicle of system-level at the earliest point in design procedure. To minimize the electrical grounding loop and the unnecessary electromagnetic interference or radiation among the electronic subsystems, we should establish the electrical grounding rules of the all electrical interfaces. The electrical interfaces among the electronic subsystems are generally classified into the electrical power and signal interfaces. Because of using the primary and secondary power system architecture in the korean space launch vehicle system such as the common space launch vehicle systems, we need to establish the electrical grounding rules between the primary and secondary power system. We also need to establish the electrical signal grounding interface rules among the electronic subsystems. In this paper, we will describe the grounding schemes of the common space launch vehicle system and propose a conceptual design for the electrical grounding architecture of korean space launch vehicle system.

• Journal of the Korean Magnetics Society
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• v.17 no.6
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• pp.238-241
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• 2007

Ni-Cu-Zn ferrites were prepared by the co-precipitation. Physical properties and Microwave absorbing properties were investigated in Ni-Cu-Zn ferrite for the aim of microwave absorbers. From the analysis of X-ray diffraction patterns, we can see that all the particles have only a single phase spinel structure. The loss factor was maximum at sintering temperature $1100^{\circ}C$. The initial permeability of sintered ferrite obtained was an average of 50. We found that the $(Ni_{0.7}Cu_{0.2}Zn_{0.1}O)_{1.02}(Fe_2O_3)_{0.98}$ can be used in ferrite rubber composite microwave absorber when sintering temperature at $1100^{\circ}C$.

• Journal of the Korean Magnetics Society
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• v.18 no.3
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• pp.115-119
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• 2008

The raw materials of permalloy were processed the ball-mill for 30 hours and the shape of permalloy particles was changed from sphere to flake type, which was observed using scanning electron microscope. The complex permittivity and permeability spectra and reflection loss of permalloy-rubber composite was measured using Network Analyzer in order to investigate the relationship between the microwave absorption and the material constants. The flake type permalloy-rubber composite showed high reflection loss, which was due to the high complex permittivity and permeability. Also, the matching frequency shifted toward lower frequency range with microwave absorber thickness, and the maximum reflection loss of -6.1 dB was observed in $1.65\;GHz{\sim}1.86\;GHz$ for a 1.3 mm thickness.

• Journal of Electrical Engineering and Technology
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• v.13 no.3
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• pp.1251-1264
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• 2018

The systematic and effective design method of a Class-D current-source resonant inverter for use in an induction cooker with zero-ripple line current is presented. The design procedure is based on the principle of the Class-D current-source resonant inverter with a simplified load network model that is a parallel equivalent circuit. An induction load characterization is obtained from a large-signal excitation test-bench based on parallel load network, which is the key to an accurate design for the induction cooker system. Accordingly, the proposed scheme provides a systematic, precise, and feasible solution than the existing design method based on series-parallel load network under low-signal excitation. Moreover, a zero-ripple condition of utility-line input current is naturally preserved without any extra circuit or control. Meanwhile, a differential-mode input electromagnetic interference (EMI) filter can be eliminated, high power quality in utility-line can be obtained, and a standard-recovery diode of bridge-rectifier can be employed. The step-by-step design procedure explained with design example. The devices stress and power loss analysis of induction cooker with a parallel load network under large-signal excitation are described. A 2,500-W laboratory prototype was developed for $220-V_{rms}/50-Hz$ utility-line to verify the theoretical analysis. An efficiency of the prototype is 96% at full load.

• Journal of Advanced Navigation Technology
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• v.22 no.2
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• pp.105-110
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• 2018

The North Korea nuclear issue is now posing a serious security threat to the Korea and Northeast Asia. Accordingly, the South Korean military is pushing for the introduction of long-range air-to-surface flights and the development of domestic nuclear facilities that can precisely hit North Korea headquarters building and nuclear facility even hundreds of kilometers above the border. In this paper, we removed the cable braid for securing the weight of the missile among several design elements for long-range air-to-surface missile development and estimated and analyzed the resulting performance. The possibility of braid removal was analyzed in terms of crosstalk inside the cable and CS114, RE101 of MIL-STD-461F.

• Korean Journal of Optics and Photonics
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• v.13 no.4
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• pp.363-369
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• 2002

We have designed conductive transparent filters using a low-emissivity coating such as [dielectric|Ag|dielectric] for display applications. The design is the repetition of [$TiO_{2}$|Ti|Ag |$TiO_{2}$] to increase the transmittance in the visible and decrease the transmittance in the near IR. The conductive transparent filters are deposited by a radio frequency(RF) magnetron sputtering system. The optical, structural and electrical properties of the filters were investigated and the optical spectra are compared with simulated spectra. The thickness of the deposited Ag films is above 13 ㎚ to increase the conductivity and that of $TiO_{2}$ films is 24 ㎚ to increase the transmittance in the visible range. Ti blockers are employed to prevent the Ag films from being oxidized by an oxygen gas during the reactive sputtering process. Also, it is shown that the thicker Ti film is necessary as the period increases. Finally, a filter with repetition of the basic structure three times shows the better cut-off near infrared(NIR) and the sheet resistance as low as 2Ω/□ which is enough to shield an unnecessary electromagnetic waves for a display panel.

• Journal of the Korean Magnetics Society
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• v.18 no.3
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• pp.120-125
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• 2008

In this study, NiCoZn ferrites with the variation of sintering temperature and chemical composition were prepared by the coprecipitation. Microstructures Crystal structure of NiCoZn ferrites were analyzed by XRD and their electric magnetic characteristics were analyzed by LCR meter and their morphology observed by SEM. We identified that these powders have a typical NiCoZn spinel structure and nanoparticles average size of 40 nm. The impurity, the initial permeability and the Q factor value are the lowest of sintered NiCoZn ferrite at $1250^{\circ}C$. Also, we measured S-parameter for $(Ni_{0.4}Co_{0.1}Zn_{0.5})Fe_2O_4$ which showed a maximum reflection loss of -3.1 dB at 6 GHz for the 2 mm thick sample. From this result, we found that the NiCoZn ferrite can be used in ferrite microwave-absorbing application at a higher frequency region (> 6 GHz).

• Journal of the Institute of Convergence Signal Processing
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• v.20 no.1
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• pp.16-23
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• 2019

Fine particulate matter known as PM 2.5 refers to the atmospheric particulate matter that has a diameter less than 2.5 micrometer identified as dangerous element for human health and its concentration can provide us a clear picture about air dust concentration. Humans stay indoor almost 90% of their life time and also there is no official indoor dust concentration data, so our study is focused on measuring the indoor air quality. Indoor dust data monitoring is very important in hospital environments beside that other places can also be considered for monitoring like classrooms, cements factories, computer server rooms, petrochemical storage etc. In this paper, visible light communication system is proposed by Manchester encoding technique for electromagnetic interference (EMI)-free indoor dust monitoring. Important indoor environment information like dust concentration is transferred by visible light channel in wide range. An average voltage-tracking technique is utilized for robust light detection to eliminate ambient light and low-frequency noise. The incoming light is recognized by a photo diode and are simultaneously processed by a receiver micro-controller. We can monitor indoor air quality in real-time and can take necessary action according to the result.