• Journal of Biomedical Engineering Research
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• v.20 no.2
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• pp.205-212
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• 1999

When we want to observe and record a patient's EEG in an operating room, the operation of electrosurgical unit(ESU) causes undesirable artifacts with high frequency and high voltage. These artifacts make the amplifiers of the conventional EEG system saturated and prevent the system from measuring the EEG signal. This paper describes a high-performance bipolar EEG amplifier for a CSA (compressed spectral array ) system with reduced ESU artifacts. The designed EEG amplifier uses a balanced filter to reduce the ESU artifacts, and isolates the power supply and the signal source of the preamplifier from the ground to cut off the current from the ESU to the amplifier ground. To cancel the common mode noise in high frequency, a high CMRR(common mode rejection ratio) diffferential amplifier is used. Since the developed bipolar EEG amplifier shows high gain, low noise, high CMRR, high input impedance, and low thermal drift, it is possible to observe and record more clean EEG signals in spite of ESU operation. Therefore the amplifier may be applicable to a high-fidelity CSA system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.10
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• pp.1837-1844
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• 2016

This paper proposes an antenna of the fork type structure that operates in the UWB (Ultra Wide Band) frequency band (3.1 ~ 10.6 GHz). The proposed antenna is attached a circular patch in order to obtain the UWB band characteristics to the fork-type patch antenna. The ground plane is implemented in a arc-shape configuration. The effect of various parameters of the modified fork type radiating patch and partial arc ground plane for UWB operation is investigated. The proposed antenna is made of $34.0{\times}50.0{\times}1.0mm^3$ and is fabricated on the permittivity 4.4 FR-4 substrate. The experiment results shown that the proposed antenna obtained the -10 dB impedance bandwidth 8200 MHz (2.7 ~ 10.9 GHz) covering the UWB bands. This result satisfied the characteristics of ultra-wideband and the proposed antenna will be applicable to an ultra wideband system.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.2 no.2
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• pp.57-62
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• 2009

In this paper, we proposed the metal tag antenna of PIFA structure with an isotropic radiation pattern when tag attached the metal material. The antenna consist of antenna body, horizontal patch and ground, and inserted a substrate with high dielectric constant between the antenna body and ground in order to miniaturize the antenna size. The antenna body with symmetric structure is designed to produce an oppositely directed currents. The simulation shows the impedance bandwidth has 20 MHz (900 ~ 920 MHz) and the maximum radiation gain satisfy the -10 dBi and -15 dBi when the tag is in air and attach the metal material. Also, the proposed antenna operates with an isotropic radiation pattern due to satisfy the gain deviation lower than 6 dB, respectively.

• Journal of Advanced Navigation Technology
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• v.10 no.3
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• pp.198-204
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• 2006

In this paper, TE(transverse electric) scattering problems by a resistive strip grating on a grounded dielectric plane according to the strip width and grating period, the relative permittivity and thickness of dielectric layer, and incident angles of a TE plane wave are analyzed by applying the FGMM(Fourier-Galerkin Moment Method) known as a numerical procedure. The induced surface current density is simply expanded in a Fourier series by using the exponential function as a simple function. The reflected power gets increased according as the relative permittivity and thickness of dielectric multilayers gets increased, the sharp variations of the reflected power are due to resonance effects were previously called wood's anomallies[7]. To verify the validity of the proposed method, the numerical results of normalized reflected power for the uniform resistivity R = 0 as a conductive strip case show in good agreement with those in the existing paper.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.23 no.3
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• pp.71-76
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• 2023

In this paper, TE(transverse electric) scattering problems by a resistive strip grating between a grounded double dielectric layer are analyzed by applying the FGMM(fourier galerkin moment method) known as a numerical method of electromagnetic fileld. The boundary conditions are applied to obtain the unknown field coefficients, the scattered electromagnetic fields are expanded in a series of Floquet mode functions, and the resistive boundary condition is applied to analysis of the resistive strip. Overall, as the resistivity decreased, the magnitude of the current density induced in the resistive strip increased, and the reflected power also increased. In case of uniform resistivity, the reflected power decreased as the relative permittivity of the dielectric layers increased or the thickness of the dielectric layer increased. The numerical results for the presented structure in this paper are shown in good agreement compared to those of the existing papers.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.10
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• pp.2619-2627
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• 2009

The ground fault is occupying 70% among the total number of faults in ungrounded distribution power system. When the ground fault occurs in ungrounded system, the fault current is so small that it is hard to detect. But fault handling is very important because to continue power supply during fault conditions may cause the fault spreading and the distribution device in trouble. This paper presents the fault line detection method by using GPT signal detecting zero sequence voltage, and the fault section detection method by detecting whether GPT signal is disappeared or not during shifting normally open switch, which is connecting switch between distribution lines with open state in order to restore the outage area under emergency situation, and during isolating each section one by one which belongs to the fault line. This method is efficient because there is no whole power interruption during the fault section detection, and it is possible to perform both the fault section detection and the service restoration for the outage area at the same time, and it can apply to various distribution system configuration. Program for the fault restoration was developed applying proposed method, and it has been validated by applying to the pilot project of distribution automation system in Vietnam which has the ungrounded distribution system.

• Journal of the Korean Vacuum Society
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• v.17 no.4
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• pp.331-340
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• 2008

A method of measuring the current and voltage is suggested in the circuit of cold cathode fluorescent lamps (CCFLs) which are driven at a high frequency of $50{\sim}100\;kHz$ and a high voltage of several kV. It is difficult to measure the current and voltage in the lamp circuit, because the impedance of the probe at high voltage side causes the leakage current and the variation of luminance. According to the analysis of equivalence circuit with the probe impedance and leakage current, the proper measuring method is to adjust the input DC voltage and to keep the specific luminance when the probe is installed at a high voltage circuit. The lamp current is detected with a current probe or a high frequency current meter at the ground side and the voltage is measured with a high voltage probe at the high voltage side of lamp. The lamp voltage($V_C$) is measured between the ballast capacitor and the lamp electrode, and the output voltage($V_I$) of inverter is measured between inverter output and ballast capacitor. As the phases of lamp voltage($V_C$) and current ($I_G$) are nearly the same values, the real power of lamp is the product of the lamp voltage($V_C$) by the lamp current($I_G$). The measured value of the phase difference between inverter output voltage($V_I$) and lamp current($I_G$) is appreciably deviated from the calculated value at $cos{\theta}=V_C/V_I$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.8
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• pp.772-780
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• 2013

The high-altitude electromagnetic pulse(HEMP) conducted environment and the HEMP radiated environment are established as the consequences of a high-altitude nuclear explosion. The IEC 61000-2-10, the international standard, defines the HEMP conducted environment. The IEC 61000-5-5 defines how protective devices for conducted disturbance proposed for HEMP protection shall be specified. The IEC 61000-4-24 deals with methods for testing protective devices for HEMP conducted disturbance. The IEC 61000-4-24:1997 mainly describes the measurement method of small protective components. However, it does not provide the measurement method for a combination filter of a protective component and a filter which is widely used in recent. It is important to consider the characteristic of the measurement setup parameters like thickness and length of the cable and its height above ground plane etc. in establishing measurement setup because HEMP conducted disturbances include the frequency spectrum below 50 MHz. This paper deals with the optimized measurement method, considering the frequency spectrum of HEMP conducted disturbance, current waveform, and analyzing the effects of cables existing in the measurement setup.

• Journal of the Institute of Convergence Signal Processing
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• v.19 no.3
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• pp.97-103
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• 2018

This paper addresses an improved naval combat UPS(Uninterruptable Power Supply) system under abnormal transients. Previously, thermistor and varistor elements were used to cope with transient overvoltage and overcurrent, however the UPS was frequently unavailable because it was vulnerable to abnormal transient voltage generated during system operation. In order to overcome this problem and protect UPS system, this paper proposes an input power cut-off circuit that detects the initial input power and abnormal transient voltage generated during operation, improvement of power control sequence, and a method to prevent malfunction of an inverter and CPU. The UPS system implementing the proposed method was simulated by input power variable test using programmable AC/DC generator, and finally validated its reliability and stability through field tests by mounting on multifunctional console of naval combat system.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.214-215
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• 2011

RF 플라즈마의 경우 일반적인 싱글 랑뮤어 프루브를 사용하여 I-V 파형을 구하는 경우에, 우리는 시평균한 값만을 구할 수 있다. 일반적인 플라즈마 반응 챔버의 구조상, 양 전극의 크기가 다르기 때문에, 시간에 따라 진동하는 플라즈마 포텐셜의 형태는 정확한 사인파의 형태가 아니다. 그렇기 때문에 플라즈마 포텐셜에 따라서 진동하는 데이터를 시평균한 값에는 DC 오프셋 성분이 나타난다. 이러한 DC 오프셋값은 랑뮤어 프루브를 통한 플라즈마 포텐셜 측정시에 오차로 나타난다. 우리는 DC 오프셋에 의한 에러값을 보정하기 위해 멀티 프루브를 사용할 수 있다. 가장 흔하게 쓰이는 듀얼 랑뮤어 프루브의 경우를 살펴보면, 내부의 전원이 플로팅되어 있으며 전압인가를 위한 회로 또한 접지에서 절연되어 있기 때문에, 플라즈마 포텐셜이 시간에 따라 흔들려도 전체적인 전위가 플라즈마 포텐셜과 함께 움직이기 때문에, 앞에서 말한 DC 오프셋에 의한 오차를 줄일 수있다는 장점이 있다. 그러나, 이를 위하여는 회로의 절대적인 플로팅이 필요하지만 실제 듀얼 랑뮤어 프루브의 전원 회로를 구현시에는, 트랜스포머 등을 사용하여 회로를 절연시켜도 회로에 기생적으로 발생하는 콘덴서 성분 때문에 플로팅에 영향을 받을 수 있다. 또한 양극과 음극 사이의 내부 임피던스가 다르게 나타난다. 실제로 기존의 듀얼 랑뮤어를 가지고 RF 플라즈마를 측정할 때에, 듀얼 랑뮤어 프루브의 두 팁 간에 서로 다른 전압-전류 파형이 나타나곤 한다. 이러한 두 팁간의 전압-전류 파형의 차이는 두 팁이 물리적으로 완전히 동일한 구조를 가질 수 없기 때문에 발생 하기도 하지만, 위에서 밝힌 원인에 의해서도 발생한다. 이로 인하여 듀얼 랑뮤어 프루브에 의한 I-V 파형은 이론 상 원점을 대칭으로 한 기함수의 형태이어야 하는데, 실제 측정 결과를 보면 이러한 대칭 형태의 모양을 보기 힘들다. 우리는 이에 이를 보정하기 위하여 위상이 180도 차이가 나는 두 개의 삼각파 발생 전원을 각각 듀얼 랑뮤어 프루브의 양 팁에 인가하여 두 팁 간의 내부 저항과 기생 임피던스 등을 일치시킨 프루브를 디자인하였으며 이 프루브를 이용한 실험에서, 비교적 완벽하게 원점에 대하여 대칭하는 I-V 커브를 구할 수 있었다. 이에 이 논문에서는 새로운 회로와 이 회로로 이루어진 듀얼 랑뮤어 프루브를 사용하여 플라즈마를 진단하는 방법에 대하여 기술한다.