• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.7 s.98
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• pp.746-752
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• 2005

In this paper, optical noise effect is reduced by using the loss characteristics of plastic fibers in an optical wireless system. The attenuation coefficient of a plastic fiber for the signal is different from that f3r the noise light, and the length difference between two fibers to the 2PD's behaves like a discriminative element. It is possible to eliminate the optical noise effect and detect only the signal without optical filters. The signal to noise ratio in a differential detector using fibers was 9.7 dB higher than in a single photodiode without optical fiber.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.7
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• pp.394-399
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• 2017

In Korean AC power railway substations, SCOTT winding transformers are under operation to have a single phase power supply together with a phase angle of $90^{\circ}$ on the secondary side of the main transformer. In the case of an internal fault of the transformer, the transformer protection relay should be cut off on the primary side, the transformer should be inoperative to the external fault of the transformer or to the normal train operation. Reducing the malfunction of the relay through an exact fault determination is very important for securing a stable power system and improving its reliability. The main transformers are protected using Buchholtz's relay and a differential relay as the internal fault detection devices, but there are some cases of the main transformer operation under the deactivation of this protection function due to a malfunction of the differential relay. In this paper, the characteristics of the SCOTT transformer and differential relay as well as the malfunctioning of the protection relays are presented. The modeling of the SCOTT transformer protection relay was accomplished by the power system analysis program and the Comtrade file from 'A substation', which was used as the input data for the fault wave, and the harmonics were analyzed to determine if the relay operates or not. In addition, an improvement plan for malfunctioning cases through wave form analysis is suggested.

• Journal of IKEEE
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• v.10 no.1 s.18
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• pp.10-15
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• 2006

In this paper, a clock and data recovery (CDR) circuit for a serial link with a half rate 4x oversampling phase and frequency detector structure without a reference clock is described. The phase detector (PD) and frequency detector (FD)are designed by 4X oversampling method. The PD, which uses bang-bang method, finds the phase error by generating four up/down signal and the FD, which uses the rotational method, finds the frequency error by generating up/down signal made by the PD output. And the six signals of the PD and the FD control an amount of current that flows through the charge pump. The VCO composed of four differential buffer stages generates eight differential clocks. Proposed circuit is designed using the 0.18um CMOS technology and operating voltage is 1.8V. With a 4X oversampling PD and FD technique, tracking range of 24% at 3.125Gbps is achieved.

• Journal of IKEEE
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• v.22 no.3
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• pp.800-804
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• 2018

This paper presents a novel HF band differential quadrature phase-shift keying (DQPSK) orthogonal frequency-division multiplexing (OFDM) communication system. The system can deliver 3.6 kbps with a bandwidth of about 3 kHz. In a digital modem, OFDM with 32-point fast Fourier transform is used. In the system, each subcarrier uses DQPSK modulation. Hence, a demodulator does not require carrier phase recovery and symbol timing recovery. And, each subcarrier employs CRC error check code individually. By using CRC code for each subcarrier, bit error caused by multipath fading can be recovered simply.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.5
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• pp.561-564
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• 2001

The cladding area of HANARO Research Reactor fuel rods should be checked not to have any defects larger than the size required at QA documents by using eddy torrent testing method doting fabrication process. To apply eddy current testing inspection to the fuel rods, encircling differential probes and standard specimen were designed and fabricated. The impedance of the fabricated probes was measured with impedance analyzer in order to cheek that the probe has a suitable impedance for the inspection frequency, and with this probe and MIZ-40A eddy current equipment, the detectability of this probes was investigated. The developed probes could detect artificial notch with 2mm length 10% depth of cladding thickness in cladding area. In addition, the probe was successfully applied to detect the defects in cladding area doting fabrication of the research reactor rods.

• Proceedings of the KIEE Conference
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• 2008.04a
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• pp.236-237
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• 2008

이 논문은 노인 및 장애인의 활동을 보조하기 위한 보행보조 로봇의 핵심 기술인 사용자의 진행하고자 하는 방향과 속도를 검출하는 보행의지 파악시스템 구현을 하고자 한다. 최근에 노인인구의 증가로 인해 노인 및 장애인을 위한 보행 보조기에 대한 관심이 증가되고 있다. 그러나 대부분의 경우 동력이 없는 시스템으로 경사 등의 공간에서 취약성을 가지고 있다. 이에 동력형 보행보조기에 대만 관심이 증가되고 있으나, 대부분의 경우 보행보조기 조종이 여의치 않다. 이에 본 논문에서는 사용자의 보행의지를 파악할 수 있는 시스템을 도입하고 이를 기초로 보행자의 안정적인 구동을 수행할 수 있도록 하였다. 사용자의 의지력은 FSR 센서를 이용하여 파악하고, 이를 기초로 사용자가 이동하고자 하는 이동 방향과 이동속도 데이터를 기초로 보행보조기의 차량 속도와 방향에 대해 구동 바퀴의 차동구동을 통해 사용자의 의지에 맞춰 구동할 수 있도록 하였다. 이를 통해 사용자의 이동하려는 의지에 대해 안정적으로 차량을 이동시킬 수 있도록 보행 시스템을 구축하였다. 또한 사용자자의 힘에 대한 속도 및 방향 매핑 기법을 개발하여 보행의지의 정확성을 높였다.

• Proceedings of the KIEE Conference
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• 2008.04a
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• pp.259-260
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• 2008

이 논문은 노인 및 장애인의 활동을 보조하기 위한 보행보조 로봇의 기술인 사용자의 진행하고자 하는 방향과 속도를 검출하는 보행 보조 로봇의 조향 장치를 구현 하고자 한다. 최근에 노인인구의 증가로 인해 노인 및 장애인을 위한 보행 보조기에 대한 관심이 증가되고 있다. 그러나 대부분의 경우 동력이 없는 시스템으로 경사 등의 공간에서 취약성을 가지 고 있다. 이에 동력형 보행보조기에 대한 관심이 증가되고 있다. 대부분의 경우 보행보조기의 제어가 조정한다는 의미가 적합하였다. 그러나 이 논문에서는 사용자의 움직임이 손에 전달되는 힘에 의해 사용자의 의지력을 파악 하는 두가지형태의 조향장치를 구현하였다. 첫째로 가변저항을 이용하여 보행의지를 파악하고, 두 번째로 힘센서를 이용하여 보행의지를 파악하였다. 위 두가지 센서를 기초로 사용자가 이동하고자 하는 이동 방향과 이동 속도 데이터를 기초로 보행보조기의 차량 속도와 방향에 대해 구동 바퀴의 차동 구동을 통해 사용자의 의지에 맞춰 구동할 수 있도록 하였다.

• The Journal of the Acoustical Society of Korea
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• v.35 no.5
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• pp.368-374
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• 2016

This paper presents constructing transmitter and receiver by using a direct sequence spread spectrum techniques to DPSK (Differential Phase-Shift Keying) scheme in underwater acoustic communication. Since DPSK signal can be demodulated if the receiver knows only the phase difference between the adjacent bits, DPSK receiver structure has the advantage of being simplified. In the conventional receiver, two adjacent symbols of transmitted signal before despread are passed to the transition correlator that detects data by comparing maximum correlation outputs. At this time, the error for maximum value of the correlator output may increase because of low SNR (Signal to Noise Ratio) or high Doppler shift frequency according to the underwater channel. In this paper, we propose a method for accurate detection result using the width as well as the magnitude among outputs produced by the correlator. The performances of the proposed method was evaluated by simulation and lake trial data.

• The Transactions of the Korea Information Processing Society
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• v.7 no.1
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• pp.235-244
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• 2000

This paper presents a low power PLL based clock geneator circuit for microprocessors. It generates 32MHz${\sim}$1GHz clocks and can be integrated inside microprocessor chips. A high speed D Flip-Flop is designed using dynamic differential latch and a new Phase Frequency Detector(PFD) based on this FF is presented. The PFD enjoys low error characteristics in phase sensitivity and the PLL using this PFD has a low phase error. To improve the linearity of voltage controlled oscillator(VCO) in PLL, the voltage to current converter and current controlled oscillator combination is suggested. The resulting PLL provides wide lock range and extends frequency of generated clocks over 1 GHz. The clock generator is designed by using $0.65\;{\mu}m$ CMOS full custom technology and operates with $11\;{\mu}s$ lock-in time. The power consumption is less than 20mW.

• Smart Media Journal
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• v.5 no.3
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• pp.49-53
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• 2016

Related researches are progressing that method of non-contact method using the electromagnetic field on the human body by detecting the motion recognition signal is the limitations of time and space, so less than the existing systems. In this paper, we designed the circuit system that can implement the hardware that can detect the electric field signal of the human body non-contact method to increase the recognition rate to screen this digital waveform. The PCB design Used to automatically increase of composition of the circuit and the linkage of the comparator digital waveform with circuit simulation of the system. At same time for evaluate the characteristics of the whole circuit system.