• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.305-308
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• 1999

In this paper, a transimpedance optical receiver based on PIN/P-HEMT with cascoded input stage and inductor peaking technique was designed for several giga bits optical communication. Analysis of the receiver shows that cascoded input stage with inductor peaking increase bandwidth without sacrificing low frequence gain. The receiver achieved a low noise characteristic and maximally flat frequence response. It is shown that the 3-dB bandwidth of the designed receiver is 8.3 ㎓ and input equivalent noise current is as low as 16pA/√Hz to 10㎓.

• Proceedings of the KWS Conference
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• 2003.11a
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• pp.227-229
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• 2003

Low heat input welding methods have been investigated in order to minimize the HAZ softening of the 600MPa grade fine grained steel weldment. The welding processes of interest were a high speed FCA welding with a multi-torch welding system, laser welding with filler feeding and hybrid laser welding. No HAZ softening was found for all the weldments formed with low heat input less than 10kJ/cm. Tensile strength of the weldments was high enough to satisfy the required value. Impact toughness of the weldments was also good even at -20$^{\circ}C$.

• Proceedings of the KWS Conference
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• 2005.06a
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• pp.294-296
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• 2005

Several duplex overlaied-weldments which have different ferrite ratio were prepared by changing welding heat input ant post weld heat treatment were carried out to understand the effect of the ferrite ratio on the precipitation during post weld heat treatment. High heat input weldment indicated low ferrite ratio, while low heat input weldment has high ferrite ratio. Low ferrite ratio weldment showed much and faster precipitation. But high ferrite ratio weldment showed less and slower precipitation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.7
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• pp.1374-1379
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• 2003

In this paper, twoㆍstage low noise amplifier(LNA) for 24㎓ is designed and fabricated using NE450284C HJ-FET of NEC CO. In order to get noise figure and input VSWR to be wanted it is considered input VSWR and noise figure simultaneously in matching-circuit designing. The fabricated two-stage low noise mph u has the gai of 16.6㏈, input VSWR of 1.6, and output VSWR under 1.5.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.210-212
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• 2018

A new switching mode has been proposed to obtain high power factor and low THD in single stage AC-DC converter. The conventional voltage mode control in critical conduction mode distorts input current shape with poor THD in flyback topology. Once TRIAC dimmer is connected, visible flicker in the LED lamp is easily detected due to a lack of TRAIC holding current near the input voltage zero cross. The newly proposed method can shape the input current by providing a desired reference voltage so that low THD is obtained by ideal sinusoidal input current in case of no dimmer connection and flat input current performs good TRIAC dimmer compatibility in phase-cut dimming condition. To confirm the validity of the proposed method, theoretical analysis and experimental result from 8W dimmable LED lighting system are presented.

• Journal of electromagnetic engineering and science
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• v.5 no.3
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• pp.112-116
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• 2005

This paper presents a broadband two-stage low noise amplifier(LNA) operating from 3 to 10 GHz, designed with 0.18 ${\mu}m$ RF CMOS technology, The cascode feedback topology and broadband matching technique are used to achieve broadband performance and input/output matching characteristics. The proposed UWB LNA results in the low noise figure(NF) of 3.4 dB, input/output return loss($S_{11}/S_{22}$) of lower than -10 dB, and power gain of 14.5 dB with gain flatness of $\pm$1 -dB within the required bandwidth. The input-referred third-order intercept point($IIP_3$) and the input-referred 1-dB compression point($P_{ldB}$) are -7 dBm and -17 dBm, respectively.

• Journal of Communications and Networks
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• v.9 no.1
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• pp.18-27
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• 2007

The conventional normalized least mean square (NLMS) algorithm is the most widely used for adaptive identification within a non-stationary input context. The convergence of the NLMS algorithm is independent of environmental changes. However, its steady state performance is impaired during input sequences with low dynamics. In this paper, we propose a new NLMS algorithm which is, in the steady state, insensitive to the time variations of the input dynamics. The square soot (SR)-NLMS algorithm is based on a normalization of the LMS adaptive filter input by the Euclidean norm of the tap-input. The tap-input power of the SR-NLMS adaptive filter is then equal to one even during sequences with low dynamics. Therefore, the amplification of the observation noise power by the tap-input power is cancelled in the misadjustment time evolution. The harmful effect of the low dynamics input sequences, on the steady state performance of the LMS adaptive filter are then reduced. In addition, the square root normalized input is more stationary than the base input. Therefore, the robustness of LMS adaptive filter with respect to the input non stationarity is enhanced. A performance analysis of the first- and the second-order statistic behavior of the proposed SR-NLMS adaptive filter is carried out. In particular, an analytical expression of the step size ensuring stability and mean convergence is derived. In addition, the results of an experimental study demonstrating the good performance of the SR-NLMS algorithm are given. A comparison of these results with those obtained from a standard NLMS algorithm, is performed. It is shown that, within a non-stationary input context, the SR-NLMS algorithm exhibits better performance than the NLMS algorithm.

• Journal of the Korean Institute of Telematics and Electronics
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• v.9 no.4
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• pp.17-24
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• 1972

A simply constructed and inexpensive amplifier that exhibits unusually low noise is studied. The high-performance differential amplifier combines high input impedence, adjustable gain, low in put noise and low output impedance. The amplifier is particularly useful in applications which call for large amplificaions of very low level signals.

• Journal of Electrical Engineering and Technology
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• v.2 no.1
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• pp.29-34
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• 2007

The input and output impedances in a low voltage distribution system is one of the most important matters for power line communication because from the viewpoint of communication, the attenuation characteristic of the high frequency signals is greatly caused by impedance mismatch during sending and receiving. The frequency range is from 1MHz to 30MHz. Therefore, this paper investigates the input and output impedances in order to understand the characteristic of high frequency signals in the low voltage distribution system between a pole transformer and an end user. For power line communication, the model of Korea's low voltage distribution system is proposed in a residential area and then the low voltage distribution system is set up in a laboratory. In the low voltage distribution system, S parameters are measured by using a network analyzer. Finally, input and output impedances are calculated using S parameters.

• Proceedings of the KIPE Conference
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• 2012.11a
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• pp.88-90
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• 2012

A study on an integrated single stage AC/DC converter is presented in this paper. The input current can be controlled by the auxiliary winding($L_{aux}$), auxiliary primary winding($N_3$), and the boost inductor($L_B$) which are designed to operate in discontinuous conduction mode(DCM) to reduced the total harmonic distortion(THD) of input current. The auxiliary primary winding($N_3$) is critically selected in order to compress the input capacitor voltage($V_{in}$) as well as to reduce the current stress of the switch(Q). Low total harmonic distortion(THD), low input voltage($V_{in}$) in universal input voltage($V_{AC}$), low current stress at the switching device and high efficiency are the main consideration keys in this design to achieve high performance system with low cost of single stage AC/DC converter. A 30W single stage AC/DC prototype converter is under study.