• Journal of Korea Society of Industrial Information Systems
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• v.18 no.5
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• pp.1-8
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• 2013

This paper presents a variable gain amplifier(VGA) without passive devices. This VGA employes the architecture of current feedback amplifier and variable gain can be achieved by using the GM ratios of two trans-conductance(gm) circuits. To obtain linearity and high gain, it uses current division technique and source degeneration in feedback GM circuits. Input trans-conductance(GM) circuit was biased by using a tunable voltage controller to obtain variable gain. The prototype of the VGA is designed in $0.35{\mu}m$ CMOS technology and it is operating in sub-threshold region for low power consumption. The the gain of proposed VGA is varied from 23dB to 43dB, and current consumption is $2.82{\mu}A{\sim}3{\mu}A$ at 3.3V. The area of VGA is 1$120{\mu}m{\times}100{\mu}m$.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.2
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• pp.41-47
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• 2008

Most of media compression CODECs adopts the variable length coding method. This paper proposes special registers and instruction set for bit stream process in order to accelerate the decoding process of the variable length code. The instruction set shares the conventional data path to minimize additional costs. And bit stream is read from the memory instead of the special port. Therefore the instruction set minimizes the change of the processor, and is adopted without any additional input controller and buffer, and accelerate decoding process of variable length code. The data path of the instruction set needs additional 65 bits memory and 344 equivalent gates, 0.19 ns delay under TSMC $0.25{\mu}m$ technology. The instruction set reduced the execution time of the variable length code decoding process in H.264/AVC by about 55%.

• Journal of Astronomy and Space Sciences
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• v.11 no.2
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• pp.281-295
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• 1994

In this paper, the Variable Structure System(VSS) theory with new continuous switching dynamic equation is used to design an automatic controller for the active nutation damping in momentum bias stabilized spacecraft. In the application of VSS theory to a linearized multivariable system with the nutation damping systems, there exist some disadvantages such as how to determine the switching gains and how to reduce the chattering phenomina and reaching phase in input and state trajectories. To solve these drawbacks, this paper presents the continuous switching dynamic equation instead of the discontinuous switching logics to obtain the sliding mode. The new design approach is much simpler than the VSS theory. And there do not exist chattering phenomina in this method because the obtained control inputs are continuous. Simultaneously the reaching phase is reduced by a suitable choice of design factor.

• The Journal of the Acoustical Society of Korea
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• v.26 no.2
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• pp.69-74
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• 2007

In signal processing applications with highly correlated input signals, subband affine projection algorithm and step size controlling is a good solution for improving the slow convergence rate and large computational complexity of LMS-type algorithms. This paper proposes a subband affine projection algorithm using a variable step size. The proposed method achieves fast convergence rate and small steady-state error with a small computational complexity by combining the SAP and step size controlling in a subband structure. Experimental results on highly correlated input signal show that the proposed method is superior to the conventional methods.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2000.11a
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• pp.146-149
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• 2000

SiGe HUT뜰 이용하여 Cellular 주파수 대역(824-849 MHz)에서 MMIC 상향 주파수 혼합기와 가변이득 증폭기를 설계하였다. 동작 전압은 2.7 V 이며, 이중평형 구조의 상향 주파수 혼합기는 12 dB의 변환이득, -0.6 dBm의 1dB 이득압축 출력전력, 30 dB 이상의 LO-RF 단자 격리도 특성, 1.25의 LO-VSWR. 1.34의 RF-VSWR을 가지며, 상호컨덕턴스형 가변이득 증폭기는 35 dB의 최대 선형이득, 13 dBm의 1dB 이득압축 출력전력, 42dB의 가변이득, 23dB의 3차 상호변조 교점 출력전력(OIP$_3$), 1.27의 입력 VSWR, 1.1의 출력 VSWR 특성을 보인다.

• Journal of IKEEE
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• v.6 no.2 s.11
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• pp.111-118
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• 2002

In this paper, we present a variable block method to reduce additive computational requirements in determining step-size of variable step-size LMS (VS-LMS) algorithms. The block length is inversely proportional to the changing of step-size in VS-LMS algorithm. The technique reduces computational requirements of the conventional VS-LMS algorithms without a degradation of performance in convergence rate and steady state error. And a method for deriving initial step-size, when the input is zero mean, white Gaussian sequence, is proposed. For demonstrating the good performances of the proposed method, simulation results are compared with the conventional variable step-size algorithms in convergence speed and computational requirements.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.7
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• pp.127-134
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• 2015

In this note, a continuous sliding surface transformed variable structure systems by the saturation function is presented for MIMO uncertain linear plants. A discontinuous sliding surface transformed VSS is proposed theoretically. The closed loop exponential stability together with the MIMO existence condition of the sliding mode on the predetermined sliding surface is investigated. For practical applications, a continuous approximation of the discontinuous VSS is made by means of the saturation function. The discontinuity of the control input as the inherent property of the VSS is much improved in view of the practical aspects. Through a design example and simulation studies, the usefulness of the proposed continuous transformed VSS controller is verified.

• Proceedings of the KIEE Conference
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• 2007.04c
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• pp.173-176
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• 2007

본 논문에서는 풍속이 가변하는 상황에서 풍력 발전 시스템의 동작을 모의 할 수 있는 풍력 터빈 시뮬레이터를 설계 구현하였다. 실제 풍속과 회전 속도를 실시간으로 입력받으며, 토크 계산에 필요한 블레이드의 효율을 주속비에 관한 함수로 처리하여 사용함으로써 복잡한 조작 없이 가변 풍속조건에서 블레이드에 의한 토크입력을 모의할 수 있게 하였다. 또한 풍력터빈 시뮬레이터를 이용하여 농형 유도발전기식 풍력발전시스템을 구성하여 계통에 연계하였을 경우 발생되는 무효전력을 보상하기 위해 펄스 다중화 보조브리지회로를 이용한 새로운 구조의 36-펄스 전압원 컨버터방식의 실시간 무효전력보상기(STATCOM)를 적용하였다. 그리고 동작특성을 분석하고 제어시스템의 성능해석을 위하여 시뮬레이션 프로그램인 EMTDC/PSCAD를 이용한 시뮬레이션을 실시하였으며, 축소모형 하드웨어 실험을 통해 실험을 통한 분석을 실시하였다.

• Journal of the Korean Institute of Telematics and Electronics
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• v.11 no.1
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• pp.23-33
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• 1974

This study has developed a new system of character generator which is able to display more thats 14,364 different Korean characters by the 24 fundamental input elements. That is. in this system, all of the Korean characters are fomalized into 30 kinds of character forms (each having 70-980 characters), from which six form featuares are detacted to control and combine the fundamental input elements at their proper sizes and positions in a character frame. The device is very simple and all of the Korean characters can be displayed on CRT by the operation of only 24 input keys in good character quality.

• Proceedings of the KAIS Fall Conference
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• 2006.05a
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• pp.227-231
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• 2006

카메라를 통하여 실시간으로 입력되는 객체의 움직임은 잡음이나 조명의 변화에 따라 정확하게 추출하고 추적하는 것이 어렵다. 따라서 실시간으로 입력되는 영상에서 객체를 추출하고 움직임을 추적하기 위해서는 고속탐색 알고리즘이 필요하다. 본 논문은 실시간영상에서 객체의 움직임을 추출하고 추적을 위하여 배경영상의 변화에 강인한 배경영상 갱신 방법과 가변적인 탐색영역을 이용한 객체추적의 빠른 알고리즘을 제안한다. 배경영상 갱신 방법은 임계값이 실험적 기준치 보다 작은 경우에는 배경영상을 갱신하고, 큰 경우에는 객체가 유입된 시점으로 판단하여 픽셀검사를 통해 객체의 윤곽점을 추출한다. 추출된 윤곽점은 객체 영역블록의 생성과 일정한 거리를 유지하는 탐색블록을 생성하여 정확하고 빠른 객체의 움직임을 추적한다. 실험결과, 제안한 방법은 95% 이상의 높은 정확도를 보였다.