• Proceedings of the Korean Society of Computer Information Conference
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• 2018.07a
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• pp.127-128
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• 2018

본 논문에서는 채널추정에러가 존재하는 셀룰라시스템 환경에서 D2D 통신을 위한 전력제어 알고리즘 운용방안을 제안한다. 전력제어의 목적은 요구하는 SIR 값을 유지하는 것이다. 하지만, 채널 추정에러 환경에서의 SIR 성능은 확률적 분포를 가지게 된다. 이러한 확률적 SIR 성능 분포를 고려하여, 채널추정에러를 보상하는 가변적인 SIR 적용과 재전송 기법을 복합하여 D2D 통신을 위한 전력제어 기법을 제안하도록 한다.

• Proceedings of the IEEK Conference
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• 2003.07e
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• pp.2068-2071
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• 2003

최근 표준화가 완성된 H.264 는 가변 블록 움직임 보상, 복수 참조 영상, 그리고 1/4 화소 움직임 벡터 정확도를 지원하고 있다. 그러나 이러한 새로운 부호화기술은 부호화 효율 향상의 주된 요인이면서, 동시에 높은 복잡도의 요인이기도 하다 따라서 H.264 비디오 표준의 실제 응용 확대를 위해서는 이러한 기술의 속도향상이 필수적이다. [1]에서 제안한 고속 모드 결정법은 조기에 모드 결정을 할 수 있기 때문에, 움직임 벡터 탐색과 비트율-왜곡치 (Rate-Distortion cost) 계산 과정을 효율적으로 생략할 수 있는 방법이다. 하지만 [1]에서 제안된 측정치 r은 주변 블록의 정보를 이용하지 않기 때문에 모드 결정 에러를 좀 더 효과적으로 줄이지 못했다. 본 논문에서는 주변 블록의 정보를 이용하여 [1]의 방법을 개선시킨 것으로 실험 결과 큰 부호화 손실 없이 계산 량 감소에 있어 매우 높은 효율을 제공함을 확인하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.7
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• pp.580-583
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• 2017

To compensate the degraded SAR image due to the residual errors and the spatial variant errors remaining after the motion compensation in the airborne SAR, we have introduced the autofocus method based on the partition processing. Thus, after we perform the spatial partition for the spotlight SAR data and the time partition for the stripmap SAR data, we reconstruct the subpatch images for the partitioned data. Then, we perform the local autofocus with the suitability analysis process for the phase errors estimated by the autofocus. Moreover, if the estimated phase errors are not properly compensated for the subpatch images, we perform the phase compensation method with the weight to the estimated phase error close to the degraded subpatch image to increase the SAR image quality.

• The Transactions of the Korea Information Processing Society
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• v.6 no.8
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• pp.2271-2280
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• 1999

In this paper, a variable motion estimation scheme based on HBMA(Hierarchical Block Matching Algorithm) to improve the performance and to reduce heavy computational and transmission load, is presented. The proposed algorithm is composed of four steps. First, block activity for each block is defined using the edge information of differential image between two sequential images, and then average block activity of the present image is found by taking the mean of block activity. Secondly, camera pan compensation is carried out, according to the average activity of the image, in the hierarchical pyramid structure constructed by wavelet transform. Next, the LUT classifying each block into one among Moving, No Moving, Semi-Moving Block according to the block activity compensated camera pan is obtained. Finally, as varying the block size and adaptively selecting the initial search layer and the search range referring to LUT, the proposed variable HBMA can effectively carries out fast motion estimation in the hierarchical pyramid structure. The cost function needed above-mentioned each step is only the block activity defined by the edge information of the differential image in the sequential images.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.513-514
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• 2016

본 논문에서는 스위칭 셀 구조의 직접형 PWM ac-ac 컨버터를 이용한 새로운 단상 무효전력 보상 장치를 제안한다. 제안한 보상기는 최근에 개발된 가변 임피던스 개념을 이용한 무효전력 보상기에서 발전된 형태이다. 기존 보상기에는 시스템 신뢰성에 심각한 악영향을 주는 커뮤테이션 문제가 존재하는데 제안한 보상기에서는 스위칭셀 구조와 결합인덕터로 구성된 ac-ac 컨버터를 사용하여서 커뮤테이션 문제를 해결하였다. 이로인해 기존 시스템에 비해 스위칭 신호 구현이 매우 간편하고 RC 스너버가 필요하지 않으며 결과적으로 매우 신뢰성이 높은 시스템을 구현할 수 있다. 간략화 된 단상시스템을 구축하여 실험을 통해 성능을 검증하였다.

• The Transactions of the Korean Institute of Power Electronics
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• v.2 no.4
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• pp.28-35
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• 1997

본 논문에서는 송전선로에 직렬로 삽입되어 선로의 리액턴스를 동적으로 보상하는 인버터식 직렬보상기에 대한 동적 응동 해석을 기술하고 있다. 이 직렬보상기는 다중펄스로 동작하는 전압원인버터와 결합변압기, 그리고 제어장치로 구성되어 있으며, 점호각을 조절하여 선로의 리액턴스를 가변하고 용량성 뿐만 아니라 유도성 보상도 가능하다. 이 보상기로 선로의 리액턴스를 감소시키면 전송 유효전력의 증각가 가능한데, 이러한 효과를 본 논문에서는 단일기-무한대-버스 전력계통에 대해 EMTP를 이용한 시뮬레션으로 확인하였으며, 또한 축소모형 제작과 실험을 통해 실험적으로 확인하였다.

• Journal of Satellite, Information and Communications
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• v.3 no.1
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• pp.1-7
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• 2008

This Paper studied the design and measured results of a flight model for Ku-Band Linearized Channel Amplifier (LCAMP) for communication satellite onboard system. All MMICs, i.e. Variable Gain Amplifier (VGA), Variable Voltage Attenuator (VVA) with analog/digital attenuator, Branch line Hybrid Coupler and Detector for Pre-distorter are fabricated using Thin-Film Hybrid process. The performance of the fabricated module is verified through Radio Frequency circuit simulations and electrical function test in space environment for flight model at 12.25 to 12.75 GHz.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.8 no.3
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• pp.88-95
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• 1994

A scheme of IESFVSC(Integral Error State Feedback Variable Structure Controller) is proposed for a DC servo position control system with the disturbances which do not satisfy the matching condition. The proposed control system is composed of servo compensator and state feedback VSC. The servo compensator enhances the robustness of the control system against various types of disturbance, and makes effective tracking possible without using error dynamics. The IESFVSC is applied to the practical design of a robust DC servo control system and the control performances are verified through theoretical analyses and simulations.

• The Journal of the Korea Contents Association
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• v.10 no.4
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• pp.28-35
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• 2010

The variable block size motion estimation (ME) and compensation (MC) using multiple reference frames is adopted in H.264/AVC to improve coding efficiency. However, the computational complexity for ME/MC increases proportional to the number of reference frames and variable blocks. In this paper, we propose a new efficient reference frame selection algorithm to reduce the complexity while keeping the visual quality. First, a motion vector reference map is constructed by SAD of $4{\times}4$ block unit for multi reference frames. Next, the variable block size motion estimation and motion compensation is performed according to the motion vector reference map. The computer simulation results show that the average loss of BDPSNR is -0.01dB, the increment of BDBR is 0.27%, and the encoding time is reduced by 38% compared with the original method for H.264/AVC.

• Journal of IKEEE
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• v.24 no.4
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• pp.1104-1108
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• 2020

This paper propose a variable proportional resonant feedforward algorithm for reducing the speed ripple of a three-phase permanent magnet synchronous motor. In general, the torque ripples can be generated by electrical pulsation due to current measurement errors and dead time and mechanical pulsation because of rotor eccentricity and eccentric load. These torque pulsations can cause speed pulsations of the motor and degrade the operating performance of the motor drive system. Therefore, in this paper, the factors of the speed ripple is analyzed and an algorithm to reduce the speed ripple is proposed. The proposed algorithm applied a variable proportional resonant controller in order to reduce the specific operating frequency included in the speed pulsation, and utilized a feedforward compensation controller structure to perform the compensation operation. The proposed algorithm is verified through various experiments.