• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.4A
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• pp.197-204
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• 2012

We propose a new scheme combining the compensation of HPA nonlinearity and the calibration of the path imperfections in the downlink OFDM smart antenna systems. We use a two term third-order polynomial (without second-order term) and the feedforward method for compensation and calibration to make each path of the antenna array have equal characteristics. Since the proposed scheme does not alter the base-band signal, it can be applied to the smart antenna system independently of the base-band signal processing section. The result of computer simulations shows that, with the addition of only one third-order term, the adverse nonlinear effects can be effectively compensated, and the those of linear imperfections can be calibrated as well.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.6A
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• pp.965-979
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• 2001

본 논문에서는 OFDM 시스템의 송신기에서 사용되는 선형 필터와 고출력 증폭기의 결합에 의한 \"기억성을 갖는 비선형 왜곡\"을 실제 하드웨어 구현에 적합하게 적은 계산량으로 보상할 수 있는 참조 테이블(look up table; LUT) 기반의 사전왜곡기를 제안한다. LUT를 이용하는 사전왜곡기들은 이미 많이 연구되었으나, 본 논문에서는 다중 입력/단일 출력 형태의 기억성을 갖는 비선형 왜곡을 작은 크기의 LUT를 이용하여 효율적으로 보상한다는 점에서 큰 차이가 있다. 제안 방법에서는 먼저 기억성이 없는 고출력 증폭기만이 존재할 때의 사전왜곡기를 우리가 이미 제안한 고정점 반복 사전왜곡기 알고리즘에 기반하여 LUT로 구현하고, 여기에 선형 역 시스템을 결합하여 기억성을 갖는 비선형 왜곡을 보상한다. 실제 구현 가능성 검토를 위해 제안된 사전왜곡기와 16-QAM, 256-IFFT/FFT OFDM 시스템 기저대역 모뎀을 TMS320C30 DSP를 이용하여 구현하였으며, 실험 결과 작은 크기의 LUT를 이용하여도 원래의 고정점 반복 사전왜곡기에 비해 매우 적은 계산량을 요구하면서 동일한 성능을 얻을 수 있음을 확인하였다.있음을 확인하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.7
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• pp.1015-1020
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• 2018

The cavity resonator is one of the widely used components in the microwave applications. The unloaded Q, the resonant frequency, and the coupling factor are basic parameters of a cavity. A simple unloaded Q factor measurement procedure of a cavity is proposed in a lossy coupling. The equivalent circuit of a cavity with coupling loss at near the resonant frequency is presented. The coupling loss resistance was found by the measurement of a cavity impedance. The cavity impedance compensated coupling loss was redrawn on the Smith Chart. The loaded Q and coupling factor were obtained based on the compensated impedance locus and then the unloaded Q factor was calculated. To verify the proposed procedure, the cavity with lossless coupling was measured. The two measurement results in the lossy and lossless coupling agree well. The results confirm the proposed procedure is valid.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.6
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• pp.102-111
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• 2009

In this paper, we propose a de-interlacing algorithm that combines a motion compensation (MC) method and the vertical-temporal filter with motion compensation (MC V-T filter) according to motion compensation reliability. The MC method represent one of the best ways of improving the resolution of de-interlaced frames, but it may introduce motion compensation artifacts in regions with incorrect motion information. In these regions, the MC V-T filter that is very robust to motion vector errors can be used to correct motion compensation artifacts. The combination between two methods is controlled by the motion compensation reliability that is measured by analyzing the estimated motion vectors and the results of MC. The motion compensation reliability contains information about motion compensation artifacts of MC results and determines the combination weight according to this information. Therefore, the combination rule of the proposed method is more accurate than those of the conventional methods and it enables the proposed method to provide high quality video sequences without producing any visible artifacts. Experimental results with various test sequences show that the proposed algorithm outperforms conventional algorithms in terms of both visual and numerical criteria.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.4
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• pp.9-17
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• 2012

In this paper, we show the memory effect of the high-power amplifiers for wied-band signals, present a compensation method for the nonlinearity combined with memory effect, and analyze its performance. For the modeling and the compensation of the nonlinear high-power amplifier with memory effect, we investigate the Volterra series model, the Wiener model, and the Hammerstein model. As a compensator scheme, we propose a digital feedforward technique. Compared to analog feed-forward scheme, the proposed scheme has better stability and adaptability to the environmental changes. It has a simpler structure than the conventional digital nonlinear compensation schemes. The result of computer simulations using ADS of the Agilent shows that spectral re-growth is suppressed by more than 20 dB, which amounts to at least 10 dB back-off. Considering the compensation performance, implementation complexity, and convergence rate, we could conclude the Wiener model is most suitable for the proposed scheme.

• The Journal of the Acoustical Society of Korea
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• v.23 no.6
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• pp.473-480
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• 2004

In this paper we propose an effective feature compensation scheme based on the speech model in order to achieve robust speech recognition. The proposed feature compensation method is based on parallel combined mixture model (PCMM). The previous PCMM works require a highly sophisticated procedure for estimation of the combined mixture model in order to reflect the time-varying noisy conditions at every utterance. The proposed schemes can cope with the time-varying background noise by employing the interpolation method of the multiple mixture models. We apply the‘data-driven’method to PCMM tot move reliable model combination and introduce a frame-synched version for estimation of environments posteriori. In order to reduce the computational complexity due to multiple models, we propose a technique for mixture sharing. The statistically similar Gaussian components are selected and the smoothed versions are generated for sharing. The performance is examined over Aurora 2.0 and speech corpus recorded while car-driving. The experimental results indicate that the proposed schemes are effective in realizing robust speech recognition and reducing the computational complexities under both simulated environments and real-life conditions.

• Journal of Science and Technology Studies
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• v.7 no.2
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• pp.47-90
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• 2007

과학상은 과학자 사회를 유지하는 중요한 기제인 보상체계의 한 요소로 과학사회학에서 많은 연구가 이루어졌다. 전통적으로 보상의 기능은 과학적 업적에 대한 인정의 배분으로 간주되었다. 그러나 머튼 이후 여러 학자들은 과학상을 비롯한 보상이 당대의 인지적 규범에 순응하게 만드는 사회적 통제의 과정이기도 하다는 주장을 제기했다. 이 논문은 우리나라 과학상의 역사적 변천과정과 그 특성에 대한 분석을 통해 과학상이 인정의 적절한 배분으로 과학자 사회 내에서 작동했는지 살펴본다. 분석을 통해 드러난 우리나라 과학상의 특성은 다음과 같이 요약된다. 첫째, 우리나라 과학상은 정부에 의해 주도되었고, 상의 가시성의 원천은 정부 또는 국가에서 나온다. 둘째, 과학상은 과학자 사회 내부의 인정 배분이라는 전통적 기능보다 정부의 정책 목표달성을 위한 통제 방식으로 기능하는 경향이 있다. 셋째, 최근 과학상은 연구비와 결합되면서 과학엘리트를 형성하고 그 구조를 강화시키는 하나의 통로가 되고 있다.

• Journal of Satellite, Information and Communications
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• v.8 no.4
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• pp.37-42
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• 2013

In this paper, we propose a compensation method of a non-ideal antenna array and a computationally efficient estimation method of the direction of arrival (DOA) for the antenna array. For DOA estimation, an antenna array is essential. By using the phase difference between the output signals of antennas, we can derive the DOA. In practice, however, mutual coupling between the elements of an antenna array change the beam pattern of each element and degrade the performance of DOA estimation. In the proposed method, we first estimate the DOA for the mid-subarray of the array, where all elements undergo relatively same coupling effect. We use the estimation of signal parameters via rotational invariance techniques (ESPRIT) algorithm to estimate the DOA. Then, we expand the array based on the estimated DOA by compensating the coupling effect. Simulation results show that the proposed method is effective when jamming to noise power ratio (JNR)is relative low.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.141-142
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• 2016

전계결합을 이용한 무선전력전송 시스템은 송 수신부 사이에 형성된 링크 캐패시턴스를 사용해서 에너지를 전송한다. 이러한 용량 리액턴스를 상쇄하기 위한 방안으로 인덕터나 변압기를 응용한 여러 종류의 임피던스 정합구조가 연구되고 있다. 본 논문에서는 다양한 리액턴스 보상 방법에 대한 장 단점을 비교하고 이 중에서 전계결합 시스템에 가장 적합한 임피던스 정합구조를 선정한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.2
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• pp.438-446
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• 2013

Generally, a camera isn't located at the center of display in a tele-presence system and it causes an incorrect eye contact between speakers which reduce the realistic feeling during the conversation. To solve this incorrect eye contact problem, we newly propose an intermediate view reconstruction algorithm using both a color camera and a depth camera and applying for the depth image based rendering (DIBR) algorithm. In the proposed algorithm, an efficient hole filling method using the arithmetic mean value of neighbor pixels and an efficient boundary noise removal method by expanding the edge region of depth image are included. We show that the generated eye-contacted image has good quality through experiments.