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길행복,주현,이철호,정의림,Kil, Haeng-bok,Joo, Hyun,Lee, Chulho,Jeong, Eui-Rim 한국정보통신학회 2018 한국정보통신학회논문지 Vol.22 No.4
본 논문에서는 배열 안테나 기반의 MVDR (minimum variance distortionless response) 항 재밍 GPS (global positioning system) 수신기에서 안테나 경로 사이에 존재하는 이득, 위상, 지연 편차를 교정하기 위한 안테나 교정 기법을 제안한다. 제안하는 기법은 다중 안테나 시스템에서 안테나 경로들 사이의 이득, 위상, 지연 편차를 추정하고 이를 보상한다. 경로 간 이득, 위상, 지연 편차를 정확히 추정하기 위해 좋은 상관 특성을 갖는 파일럿 신호가 사용된다. 교차 상관에 기반하여 지연 편차가 먼저 추정되며 이후에 이득과 위상 편차가 추정된다. 정밀한 지연 편차 추정 및 보상을 위해 보간기법을 사용하는데 이산 푸리에 변환 (DFT) 기반의 보간기법으로 계산 복잡도를 감소시킨다. 제안된 기법은 MATLAB을 이용한 컴퓨터 모의실험을 통해 검증한다. 모의실험 결과에 따르면 제안하는 기법을 적용하면 이득, 위상 시간 지연 편차를 각각 0.01 dB, 0.05 도, 0.5 ns 이내로 줄일 수 있다. In this paper, a new signal processing technique is proposed for calibrating gain, phase, delay offsets in array antenna based anti-jamming minimum variance distortionless response (MVDR) global-positioning-system (GPS) receivers. The proposed technique estimates gain, phase and delay offsets across the antennas, and compensates for the offsets based on the estimates. A pilot signal with good correlation characteristics is used for accurate estimation of the gain, phase and delay offsets. Based on the cross-correlation, the delay offset is first estimated and then gain/phase offsets are estimated. For fine delay offset estimation and compensation, an interpolation technique is used, and specifically, the discrete Fourier transform (DFT) is employed for the interpolation technique to reduce the computational complexity. The proposed technique is verified through computer simulation using MATLAB. According to the simulation results, the proposed technique can reduce the gain, phaes and delay offset to 0.01 dB, 0.05 degree, and 0.5 ns, respectively.
경도인지장애 및 초기 치매 노인에서 일상생활 수행능력의 관련 요인
김장래(Jang Rae Kim),길주현(Joo Hyun Kil),조아라(MA,Ara Cho),이동우(Dong Woo Lee),김민숙(Min Sook Kim),최영민(Young Min Choi) 대한노인정신의학회 2011 노인정신의학 Vol.15 No.2
Objectives:To identify the factors that are most significantly associated with the decline of Activities of Daily Living (ADL) status in subjects with Mild Cognitive Impairment (MCI) and early dementia of primary degenerative cause. Methods: Medical records results of neuropsychological tests and Activities of Daily Living scale were retrospectively analyzed in 134 subjects meeting the diagnostic criteria of MCI or early dementia respectively. Demographic factors memory functions depressive symptoms and executive functions of the participants were also analyzed. Results:Correlations revealed that measures of executive functions were significantly associated with ADL status in participants with MCI while both memory and executive functions were significantly associated in early demented elderly. Stroop test which measures the ability of inhibition showed the closest relation to executive function. Depressive symptoms did not have a significant influence on ADL status. Conclusion:Among participants with MCI the early functional difficulties are associated mainly with executive function which enables inhibition in particular. In participants with early dementia on the contrary the ADL status was associated with both executive function and memory. Further studies on the symptom pattern and related neuropathology in process of dementia progression are needed for Quality of Life (QoL) in elderly population.