• 한국전자파학회논문지
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• 제13권3호
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• pp.288-300
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• 2002

본 논문에서는 최근 IMT-2000 시스템에서 고속데이타 통신을 수용하기 위해 연구되고 있는 다중입력다중 출력(Multiple Input Multiple Output) 안테나를 이용한 공간분할기법을 현실화하기 위한 새로운 등화된 RF 수신부 구성방법을 제안하였다. 제안된 방법의 핵심은 보정시간 동안 궤환회로 및 기억회로를 통해 보정시간중 등화된 다수의 RF 수신부 구성방법에 있으며, 이를 이용할 경우 중간주파 영역에서 weighting 하는 것이 가능하게된다 이는 기존에 연구된 전파노래 각 알고리듬을 사용 가입자 분포에 따라 안테나 빔 형성하는 것을 가능케 하며, 공간분할에 의한 최적 셀 형성을 가능하게 학 것이다. 또한 제시된 RF 전단부의 동작을 확인하기 위하여 Envelope Simulation을 사용 이의 동작을 검증하였다.

• 한국정보통신학회논문지
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• 제23권8호
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• pp.981-987
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• 2019

본 논문에서는 파일럿으로 발생하는 파일럿 오버헤드를 감소시키면서 협대역 간섭신호 혹은 재머에 대응할 수 있는 새로운 SC-FDE (single carrier frequency domain equalization) 구조를 제안한다. 기존의 SC-FDE 구조는 협대역 재머가 존재할 때 시간영역 채널 추정이 어려워 수신기의 성능이 저하되는 단점이 있다. 또한 매 SC-FDE마다 채널추정을 위한 파일럿을 전송하여 스펙트럼 효율이 저하되는 문제도 있다. 이와 같은 문제를 해결하기 위해 제안된 구조는 시간영역 채널 추정 없이 곧바로 주파수 영역 채널 추정을 수행할 수 있도록 설계된다. 또한 파일럿 오버헤드를 감소시키기 위해서 두 개의 파일럿 사이에 여러 개의 SC-FDE 데이터 블록을 전송하고, 두 개의 파일럿을 이용한 선형 보간 채널 추정을 통해 각 데이터 블록에서의 채널 특성을 찾는다. 이렇게 구한 채널 추정값을 사용하여 주파수 영역 등화를 수행하면 협대역 재머가 있는 상황에서도 재머 제거와 함께 안정적인 등화가 가능하다. 제안하는 구조의 성능은 컴퓨터 모의실험을 통해 확인한다.

• IEIE Transactions on Smart Processing and Computing
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• 제5권1호
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• pp.5-9
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• 2016

The modulation bandwidth of a reflective semiconductor optical amplifier (RSOA) is limited by carrier lifetime. Therefore, it is hard to directly modulate an RSOA with high-speed electrical signals. We theorize that an optical filter can act as an optical equalizer, compensating for the narrow bandwidth limitation imposed by the RSOA. By modeling a time-varying RSOA with a modified transfer matrix method (TMM), we simulated 25 Gbps operation of an RSOA with optical filtering effects. We investigated the impact of detuning the center wavelength of the optical filter on the modulation of an RSOA. The numerical results show that it is possible to modulate an RSOA with an optical filtering effect at 25 Gbps without electronic equalization or digital signal processing.

• 한국통신학회:학술대회논문집
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• 한국통신학회 2006년도 하계종합학술발표회 논문 초록집
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• pp.426-426
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• 2006

• Journal of Communications and Networks
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• 제12권6호
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• pp.600-604
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• 2010

A method of width adaptation in the radial basis function network (RBFN) using stochastic gradient (SG) algorithm is introduced. Using Taylor's expansion of error signal and differentiating the error with respect to the step-size, the optimal time-varying step-size of the width in RBFN is derived. The proposed approach to adjusting widths in RBFN achieves superior learning speed and the steady-state mean square error (MSE) performance in nonlinear channel environment. The proposed method has shown enhanced steady-state MSE performance by more than 3 dB in both nonlinear channel environments. The results confirm that controlling over step-size of the width in RBFN by the proposed algorithm can be an effective approach to enhancement of convergence speed and the steady-state value of MSE.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.1113-1114
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• 2008

WiBro(Wireless Broadband) is the standard of high-speed portable internet based on OFDMA/TDD (orthogonal frequency division multiple access / time division duplexing) techniques, and the subset of consolidated version of IEEE802.16e Wireless MAN standard. In this paper, we propose the design method of WiBro system. Proposed method used KSFM neural network blind equalization with Bussgang algorithms.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(1)
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• pp.69-72
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• 2001

Blind equalization of transmission channel is important in communication areas and signal processing applications because it does not need training sequence, nor does it require a priori channel information. Recently, Tong et al. proposed solutions for this problem exploit the diversity induced by antenna array or time oversampling, leading to the second order statistics techniques, fur example, subspace method, prediction error method, and so on. The linear prediction error method is perhaps the most attractive in practice due to the insensitive to blind equalizer length mismatch as well as for its simple adaptive filter implementation. Unfortunately, the previous one-step prediction error method is known to be limited in arbitrary delay. In this paper, we induce the optimal delay, and propose the adaptive blind equalizer with multi-step linear prediction using RLS-type algorithm. Simulation results are presented to demonstrate the proposed algorithm and to compare it with existing algorithms.

• 한국통신학회논문지
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• 제34권5C호
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• pp.521-526
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• 2009

In this paper, a complex-valued recursive least squares escalator filter algorithm with reduced computational complexity for complex-valued signal processing applications is presented. The local tap weight of RLS-ESC algorithm is updated by incrementing its old value by an amount equal to the local estimation error times the local gain scalar, and for the gain scalar, the local input autocorrelation is calculated at the previous time. By deriving a new gain scalar that can be calculated by using the current local input autocorrelation, reduced computational complexity is accomplished. Compared with the computational complexity of the complex-valued version of RLS-ESC algorithm, the computational complexity of the proposed method can be reduced by 50% without performance degradation. The reduced computational complexity of the proposed algorithm is even less than that of the LMS-ESC. Simulation results for complex channel equalization in 64QAM modulation schemes demonstrate that the proposed algorithm has superior convergence and constellation performance.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 학술회의 논문집 정보 및 제어부문 B
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• pp.400-403
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• 2003

This paper presents the signal processing of the panoramic thermal warning system that detects the small target such as aircraft and helicopter from afar. We develope the all round looking thermal imaging system which can scan all the way. This system acquires the panoramic images to reconstruct the IR images by revolving head of sensor typed line sensor at high speed. For detection, where the object of interest may be small, it is sometimes difficult to specify from object and background by conventional contrast enhancement methods. Therefore we use the adaptive plateau equalization algorithm each region to improve the contrast and make the hardware system which consists of the signal processing board for real-time display. We can verify the proposed method by the computer simulation and the hardware implementation.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2011년도 학술대회 및 정기총회
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• pp.189-192
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• 2011