• 한국위성정보통신학회논문지
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• 제10권2호
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• pp.24-29
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• 2015

최근, 휴대용 무선 통신 단말기 사용이 보편화 되고 다양한 통신 기술이 서비스되면서 단말의 소형화, 사용 지속성 측면에서 에너지 효율이 중요하게 다루어지고 있다. 단말이 지속적으로 다양한 통신서비스를 제공받기 위해 단말 주변 수 m 내에서 RF 에너지 신호를 방사하는 source로부터 RF 신호를 자원으로 무선으로 전력을 충전하는 무선 에너지 하비스팅 시나리오를 가정한다. 본 논문에서는 무선 에너지 하비스팅 효율을 증대시키기 위해 RF 신호를 송신하는 송신부(Tx)와 에너지 하비스팅 장치인 수신부(Rx)간 주기적으로 할당된 전체 주파수 범위 내에서 하비스팅 효율 맵을 형성하는 알고리즘을 제안한다. 제안한 알고리즘을 통해서 주파수에 따른 페이딩 정도를 파악하고 가장 높은 효율 값을 갖는 주파수를 선택하여 source 신호로 송신하여 에너지 하비스팅 효율 최적화를 달성한다. 컴퓨터 시뮬레이션 결과 제안한 알고리즘을 통해 가장 높은 효율을 갖는 신호는 가장 낮은 효율의 신호에 비해 동일 거리에서 최대 4.45dB 이득이 있음을 확인하였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.699-702
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• 1998

This paper presents a 500MHz 1.1㎱ 32kb synchronous CMOS SRAM macro using $0.35\mu\textrm{m}$ CMOS technology. In order to operate at high frequency and reduce power dissipation, the designed SRAM macro is realized with optimized decoder, multi-point sense amplifier(MPSA), selective precharge scheme and etc. Optimized decorder and MPSA respectively reduce 50% and 40% of delay time. Also, a selective precharge scheme reduces 80% of power dissipation in that part.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 추계종합학술대회 논문집(2)
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• pp.79-82
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• 2000

This paper describes a delay locked loop with selective starting point for use in a high-frequency systems. SSRDLL (selective starting point RDLL) has been simulated in a 0.25$\mu\textrm{m}$ standard n-well CMOS process parameter to realize a fast lock-on time. This DLL is shown to be insensitive to variations in PVTL. The simulated lock time of the proposed SSRDLL is within 4 clock cycles at 333㎒ clock input.

• 제어로봇시스템학회논문지
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• 제20권2호
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• pp.107-111
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• 2014

An SIW cavity is a useful tool to design an FSS which shows a rapid roll-off rate and insensitivity to polarizations and incident angles of electromagnetic waves. However, due to its high Q-factor, the FSS also shows narrow bandwidth which is undesirable for high-capacity communication. To address this drawback, we propose a novel technique to enhance the bandwidth while maintaining similar frequency response characteristics and minimizing the increase of the overall thickness of the SIW cavity FSS. In order to verify the performance of the technique, simulated frequency responses will be provided. Also, a parameter which affects the bandwidth will be studied. Finally the stability to polarizations and incident angles will be observed through the simulated results.

• 전자공학회논문지S
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• 제34S권2호
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• pp.94-103
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• 1997

The WCHF-FSJTC (wavelet circular harmonic function frequency selective joint transform correlator) using th wavelet transformed CHF as the reference image in FSJTC is proposed for rotation invariant pattern recognition. Since the wavelet transform has the property of feature extraction, the proposed system can have the better DC (discrimination cpability) and the higher SNR(signal to noise ratio) compared with the conventional CHF-CJTC(circular harmonic function conventional joint transform correlator). And since the structure of the proposed system is FSJTC which can eliminate auto-correlation and cross-correlation between input images, it can eliminate false alarm caused by the overlapping among correlation peaks. The used wavelet functio is the morlet function, which is proper for the reference image used in this paper. the optimal dialation parameter and oscillation frequency of the wavelet function are also achieved with varying the parameters of the wavelet function. The computer simulation shows that the proposed system has the best performance when the dilation parameter is 0.8 and the oscillation frequency is 0.48.

• 한국항행학회논문지
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• 제11권1호
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• pp.37-42
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• 2007

본 논문에서는 비선택성 페이딩과 주파수 오프셋이 함께 존재하는 채널과 마이크로파 대역의 2경로 Rummer's 채널 환경에서 적응 등화기를 채용한 OFDM 시스템의 성능을 분석하였다. 주파수 비선택성 페이딩과 주파수 오프셋이 함께 존재하는 채널에서 시스템 성능 분석 결과 주파수 오프셋의 증가에 따른 성능이 급격히 열화 됨을 알 수 있다, 그리고 시스템에서 적응 등화기를 채용한 경우에는 일정 범위 내에서 성능 향상이 이루어짐을 확인할 수 있었다.

• Journal of Communications and Networks
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• 제8권1호
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• pp.38-48
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• 2006

A synchronous multicarrier (MC) code-division multiple access (CDMA) system using inverse fast Fourier transform (IFFT) and fast Fourier transform (FFT) for the downlink mobile communication system operating in a frequency selective Rayleigh fading channel is analyzed. Both carrier frequency offset and timing offset are considered in the analysis. Bit error rate performance of the system with both equal gain combining and maximum ratio combining are obtained. The performance is compared to that of the conventional system using correlation receiver. It is shown that when subcarrier number is large, the system using IFFT/FFT has nearly the same performance as the conventional one, while when the sub carrier number is small, the system using IFFT/FFT will suffer slightly worse performance in the presence of carrier frequency offset.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 I
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• pp.202-205
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• 2003

The performance of space-frequency trellis coded (SFTC) OFDM system is analyzed in frequency selective fading channel. Using a pairwise error probability upper bound expression, we design the code and interleaver that can maximize the diversity and coding gain. To alleviate the performance degradation due to the inter-antenna product terms, we propose a new SFTC scheme that employs non-overlapped interleaving for each antenna A new code is optimized for the non-overlapped interleaving and a practical sub-optimal decoding algorithm is proposed. It is shown that the proposed scheme can substantially improve the performance compared to the conventional scheme that employs identical interleaving for all antennas.

• 한국통신학회논문지
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• 제25권10B호
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• pp.1813-1820
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• 2000

In this paper we proposed an efficient multiresolution motion estimation(MRME) algorithm using half-pixel accuracy motion estimation (HPAME) and characteristics of motion vectors in the baseband. Conventional MRME method needs exact motion vectors in the baseband because those are used as initial motion vectors in higher frequency subbands. Therefore the proposed method uses HPAME to estimate the motion vectors exactly in the baseband. Based on the characteristics of these motion vectors the motion vectors in the higher frequency subbands are selectively estimatied. That is motion vectors in the higher frequency subbands are estimated only for the blocks which have the half-pixel accuracy motion vectors in the baseband. In the proposed method by using HPAME in the baseband and selective motion estimation in the higher frequency subbands we can obtain reconstructed image with the similar quality with the conventional method though we reduce the computational complexity and the bit rate considerably.

• 대한전자공학회논문지TC
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• 제45권12호
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• pp.49-57
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• 2008

분산할당 OFDMA 시스템에서 순환지연 다이버시티를 적용하면 주파수 다이버시티의 증가로 인해 성능의 증대를 가져온다. 그러나 분산할당 SC-FDMA 시스템에 순환지연 다이버시티를 적용하는 것은 주파수 다이버시티의 증가로 인한 성능증대 효과와 주파수 선택적 채널로 인한 성능감소 효과를 동시에 가져온다. 본 논문에서는 이 상반되는 두 가지 효과에 대해서 논하며 분산할당 SC-FDMA 시스템에서 순환지연 다이버시티를 적용하는 것이 언제 유리하고 언제 불리한지 논의한다.