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VLSI Implementation of Auto-Correlation Architecture for Synchronization of MIMO-OFDM WLAN Systems
Jongmin Cho,Jinsang Kim,Won-Kyung Cho 대한전자공학회 2010 Journal of semiconductor technology and science Vol.10 No.3
This paper presents a hardware-efficient auto-correlation scheme for the synchronization of MIMO-OFDM based wireless local area network (WLAN) systems, such as IEEE 802.11n. Carrier frequency offset (CFO) esti mation for the frequency synchronization requires high complexity autocorrelation operations of many training symbols. In order to reduce the hardware complexity of the MIMO-OFDM synchronization, we propose an efficient correlation scheme based on timemultiplexing technique and the use of reduced samples while preserving the performance. Compared to a conventional architecture, the proposed architecture requires only 27% logic gates and 22% power consumption with acceptable BER performance loss.
Investigation and Optimization of Double-gate MPI 1T DRAM with Gate-induced Drain Leakage Operation
Jongmin Ha,Jae Yoon Lee,Myeongseon Kim,Seongjae Cho,Il Hwan Cho 대한전자공학회 2019 Journal of semiconductor technology and science Vol.19 No.2
In this paper, we propose a double-gate one-transistor dynamic random-access memory (1T DRAM) with middle partial insulation (MPI) structure for low power application. Low power operation with the gate-induced drain leakage (GIDL) programming method can be obtained while maintaining the original advantages of MPI 1TDRAM. The optimization of the MPI 1T-DRAM device for the GIDL method is investigated with technology computer-aided design (TCAD). High current ratio and low power consumption are obtained from the proposed 1T-DRAM device. Optimal device design in terms of barrier insulator length and fin width have been carried out for improvements of device performances and reliability.
IEEE 802.11n 무선 LAN 시스템의 시간 동기화 하드웨어 구조
조종민(Jongmin Cho),김진상(Jinsang Kim),조원경(Won-Kyung Cho) 한국통신학회 2008 韓國通信學會論文誌 Vol.33 No.11A
본 논문에서는 MIMO-OFDM 기반의 차세대 무선 LAN(Local Area Network) 시스템, IEEE 802.11n 드래프트 표준의 시간 동기화 구조의 알고리즘과 하드웨어 구조를 제안한다. 제안된 시간 동기화 구조는 일반적인 대략추정과 상세추정 과정으로 이루어져 있고 자기 상관기를 이용하여 구현하였고, 대략추정에서는 자기상관함수의 최대치에서 발생하는 평탄면 문제를 해결하기 위해 슬라이딩 윈도우를 사용하였고, 상세추정을 위해서는 긴 훈련 심볼(L-LTS)의 공액복소수 대칭특성을 이용하여 연산구조를 단순화하였다. 또한, 제안된 구조에서는 기존의 시간 동기에서 필요한 상호상관이 쓰이지 않았기 때문에 곱셈 연산량이 감소되며 하드웨어 복잡도를 감소시키기 위해서 복소수 곱셈기를 부호비트만으로 양자화하여 사용하였다. 시뮬레이션 결과에 따라, 제안된 시간 동기화 구조는 기존의 알고리즘보다 시간 동기화 실패 확률이 감소함을 확인하였고, 추후 IEEE 802.11n 표준의 주파수 동기 구조와 쉽게 결합될 수 있다는 장점이 있다. In this paper, we propose a timing synchronization scheme and its hardware architecture of the next generation IEEE 802.11n wireless LAN standard which is based on MIMO-OFDM technique. Proposed timing synchronization method takes two steps which consist of two modified auto-correlators. For coarse timing synchronization, a sliding window differentiator is used after a conventional auto-correlation in order to avoid plateau problem. The conjugate symmetry property of L-LTS is utilized for the simplification of fine timing synchronization. Since cross-correlation based methods are not required, the computational complexity and the number of multipliers can be reduced. In order to reduce the hardware complexity, we have used sign multipliers. Based on simulation results, the proposed method outperforms a conventional method. The proposed scheme can be applied to IEEE 802.11n systems and can easily be expanded to frequency synchronization scheme.
Enhanced Photosensitivity in Monolayer MoS<sub>2</sub> with PbS Quantum Dots
Cho, Sangeun,Jo, Yongcheol,Woo, Hyeonseok,Kim, Jongmin,Kwak, Jungwon,Kim, Hyungsang,Im, Hyunsik The Korean Vacuum Society 2017 Applied Science and Convergence Technology Vol.26 No.3
Photocurrent enhancement has been investigated in monolayer (1L) $MoS_2$ with PbS quantum dots (QDs). A metal-semiconductor-metal (Au-1L $MoS_2$-Au) junction device is fabricated using a standard photolithography method. Considerably improved photo-electrical properties are obtained by coating PbS QDs on the Au-1L $MoS_2$-Au device. Time dependent photoconductivity and current-voltage characteristics are investigated. For the QDs-coated $MoS_2$ device, it is observed that the photocurrent is considerably enhanced and the decay life time becomes longer. We propose that carriers in QDs are excited and transferred to the $MoS_2$ channel under light illumination, improving the photocurrent of the 1L $MoS_2$ channel. Our experimental findings suggest that two-dimensional layered semiconductor materials combined with QDs could be used as building blocks for highly-sensitive optoelectronic detectors including radiation sensors.
Cho, Sangeun,Kim, Jongmin,Jo, Yongcheol,Ahmed, Abu Talha Aqueel,Chavan, H.S.,Woo, Hyeonseok,Inamdar, A.I.,Gunjakar, J.L.,Pawar, S.M.,Park, Youngsin,Kim, Hyungsang,Im, Hyunsik ELSEVIER SCIENCE 2017 JOURNAL OF ALLOYS AND COMPOUNDS Vol.725 No.-
<P><B>Abstract</B></P> <P>Ruthenium oxide (RuO<SUB>2</SUB>) is fabricated on graphene (Gr)-coated Copper (Cu) foil by using a cathodic electroplating technique for flexible supercapacitor electrode applications. The electrochemical properties of the RuO<SUB>2</SUB>/Gr/Cu electrode are investigated with a conventional three electrode configuration in 0.5 M H<SUB>2</SUB>SO<SUB>4</SUB> electrolyte. The graphene insertion layer plays a key role in improving the structural and electrochemical properties of the RuO<SUB>2</SUB> electrode film under the bent condition. The electrode exhibits a specific capacitance of 1561 F g<SUP>−1</SUP> (0.015 F cm<SUP>−1</SUP>) at a scan rate of 5 mV s<SUP>−1</SUP> and a significantly improved retention of 98% under the bent condition. The flexible RuO<SUB>2</SUB>/Gr/Cu electrode exhibits a high energy density of ∼13 Wh kg<SUP>−1</SUP> at a power density of ∼21 kW kg<SUP>−1</SUP>. The excellent capacitance retention and electrochemical stability of the flexible RuO<SUB>2</SUB>/Gr/Cu electrode are due to the improved mechanical adhesion between the RuO<SUB>2</SUB> and the current collector. This flexible RuO<SUB>2</SUB>/Gr/Cu film could be used as a supercapacitor electrode with a high capacity and long-cycle life for the next-generation flexible electronic applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A binder-free Bendable RuO<SUB>2</SUB> thin film is fabricated on a graphene/Cu substrate using an electroplating method. </LI> <LI> Electrochemical energy storage properties of RuO<SUB>2</SUB> are investigated for supercapacitor applications. </LI> <LI> Excellent capacitance retention and electrochemical stability are obtained. </LI> </UL> </P>