• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.10a
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• pp.398-401
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• 2011

This paper presents a high-efficiency CMOS PWM DC-DC buck converter. It generates a constant output voltage(1-2.8V), from an input voltage(3.4-3.9V). Inductor-based type is chosen and inductor current is controlled with PWM operation. The designed circuit consists of power switch, Pulse Width Generation, Buffer, Zero Current Sensing, Current Sensing Circuit, Clock & Ramp generation, V-I Converter, Soft Start, Compensator and Modulator. Switching Frequency is 1MHz, It operates in CCM when the load current is more than 40mA, and the maximum efficiency is 98.71% at 100mA. Output voltage ripple is 0.98mV(input voltage:3.5V, output voltage:2.5V). The performance of the designed circuit has been verified through extensive simulation using a CMOS $0.18{\mu}m$ technology.

• Journal of IKEEE
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• v.23 no.3
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• pp.1061-1067
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• 2019

In this paper, a highly integrated 3-channel DC-DC converter is designed using power transistor width scaling (PTWS). For positive voltage, $V_{POS}$, a boost converter is designed using the set-time variable pulse width modultaion (SPWM) dual-mode and PTWS to improve efficiency at light load. For negative voltage, $V_{NEG}$, a 0.5 x regulated inverting charge pump is designed with pulse skipping modulation (PSM) controller to reduce power consumption, and for an additional positive voltage, $V_{AVDD}$, a LDO circuit is designed. The proposed DC-DC converter has been designed using a $0.18{\mu}m$ BCDMOS process. Simulation results show that the proposed converter has power efficiency of 56%~90% for load current range of 1 mA~70 mA and output ripple voltage less than 5 mV at positive voltage.

• Journal of Broadcast Engineering
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• v.13 no.5
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• pp.732-743
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• 2008

In H.264/AVC, 4$\times$4 block transform is used for intra and inter prediction instead of 8$\times$8 block transform. Using small block size coding, H.264/AVC obtains high temporal prediction efficiency, however, it has limitation in utilizing spatial redundancy. Motivated on these points, we propose a multi-dimensional transform which achieves both the accuracy of temporal prediction as well as effective use of spatial redundancy. From preliminary experiments, the proposed multi-dimensional transform achieves higher energy compaction than 2-D DCT used in H.264. We designed an integer-based transform and quantization coder for multi-dimensional coder. Moreover, several additional methods for multi-dimensional coder are proposed, which are cube forming, scan order, mode decision and updating parameters. The Context-based Adaptive Variable-Length Coding (CAVLC) used in H.264 was employed for the entropy coder. Simulation results show that the performance of the multi-dimensional codec appears similar to that of H.264 in lower bit rates although the rate-distortion curves of the multi-dimensional DCT measured by entropy and the number of non-zero coefficients show remarkably higher performance than those of H.264/AVC. This implies that more efficient entropy coder optimized to the statistics of multi-dimensional DCT coefficients and rate-distortion operation are needed to take full advantage of the multi-dimensional DCT. There remains many issues and future works about multi-dimensional coder to improve coding efficiency over H.264/AVC.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.5
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• pp.1-10
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• 1999

A low power concumption 2.4 GHz one-chip transceiver MMIC was designed and fabricated using $1.0\mu\textrm{m}$ ion-implantation MESFET process and packaged on a 24 lead SSOP. In the transmitter mode, it revealed conversion gain of 7.5 dB, output IP3 of -3.5 dBm, and noise figure of 3.9 dB at 2.44 GHz with 3.9 mA current consumption. In the receiver mode, it revealed voltage sensitivity of 6.5 mV/$\mu\$W with 2 .0 mA current consumption. Comparing the fabricated MMIC with the results of MMICs reported elsewhere, it was shown that the fabricated MMIC had good performance. The low power consumption 2.4 GHz transceiver MMIC is expected to be used for various applications such as wireless local area networks, wireless local loops and RFID tags in ISM-band.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.2
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• pp.198-203
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• 2010

In this paper, study on the mode characteristics analysis of the SH-EMAT (shear horizontal, electromagnetic acoustic transducer) waves for evaluating the thickness reduction in plates such as corrosion and friction is presented. Noncontact methods for ultrasonic wave generation and detection have been a great concern and highly demanded due to their capability of wave generation and reception on surface of high temperature or on rough surface. Mode identification of the SH-EMAT wave is carried out in an aluminum plate with thinning defects using time frequency analysis method such as wavelet transform, compared with theoretically calculated group velocity dispersion curve. The changes of various wave features such as the amplitude and the time-of-flight have been observed and the correlations with the thickness reduction have been investigated. Firstly, experiments have been conducted to confirm that it is possible to selectively generate and receive specific desired SH modes. These modes have then been analyzed to select the parameters that are sensitive to the thickness change. The results show that the mode cutoff and the time-of-flight changes are feasible as key parameters to evaluate the thickness reduction.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.576-583
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• 2000

A robust position control using a sliding mode controller is adopted for the stable dynamic walking of the biped. For the biped robot that is modeled with 14 degrees of freedom rigid bodies using the method of the multibody dynamics, the joint angles for simulation are obtained by the velocity transformation matrix using the given Cartesian foot and trunk trajectories. Hertz force model and Hysteresis damping element which is used in explanation of the energy dissipation during contact with ground are used for modeling of the ground reactions during the simulation. By the obtained that forces which contains highly confused noise elements and the system modeling uncertainties of various kinds such as unmodeled dynamics and parameter inaccuracies, the biped system will be unstable. For that problems, we are adopting a nonlinear robust control using a sliding mode controller. Under the assumption that the esimation error on the unknown parameters is bounded by a given function, that controller provides a successful way to preserve stability and achieve good performance, despite the presence of strong modeling imprecisions or uncertainties.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.4
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• pp.89-101
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• 2006

This paper addresses Electrical Power Subsystem(EPS) design and verification of HAUSAT-2 small satellite through energy balance analysis(EBA) depending on individual operation modes. GaAs solar cells are used for satellite power generation and digital peak power tracking is implemented for EPS architecture. One battery pack is consisted of 4 Li-Ion cells. Battery charge is accomplished by peak power tracker and battery charge regulator. Power conditioning assembly uses three DC-DC converters, and power distribution assembly which consists of commercial IC and MOSFET switch distributes power to subsystems and payloads. The altitude of 650km and sun-synchronous LEO with various local time ascending node(LTAN) are considered in EBA.

• Aerospace Engineering and Technology
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• v.5 no.2
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• pp.67-76
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• 2006

This paper describes the analysis method to define the system specification for conducted EMI environment and verification method to evaluate the conducted EMI performance. Conducted EMI environment is characterized by the electrical power subsystem which is mainly issued by the switching circuit noise, common ground impedance coupling. To define and control these EMI problems, EMI assesment through system analysis are preceded at the early design phase and then EMI reduction methods are applied during the unit/system development phase. System EMC should be carefully controlled and designed in the consideration of EMC safety margin and its performance is fully evaluated at the whole development period.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.7
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• pp.142-148
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• 2014

Krylov-Schur iteration method has been applied to the 3-Dim. resonant cavity of a cylindrical form. The vector Helmholtz equation has been analysed for the resonant field strength in homogeneous media by FEM. An eigen-equation has been constructed from element equations basing on tangential edges of the tetrahedra element. This equation made up of two square matrices associated with the curl-curl form of the Helmholtz operator. By performing Krylov-Schur iteration loops on them, Eigen-values and their modes have been determined from the diagonal components of the Schur matrices and its transforming matrices. Eigen-pairs as a result have been revealed visually in the schematic representations. The spectra have been compared with each other to identify the effect of boundary conditions.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.187-190
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• 2010

기초세굴에 따른 교각에서의 1차 모드 고유진동수 변화를 이용하여 교량 세굴 건전성을 정량적으로 평가하기 위하여 공용중인 광탄1교의 T형 교각 1기에 대하여 충격진동실험을 수행하였으며, 교축직각방향의 1차 모드 고유진동수를 수치해석결과와 비교하였다. 교량 상부구조물의 모델링 방법에 따라 상부구조물을 전체 모델링한 방법과 교각만을 모델링하고 상부구조물의 영향범위를 가정하여 교량받침 위치에 질점질량으로 변환하여 적용한 방법으로 구분하여 수치해석을 수행하였다. 상부구조물을 전체 모델링한 경우와 집중하중 형태로 상부구조물을 모델링한 경우 모두 고유진동수는 충격진동실험결과와 큰 차이를 보였다. 충격진동실험을 통해 얻은 고유진동수는 교각의 국부적인 진동수로 사료되는 반면, 수치해석을 통해 구한 결과는 교량 상부와 하부의 Coupling 효과가 반영된 시스템 전체의 고유진동수이기 때문에 결과의 큰 편차가 생기는 것으로 판단된다. 따라서 충격진동실험에서 구한 고유치 양상을 올바로 구현하기 위한 모델링을 찾기 위해서는 새로운 접근 방법이 필요할 것으로 사료된다.