• Proceedings of the IEEK Conference
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• 2002.07b
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• pp.1046-1049
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• 2002

In this paper, a sub-harmonic dual-gate FET mixer for IMT-2000 base-station was designed by using single-gate FET cascode structure and driven by the second order harmonic component of LO signal. The dual-gate FET mixer has the characteristic of high conversion gain and good isolation between ports. Sub-harmonic mixing is frequently used to extend RF bandwidth for fixed LO frequency or to make LO frequency lower. Furthermore, the LO-to-RF isolation characteristic of a sub-harmonic mixer is better than that of a fundamental mixer because the frequency separation between the RE and LO frequency is large. As RF power is -30dBm and LO power is 0dBm, the designed mixer shows the -47.17dBm LO-to-RF leakage power level, 10dB conversion gain, -0.5dBm OIP3, -10.5dBm IIP3 and -1dBm 1dB gain compression point.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.12
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• pp.2240-2246
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• 2007

Optically coupled linear isolation amplifier requires special care to avoid oscillation in actual applications. In this paper methods to analyze the frequency characteristics of the amplifier are proposed to reveal the cause of oscillation and to provide design guidelines. The loop gain of the amplifier obtained through the equivalent circuit model shows that the phase margin is too small to ensure stable operations. Methods to get non-oscillatory response are proposed and the resulting frequency responses are analyzed. The common method adding a small capacitor to the amplifier is shown to degrade the frequency bandwidth. The frequency response of output voltage explains the need of filter capacitor in output stage. The usefulness of the method is verified through experiments.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.183-187
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• 2002

In this paper, the effects of encoder fault and current sensor fault in direct torque controlled induction motor drives are analyzed. On the basis of the analyzed results, a observer based fault detection and isolation scheme is presented. To verify the performance of proposed algorithms, the speed control system is designed for induction motor and evaluated by experimental study. Experimental results various type of sensor faults show the detection and isolation performance of the SFDIS and the applicability of this scheme to fault tolerant control system design.

• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.969-972
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• 2003

This paper deal with a necessary factors for design grid connected photovoltaic system with stand-alone operation, and show simulation results of individual functions and multi- operation according to utility condition. Generally, photovoltaic system have only one operation of either stand-alone or line interactive, and have a isolation transformer for electrical isolation from utility therefore it is bulky, weighty, and a high price system as compared with usefulness. In this paper, A topology and algorithm adequate for lightweight, high efficiency, low price, multi function is selected and inquired into the validity using simulation of variable conditions.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.7
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• pp.1247-1253
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• 2008

A design method of a T-S fuzzy model based reduced order nonlinear unknown input observer(NUIO) is presented. The fuzzy NUIO is designed based on the parallel distributed compensation(PDC) concept. It consists of a number of the linear UIOs, each of which is designed for each local linear model in the T-S fuzzy model of a class of nonlinear systems. The fuzzy NUIO provides not only the state estimates insensitive to the unknown inputs, for example, disturbances and faults etc., but also the estimates of the unknown inputs. Therefore, It can be employed in the state feedback control and disturbance rejection control of a class of nonlinear systems with unknown disturbances. It also applied to the robust residual generation for the fault detection and isolation systems and to the design of fault tolerant control systems. As an example, the NUIO is applied to an inverted pendulum system to show the state and disturbance estimation performance and to illustrate the fuzzy reduced order NUIO design method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.189-192
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• 2001

Recently, STI process is getting attention as a necessary technology for making high density of semiconductor by devices isolation method. However, it does have various problems caused by CMP nprocess, such as torn oxide defects, nitride residues on oxide, damages of si active region, contaminations due to post-CMP cleaning, difficulty of accurate end point detection in CMP process, etc. In this work, the various defects induced by CMP process was introduced and the above mentioned problems of CMP process was examined in detail. Finally, the guideline of future CMP process was presented to reduce the effects of these defects.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.2
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• pp.81-86
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• 2005

In this paper we consider an optimal configuration problem for redundant inertial sensors which have uncertainty such as misalignment, scale factor error. The optimal configuration problem is treated from the viewpoint of navigation accuracy. We propose a necessary and sufficient condition for the optimal configuration of redundant sensors with no uncertainty, and a sufficient condition for the optimal configuration of redundant sensors with uncertainty. Finally we propose a condition for the optimal configuration based both navigation performance and FDI(fault detection and isolation).

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.7
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• pp.311-315
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• 2002

Chemical mechanical polishing (CMP) process was required for the global planarization of inter-metal dielectric(IMD), inter-level dielectric (ILD) layers of multi-layer interconnections. In this paper, we studied the characteristics of polishing pad, which can apply shallow trench isolation (STI)-CMP process for global planarization of multi-level interconnection structure. Also, we investigated the effects of different sets of polishing pad, such as soft and hard pad. As an experimental result, hard pad showed center-fast type, and soft pad showed edge-fast type. Totally, the defect level has shown little difference, however, the counts of scratch was detected less than 2 on JR111 pad. Through the above results, we can select optimum polishing pad, so we can expect the improvements of throughput and device yield.

• International Journal of Control, Automation, and Systems
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• v.5 no.3
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• pp.329-336
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• 2007

This paper considers a fault accommodation problem for inertial navigation systems (INS) that have redundant inertial sensors such as gyroscopes and accelerometers. It is wellknown that the more sensors are used, the smaller the navigation error of INS is, which means that the error covariance of the position estimate becomes less. Thus, when it is decided that double faults occur in the inertial sensors due to fault detection and isolation (FDI), it is necessary to decide whether the faulty sensors should be excluded or not. A new accommodation rule for double faults is proposed based on the error covariance of triad-solution of redundant inertial sensors, which is related to the navigation accuracy of INS. The proposed accommodation rule provides decision rules to determine which sensors should be excluded among faulty sensors. Monte Carlo simulation is performed for dodecahedron configuration, in which case the proposed accommodation rule can be drawn in the decision space of the two-dimensional Cartesian coordinate system.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.2
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• pp.85-91
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• 2002

A novel multi-section power divider configuration is Proposed to obtain wide-band frequency performance up to microwave frequency region. Design procedures for the proposed microwave broadband power divider are composed of a Planar multi-section three-Ports hybrid and a waveguide transformer design procedures. The multi∼section power divider is based on design theory of the optimum quarter- wave transformer Furthermore, in order to obtain the broadband isolation performance between the two adjacent output ports, the odd mode equivalent circuit should be matched by using the lossy element such as resistor. The derived design formula for calculating these odd mode∼matching elements is based on the singly terminated filter design theory. The waveguide transformer section is designed to suppress the propagation of the higher order modes such as waveguide modes due to employing the metallic electric wall. Simulation and experiment show excellent performance of multi section power divider.