• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.1
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• pp.99-106
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• 2001

In this paper, an 1-Watt amplifier for IMT-2000 was designed and fabricated using feedfarward method which has the highest linearity and wide bandwidth. Since feedforward is sensitive to surroundings for example heat, input power level, time and so on, adaptive controller using micro controller is adopted. We fabricated a HPA with 35 dB gain, 40 dBm of 1-dB compression point, and utilized variable attenuator and variable phase shifter using reflection type to cancel loop signal. From the measured results, the fo11owing facts were obtained, in signal loop, main carrier over 35 dB was suppressed and error signal over 30 dB is cancelled in error loop, IMD characteristics above 60 dBc were obtained.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.10
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• pp.1477-1483
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• 2013

This paper proposes a low-voltage current-mode integrator for a continuous-time current-mode baseband channel selection filter. The low-voltage current-mode linear cascode integrator is introduced to offer advantages of high current gain and improved unity-gain frequency. The proposed current-mode integrator has fully differential input and output structure consisting of CMOS complementary circuit. Additional cascode transistors which are operated in linear region are inserted for bias to achieve the low-voltage feature. Frequency range is also controllable by selecting proper bias voltage. From simulation results, it can be noticed that the implemented integrator achieves design specification such as low-voltage operation, current gain, and unity gain frequency.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.4
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• pp.160-169
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• 1999

Linear pulse rootor (LPM) be suitable a field where smooth linear rootion of high precision is required, because it's structured with minute teeth pitch in airgap of between and stator and roover(forcer). Force and position of LPM are effected sensitively by the teeth pitch, air gap, permanent magnet and excitation current. So, LPM is much important to analyze the force characteristics. llis paper was awlied to perrreance roothed for force calculation at airgap. The airgap of LPM is maintained from the pressure generated by an air-bearing. Simplified airflow and permeance methods will be used to calculate the air gap under static conditions. Therefore, the maximum available force is then derived using the coenergy method with variable air gap, also normal force and linear thrust was acquired from variable minute displacement 1[mm]. 1[mm].

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.8
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• pp.122-131
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• 2011

In this paper, the design and analysis of a reconfigurable modular structure, which reforms itself according to the change of the environment and realize appropriate forms and motions, are dealt with. This modular is a free structure from the restrictions with constraints about fixed environment and has various forms and motions by combining units. The form of this unit has a shape of a square with 7 centimeters side each, and has a structure which can be combined in a chain-shape or a lattice-shape. Additionally, The structure has a mobility by being equipped with wheels so that it can be combined for itself. In this paper, all the wireless controllers, sensor system, and communicating method between modules according to module structures were suggested and transformation method to be transformed to shape of snakes, caterpillars were presented. Moreover, simulations for each method were performed to show the validity of the motions including motor torque analysis. All the motions suggested were realized and experimented, whereby the availability of the designed mechanism and algorithm was verified with the result of experiments.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.4
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• pp.331-338
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• 2005

In this paper the novel pulsewidth modulation(PWM) technique for the two-leg and four-leg two-phase inverter is proposed. The conventional space vector PWM technique for two-phase inverter was complex. The proposed PWM for two-leg inverter, which is used by sinusoidal PWM method, is simpler than the conventional SVPWU technique. Also, a simple PWM technique for four-leg two-phase inverter is proposed. Such PWM technique is based on PWM technique for two-leg inverter. Practical verification of theoretical predictions is presented to confirm the capabilities of the new techniques.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.12
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• pp.609-615
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• 2005

A 30kW electrical power conversion system is developed for a variable speed wind turbine. In the wind energy conversion system(WECS) a synchronous generator with field current excitation converts the mechanical energy into electrical energy. As the voltage and the frequency of the generator output vary according to the wind speed, a 6-bridge diode rectifier and a PWM boost chopper is utilized as an ac-dc converter maintaining the constant dc-link voltage with only single switch control. An input current control algorithm for maximum power generation during the variable speed operation is proposed without any usage of speed sensor. Grid connection type PWM inverter converts dc input power to ac output currents into the grid. The active power to the grid is controlled by q-axis current and the reactive power is controlled by d-axis current with appropriate decoupling. The phase angle of utility voltage is detected using software PLL(Phased Locked Loop) in d-q synchronous reference frame. Experimental results from the test of 30kW prototype wind turbine system show that the generator power can be controlled effectively during the variable speed operation without any speed sensor.

• The KIPS Transactions:PartC
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• v.9C no.6
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• pp.953-960
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• 2002

Rel-time application programs have constraints which need to be met between media-data. It is client-leading synchronization that is absorbing variable transmission delay time and that is synchronizing by feedback control and palyout control. It is the important factor for playback rate and QoS if the buffer level is normal or not. This paper, The method of maintenance buffer normal state transmits in multimedia server by appling feedback of filtering function. And synchronization method is processing adaptive playout time for smooth presentation without cut-off while media frame is skip. When audio frame which is master media is in upper threshold buffer level we decrease play out time gradually, low threshold buffer level increase it slowly.

• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.647-652
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• 2016

To reduce drag force at supersonic speeds, sharp leading edge is hugely efficient. It is, however, incompatible with leading edge shape to have fine aerodynamic characteristics at subsonic and transonic speeds. It is critical to reduce drag force for enhanced cruise performance and higher efficiency. An air superiority fighter, however, required to have high maneuverability for survivability, and sharp leading edge is not proper. Consequently, variable leading edge is demanded to reduce drag force significantly at supersonic speeds for cruise performance. Leading edge altering system is constructed with rigid material to improve possibility of realization, and minimized movement of its components in altering for reduce effects on flight. It is compared with bi-convex airfoil and NACA 65-006 airfoil, which have comparable maximum thickness. At Mach number 1.7 and zero angle of attack, supersonic mode of designed airfoil indicates approximately 17% higher drag coefficient than the bi-convex airfoil indicates, it is, however, 23% lower than the NACA 65-006 indicates. Also, subsonic mode of the designed airfoil shows fine aerodynamic characteristics in comparison with NACA 65-006 airfoil in subsonic and transonic speed range. In this regard, design of the airfoil achieved the object of this study satisfactorily.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.10
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• pp.1402-1411
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• 2014

In this paper, the Maximum Power Point Tracking(MPPT) control of the small scale wind power generation system with a three-phase diode rectifier and the grid-connected inverter is studied. Without the need for the converter circuits to control speed of the generator, it is economical and the structure is simple. Compared with existing systems, it can be to reduce the power semiconductor switches and passive elements, and to implement the MPPT control with only DC-Link voltage control of the grid-connected inverter. In order to allow MPPT control without the characteristic information of the wind turbine, the P&O algorithm is applied, and these are verified by the simulation and experiment.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.12 no.4
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• pp.81-89
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• 1998

In the field of industrial drives, the vector control of the induction motor has been widely used to achieve the good control performance. In this paper, to require the information of rotor flux in direct vector control scheme, the flux observer by current model of rotor circuit is used. This flux observer is not only available at low-speed region bt good for the error reduction by feedback properties. Also, employing the flux observer on rotor reference frame, the robustness of decoupling control to the observation of rotor flux can be achieved. Through digital simulation and DSP-based IGBT inverter system, the validity for practical implementation is verified.