• The Transactions of the Korean Institute of Electrical Engineers
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• v.35 no.7
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• pp.272-277
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• 1986

The system that follows to the resonance frequency of high frequency MOSFET inverter and varies according to the changes of load characteristics is proposed. Also we suggested a method how to select the resonant load type between series and parallel circuit for a given inverter type. It leads to the conclusion that in the case of high impedance loads, parallel resonant circuits are preferable, on the other hand, for low impedance loads, series resonant circuits are more preferable. For frequency tracking, a PLL circuit is used as main control element to detect the phase difference of current and voltage of load. The realized apparatus composed of control circuit and voltage type full-bridged MOSFET elements as main parts of inverter. A stable frequency follow-up characteristics are obtained for 1.2MHz, 1.5KW high frequency output and power is always supplied to the load with unity power factor.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.5 s.335
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• pp.9-14
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• 2005

Simulation method for a pure radio-frequency (rf) mode of reflection-type and a pure rf mode of transmission-type radio-frequency single-electron transistor (RF-SET) operation is introduced. In this method, the solutions of differential equations based on Kirchhoff's law are obtained self-consistently at frequency-domain. Also, the steady-sate single-electron transistor (SET) current model and the time-dependent SET current model are used in this method. The reflected wave of a typical reflection-type RF-SET and the transmitted wave of a typical transmission-type RF-SET are calculated, and the accuracy of our developed method including the steady-state SET current model is verified with the method introduced by reference 2. At high frequency over GHz, results of our developed method including the time-dependent SET current model are considerably different from that including the steady-state SET current model. At high frequency over GHz, an exact time-dependent SET current model is needed to analyze RF-SET operation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.9
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• pp.878-885
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• 2009

One of important factors in designing MEMS resonators for RF filters is obtaining a desired frequency response function (FRF) within a specific frequency range of interest. Because various array-type MEMS resonators have been recently introduced to improve the filter characteristics such as bandwidth, pass-band, and shape factor, the degrees of freedom (DOF) of finite elements for their FRF calculation dramatically increases and therefore raises computational difficulties. In this paper the Krylov subspace-based model order reduction using moment-matching with non-zero expansion points is represented as a numerical solution to perform the frequency response analyses of those array-type MEMS resonators in an efficient way. By matching moments at a frequency around the specific operation range of the array-type resonators, the required FRF can be efficiently calculated regardless of their operating frequency from significantly reduced systems. In addition, because of the characteristics of the moment-matching method, a minimal order of reduced system with a prearranged accuracy can be determined through an error indicator using successive reduced models, which is very useful to automate the order reduction process and FRF calculation for structural optimization iterations. We also found out that the presented method could obtain the FRF of a $6\times6$ array-type resonator within a seventieth of the computational time necessary for the direct method and in addition FRF calculation by the mode superposition method could not even be completed because of a data overflow with a half after calculation of 9,722 eigenmodes.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.8 s.111
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• pp.719-724
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• 2006

In this paper, we designed the double conversion down mixer by using Half-LO frequency in 2.3 GHz band. The IF frequency is obtained by supplying two LO frequencies to HEMT in both gate type and resistive type. The proposed mixer uses Half-LO frequency the same way as conventional sub-harmonic mixers. However the proposed one uses fundamental component of Half-LO frequency in first stage instead of using second harmonic components of Half-LO frequency, and the IF frequency is obtained by resistive type mixer in second stage, thereby the proposed mixer can improve linearity in comparison with conventional active mixer. We can verify that the proposed mixer has an conversion loss of 5dBm and IIP3 of 16.25dBm by using 10 dBm Power.

• Journal of IKEEE
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• v.27 no.4
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• pp.587-600
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• 2023

This paper presents an optimal design of the slim type high frequency transformer used in the LLC DC to DC resonant converter for 65-inch UHD-TV with the rated power of 315W. This paper also performs an optimal design of the slim type high frequency through core loss analysis, AC winding loss analysis, and optimization design of the winding arrangement of the LLC resonant transformer. Particularly, the high-efficiency and slim type high frequency transformer based on the obtained results from theoretical analysis in this paper is constructed in the interleaved and vertical winding structures of its transformer to realize the winding method of automatic type and minimize AC winding loss. The primary and secondary windings of the slim type high frequency transformer the vertical winding structure proposed in this paper used the Litz-wire windings, PCB and copper plate windings, respectively. Finally, an optimal design of the slim type high frequency transformer proposed in this paper was carried out through the experimental results to confirm the validity of theoretical analysis based on the simulation results using Maxwell 2D and 3D tool.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.110-113
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• 2000

In general, speed control method of the elevator system has used motor pole change type or motor primary voltage control type. But it will change to vector control type in order to increase it's reliability, riding comfort and decrease material cost. It is the conception of vector control type in order to increase it's reliability, riding comfort and decrease material cost. It is the conception of vector control that primary current of the induction motor be controlled independently with magnetizing current(field current of DC motor) and torque current(armature current of DC motor). In this paper, by analyzing the effect of the time constant variation of rotor of the induction motor on the slip frequency type indirect vector control, a drive system for the motor will be constructed using a fuzzy slip frequency type indirect vector controller with fuzzy control method for estimating the vector time constant in the slip frequency type indirect vector control. The goal of this study is to enabling even more efficient speed control by constructing on elevator driver based on the newly developed drive system.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.5
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• pp.235-238
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• 2013

In this paper, ㄷ-type MSA for the QMSA structure is proposed. Transformed ㄷ-type MSA is stacked three dielectrics. ㄷ-type MSA structure was load upper & lower surface of the dielectric radiating patch and the ground turn-up left right capacity between parallel plates and radiating patch. Between the dielectric permittivity of the dielectric insert by 2.55 by varing the frequency was shifted. Designed ㄷ-type MSA sturcture of L1 was varied up to 1mm~22mm and frequency was shifted from 3.65GHz~3.84GHz. Also Designed ㄷ-type MSA was measured 1.95dBi maximum gain and bandwidth of 1.61 to 3.64%.

• The Journal of the Korean dental association
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• v.12 no.6
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• pp.369-371
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• 1974

Using 316 plaster models of dental arches of Korean, (ages from 16 to 53) the auther observed the occlusion forms by the Welcker's classifying method. The results were as follows: Psalidontie type is most frequency seen, and its frequency is about 87% in male and about 91% in female. The frequency of occlusal form was decreased in the order of Stegodontie, Lalidodontie and Opisthodontie. Type. There were seldom appeared Progenie and Hiatodontie type.

• 전기의세계
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• v.30 no.1
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• pp.47-54
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• 1981

The fabrication of Langevin type vibrators producing relatively high sonic and ultrasonic energy is described. The dependence of the acoustic output and the frequency characteristics on the thickness of the steel plates and the pressure at the ceramics are investigated. As results, the acoustic output of Langevin type vibrators are relatively high, and the resonant frequency is decreassed by thickening the steel plates and lowering the pressure at the ceramics. Using these results, sonic and ultrasonic vibrator whose resonant frequency is determined can be designed.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.568-572
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• 2001

An industrial vibratory conveyor system is devised for large-scale feeding by the low-power, using natural frequency of the system. The important thing in this system is to determine the natural frequency and to drive by it. The purpose of this study is to build up reliance on the system with changing of element parameters for vibration characteristics of balancing type vibratory conveyor by using F.E.M. modeling. For investigating the natural frequency, modal testing is performed by using impact hammer, accelerometer and LMS/Vibration Analysis System. Experimental results are compared with F.E.M results. The results of the comparisons within the errors of less than 2 percent can verify the reliability of the F.E.M. analysis of the system. Also we can verify that the characteristics of natural frequency have linearly decreased(-6%) as adding the mass($50{\sim}600kg$). We can find that controlling driving frequency is necessary for triggering the natural frequency, but natural frequency is less affected by adding the mass on the balancing weight.