• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.6
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• pp.847-854
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• 1999

In this paper, we have analysed frequency-dispersion characteristics of higher-order modes for uniform planar transmission lines, using the 2-dimensional finite-difference time-domain method. The method presented in this paper uses both informations of amplitude and phase of the electromagnetic spectrum to determine resonant frequencies, while methods previously reported use the magnitude only. This algorithm is very useful when a resonant mode has a relatively small magnitude, where the identification of the resonant mode is quite difficult. Numerical results show that a strip line supports few higher-order modes within the frequency range of 20 GHz, but there occur many higher-order modes in the structure of grounded coplanar waveguide, where resonant frequencies of the first higher-order mode is very close to those of the fundamental mode and there occur lots of very adjacent higher-order modes. As in this example, for the analysis of planar transmission lines which support many resonant modes very close each other, the method presented in this paper can be applied very efficiently.

• 한국연소학회:학술대회논문집
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• 2003.05a
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• pp.167-171
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• 2003

Acoustic characteristics of baffled combustion chamber to elucidate suppressing effect of baffle on combustion instability are numerically investigated by linear acoustic analysis. A hub-blade baffle of 5 blades is selected as a candidate one and five variants of baffles with various configuration are designed. Resonant-frequency shift and damping factor are analyzed quantitatively as damping parameters. When the hub is located radially at the pressure node, the decrease of resonant frequency and increase of damping factor in 1R mode are dominant. But sub-1T mode is formed within hub, therefore, there would be a possibility of initiating 1T mode in unbaffled region, which would occur another problem. For smaller hub size, four kinds of axial baffle length is selected. As the axial baffle length increases, resonant frequency shift and increase of damping factor of transverse acoustic modes is obtained. Especially, two close acoustic modes such as 1L and 1T could be overlapped for a certain axial length, resulting in extreme increase of damping factor. The present study based on linear acoustic analysis is expected to be a useful confirming tool to predict acoustic field and design a passive control devices such as baffle and acoustic cavity.

• Journal of Power Electronics
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• v.18 no.3
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• pp.766-777
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• 2018

In this paper, a sliding mode and proportional plus integral (SM-PI) control combined with self-sustained phase shift modulation (SSPSM) for LLC resonant converters is presented. The proposed control scheme improves the transient response while preserving good steady-state performance. An averaged large signal model of an LLC converter with the ZVS modulation technique is developed for the SM control design. The sliding surface is obtained based on the input-output linearization concept. A system identification method is adopted to obtain the transform function of the LLC resonant converter, which is used to design the PI control. In order to reduce the inherent chattering problem in the steady state, the combined SM-PI control strategy is derived with fuzzy control, where the SM control is responsive during the transient state while the PI control prevails in the steady state. The combination of SSPSM and the SM-PI control provides ZVS operation, robustness and a fast transient response against step load variations. Simulation and experimental results validate the theoretical analysis and the attractive features of the proposed scheme.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.3
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• pp.188-194
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• 2020

This paper presents a high-efficiency Switch Mode Line Transformer (SMLT) composed of load-shared dual modules, which is based on the AC/AC LLC resonant converter. Given that the conventional adaptor is usually composed of two power stages, namely, the PFC and DC/DC converters, its system size can be increased according to the output power. However, given that the proposed SMLT can separate the PFC converter from the adaptor, the size reduction of the system can be achieved. Meanwhile, the SMLT with a single module has the limit of the size reduction because of a high resonant current. Thus, it can be configured with dual or multiple modules to reduce the resonant current. Then, their load sharing can be guaranteed by only the proposed transformer structure without an extra current controller. The validity of the proposed converter is proven through a 850-W prototype.

• The Journal of the Acoustical Society of Korea
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• v.29 no.7
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• pp.439-447
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• 2010

In this paper, the resonant characteristic of a Tonpilz transducer with a fixed tail mass has been researched and the feasibility to utilize the transducer in that resonant frequency has been analyzed. The additional resonance is occurred by adhering an elastic tube to the tail mass of a conventional Tonpilz transducer and fixing the other end of the tube. The characteristic of this low resonant mode is analyzed by means of the finite element method, then it is shown that this mode is affected by the variation of the stiffness of the tube as well as the mass of the head mass and tail mass. Based on the analysis results, the Tonpilz transducer is designed to meet specific performance conditions.

• Korean Journal of Optics and Photonics
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• v.2 no.1
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• pp.20-25
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• 1991

Using evanescent field coupling between single ($LP_{01}$) and double ($LP_{01}, LP_{11}$) mode optical fiber, we selected LPII mode beam. With a $LP_{11}$ mode beam from a double mode fiber. we fabricated $LP_{11}$ mode fiber optic resonant ring interferometer, and assured that the guided mode is $LP_{11}$ mode from a radiation beam coming through the prism output coupler. When an external perturbation applied to the signal arm of the $LP_{11}$ fiber optic resonant ring interferometer, we examined the change of radiation mode coming from a prism output coupler and an end of optical fiber. Using two photodiode, LPn mode beam converted to voltage. This two output voltages is applied to X and Y terminal of oscilloscope to display circular motion on oscilloscope.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.7
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• pp.1250-1254
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• 2007

The multi-resonant(MR) converter has a characteristics that the parasitic components existing in the converter are absorbed into the resonant circuits. The designed MR converter could be got a high efficiency and a high power density because the switching power losses are reduced effectively due to resonant switching circuit. However, the high resonant voltage stress of switching power devices leads to the conduction loss. In this paper, it is proposed the novel alternated(AT) flyback multi-resonant converter to overcome such a drawback. The suggested converter dc input is divided by two series input filter capacitors. The resonant stress voltage is reduced to 2-3 times the input voltage without any complexity and it provides the various circuit schemes in lots of applications. The proposed flyback MR converter is verified through simulation and experiment.

• Proceedings of the KIEE Conference
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• 2007.11a
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• pp.154-155
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• 2007

This paper describes frequency response of two-mass system for gyroscope applications. The two-mass system of the proposed device is adapted to the sensing part of the gyroscope in this research. Two-mass system has two resonant peaks and wide flat region between two resonant peaks. The resonant frequency of driving part is in this flat region. Therefore, frequency tuning is not necessary for mode matching. In the proposed device, resonant frequency is designed as 7183 Hz in driving part. Mass ratio of two masses in sensing part is 0.1 and device size is 6 mm $\times$ 6 mm. The device is fabricated by SiOG process. The fabricated spring width is increased from $4{\mu}m$ to $4.5{\sim}4.7{\mu}m$, and the measured resonant frequency is 8392 Hz in driving mode. We operated the sensing part using parallel plate of proof mass to verify the sensing part. It is confirmed the device has a wide fiat region in frequency response curve and the resonant frequency of the driving part is in the wide flat region of sensing mode.

• Proceedings of the IEEK Conference
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• 2001.06e
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• pp.249-252
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• 2001

A large number of soft switching topologies included a resonant circuit have been proposed. But these circuits increase number of switch in circuit and complicate sequence of switching operation. In this Paper, the authors propose power conversion system, DC-AC inverter of high efficiency and high power factor with soft switching mode by partial resonant method. The result is that the switching loss is very low and the efficiency of system is high. And the snubber condenser used in partial resonant circuit makes charging energy regenerated at input power source for resonant operation.

• Proceedings of the KIEE Conference
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• 2000.07e
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• pp.52-55
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• 2000

In this paper, the coupled and the non-coupled vibration mode AE sensor for GIS were simulated by finite element analysis and manufactured, and characterized. The maximum sensitivity was 64.3 dB when the resonant frequency of the coupled vibration mode AE sensor was 166 kHz and the maximum sensitivity was 58.9 dB when the resonant frequency of the non-coupled mode AE sensor was 265 kHz. The coupled vibration mode AE sensor responded higher than the non-coupled vibration mode AE sensor at the partial discharge detection in GIS.