• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.6 s.121
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• pp.584-590
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• 2007

In this paper, the efficiency of power amplifier has been maximized by the application of EER structure, and the linearity has been improved by using PBG structure. This paper has proposed a design of power amplifier in class-F to get the PAE, and to control dynamic power using envelope detector. PBG structure gets high-linearity by removing harmonics arisen from the mismatching of matching circuit. The PAE and the 3rd order IMD have been improved 34.64%, 6.65 dB compared with those of conventional Doherty amplifier, respectively.

• Journal of Power Electronics
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• v.10 no.6
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• pp.694-701
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• 2010

In this paper an effective direct torque control (DTC) and stator flux control is developed for a quasi six-phase induction motor (QIM) drive with sinusoidally distributed windings. Combining sliding-mode (SM) control and adaptive input-output feedback linearization, a nonlinear controller is designed in the stationary reference frame, which is capable of tracking control of the stator flux and torque independently. The motor controllers are designed in order to track a desired second order linear reference model in spite of motor resistances mismatching. The effectiveness and capability of the proposed method is shown by practical results obtained for a QIM supplied from a voltage source inverter (VSI).

• Journal of Sensor Science and Technology
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• v.27 no.1
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• pp.31-35
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• 2018

This paper describes a low-power, SNDR (signal-to-noise and distortion ration) enhanced SAR (successive approximation register) type 12b ADC (analog-to-digital converter) with noise shaping technique. For low power consumption and small chip size of the DAC (digital-to-analog converter), the top plate sampling technique and the dummy capacitor switching technique are used to implement 12b operation with a 10b capacitor array in DAC. Noise shaping technique is applied to improve the SNDR by reducing the errors from the mismatching of DAC capacitor arrays, the errors caused by attenuation capacitor and the errors from the comparator noise. The proposed SAR ADC is designed with a $0.18{\mu}m$ CMOS process. The simulation results show that the SNDR of the SAR ADC without the noise shaping technique is 71 dB and that of the SAR ADC with the noise shaping technique is 84 dB. We can achieve the 13 dB improvement in SNDR with this noise shaping technique. The power consumption is $73.8{\mu}W$ and the FoM (figure-of-merit) is 5.2fJ/conversion-step.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.3
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• pp.1-11
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• 1999

It is now common practice to utilize the quadrature RF coils to improve the signal-to-noise ratio (SNR) in the Magnetic Resonance Imaging (MRI) System. In addition, to make such an available SNR improvement, it is mandatory to use a well-designed quadrature coupler, which facilitates a perfect 3-dB coupling and quadrature-phase shift. However, the four ports matching condition has to be well considered during the RF excitation and the signal detection period. This work investigates the effects of such a mismatching condition (especially, due to patient) from the analysis, simulation, and real implementation and firstly proposes dynamic loading technique for a quadrature coupler and transmitting/receiving switch module to minimize a patient mismatching and enhance a system reliability. Also, we designed and implemented the quadrature coupler and transmitting/receiving switch module using microstrip. As a result, the SNR of our MRI system using the microstrip quadrature coupler and transmitting/receiving switch module with dynamic load increases 3 dB compared with the old one using USA quadrature switch. Also, the power capability of quadrature coupler and transmitting/receiving switch module is 5-kw peak power. Considering power loss and reduction of size, we used a RT/duroid 6010 substrate with high permittivity and for simulation we use Compact Software.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.7 no.6
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• pp.38-47
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• 2008

In this paper, the narrow band-pass filter with compact-size using the ${\lambda}g/2$ open stubs is proposed. The filter size is reduced by realization of transmission line at second harmonics and at the same time the power can be transferred to the output by using the fundamental wave generated in the resonator and the transmission line in which the impedance mismatch technique is adopted. Thus, the proposed filter can be reduced to half-length of horizontal transmission line than the conventional one. The experimental results show that insertion loss is 1.58 dB and return loss is 9.86 dB, and the fractional bandwidth is 10 % at the center frequency of 5.8 GHz. The filter size is $10.34{\times}18.56\;mm2$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.8B
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• pp.1464-1471
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• 1999

A wide-band high power amplifier to use for radiated electromagnetic field immunity testing of EMS(Electromagnetic Susceptibility) standards has to meet IEC1000-4-3 specification in the frequency bandwidth of 80MHz to 1000MHz. The power amplifier to be described in this paper consists of driving and power stages with wide-band matched circuits by estimated impedances. The mismatching protection circuit is inserted in it to prevent from damage of power device when the output port of power amplifier is opened or shorted by user's mistake. The characteristics of the power amplifier are obtained output power over 100watts, gain over 40dB and flatness of $\pm$0.3dB in the frequency range of 80 ~300MHz. The harmonics suppression characteristics is measured over 20dBc. This wide-band high power amplifier can be useful fur radiated electromagnetic field immunity testing of IEC 1000-4-3 standard.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.243-246
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• 1998

This paper presents a 6-bit self-calibrated D/A converter designed with current cell matrix structure. This structure is based on the current-cell matrix configuration using a regulated gate cascode current cell with 3-way switch. using from CMOS process and 5V power supply, the simulated conversion rate is 45.78MHz and the average mismatching properties among current sources are reduced to 0.02% and 0.005%, respectively when 1% and 0.5% errors of current sources are considered.

• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.371-372
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• 2015

Dc microgrid has the advantage of high efficiency as compared to the ac system. Droop method has been realized to suppress the current mismatching among the distributed sources. However, this method involves distribution loss due to the line impedance. In this paper, a novel droop method is proposed to minimize the distribution loss as well as the voltage deviation by adjusting the droop coefficient. The proposed droop method is verified by using the simulation based on PSCAD/EMTDC.

• International Journal of Naval Architecture and Ocean Engineering
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• v.7 no.4
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• pp.739-749
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• 2015

A new conceptual dual-buoy Wave Energy Converter (WEC) for the enhancement of energy extraction efficiency is suggested. Based on actual wave data, the design process for the suggested WEC is conducted in such a way as to ensure that it is suitable in real sea. Actual wave data measured in Korea's East Sea (position: $36.404N^{\circ}$ and $129.274E^{\circ}$) from May 1, 2002 to March 29, 2005 were used as the input wave spectrum for the performance estimation of the dual-buoy WEC. The suggested WEC, a point absorber type, consists of two concentric floating circular cylinders (an inner and a hollow outer buoy). Multiple resonant frequencies in proposed WEC affect the Power Ttake-off (PTO) performance of the WEC. Based on the numerical results, several design strategies are proposed to further enhance the extraction efficiency, including intentional mismatching among the heave natural frequencies of dual buoys, the natural frequency of the internal fluid, and the peak frequency of the input wave spectrum.

• Proceedings of the KIEE Conference
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• 2004.11b
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• pp.63-65
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• 2004

The recent advancement in the power electronic technique has increased the use of induction motor fed by inverter using high-frequency switching devices. Also the tendency is toward larger size and higher voltage. Therefore, The IGBT (Insulated-Gate Bipolar Transistor) that is high switching frequency element has been using increase. But, The switching surge voltage was occurred by high switching frequency of inverter has appeared a voltage doubling in the motor input terminal due to mismatching of cable characteristic impedance and motor characteristic impedance. Actually, The Switching surge voltage became the major cause to occur the insulation failure by serious voltage stress in the stator winding of induction motor. The short during rise time of switching surge and cable length is increased, the maximum transient voltage seen at the motor terminals increases. In this paper, Analyzed switching surge transient voltage of power cable pulling is used EMTP(Electromagnetic Transient Program) at the induction motor terminal and in cable.