• ETRI Journal
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• v.35 no.3
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• pp.538-541
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• 2013

A compact microstrip lowpass filter (LPF) with an elliptic function response is proposed. A high equivalent capacitance and inductance between the structures of the resonator result in the sharp transition band of 0.04 GHz from 4 GHz to 4.04 GHz with an attenuation level of -3 dB and -20 dB, respectively. To improve the LPF rejection band, multiple open stubs are connected to the proposed resonator. A filter with a 3-dB cut-off frequency at 4 GHz is designed, fabricated, and measured, and agreement between the measured and simulated results is achieved. The results show that a stopband bandwidth of 131% with a suppression level better than -20 dB is obtained while achieving a compact size with a wide stopband.

• Bulletin of the Korean Chemical Society
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• v.35 no.5
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• pp.1469-1478
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• 2014

Use of acetonitrile in electrolytes promotes better operation of supercapacitors. Recent efforts show that electrolytes containing acetonitrile can also function in a wide range of operating temperatures. Therefore, this paper addresses the dielectric relaxation processes, structure and dynamic properties of the bulk acetonitrile at various temperatures. Systems of acetonitrile were modeled using canonical ensemble and simulated by employing Molecular Dynamics method. Results show that interactions among the molecules were correlated within a cut-off radius while parallel and anti-parallel arrangements are observed beyond this radius at relatively high and low temperatures respectively. Furthermore, effects of C-C-N and C-H bending modes were greatly appreciated on the power spectral density of time rate change of dipole-dipole correlations whereas frequency shifts were observed on all modes at the lowest temperature under consideration. Linear variations with temperature were depicted for reorientation times and self-diffusion coefficients. Shear viscosity was also computed with a good accuracy within a certain range of the temperature as well.

• 전기의세계
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• v.27 no.4
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• pp.45-51
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• 1978

A new method of realizing the field effect transistor with a sub-.mu. channel width is described. The sub-.mu. channel width is made possible by etching grooves into n$^{+}$ pn$^{[-10]}$ n$^{[-10]}$ structure and using p region at the wall for the channel region of the Metal-Oxide-Semiconductor transistor (MOST), or by diffusing two different types of impurities through the same diffusion mask and using p region at the surface for the channel region of MOST. When the drain voltage is increased at the pn$^{[-10]}$ drainjunction the depletion layer extends into the n$^{[-10]}$ region instead of into p region; this is also the secret of success to realize the sub-.mu. channel width. As the result of the experimental fabrication, a microwave MOST was obtained. The cut-off frequency was calculated to be 15.4 GHz by Linvill's power equation using the measured capacitances and transconductance.

• Journal of Electrical Engineering and Technology
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• v.11 no.1
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• pp.241-246
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• 2016

This paper presents a method that can improve the performance of permanent magnet synchronous motor current control by minimizing the measured current phase delay caused by the Low Pass Filter(LPF) used to cut off the noises that flowed in when feedback currents are measured. Although existing methods that change the Cutoff Frequency of the LPF can minimize phase delays during high speed rotations, their noise cutoff effects are much lower and this may lead to the decline of control performance. Therefore, in this study, an algorithm that can compensate current phase delays through relatively simple calculations from the synchronous motor d-q axis coordinate transformation matrix and the inverse transformation matrix is proposed and the validity of the proposed method is verified by comparing the waveform of the calculated current with the waveform of actual currents through simulations and experiments.

• Journal of the Korean Vacuum Society
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• v.8 no.4B
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• pp.536-540
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• 1999

We have developed a refractory WNx self-aligned gate GaAs metal-semiconductor field-effect transistor(MESFET) using $SiO_2$ side-wall process. The MESFET hasa fully ion-implanted, planar, symmetric self-alignment structure, and it is quite suitable for integration. The uniform trans-conductance of 354nS/mm up to Vgs=+0.6V and the saturation current of 171mA/mm were obtained. As high as 43GHz of cut-off frequency hs been realized without any de-embedding of parasitic effects. The refractory WNx self-aligned gate GaAs MESFET technology is one of the most promising candidates for realizing linear power amplifier ICs and multifunction monolithic ICs for use in the digital mobile communication systems such as hand-held phone(HHP), personal communication system (PCS) and wireless local loop(WLL).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.20 no.5
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• pp.457-462
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• 1987

Stochastic stability criterias for ocean wave analysis add simulation are studied using the data simulated by the linear superposition method. To clarify the criterias, the effects of the simulation parameters on the variance of stochastic properties of ocean waves are investigated, and the stable conditions of the parameters are estimated through the comparative study on the stochastic properties of simulated waves and well-known ocean waves. The simulation parameters considered are high frequency cut-off, data length, and number and phase angle of component waves. Statistical characteristics analysed are wave height, period and steepness, and the formation of groups of higher waves, resonance periods, steeper higher waves and extreme run-length of the run.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.1
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• pp.30-36
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• 2004

An iterative sliding mode observer is proposed to sensorless control of a PMSM(Permanent Magnet Synchronous Motor). The proposed sliding mode observer has the character which is robust to the disturbance and parameters variation. A low pass filter with the variable cut-off frequency is also proposed to compensate the delay of the rotor angle according to the rotor speed, it is led to save memory and minimize operation time. Experimental results show that the proposed sliding mode observer leads to the proper performance.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.8
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• pp.430-435
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• 2006

This paper presents a method about the efficiency analysis and the harmonic reduction of single phase NPC multi-level inverter with LC-trap filter and LCR output filter. The proposed LC-trap filter is comprised of a conventional LC output filter, by using LC-trap filter the need for high damping resistor and low LC cut-off frequency is eliminated. Also, low damping resistor is increased the efficiency of the output filter. Experimental verification of the proposed circuit is provided with single phase NPC multilevel inverter system and DSP controller.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.1
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• pp.51-58
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• 1990

NPN Si bipolar transistors with two different emitter widths are designed and fabricated. The effects of the emitter width on the small signal parameters of BJTs are measured and discussed. A new ac method for determining the current gain, the cut off frequency and the internal capacitances from the input impedance circle characteristics as a function of the varied external series resistances is presented. This method allows an accurate characterization of bipolar transistors with high current gain. The variation of the I-V curves of the emitter junction with the reverse collector junction voltages is discussed from the changes in the intsrinsic base resistances.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.584-586
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• 2005

The stroke of piston in the linear compressor driven by LPMSM can be obtained from integrating the input voltage and current of LPMSM, and may be diverged due to dc components In the voltage and current. The strategy to prevent the divergence of stroke using both the high-pass filter and dc offset compensation was suggested. The equations for the magnitude and phase of the stroke and also dc offset including the stroke are derived as a function of the cut-off frequency of HPF. The performance of stroke calculation scheme has been verified by experimentally on a linear compressor drive system, where the control was implemented by a 16-bit DSP.