• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.12
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• pp.2370-2378
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• 2009

The enhanced phase angle estimation algorithm is essential to supply the power stably under synchronizing with grid source. In this paper, we are proposed the novel phase angle estimation algorithm and verified the validity of proposed method as simulation with PSIM and experiments. We sort the harmonics element using high-pass filter(HPF) that have the cut-off frequency below basic element and make reverse d-q transformation. So, it can be restored the harmonics element at stationary axis, and we can get the fundamental voltage element of AC grid. Proposed PLL method have a rapid responsibility and a large margin at controller design than conventional method because it have a small phase delay and a sufficient controller gain margin. And, it can reduce the error of voltage rms value and axis transformation according to robust PLL algorithm against the harmonic and phase unbalance.

• Proceedings of the ESK Conference
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• 1994.04a
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• pp.49-51
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• 1994

The aims of this study were first to determine the influence of vibration displacement amplitude $(200{\mu}m, 300{\mu}m peak-to-peak)$ at selected frequencies (40-200Hz) on a commonly observed but often undesired motor response elicited bylocal vibratory stimulation, the Tonic Vibration Reflex (TVR). Second, to determine the degree of synchronization of motor unit (MU) activity with vibratory stimuli. Vibration was applied to the distal tendons of the hand flexor muscles. Changes in root- mean-square electromyographic (EMG) activity of the finger and wrist flexor muscles were analyzed both as a function of their initial contraction level (0%, 10%, 20% of the maximal voluntarycontraction: MVC) and as a function of the vibration parameters. The results indicate that the TVR increased with the initial muscle contraction up to 10% MVC: The TVR increased with vibration frequency up to 100-150 Hz and decreases beyond; A significant increase of the TVR with vibration displacement amplitude was observed only for the wrist flexor muscle; MU synchronization at vibration frequency (VF) was found more often in the low frequency range $(f{\leq}100 Hz)$ and tended todecrease beyond; In the high frequency range $(f{\geq}120 Hz)$, MU activity at subharmonic frequency was predominant; The "cut-off" frequency of the synchronization with VF was neither affected by the vibration displacement amplitude nor initial muscle contraction level. The surface EMG turned out to be a useful means to analyze MU synchronization since it is noninvasive, and it can be easily used for analysis of different muscle contraction levels, while single MU technique might have some difficulties at high muscle contraction levels. Furthermore, these results indicate that high frequencyvibration (f>150 Hz) tends to induce less muscle/tendon stress and MU synchronization. Such remarks are of importance for the design of hand-held vibrating tools.ing tools.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.553-554
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• 2006

In this paper, 77 GHz CPW power amplifier MMIC, which are consisted of a 2 stage driver stage and a power stage employing $8{\times}50um$ gate width, have been successfully developed by using 120nm $In_{0.4}AlAs/In_{0.35}GaAs$ Metamorphic high electron mobility transistors (MHEMTs). The devices show an extrinsic transconductance $g_m$ of 660 mS/mm, a maximum drain current of 700 mA/mm, and a gate drain breakdown voltage of -8.5 V. A cut-off frequency ($f_T$) of 172 GHz and a maximum oscillation frequency ($f_{max}$) of over 300 GHz are achieved. The fabricated PA exhibited high power gain of 20dB only with 3 stages. The output power is measured to be 12.5 dBm.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2002.11a
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• pp.85-90
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• 2002

$RuO_2$/GaN and related contacts were investigated for Schottky contacts in GaN-Based optical and electronic devices. We demonstrated that an $RuO_2$ film forms a stable Schottky contact on a GaN layer with a barrier height (${\Phi}_B$) of 1.46 eV and transmittance of 70% in the visible and near UV region. $RuO_2$/GaN Schottky diode showed a breakdown at over -50V and leakage current of only 0.3 nA at -5V. The $RuO_2$/GaN Schottky type photodetector had the UV/Visible rejection ratio of over $10^5$ and the responsivity of 0.23 A/W at 330 nm. The $RuO_2$ gate AlGaN/GaN EFET exhibited high drain current ($I_d$) of 689.3 mA/mm and high transconductance ($g_m$) of 197.4 mS/mm. Cut-Off frequency ($f_t$) and maximum operating frequency ($f_{max}$) were measured as 27.0 GHz and 45.5 GHz, respectively.

• Journal of Advanced Navigation Technology
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• v.13 no.1
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• pp.41-47
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• 2009

In this paper, a band pass filter with a rejection band is proposed for UWB(Ultra Wide Band) communication system. First, low pass filter accessed cut off frequency of 10.2 GHz was designed using structure stepped impedance. And high pass filter accessed cut of frequency of 3.2 GHz was designed using parallel short-stub. There was implemented composite connection of designed low pass filter and high pass filter. The relative dielectric constant, the height, the loss tangent of the PCB substrate were ${\varepsilon}_r$=2.2, h=0.508 mm and loss tangent = 0.0009 respectively. The fabricated band pass filter shows a compact size of 3 cm. The fabricated band pass filter was characterized using 37169A VNA(Vector Network Analyzer). And measured result were obtained 7.5 GHz of bandwidth and -10 dB of return loss and -3 dB of insertion loss from pass band. The result of the research can be used for the UWB communications and MIC/MMIC, RFIC system.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.10
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• pp.14-22
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• 2010

The source/channel/drain regions are formed by ion implantation with different dopant types of $n^+/p^{(+)}/n^+$ in the fabrication of the conventional n-type metal-oxide-semiconductor field effect transistor(NMOSFET). In implementing the ultra-small devices with channel length of sub-30 nm, in order to achieve the designed effective channel length accurately, low thermal budget should be considered in the fabrication processes for minimizing the lateral diffusion of dopants although the implanted ions should be activated as completely as possible for higher on-current level. Junctionless (JL) MOSFETs fully capable of the the conventional NMOSFET operations without p-type channel for enlarging the process margin are under researches. In this paper, the optimum design of the JL MOSFET based on silicon nanowire (SNW) structure is carried out by 3-D device simulation and the basic radio frequency (RF) characteristics such as conductance, maximum oscillation frequency($f_{max}$), current gain cut-off frequency($f_T$) for the optimized device. The channel length was 30 run and the design variables were the channel doping concentration and SNW radius. For the optimally designed JL SNW NMOSFET, $f_T$ and $f_{max}$ high as 367.5 GHz and 602.5 GHz could be obtained, respectively, at the operating bias condition $V_{GS}$ = $V_{DS}$ = 1.0 V).

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.599-602
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• 2005

In this paper, we have performed a study that modifies the CPW Pad configurations to improve an $f_{max}$ characteristic of metamorphic HEMT. To analyze the CPW Pad structures of MHEMT, we use the ADS momentum simulator developed by $Agilent^{TM}$. Comparing the employed structure (G/W = 40/100 m), the optimized structure (G/W = 20/25 m) of CPW MHEMT shows the increased $S_{21}$ by 2.5 dB, which is one of the dominant parameters influencing the $f_{max}$ of MHEMT. To compare the performances of optimized MHEMT with the employed MHEMT, DC and RF characteristics of the fabricated MHEMT were measured. In the case of optimized CPW MHEMT, the measured saturated drain current density and transconductance $(g_m)$ were 693 mA/mm and 647 mS/mm, respectively. RF measurements were performed in a frequency range of $0.1{\sim}110$ GHz. A high $S_{21}$ gain of 5.5 dB is shown at a millimeter-wave frequency of 110 GHz. Two kinds of RF gains, $h_{21}$ and maximum available gain (MAG), versus the frequency, and a cut-off frequency ($f_t$) of ${\sim}154$ GHz and a maximum frequency of oscillation ($f_{max}$) of ${\sim}358$ GHz are obtained, respectively, from the extrapolation of the RF gains for a device biased at a peak transconductance. An optimized CPW MHEMT structure is one of the first reports among fabricated 0.1 m gate length MHEMTs.

• Journal of the Korean Society for Railway
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• v.11 no.5
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• pp.477-481
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• 2008

This paper dealt with a detection method of series arc existence which is a symptom of electric fires in low-voltage system. The proposed detection circuit consists of a high-pass filter with a low cut-off frequency of 3kHz to attenuate power frequency voltage by 80 dB and an active band-pass filter with a center frequency of 4kHz to detect only the series arc signals. The performance of the circuit was evaluated in a phase-controlled incandescent lamp as a non-linear load and an inverted-fed induction motor as a high frequency load by using the arc generator specified in UL1699. From the experimental results, it was confirmed that the proposed method solved the detection error, which is being the most problem, by discriminating the series arc signal even in non-linear and high frequency loads.

• Journal of Biomedical Engineering Research
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• v.17 no.4
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• pp.449-458
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• 1996

Most of the conventional electrocardiowaphs foil to detect signals other than P-QRS-T due to the limited SNR and bandwidth. High-resolution electrocardiography(HRECG) provides better SNR and wider bandwidth for the detection of micro-potentials with higher frequency components such as vontricular late potentials(LP). We have developed a HRECG using uncorrected XYZ lead for the detection of LPs. The overall gain of the amplifier is 4000 and the bandwidth is 0.5-300Hz without using 60Hz notch filter. Three 16-bit A/D converters sample X, Y, and Z signals simultaneously with a sampling frequency of 2000Hz. Sampled data are transmitted to a PC via a DMA-controlled, optically-coupled serial communication channel. In order to further reduce the noise, we implemented a signal averaging algorithm that averaged many instances of aligned beats. The beat alignment was carried out through the use of a template matching technique that finds a location maximizing cross-correlation with a given beat tem- plate. Beat alignment error was reduced to $\pm$0.25ms. FIR high-pass filter with cut-off frequency of 40Hz was applied to remove the low frequency components of the averaged X, Y, and Z signals. QRS onset and end point were determined from the vector magnitude of the sigrlaIL and some parameters needed to detect the existence of LP were estimated. The entire system was designed for the easy application of the future research topics including the optimal lead system, filter design, new parameter extraction, etc. In the developed HRECG, without signal averaging, the noise level was less than 5$\mu$V$_rms RTI$. With signal averaging of at least 100 beats, the noise level was reduced to 0.5$\mu$V$_rms RTI$, which is low enough to detect LPs. The developed HRECG will provide a new advanced functionality to interpretive ECG analyzers.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.3
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• pp.267-273
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• 2008

The circular cylinder pipes are used in the many industrial areas. In this paper, the acoustic wave propagation in the pipe containing a gas is researched. First of all, the theory for the coupled acoustic wave propagation in a pipe is investigated. Acoustic wave propagation in pipe can not be occurred independently between the wave of the fluid and the shell. It requires complicated analysis. However, as a special case, the coupled wave in a high density pipe containing a light density medium is corresponded closely to the uncoupled in-vacuo shell waves and to the rigid-walled duct fluid waves. The coincidence frequencies of acoustic and shell modes contribute to the predominant energy transmission. The coincidence frequency means the frequency corresponding to the coincidence of the wavenumber in both acoustic and shell. In this paper, it is assumed that the internal medium is much lighter than the pipe shell. After the uncoupled acoustic wave in the internal medium and uncoupled shell wave are considered, the coincidence frequencies are found. The analysis is successfully confirmed by the verification of the experiment using the real long steel pipe. This work verifies that the coupled wave characteristic of the shell and the fluid is occurred as predominant energy transmission at the coincidence frequencies.