• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.5 s.120
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• pp.539-546
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• 2007

In this paper, a 3-D EM simulation methodology for on-chip spiral inductor analysis has provided and it is shown that the methodology can be adapted to the highly predictable design for CMOS VCO. LC-resonator type VCO have fabricated by using standard 0.25 um CMOS process. And the LC VCO layout case which has pattern ground shielded inductors and the other layout case which has no pattern grounded inductors were fabricated for the verification of their effects on the VCO's phase noise by reducing the Q-factor of inductors. Fabricated VCO has 3.094 GHz, -12.15 dBm output at the tuning voltage of 2.5 V, and from the simulation, Q-factor of the pattern grounded inductor has increased 8% at 3 GHz, and from the measurement results, the phase noise has reduced by 9 dB at the 3 MHz off-set frequency for the pattern grounded inductor layout case.

• Journal of Electrical Engineering and Technology
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• v.9 no.2
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• pp.514-522
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• 2014

A new type of high precision electromagnetic suspension (EMS) which can support heavy tray along long stroke rail is proposed in this paper. Compared with the conventional EMS, the suggested moving-core typed EMS has the levitation electromagnets (EMs) on the fixed rail. This scheme has high load capability caused by iron-core and enables simple tray structure. Also it does not have precision degradation caused by heat generation from EMs, which is a drawback of conventional EMS. With these merits, the proposed EMS can be an optimal contactless linear bearing in next generation flat panel display (FPD) manufacturing process if the ability of long stroke movement is proved. So a special Section Switching Algorithm (SSA) is derived from the resultant force and moment equations of the levitated tray which enables long stroke movement of the tray. In order to verify the feasibility of the suggested SSA, a simple test-setup of the EMS with 2 Section-changes is made up and servo-controlled in the simulation and experiment. The simulation shows the perfect changeover the EMs, and the experiment shows overall control performance of under ${\pm}40{\mu}m$ gap deviations. These results reveal that the newly suggested contactless linear bearing can simultaneously achieve high load capability and precision gap control as well as long stroke.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.11
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• pp.834-841
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• 2018

A power amplifier for subgigahertz short-range wireless communication using $0.18-{\mu}m$ CMOS technology is presented. It is designed as a differential structure to form easily a virtual ground node, to increase output power, and to design a cascode structure to prevent breakdown. The transistor gate width was determined to maximize the output power and power-added efficiency(PAE), and the balun was optimized through electromagnetic simulation to minimize the loss caused by the matching network. This power amplifier had a gain of more than 49.5 dB, a saturation power of 26.7 dBm, a peak PAE of 20.7 % in the frequency range of 860 to 960 MHz, and a chip size of $2.14mm^2$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.12
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• pp.1069-1077
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• 2011

In this paper, a design and fabrication of a miniaturized 2.5 GHz 8 W power amplifier using selectively anodized aluminum oxide(SAAO) substrate are presented. The process of SAAO substrate is recently proposed and patented by Wavenics Inc. which uses aluminum as wafer. The selected active device is a commercially available GaN HEMT chip of TriQuint company, which is recently released. The optimum impedances for power amplifier design were extracted using the custom tuning jig composed of tunable passive components. The class-F power amplifier are designed based on EM co-simulation of impedance matching circuit. The matching circuit is realized in SAAO substrate. For integration and matching in the small package module, spiral inductors and single layer capacitors are used. The fabricated power amplifier with $4.4{\times}4.4\;mm^2$ shows the efficiency above 40 % and harmonic suppression above 30 dBc for the second(2nd) and the third(3rd) harmonic at the output power of 8 W.

• The Korean Journal of Applied Statistics
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• v.29 no.7
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• pp.1459-1473
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• 2016

Both longitudinal data and survival data are collected simultaneously in longitudinal data which are observed throughout the passage of time. In this case, the effect of the independent variable becomes biased (provided that sole use of longitudinal data analysis does not consider the relation between both data used) if the missing that occurred in the longitudinal data is non-ignorable because it is caused by a correlation with the survival data. A joint model of longitudinal data and survival data was studied as a solution for such problem in order to obtain an unbiased result by considering the survival model for the cause of missing. In this paper, a joint model of the longitudinal zero-inflated count data and survival data is studied by replacing the longitudinal part with zero-inflated count data. A hurdle model and proportional hazards model were used for each longitudinal zero inflated count data and survival data; in addition, both sub-models were linked based on the assumption that the random effect of sub-models follow the multivariate normal distribution. We used the EM algorithm for the maximum likelihood estimator of parameters and estimated standard errors of parameters were calculated using the profile likelihood method. In simulation, we observed a better performance of the joint model in bias and coverage probability compared to the separate model.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.11
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• pp.1172-1182
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• 2014

In these days, many kinds of goods are more light and more integrated. As frequency range of mobile applications have increased to improve performance of antenna furthermore, EMI(ElectroMagnetic Interference) problem has frequently caused by disturbance of antenna in device which aggravates other circuit. This paper proposes a technique for the prediction of noise power to the transmission line from antenna located near the line. Although noise power transferred to transmission line is varied by source impedance of antenna and load impedance of transmission line basically, the power magnitude can be presented in a square form of S-parameter between antenna and transmission line due to small variation of transferred power. For this reason, we can use the index expressed the transferred power varied along geometrical shapes of transmission line. As a result, big difference is occurred along location of antenna especially the bended line. And this such experiment is correspond with simulation, these results have meaning physically considering electromagnetic field distribution in near and far field. HFSS of Ansys and CPW with ground is used in this paper.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2003.11a
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• pp.177-184
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• 2003

Numerical simulation on marine wind and sea surface elevation was carried out using both three-dimensional hydrostatic and non-hydrostatic models and a simple oceanic model from 0900 LST, August 13 to 0900 LST, August 15, 1995. As daytime easterly meso-scale sea-breeze from the eastern sea penetrates Kangnung city in the center part as basin and goes up along the slope of Mt. Taegullyang in the west, it confronts synoptic-scale westerly wind blowing over the top of the mountain at the mid of the eastern slope and then the resultant wind produces an upper level westerly return flow toward the East Sea. In a narrow band of weak surface wind within 10km of the coastal sea, wind stress is generally small, less than l${\times}$10E-2 Pa and it reaches 2 ${\times}$ 10E-2 Pa to the 35 km. Positive wind stress curl of 15 $\times$ 10E-5Pa $m^{-1}$ still exists in the same band and corresponds to the ascent of 70 em from the sea level. This is due to the generation of northerly wind driven current with a speed of 11 m $S^{-1}$ along the coast under the influence of south-easterly wind and makes an intrusion of warm waters from the southern sea into the northern coast, such as the East Korea Warm Current. On the other hand, even if nighttime downslope windstorm of 14m/s associated with both mountain wind and land-breeze produces the development of internal gravity waves with a hydraulic jump motion of air near the coastal inland surface, the surface wind in the coastal sea is relatively moderate south-westerly wind, resulting in moderate wind stress. Negative wind stress curl in the coast causes the subsidence of the sea surface of 15 em along the coast and south-westerly coastal surface wind drives alongshore south-easterly wind driven current, opposite to the daytime one. Then, it causes the intrusion of cold waters like the North Korea Cold Current in the northern coastal sea into the narrow band of the southern coastal sea. However, the band of positive wind stress curl at the distance of 30km away from the coast toward further offshore area can also cause the uprising of sea waters and the intrusion of warm waters from the southern sea toward the northern sea (northerly wind driven current), resulting in a counter-clockwise wind driven current. These clockwise and counter-clockwise currents much induce the formation of low clouds containing fog and drizzle in the coastal region.

• Journal of radiological science and technology
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• v.35 no.4
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• pp.353-360
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• 2012

Diverse designs of collimator have been applied to Single Photon Emission Computed Tomography (SPECT) according to the purpose of acquisition; thus, it is necessary to reflect geometric characteristic of each collimator for successive image reconstruction. This study carry out reconstruction algorithm for imaging system in nuclear medicine with pinhole collimator. Especially, we study to solve sampling problem which caused in the system model of pinhole collimator. System model for a maximum likelihood expectation maximization (MLEM) was developed based on the geometry of the collimator. The projector and back-projector were separately implemented based on the ray-driven and voxel-driven methods, respectively, to overcome sparse sampling problem. We perform phantom study for pinhole collimator by using geant4 application for tomographic emission(GATE) simulation tool. The reconstructed images show promising results. Designed iterative reconstruction algorithm with unmatched system model effective to remove sampling problem artefact. Proposed algorithm can be used not only for pinhole collimator but also for various collimator system of imaging system in nuclear medicine.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.3
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• pp.432-438
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• 2001

In this paper, after applying Defected Ground Structure(DGS) to DC block, changes of gap and length of λ/4 coupled line are investigated by EM simulation and fabrication. As a result, on condition of the same output with the case using typical DC block, the gap between λ/4 coupled line is widen from 0.1 mm to 0.46 mm by 0.36 mm and the length of λ/4 coupled line gets shorter from 17.7 mm to 13.2 mm by 4.5 mm. Also three type power amplifiers using blocking capacitor, typical DC block and DGS DC block are fabricated and investigated. At first, when S parameter characteristics of each amplifier are considered at frequency band of 3.2 +-0.O5 GHz, every amplifier has similar characteristics of gain and S parameter. Second when the output power of amplifiers is 25 dBm after putting CW signal of 3.2 GHz into three type amplifiers, the difference of dominant signal and 2nd harmonic signal using blocking capacitor, typical DC block and DGS DC block is each -44.83 dBc, -66.84 dBc and -64.33 dBc. Therefore harmonic characteristics of amplifiers using typical DC block and DGS DC block is almost same.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.5
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• pp.3074-3078
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• 2014

We implemented a dual-band slot-coupled patch (SCP) antenna for the external access point (AP) of the wireless local area network (WLAN) band. The antennas consist of two radiators on three layers. The first radiator is a slotted bow tie antenna operating at the 2.4-2.483 GHz band. The second radiator is a patch antenna with parasitic elements operating at 4.095-5.845 GHz. The high gain and broad bandwidth is important element of wireless access. To enhance the bandwidth, a coupled feeding was used in the first radiator and a parasitic patch was used in the second radiator. We used a parasitic patch and chock to improve the directivity and isolation in both radiators. The porposed antenna was designed by EM simulation tool and measured. The S11 of the antenna was less than -11dB (VSWR 1.8:1) at operating frequency. The peak gain was more than 6 dBi in the first antenna and more than 8 dBi in the second antenna.