• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.10
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• pp.159-168
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• 2012

In this paper, a W-band single-chip receiver MMIC for FMCW(Frequency-modulated continuous-wave) radar is presented using $0.15{\mu}m$ GaAs pHEMT technology. The receiver MMIC consists of a 4-stage low noise amplifier(LNA), a down-converting mixer and a 3-stage LO buffer amplifier. The LNA is designed to exhibit a low noise figure and high linearity. A resistive mixer is adopted as a down-converting mixer in order to obtain high linearity and low noise performance at low IF. An additional LO buffer amplifier is also demonstrated to reduce the required LO power of the W-band mixer. The fabricated W-band single-chip receiver MMIC shows an excellent performance such as a conversion gain of 6.2 dB, a noise figure of 5.0 dB and input 1-dB compression point($P_{1dB,in}$) of -12.8 dBm, at the RF frequency of $f_0$ GHz, LO input power of -1 dBm and IF frequency of 100 MHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.12
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• pp.1350-1359
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• 2008

This paper presents a wideband doubly balanced resistive mixer fabricated using $0.5{\mu}m$ GaAs p-HEMT process. Three baluns are employed in the mixer. LO and RF baluns operating over an 8 to 20 GHz range were implemented with Marchand baluns. In order to reduce chip size, the Marchand baluns were realized by the meandering multicoupled line and inductor lines were inserted to compensate for the meandering effect. IF balun was implemented through a DC-coupled differential amplifier. The size of IF balun is $0.3{\times}0.5\;mm^2$ and the measured amplitude and phase unbalances were less than 1 dB and $5^{\circ}$, respectively from DC to 7 GHz. The mixer is $1.7{\times}1.8\;mm^2$ in size, has a conversion loss of 5 to 11 dB, and an output third order intercept(OIP3) of +10 to +15 dBm at 16 dBm LO power for the operating bandwidth.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.344-344
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• 2014

Transparent amorphous oxide semiconductors such as a In-Ga-Zn-O (a-IGZO) have advantages for large area electronic devices; e.g., uniform deposition at a large area, optical transparency, a smooth surface, and large electron mobility >10 cm2/Vs, which is more than an order of magnitude larger than that of hydrogen amorphous silicon (a-Si;H).1) Thin film transistors (TFTs) that employ amorphous oxide semiconductors such as ZnO, In-Ga-Zn-O, or Hf-In-Zn-O (HIZO) are currently subject of intensive study owing to their high potential for application in flat panel displays. The device fabrication process involves a series of thin film deposition and photolithographic patterning steps. In order to minimize contamination, the substrates usually undergo a cleaning procedure using deionized water, before and after the growth of thin films by sputtering methods. The devices structure were fabricated top-contact gate TFTs using the a-IGZO films on the plastic substrates. The channel width and length were 80 and 20 um, respectively. The source and drain electrode regions were defined by photolithography and wet etching process. The electrodes consisting of Ti(15 nm)/Al(120 nm)/Ti(15nm) trilayers were deposited by direct current sputtering. The 30 nm thickness active IGZO layer deposited by rf magnetron sputtering at room temperature. The deposition condition is as follows: a rf power 200 W, a pressure of 5 mtorr, 10% of oxygen [O2/(O2+Ar)=0.1], and room temperature. A 9-nm-thick Al2O3 layer was formed as a first, third gate insulator by ALD deposition. A 290-nm-thick SS6908 organic dielectrics formed as second gate insulator by spin-coating. The schematic structure of the IGZO TFT is top gate contact geometry device structure for typical TFTs fabricated in this study. Drain current (IDS) versus drain-source voltage (VDS) output characteristics curve of a IGZO TFTs fabricated using the 3-layer gate insulator on a plastic substrate and log(IDS)-gate voltage (VG) characteristics for typical IGZO TFTs. The TFTs device has a channel width (W) of $80{\mu}m$ and a channel length (L) of $20{\mu}m$. The IDS-VDS curves showed well-defined transistor characteristics with saturation effects at VG>-10 V and VDS>-20 V for the inkjet printing IGZO device. The carrier charge mobility was determined to be 15.18 cm^2 V-1s-1 with FET threshold voltage of -3 V and on/off current ratio 10^9.

• Journal of the Korean Magnetics Society
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• v.23 no.2
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• pp.49-53
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• 2013

A current sensor is one of important component which is used for the electrical current measurement during charge and discharge of the battery, and monitoring system of the motor controller in the electric and hybrid vehicle. In this study, we have developed an open loop type current sensor using GaAs Hall sensor and magnetic core has an air gap. The Hall sensor detect magnetic field produced by the current to be measured. The 3 mm air gap core was made by HGO electrical steel sheets after slitting, winding, annealing, molding, and cutting. Developed current sensor shows 0.03 % linearity within DC current range from -400 A to +400 A. Operating temperature range was extended to the range of $-40{\sim}105^{\circ}C$ using temperature compensating electronic circuit. To Improve frequency bandwidth limit due to the air flux of PCB (Printed Circuit Board) and Hall sensor, We employed an air flux compensating loop near Hall sensor or on PCB. Frequency bandwidth of the sensor was 100 kHz when we applied sine wave current of $40A{\cdot}turn$ in the frequency range from 100 Hz to 100 kHz. For the dynamic response time measurement, 5 kHz square wave current of $40A{\cdot}turn$ was applied to the sensor. Response time was calculated time reach to 90 % of saturation value and smaller than $2{\mu}s$.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.44 no.2
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• pp.141-148
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• 2011

This feeding experiment was conducted to investigate the effects of dietary inclusion of various additives on growth performance, hematological parameters, fatty acid composition, gene expression and histopathological changes in juvenile olive flounder (Paralichthys olivaceus). Eleven isonitrogenous (49% crude protein) and isolipidic (10% crude lipid) experimental diets were formulated: no additives (Con); 5% kelp meal (Ke); 10% krill meal (Kr); 1% garlic powder (Ga); 1% citrus meal (Ci); 3% onion powder (On); 1% ginger powder (Gi); 1% mugwort powder (Mu); 1% licorice powder (Li); 1% wasabi powder (Wa); and a mixture (Mix) of these additives. Three replicate groups of juvenile flounder (average weight of 8.5 g) were fed one of the experimental diets to visual satiety twice a day for 15 weeks. The dietary inclusion of additives did not affect survival, weight gain, specific growth rate feed efficiency, daily feed intake, daily protein intake, protein efficiency ratio, hepatosomatic index and visceralsomatic index of the fish. Plasma triglyceride levels were significantly lower in fish fed the Ke, Ga, On, Gi, Mu, Li, and Mix diets than in fish fed the control diet. Plasma glucose, glutamic oxaloacetic transaminase and total cholesterol did not differ among dietary treatments. No significant difference was observed in fatty acid composition and lipid content of the dorsal muscle in fish fed the experimental diets. Myosin gene expression did not differ significantly among treatments after 5 weeks but was significantly lower in fish fed the Kr, Ci, Li, and Mix diets than in control group after 15 weeks. Histopathological analysis showed mild gill hyperplasia and mild necrosis of liver parenchymal cells in several individuals of each experimental group. These conditions were also observed in the control group and were not thought to be related to the inclusion of feed additives. The present findings indicate that the dietary inclusion of additives did not affect growth performance, fatty acid composition, gene expression, and histopathological changes in juvenile flounder. However, plasma triglyceride content may be reduced by supplementation with 5% kelp meal, 3% onion powder, 1% garlic powder, 1% ginger powder, 1% mugwort powder, and the additive mixture.

• Korean Journal of Optics and Photonics
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• v.24 no.5
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• pp.224-230
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• 2013

Laser Lift-Off (LLO) is a process that removes a GaN or AIN thin layer from a sapphire wafer to manufacture vertical-type LEDs. It consists of a light source, an attenuator, a mask, a projection lens and a beam homogenizer. In this paper, we design an attenuator and a projection lens. We use the 'ZEMAX' optical design software for analysis of depth of focus and for a projection lens design which makes $7{\times}7mm^2$ beam size by projecting a beam on a wafer. Using the 'LightTools' lighting design software, we analyze the size and uniformity of the beam projected by the projection lens on the wafer. The performance analysis found that the size of the square-shaped beam is $6.97{\times}6.96mm^2$, with 91.8 % uniformity and ${\pm}30{\mu}m$ focus depth. In addition, this study performs dielectric coating using the 'Essential Macleod' to increase the transmittance of an attenuator. As a result, for 23 layers of thin films, the transmittance total has 10-96% at angle of incidence $45-60^{\circ}$ in S-polarization.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.9
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• pp.18-24
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• 2007

We report broadband cascode amplifiers of a single-ended and a balanced amplifier for the millimeter-wave applications. The amplifiers were fabricated using 0.1 ${\mu}m\;{\Gamma}-gate$ PHEMT technology on GaAs substrate. The single-ended cascode amplifier was designed and fabricated by using shunt peaking technology. The fabricated single-ended cascode amplifier shows 3 dB bandwidth of 37 GHz($18.5{\sim}55.5$ GHz) and the maximum $S_{21}$ gain of 9.38 dB. The balanced cascode amplifier using tandem couplers achieves 3 dB bandwidth and the maximum $S_{21}$ gain of 44.5 GHz($21{\sim}65.5$ GHz) and 10.4 dB at 60 GHz, respectively. The 3 dB bandwidth of the balanced cascode amplifier shows 20% lager than the single-ended cascode amplifier.

• Korean Journal of Materials Research
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• v.21 no.11
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• pp.634-638
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• 2011

We report growth of epitaxial AlN thin films on c-plane sapphire substrates by plasma-assisted molecular beam epitaxy. To achieve two-dimensional growth the substrates were nitrided by nitrogen plasma prior to the AlN growth, which resulted in the formation of a two-dimensional single crystalline AlN layer. The formation of the two-dimensional AlN layer by the nitridation process was confirmed by the observation of streaky reflection high energy electron diffraction (RHEED) patterns. The growth of AlN thin films was performed on the nitrided AlN layer by changing the Al beam flux with the fixed nitrogen flux at 860$^{\circ}C$. The growth mode of AlN films was also affected by the beam flux. By increasing the Al beam flux, two-dimensional growth of AlN films was favored, and a very flat surface with a root mean square roughness of 0.196 nm (for the 2 ${\mu}m$ ${\times}$ 2 ${\mu}m$ area) was obtained. Interestingly, additional diffraction lines were observed for the two-dimensionally grown AlN films, which were probably caused by the Al adlayer, which was similar to a report of Ga adlayer in the two-dimensional growth of GaN. Al droplets were observed in the sample grown with a higher Al beam flux after cooling to room temperature, which resulted from the excessive Al flux.

• KSBB Journal
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• v.21 no.5
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• pp.376-383
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• 2006

Pine needle(Pinus densiflora sieb, et zucc) extract has been used to improve cardiovascular disorders, detoxification of nicotine, the infirmities of age and curing diseases of unidentified symptoms. It has various useful components including amino acids, vitamin C, terpenoids and chlorophyll. In this study we have identified 8 different yeast strains that are developed spontaneously causing self fermentation in the extract. The self-fermented pine extract(SFPE) inhibited the growth of some bacterial strains like E. coli, Bacillus subtilis and Staphylococcus aureus. The SFPE($0.2{\mu}{\ell}/ml{\sim}0.3{\mu}{\ell}/ml$) showed 90% NBT superoxide scavenging activities which is similar for all tested samples of different ages. The 7 years old SFPE(0.15 mg/ml and 0.3 mg/ml) caused relaxation of spontaneous contraction and relaxation rhythm of thoracic arterial tissues from rat. Therefore, SFPE has useful effects such as antibacterial, antioxidant and improved blood circulation and could be a good source of functional food development.

• Analytical Science and Technology
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• v.16 no.6
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• pp.488-498
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• 2003

By LC/MS/MS, the analytical method of sildenafil and its analogues (homosildenafil, vardenafil and tadalafil) used as used medical treatment of impotence was established. electrosprary ionization (ESI) and atmospheric pressure chemical ionization (APCI) as a ionization method were applied. Several parameter were varied and the sensitivity and reproducibility were compared. In LC/ESI-MS method, capillary voltage, cone voltage, extractor, entrance and RF lens to create appropriate productr ions for multiple reaction monitoring (MRM) were variable parameter, but the formation of the other product ions except the precursor ion could not detect. And the value of entrance, collision energy, exit, corona voltage, cone voltage, extractor, RF lens, cone gas, and desolvation gas in APCI mode were varied, only the creation pattern of fragment ions by the change of RF lens value were detected, and the limit of detection was decreased due to the increase of S/N. Ten millimole ammonium formate (pH 4.8):acetonitrile=70:30 by isocratic elution in HPLC system was shown the maximum sensitivity in MS, the detection limit of sildenafil, homosildenafil, vardenafil and tadalafil obtained by ESI-MRM were 0.10, 0.025, 0.025, and $0.25{\mu}g/mL$ at S/N>5, respectively.