• JSTS:Journal of Semiconductor Technology and Science
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• 제3권4호
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• pp.211-216
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• 2003

This work describes a 3 V 12b 100 MS/s CMOS digital-to-analog converter (DAC) for high-speed communication system applications. The proposed DAC is composed of a unit current-cell matrix for 8 MSBs and a binary-weighted array for 4 LSBs, trading-off linearity, power consumption, chip area, and glitch energy with this process. The low-glitch switch driving circuits are employed to improve linearity and dynamic performance. Current sources of the DAC are laid out separately from the current-cell switch matrix core block to reduce transient noise coupling. The prototype DAC is implemented in a 0.35 um n-well single-poly quad-metal CMOS technology and the measured DNL and INL are within ${\pm}0.75$ LSB and ${\pm}1.73$ LSB at 12b, respectively. The spurious-free dynamic range (SFDR) is 64 dB at 100 MS/s with a 10 MHz input sinewave. The DAC dissipates 91 mW at 3 V and occupies the active die area of $2.2{\;}mm{\;}{\times}{\;}2.0{\;}mm$

• 대한기계학회논문집A
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• 제25권6호
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• pp.959-964
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• 2001

An experimental investigation on the near-field electromagnetic loss of thin copper layers has been presented using microfabricated microwave transceivers for applications to multi-chip microsystems. Copper layers in the thickness range of 0.2$\mu$m∼200$\mu$m have been electroplated on the Pyrex glass substrates. Microwave transceivers have been fabricated using the 3.5mm$\times$3.5mm nickel microloop antennas, electroformed on the silicon substrates. Electromagnetic radiation loss of the copper layers placed between the microloop transceivers has been measured as 10dB∼40dB for the wave frequency range of 100MHz∼1GHz. The 0.2$\mu$m-thick copper layer provides a shield loss of 20dB at the frequencies higher than 300MHz, whereas showing a predominant decreases of shield loss to 10dB at lower frequencies. No substantial increase of the shield effectiveness has been found for the copper shield layers thicker that 2 $\mu$m.

• 한국정보기술응용학회:학술대회논문집
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• 한국정보기술응용학회 2005년도 6th 2005 International Conference on Computers, Communications and System
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• pp.305-310
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• 2005

Recently, many organizations in various industries have introduced e-businesses for the purpose of adding value to their businesses. However, due to no comparable business models to e-business in the past, there are no reliable yardsticks to predict the performance of an e-business. This paper considers an environmental change analysis as a means to resolve this difficulty. System Dynamics (SD) could be a useful tool to generate effective results by examining the e-business model. SD model is developed to analyze the effects of an e-sales channel which was appended to the existing sales channels in the steel manufacturing industry. The results show an increase in average price and sales volume through the use of an auction process on the e-marketplace. Stocking expenses are reduced as well by the increase of the sales turnover. A possible scenario was adopted to the developed simulation model and investigated strategic issues to draw desirable strategies with market changes.

• Journal of electromagnetic engineering and science
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• 제18권4호
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• pp.261-266
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• 2018

This paper reports on the proposed design of a low profile broadband array antenna for home repeater applications. The proposed antenna consists of $1{\times}4$ patch elements and two ground planes, one of which is slitted. By using the gap feeding method, the impedance matching of the antenna is improved by a multi-resonance phenomenon. The proposed antenna provides a wide -10 dB reflection coefficient bandwidth simultaneously covering the Global System for Mobile communications (GSM-1800), Personal Communications Service (PCS), and the Universal Mobile Telecommunication System (UMTS) bands (1.67-2.32 GHz). In order to reduce the mutual coupling between adjacent patch elements, slits are embedded in the ground plane. An isolation level of -20 dB is realized over the entire operating frequency band.

• ETRI Journal
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• 제34권1호
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• pp.118-121
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• 2012

In this letter, a miniaturized log-periodic dipole array (LPDA) antenna operating from 1 GHz to 6 GHz is proposed for portable direction finding applications. To reduce the lateral size of an LPDA antenna, bow-tie elements and a top-loading technique are utilized and spacing factor is decreased to reduce the spacing between the LPDA elements. The proposed miniaturized LPDA antenna has the measured gain and front-to-back ratio ranging from 1.2 dBi to 3 dBi and from 7 dB to 22 dB, respectively.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 I
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• pp.346-349
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• 2003

A SiGe HBT MMIC double balaced up-converter has been designed and fabricated for C-band WLAN applications. The up-converter is based on the Gilbert cell mixer with an active baluns for differential inputs of LO and IF signals. The designed up-converter exhibits a conversion gain 12.5dB for a -10 dBm LO power. It also exhibits LO-RF isolation of 19.3dBc, and IF-RF isolation of 23.3 dBc at a 1-dB compression point of -14.2dBm

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 C
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• pp.1969-1971
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• 2002

This paper presents the design and performance of low pull-in voltage MEMS switches for commercial cellular/PCS applications. The switches have all-metal (3 ${\mu}m$ thick Au) movable plates over CPW(Coplanar Waveguide) transmission line. The stress gradient in a movable plate is considered in mechanical design to obtain an accurate pull-in voltage. Series metal-to-metal contact switches are fabricated and evaluated. Those switches exhibit the low loss(<0.2 dB @1.9 GHz) with good isolation(55 dB @1.9 GHz).

• Journal of electromagnetic engineering and science
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• 제14권3호
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• pp.306-313
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• 2014

A Fabry-Perot resonator cavity antenna for Ku-band application is presented in this paper. The Fabry-Perot cavity is formed by a ground plane and a frequency selective surface (FSS) made of a circular hole array. The cavity resonance is excited by a single-feed microstrip patch located inside the cavity. The measured results show that the proposed antenna has an impedance bandwidth of approximately 13% ($VSWR{\leq}2$) and a 3-dB gain bandwidth of approximately 7%. The antenna produces a maximum gain of 18.5 dBi and good radiation patterns over the entire 3-dB gain bandwidth. The antenna's very thin profile, high directivity, and single excitation feed make it promising for use in wireless and satellite communication applications in a Ku-band frequency.

• Nonlinear Functional Analysis and Applications
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• 제29권2호
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• pp.435-450
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• 2024

This study depends on the modified conformable fractional derivative definition to generalize and proves some theorems of the classical power series into the fractional power series. Furthermore, a comprehensive formulation of the generalized Taylor's series is derived within this context. As a result, a new technique is introduced for the fractional power series. The efficacy of this new technique has been substantiated in solving some fractional differential equations.

• 한국미생물·생명공학회지
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• 제50권3호
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• pp.319-327
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• 2022

γ-Aminobutyric acid (GABA) is a multi-functional compound with broad applications for food industry. GABA producing bacteria were isolated from cabbage kimchi. Among them, B737 was the best GABA producer when culture supernatants were analyzed by TLC. B737 was identified as Levilactobacillus brevis by 16S rRNA gene sequencing. Its glutamate decarboxylase (GAD) gene was cloned by PCR and the nucleotide sequence determined. B737 GAD consisting of 485 amino acids is the largest in size among GADs reported from LAB so far. gadB from L. brevis B737 was overexpressed in Escherichia. coli BL21(DE3) using pET26b(+).pET26b(+). The recombinant GAD was purified and its size was 55 kDa by SDS-PAGE. Maximum GAD activity was observed at pH 5 and 40℃ and the activity was dependent on pyridoxal 5'-phosphate. K_m and V_max of recombinant GAD were 6.2 ± 0.06 mM and 0.34 ± 0.002 mM/min, respectively. L. brevis B737 can be used as a starter for fermented foods with high GABA contents.