• Journal of the Korean Society of Manufacturing Process Engineers
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• v.2 no.3
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• pp.76-83
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• 2003

Recently, the field of the engineering has been studied about optimum design continuously. Verified data by comparison with simulation and dynamic characteristic analysis enables the design of a machine tool to be modified easily and effectively concerning to the mode shape of the vibration. Especially, BC-500 Line Center has got some problems causing vibration which mainly come from Column and ATC part. So it is necessary to solve those problems by the two kinds of method such as changing structural design and reinforcing with ribs. In this paper, column and ATC part of BC-500 Line center are modified by an optimum design by the analysing method of FEM to avoid vibration. As a result, a more stable machine tool was designed by this simulation as optimum condition.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.5
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• pp.967-973
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• 1997

In this paper, the designed and fabrication of a K-band push-push oscillator using miniaturized hairpin resonator have been presented. One experimenal oscillator has been designed and fabricated for K-band point-to-point operation. the miniaturized harpin resonator has been analyzed theoretically and simulated by MPIE(Mixed Potential Integral Equation) method. With this results, the analysis of hairpin resonator which coupled microstrip line has been carried out with transmission-mode using this results. an optimized output matching network for the suppression of the fundamental and the 3rd order harmonic was acquired by using a nonlinear analysis method. The fabricated oscillator shows the output power of -2.28dBm, the fundamental frequency suppression of -19dBc, the 3rd order harmonic suppressionof -24dBc and 0.33 percent effiiency at 22.8GHz. The experimental outputs are in good agreement with the theoretical and simulated results.

• Journal of electromagnetic engineering and science
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• v.14 no.4
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• pp.393-398
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• 2014

A highly efficient dual-mode linear CMOS stacked-FET power amplifier (PA) is implemented for 3G UMTS and 4G LTE handset applications. High efficiency is achieved at a backed-off output power ($P_{out}$) below 12 dBm by employing an active-bypass amplifier, which consumes very low quiescent current and has high load-impedance. The output paths between high- and low-power modes of the PA are effectively isolated by using a bypass switch, thus no RF performance degradation occurs at high-power mode operation. The fabricated 900 MHz CMOS PA using a silicon-on-insulator (SOI) CMOS process operates with an idle current of 5.5 mA and shows power-added efficiency (PAE) of 20.5%/43.5% at $P_{out}$ = 12.4 / 28.2 dBm while maintaining an adjacent channel leakage ratio (ACLR) better than -39 dBc, using the 3GPP uplink W-CDMA signal. The PA also exhibits PAE of 35.1% and $ACLR_{E-UTRA}$ of -33 dBc at $P_{out}$ = 26.5 dBm, using the 20 MHz bandwidth 16-QAM LTE signal.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.3
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• pp.517-531
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• 1999

This paper presents the development of the 2-mode variable gain high power amplifier for a transmitter of INMARSAT-M operating at L-band(1626.5-1646.5 MHz). This SSPA(Solid State Power Amplifier) is amplified 42 dBm in high power mode and 36 dBm in low power mode for INMARSAT-M. The allowable error sets +1 dBm of an upper limit and -2 dBm of a lower limit, respectively. To simplify the fabrication process, the whole system is designed by two parts composed of a driving amplifier and a high power amplifier, The HP's MGA-64135 and Motorola's MRF-6401 are used for driving amplifier, and the ERICSSON's PTE-10114 and PTF-10021 are used the high power amplifier. The SSPA was fabricated by the circuits of RF, temperature compensation and 2-mode gain control circuit in aluminum housing. The gain control method was proposed by controlling the voltage for the 2-mode. In addition, It has been experimentally verified that the gain is controlled for single tone signal as well as two tone signals. The realized SSPA has 42 dB and 36 dB for small signal gain within 20 MHz bandwidth, and the VSWR of input and output port is less than 1.5:1 The minimum value of the 1 dB compression point gets 5 dBm for 2-mode variable gain high power amplifier. A typical two tone intermodulation point has 32.5 dBc maximum which is single carrier backed off 3 dB from 1 dB compression point. The maximum output power of 43 dBm was achieved at the 1636.5 MHz. These results reveal a high power of 20 Watt, which was the design target.the design target.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.4 s.346
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• pp.75-80
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• 2006

This paper has proposed a novel dual band transmitter module which can be operating either as an amplifier or as a frequency multiplier according to the input frequency. A conventional dual band transmitter consists of separate amplifiers operating at each frequency band, but the proposed dual band module operates as an amplifier for the IEEE 802.11b/g signal, and as a frequency doubler for the IEEE 802.11a signal according to input frequency and bias voltage. In this paper, we have obtained sharp stop band characteristics by using microstrip DGS(Defected Ground Structure) to suppress the fundamental frequency of the frequency doubler as well as the second harmonic of the amplifier. From measurement result, second harmonic suppression is below -59dBc in the amplifier mode, and fundamental suppression is below -35dBc in the frequency doubler mode. And the designed module has 17.8dBm output P1dB at 2.4GHz and 10.1dBm power for 5.8GHz output, and the output power in the two modes are 0.8dB and 2.8dB larger than the module with ${\lambda}g/4$ reflector, respectively.

• Journal of electromagnetic engineering and science
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• v.16 no.4
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• pp.229-231
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• 2016

A 180-GHz signal source based on a 65-nm CMOS technology has been developed in this study. The 180-GHz signal source consists of a 90-GHz fundamental-mode Colpitts oscillator and a 180-GHz frequency doubler. A coupled-line is employed to couple two oscillator cores for generating a differential signal, which is delivered to the input of the differential-mode doubler. The fabricated signal source operates from 181.2 to 182.4 GHz with output power varying from -15.3 to -10.8 dBm. The peak output power was -10.53 dBm at 181.3 GHz with a DC power consumption of 42 mW, and the associated phase noise was -71 dBc/Hz at 1 MHz offset.

• JSTS:Journal of Semiconductor Technology and Science
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• v.14 no.3
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• pp.313-321
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• 2014

A low-power low-cost polar transmitter for EDGE is designed in $0.18{\mu}m$ CMOS. A differential delta-sigma modulator (DSM) tunes a three-terminal voltage-controlled oscillator (VCO) to perform RF phase modulation, where the VCO tuning curve is digitally pre-compensated for high linearity and the carrier frequency is calibrated by a dual-mode low-power frequency-locked loop (FLL). A digital intermediate-frequency (IF) pulse-width5 modulator (PWM) drives a complementary power-switch followed by an LC filter to achieve envelope modulation with high efficiency. The proposed transmitter with 9mW power dissipation relaxes the time alignment between the phase and envelope modulations, and achieves an error vector magnitude (EVM) of 4% and phase noise of -123dBc/Hz at 400kHz offset frequency.

• The Journal of the Korea institute of electronic communication sciences
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• v.4 no.4
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• pp.247-252
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• 2009

This paper presents an Integer-N phase-locked loop (PLL) frequency synthesizer using a novel prescaler based on a charge pump and clock triggering circuit. A quadrature VCO has been designed for the 900MHz UHF RFID application. In this circuit, a voltage-controlled oscillator(VCO), a novel Prescaler, phase frequency detector(PFD), charge pump(CP), and analog lock detector(ALD) have been integrated with 0.35-${\mu}m$CMOS process. The integer divider has been developed with a verilog-HDL module, and the PLL mixed mode simulation has been performed with Spectre-Verilog co-simulator. The sweep range of VCO is designed from 828 to 960 MHz and the VCO generates four phase quadrature signals. The simulation results show that the phase noise of VCO is -102dBc/Hz at 100 KHz offset frequency, and the maximum lock-in time is about 4us with 32MHz step change (from 896 to 928 MHz).

• Environmental Engineering Research
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• v.24 no.1
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• pp.159-172
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• 2019

To investigate the influence of pollution events on the chemical composition and formation processes of aerosol particles, 24-h integrated size-segregated particulate matter (PM) was collected during the fall season at an urban site of Gwangju, Korea and was used to determine the concentrations of mass, water-soluble organic carbon (WSOC) and ionic species. Furthermore, black carbon (BC) concentrations were observed with an aethalometer. The entire sampling period was classified into four periods, i.e., typical, pollution event I, pollution event II, and an Asian dust event. Stable meteorological conditions (e.g., low wind speed, high surface pressure, and high relative humidity) observed during the two pollution events led to accumulation of aerosol particles and increased formation of secondary organic and inorganic aerosol species, thus causing $PM_{2.5}$ increase. Furthermore, these stable conditions resulted in the predominant condensation or droplet mode size distributions of PM, WSOC, $NO_3{^-}$, and $SO{_4}^{2-}$. However, difference in the accumulation mode size distributions of secondary water-soluble species between pollution events I and II could be attributed to the difference in transport pathways of air masses from high-pollution regions and the formation processes for the secondary chemical species. The average absorption ${\AA}ngstr{\ddot{o}}m$ exponent ($AAE_{370-950}$) for 370-950 nm wavelengths > 1.0 indicates that the BC particles from traffic emissions were likely mixed with light absorbing brown carbon (BrC) from biomass burning (BB) emissions. It was found that light absorption by BrC in the near UV range was affected by both secondary organic aerosol and BB emissions. Overall, the pollution events observed during fall at the study site can be due to the synergy of unfavorable meteorological conditions, enhanced secondary formation, local emissions, and long-range transportation of air masses from upwind polluted areas.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.4
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• pp.307-313
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• 2019

The traveling wave tube amplifier (TWTA), which can be applied to the Ka-band millimeter-wave multi-mode seeker, consists of an high voltage power supply(HVPS), a grid modulator, a command and control, and an RF assembly. We designed a power supply that generates a -17.9 kV high voltage by synchronizing the pulse repetition frequency(PRF) and power supply switching frequency(i.e. synchronization frequency), and a high-speed grid-switching modulator for RF pulse modulation. The TWTA, which is fabricated through miniaturization with a volume of 3.18 L, has high pulse switching characteristics of up to 18.5 ns. The maximum rise/fall time of the grid on/bias signal and peak power is more than 564.9 W. Moreover, an excellent spurious performance of -68.4 dBc or less was confirmed within the range of PRF and PRF/2.