• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.7
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• pp.944-950
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• 1993

Diodes and GaAs have been commonly used in a mixer design until recently. However, diodes are not preferred to use at the front-end of DBS receiver due to the conversion loss large noise. HEMT has larger conversion gain and better noise characteristics comparing with GaAs MESFET. This paper describes the design procedure, structure, and performance of a mixer, utilizaing HEMT designed by OKI Co. . A mixer configuration in which the local oscillator(LO) signal is applied to the gate is used. When the LO power is 0.01 dBm, the conversion gain of 3.7dB is obtained at IF and the 3 dB bandwidth is 400MMz.

• Korean Journal of Materials Research
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• v.2 no.5
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• pp.360-365
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• 1992

Ga-doped polycrystalline ZnO films on glass substrates were prepared by sputtering the targets, which had been prepared by sintering discs consisting of ZnO powder and various amounts of G$a_2O_3$, to investigate the effects of gallium doping and sputtering conditions on electrical properties. Optimizing the RF power density, argon gas pressure and gallium content, transparent Ga-doped ZnO films with resistivity less than 1$0^{-3}$ohm-cm are obtained. Electron concentration of undoped and Ga-doped ZnO films are order of $10^{18}$, $10^{21}$/c$m^2$respectively. After heat treatment in air and $N_2atmosphere, $ the resistivity of Ga-doped ZnO films increases by about two orders of magnitude. The optical transmission is above 80% in the visible range and the optical band widens as the Ga content increases.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.3
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• pp.253-260
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• 2024

In this study, ITO thin films were fabricated on a glass substrate at different thicknesses without introducing oxygen using RF sputtering system. The structural, electrical, and optical properties were evaluated at various thicknesses ranging from 50 to 300 mm. As the thickness of deposited ITO thin film become thicker from 50 to 100 mm, carrier concentration, mobility, and band gap energy also increased while the resistivity and transmittance decreased in the visible light region. When the film thickness increased from 100 to 300 mm, the carrier concentration, mobility, and band gap energy decreased while the resistivity and transmittance increased. The optimum electrical properties were obtained for the ITO film 100 nm. After optimizing the thickness, the ITO thin films were post-annealed at different temperatures ranging from 100 to 300℃. As the annealing temperature increased, the ITO crystal phase became clearer and the grain size also increased. In particular, the ITO thin film annealed at 300℃ indicated high carrier concentration (4.32 × 10²¹ cm^-3), mobility (9.01 cm²/V·s) and low resistivity (6.22 × 10^-4 Ω·cm). This means that the optimal post-annealing temperature is 300℃ and this ITO thin film is suitable for use in solar cells and display application.

• Journal of electromagnetic engineering and science
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• v.8 no.3
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• pp.96-99
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• 2008

This paper describes a $0.13-{\mu}m$ CMOS RF switch for $3{\sim}5$ GHz UWB band(mode 1). It can improve isolation characteristics between ports by using deep n-well RF devices while their source and body terminals are separated. From the measurement results, the proposed T/R switch is comparative to the on-wafer probing measurement results of the series-shunt T/R switches. When the proposed T/R switch operates as Tx mode, measured insertion loss from Tx to output port is less than 1.5 dB and isolation between Tx and Rx is more than 27 dB for $3{\sim}5$ GHz. Return loss for the Tx port is more than -10 dB and input P1dB is +10 dBm.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.4 no.3 s.8
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• pp.45-50
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• 2005

In this paper, a broadband single balanced mixer is presented using a wideband rat-race implementation by vertical coupling. Frequency is selected as $1.5{\sim}3$ GHz for RF, $1.64{\sim}3.14$ GHz for LO, and 140 MHz for IF signals. When LO signal with 6 dBm at 2.7 GHz is injected, a conversion loss of 7.5 dB and RF to LO isolation of 30 dB are obtained. Also, an average conversion loss of 10 dB, RF to LO isolation of 30 dB, and LO to IF isolation of 45 dB are obtained for frequency band of $1.5{\sim}3$ GHz.

• Journal of electromagnetic engineering and science
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• v.3 no.2
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• pp.86-90
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• 2003

A flat conversion loss in microwave mixer is hard to achieve if integrating with an image rejection filter(IRF). This is due to the change of termination condition with respect to the LO and IF frequency at RF port where the filter has 50 ohm termination property only in the RF band. This paper describes a flatness maintenance in the down mixer concerning a diode matching condition as well as an electrical length of embedding line at RF port. The implemented single balance diode mixer is suitable for a 23 ㎓ European Terrestrial Radio. RF, LO and fixed IF frequency chosen in this paper are 21.2∼22.4 ㎓, 22.4∼23.6 ㎓ and 1.2 ㎓, respectively. The measured results show a conversion loss of 8.5 ㏈, flatness of 1.2 ㏈ p-p, input P1㏈ of 7㏈m, IIP3 of 15.42 ㏈m with nominal LO power level of 10㏈m. The return loss of RF and LO port are less than - 15 ㏈ and - 12 ㏈, respectively and IF port is less than - 6 ㏈. LO/RF and LO/IF isolation are 18 ㏈ and 50 ㏈, respectively. This approach would be a helpful reference for designing up/down converter possessing a filtering element.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.710-713
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• 2004

The design, simulation, modeling and measurement of a low temperature co-fired ceramic (LTCC) RF switch module for GSM applications is presented in this paper. RF switch module is constructed using a Rx/Tx switching circuit and integrated low pass filter. The low pass filter function was designed to operate in th GSM band. Insertion and return loss of the low pass filter were designed less than 0.3 dB and better than 12.7 dB at 900 MHz. The RF switch module contained 10 embedded passives and 3 surface mount components integrated on $4.6{\times}4.8{\times}1.2$ nm, 6-layer multi-layer integrated circuit. The insertion loss of switch module was measured at 900 MHz was 11 dB.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.6
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• pp.1143-1150
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• 2001

In this paper, we designed a downconverter for K-band satellite multipoint distribution service(SMDS). The designed downconverter consists of a low noise amplifiers, bandpass filter, stable local oscillator, drain mixer and If Amplifiers. Low noise amplifiers show 28㏈ gain and 1.5㏈ noise figure in the frequency range of 19.2㎓~20.2㎓, and a band pass filter has a -l㏈ insertion loss, and 18.25㎓ Stable local oscillator which is dielectric resonant oscillation, We obtained that the output power of the 18.25㎓ oscillation frequency is 0.5㏈m and the phase noise is the -84.67㏈c at 10KHz offset frequency. With the input RF signal the 19.2㎓~20.2㎓, conversion gain of the drain mixer shows 5㏈ at the Intermediate frequency range of 950MHz~1950MHz. We have proved that the designed downconverter satisfied the specification of a K-band satellite multipoint distribution service and it can be applied to the satellite internet receiver.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.5
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• pp.488-493
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• 2023

The effect of sputtering power on the amorphous Ga₂O₃ thin film deposited using the radio frequency sputtering system was evaluated. Amorphous Ga₂O₃ is cheaper and more efficiently fabricated than crystalline Ga₂O₃, and is studied in various fields such as RRAM, photodetector, and flexible devices. In this study, amorphous Ga₂O₃ was deposited by radio frequency sputtering system and represented a transmittance of over 80% in the visible light region and a homogeneous and dense surface. The optical band gap energy decreased as the sputtering power increased owing to the quantum size effect. Thus, the specific band gap of amorphous Ga₂O₃ can be obtained by adjusting the sputtering power, it indicates amorphous Ga₂O₃ can be used in various fields.

• Korean Journal of Food Science and Technology
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• v.29 no.3
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• pp.595-600
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• 1997

The antioxidant activity of the solvent fractions extracted from onion skin was examined. The antioxidant activity of methanol extract at the cencentration of 0.02% and 0.03% was stronger than that of mixed tocopherol. The antioxidant activity of the fractions of methanol extract increased in the order of butanol> ethyl acetate> ethyl ether> water fraction. The antioxidant activity of each fractions was strongly related with total phenol content and HDA. Further separation of butanol fraction by TLC yielded 6 fluorescent bands with Rf values of 0.20, 0.33, 0.49, 0.60 and 0.94. The total phenol content and HDA of fluorescent band, Rf 0.96, were remarkable higher than those of the other band and exhibited a strong UV absorption at 255 nm and 317 nm, which would be specifically produced by flavonol. Spectral analyses indicated that the major antioxidant component was quercetin aglycone (3,3',4',5,7-pentahydroxyflavone).