• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.4
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• pp.282-285
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• 2019

A 100-nm gate-length metamorphic high electron mobility transistor(mHEMT) with a T-shaped gate was fabricated using a two-step gate recess and characterized for DC and microwave performance. The mHEMT device exhibited DC output characteristics having drain current($I_{dss}$), an extrinsic transconductance($g_m$) of 1,090 mS/mm and a threshold voltage($V_{th}$) of -0.65 V. The $f_T$ and $f_{max}$ obtained for the 100-nm mHEMT device were 190 and 260 GHz, respectively. The developed mHEMT will be applied in fabricating W-band monolithic microwave integrated circuits(MMICs).

• Journal of the Semiconductor & Display Technology
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• v.9 no.1
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• pp.29-33
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• 2010

Recently, the growth of ZnO thin film on glass substrate has been investigated extensively for transparent thin film transistor. We have studied the phase transition of ZnO thin films from metal to semiconductor by changing RF power in the deposition process by RF magnetron sputtering system. The structural, electric, and optical properties of the ZnO thin films were investigated. The film deposited with 75 watt of RF power showed n-type semiconductor characteristic having suitable resistivity $-3.56\;{\times}\;10^{+1}\;{\Omega}cm$, carrier concentration $-2.8\;{\times}\;10^{17}\;cm^{-3}$, and mobility $-0.613\;cm^2V^{-1}s^{-1}$ while other films by 25, 50, 100 watt of RF power closed to metallic films. From the surface analysis (AFM), the number of crystal grain of ZnO thin film increased as RF power increased. The transmittance of the film was over 88% in the visible region regardless of the change in RF power.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.1
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• pp.20-23
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• 2004

In this paper, the emission properties of electrodeless fluorescent lamp were discussed using the inductively coupled plasma. To transmit the electromagnetic energy into the chamber, a RF power of 13.56 [MHz] was applied to the antenna and considering the Ar gas pressure and the RF electric power change, the emission spectrum, Ar I line, luminance were investigated. At this time, the input parameter for ICP RF plasma, Ar gas pressure and RF power were applied in the range of 10∼60 [mTorr], 10∼300 [W], respectively. From emission intensity and lumnance intensity results, the mode transition from E-mode to H-mode was observed. This implies that this method can be used to find an optimal RF power for efficient light illumination in an electrodeless fluorescent lamp.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.180-182
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• 1994

In an electron storage ring of Pohang Light Source (PLS), electrons lose their energy in every turn by the synchronous radiation. A high power RF amplifier is employed to compensate the electron energy that is lost by the synchronous radiation. The specification of RF amplifier is an continuous output power of 60 kW at 500.082 MHz operating frequency. The power is supplied to RF cavities in the storage ring tunnel. Total number of amplifier system currently required is three. Tile total number will be increased upto five as the operating condition of storage ring is upgraded. The RF amplifier is mainly consisted of a high voltage DC power supply, an intermediate RF power amplifier (IPA), and a klystron tube. In this article, the design of RF amplifier system and characteristics of the klystron tube will be discussed.

• Journal of IKEEE
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• v.12 no.2
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• pp.75-80
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• 2008

There are many researches to reduce power consumption of battery-operated Transceiver for 2.4 GHz smartRF applications. However, components such as processor, memory and LCD based power managements reach the limit of reducing power consumption. To overcome the limit, this research proposes novel low-power Transceiver and transceiver Hardware Design. Experimental results in the real smartRF Transceiver show that the proposed methods can reduce power consumption additionally than component based power managements.

• Korean Journal of Materials Research
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• v.23 no.3
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• pp.161-167
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• 2013

The ZnO thin films were grown on GaN template substrates by RF magnetron sputtering at different RF powers and n-ZnO/p-GaN heterojunction LEDs were fabricated to investigate the effect of the RF power on the characteristics of the n-ZnO/p-GaN LEDs. For the growth of the ZnO thin films, the substrate temperature was kept constant at $200^{\circ}C$ and the RF power was varied within the range of 200 to 500W at different growth times to deposit films of 100 nm thick. The electrical, optical and structural properties of ZnO thin films were investigated by ellipsometry, X-ray diffraction (XRD), atomic force microscopy (AFM), photoluminescence (PL) and by assessing the Hall effect. The characteristics of the n-ZnO/p-GaN LEDs were evaluated by current-voltage (I-V) and electroluminescence (EL) measurements. ZnO thin films were grown with a preferred c-axis orientation along the (0002) plane. The XRD peaks shifted to low angles and the surface roughness became non-uniform with an increase in the RF power. Also, the PL emission peak was red-shifted. The carrier density and the mobility decreased with the RF power. For the n-ZnO/p-GaN LED, the forward current at 20 V decreased and the threshold voltage increased with the RF power. The EL emission peak was observed at approximately 435 nm and the luminescence intensity decreased. Consequently, the crystallinity of the ZnO thin films grown with RF sputtering powers were improved. However, excess Zn affected the structural, electrical and optical properties of the ZnO thin films when the optimal RF power was exceeded. This excess RF power will degrade the characteristics of light emitting devices.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.10
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• pp.779-787
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• 2017

In this paper, we designed a RF transceiver for small unmanned aerial vehicle(UAV) using power switching method. To apply for the UAV, several characteristics such as size, weight, and power consumption are very important. To reduce power consumption, we propose a new power switching method. Using the proposed method, we fabricated the RF transceiver needed to establish the data link for a small UAV. The fabricated RF transceiver shows an output power of +25 dBm, a noise figure of 4.56 dB and a received signal strength of -100 dBm. By performing power measurement of proposed switching method, 25 % of power could be reduced. The size of the fabricated RF transceiver is $100{\times}60{\times}5.7mm^3$ and the weight is as small as 38 g.

• Proceedings of the KIEE Conference
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• summer
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• pp.1263-1265
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• 2004

RF-ID system is one of the very interesting field not only in a technical and economical point of view but also that people are still trying to realize lossless power transmission. This paper has a purpose on the efficient power transmission at the passive type IDcard by using wireless power transmission system. The most difficult but important part of the passive type RF-ID system is building the system that supplies power from Reader-antenna to IDcard-antenna. To check what is the most efficient way to deliver power depending on what kind of specifications of the power-amp in reader, antenna and antenna in IDcard is for operating IDcard circuit efficiently receiving the power from reader-antenna. For this, we used 125kHz sinewave for RF signal as a basic specification, OP-amp for amplifying signal and power-amp for amplifying power, loop type antenna.

• The Journal of the Korea institute of electronic communication sciences
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• v.3 no.4
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• pp.282-288
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• 2008

In this paper, the Passive Intermodulation Distortion(PIMD) of high power RF Filter is measured with filter inner coating materials and we suggest how to reduced the PIMD of RF filter coating methods. According to the standard measurement regulation by IEC, the Passive Intermodulation Distortion of Wibro relay high power filter are measured. We suggest the coating materials and coating methods of high power filter inner structure to reduce the PIMD generating by insert loss and worse flatness of filter delay in the design of Wibro high power filter efficiently.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.5
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• pp.560-566
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• 2004

In this paper, the electrical and emission properties of electrodeless fluorescent lamp were discussed using the inductively coupled plasma (ICP) with the variation of argon gas pressure and RF power. The RF output was applied to the antenna in the range of 5∼50 W at 13.56 MHz. The internal plasma voltage of the chamber and the probe current were measured while varying the supply voltage to the Langmuir probe in the range of －100V∼＋100V. When the pressure of argon gas was increased, electric current was decreased. There was a significant electric current increase from 10 to 30 W. Also, when the RF power was increased, electron density was increased. Also, the emission spectrum, Ar- I lins, luminance were investigated. At this time, the input parameter for ICP RF plasma, Ar gas pressure and RF power were applied in the range of 10∼60 mTorr, 10∼300 W, respectively. This implies that this method can be used to find an optimal RF power for efficient light illumination in an electrodeless fluorescent lamp.