• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.401-402
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• 2007

The preparation and characteristics of ITO anode films grown using a linear facing target sputtering (FTS) technique for use in organic light emitting diodes (OLED) and flexible OLED is described. The electrical, optical, and work function of the ITO anode, which was prepared by linear FTS at room temperature, were comparable to those of commercial ITO anode films. In particular, linear FTS-grown ITO films shows very smooth surface without defects such as pin hole and cracks due to low substrate temperature. Furthermore OLED with the linear FTS-grown ITO anode film shows comparable electrical and optical properties to those of OLED with the commercial crystalline-ITO anode film. This suggested that linear FTS is promising thin film technology for preparing high quality anode film in OLEDs and flexible OLEDs.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.7
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• pp.698-703
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• 2007

In this paper, a novel impedance tuner using a directional coupler is proposed. The design topology is analyzed by signal flow graph(SFG) and shows advantages compared with conventional single and double stub methods from the view points of easy implementation and wide tuning range, respectively. This impedance tuner consists of ten switches and its $2^{10}$ tuning points are distributed uniformly on the whole Smith chart. The measured maximum magnitude of the reflection coefficient is 0.9. And the fabricated impedance tuner has a wide bandwidth from 1.8 to 2.2 GHz. Using this impedance tuner, we did a load-pull measurement of a power transistor.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.1
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• pp.85-91
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• 2010

In this paper, a new microstrip antenna using asymmetric U-shaped slotted ground is proposed for a switchable circular polarization sense. The proposed antenna is achieved a circularly polarization from orthogonal E-field distributions with 90 degree phase difference due to the asymmetrical U-shaped slot. Moreover, the circular polarization sense of the proposed antenna can be easily switchable with changing the symmetric plane of the U-shaped slots. As a result, the proposed antenna is implemented by two PIN diodes with two different bias condition for ON/OFF states. The measured axial ratios are about 1.5 dB without the dependence of the polarization sense and 3-dB axial ratio bandwidth are achieved 29 MHz with respect to about 1.2 % at 2.46 GHz operating frequency.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.12
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• pp.1337-1342
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• 2012

In this paper, we propose a novel reconfigurable antenna that can change the electrical shape of the matching network using RF switches of PIN diodes. The designed antenna operates at two different modes that are Mode 1 (HSDPA band, 2.1~2.2 GHz) and Mode 2(WiBro WiFi band, 2.3~2.5 GHz). The antenna is built on both sides of a polyarcylate substrate. The measured reflection coefficient shows a matching bandwidth of 547 MHz($S_{11}$ <-3 dB, 2.035~2.582 GHz) for Mode 1 and 600 MHz($S_{11}$ <-3 dB, 2.2~2.8 GHz) for Mode 2, and it shows average vertical gains of -4.4 dBi and -4.5 dBi in x-y plane, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.3
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• pp.241-245
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• 2022

In this study, we measured and comparatively analyzed the characteristics of MPS (Merged Pin Schottky) diodes in 4H-SiC by changing the areal ratio between the Schottky and PN junction region. Increasing the temperature from 298 K to 473 K resulted in the threshold voltage shifting from 0.8 V to 0.5 V. A wider Schottky region indicates a lower on-resistance and a faster turn-on. The effective barrier height was smaller for a wider Schottky region. Additionally, the depletion layer became smaller under the influence of the reduced effective barrier height. The wider Schottky region resulted in the ideality factor being reduced from 1.37 to 1.01, which is closer to an ideal device. The leakage saturation current increased with the widening Schottky region, resulting in a 1.38 times to 2.09 times larger leakage current.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.7
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• pp.4842-4848
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• 2015

This paper presents a comparison of communication performance between the reconfigurable beam-steering antenna and the omni-directional (loop) antenna during standstill and walking motion. Both omni-directional and reconfigurable antennas were manufactured on the same fabric (${\varepsilon}_r=1.35$, $tqn{\delta}=0.02$) substrate and operated around 5 GHz band. The reconfigurable antenna was designed to steer the beam directions. To implement the beam-steering capability, the antenna used two PIN diodes. The measured peak gains were 5.9-6.6 dBi and the overall half power beam width (HPBW) was $102^{\circ}$. In order to compare the communication efficiency, both the bit error rate (BER) and the signal-to-noise ratio (SNR) were measured using a GNU Radio Companion software tool and user software radio peripheral (USRP) devices. The measurement were performed when both antennas were standstill and walking motion in an antenna chamber as well as in a smart home environment. From these results, the performances of the reconfigurable beam steering antenna outperformed that of the loop antenna. In addition, in terms of communication efficiencies, in an antenna chamber was better than in a smart home environment. In terms of movement of antennas, standstill state has better results than walking motion state.