• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2000.11a
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• pp.179-182
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• 2000

BWLL용 Ka-Band MMIC 저잡음 증폭기 칩을 InGaAs/GaAs 0.15um Gate 길이의 p-HEMT 공정을 이용하여 개발하였다. 칩 크기 2.5$\times$1.5$\textrm{mm}^2$의 2단으로 설계된 칩의 On-wafer 측정 결과, 24～27 GHz BWLL 주파수 대역에서 최소 19$\pm$0.2dB 이득과 최대 1.7dB의 잡음 지수와 최소 13dB의 반사손실의 특성을 얻었다.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.5
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• pp.675-681
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• 2016

A 41dB gain control range $6^{th}$-order band-pass receiver front-end (RFE) using CMOS switched frequency translated impedance (FTI) is presented in a 40 nm CMOS technology. The RFE consists of a frequency tunable RF band-pass filter (BPF), IQ gm cells, and IQ TIAs. The RF BPF has wide gain control range preserving constant filter Q and pass band flatness due to proposed pre-distortion scheme. Also, the RF filter using CMOS switches in FTI blocks shows low clock leakage to signal nodes, and results in low common mode noise and stable operation. The baseband IQ signals are generated by combining baseband Gm cells which receives 8-phase signal outputs down-converted at last stage of FTIs in the RF BPF. The measured results of the RFE show 36.4 dB gain and 6.3 dB NF at maximum gain mode. The pass-band IIP3 and out-band IIP3@20 MHz offset are -10 dBm and +12.6 dBm at maximum gain mode, and +14 dBm and +20.5 dBm at minimum gain mode, respectively. With a 1.2 V power supply, the current consumption of the overall RFE is 40 mA at 500 MHz carrier frequency.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.4
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• pp.811-817
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• 2014

In this paper, a design method for a dual-band monopole antenna operating in the bands of 2.45 GHz WLAN and UWB is studied. A monopole antenna operating in UWB band is first designed, and a slot is inserted on the monopole to operate in 2.45 GHz WLAN band. The optimized dual-band monopole antenna is fabricated on an FR4 substrate, and the experimental results show that the antenna has a dual-band characterisitc in WLAN and UWB bands with the frequency bands of 2.35-2.50 GHz and 2.99-11.82 GHz for a VSWR < 2. Measured gain is 1 dBi at 2.45 GHz, and ranges 1.5-4.6 dBi in the frequency band of 3.1-10.6 GHz.

• Journal of IKEEE
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• v.23 no.1
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• pp.181-187
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• 2019

In this paper, we demonstrated a power amplifier monolithic microwave integrated circuit (MMIC) for X-band radar applications. It utilizes commercial $0.25{\mu}m$ GaN-based high electron mobility transistor (HEMT) technology and delivers more than 20 W of output power. The developed GaN-based power amplifier MMIC has small signal gain of over 22 dB and saturated output power of over 43.3 dBm (21.38 W) in a pulse operation mode with pulse width of $200{\mu}s$ and duty cycle of 4% over the entire band of 9 to 10 GHz. The chip dimensions are $3.5mm{\times}2.3mm$, generating the output power density of $2.71W/mm^2$. Its power added efficiency (PAE) is 42.6-50.7% in the frequency bandwidth from 9 to 10 GHz. The developed GaN-based power amplifier MMIC is expected to be applied in a variety of X-band radar applications.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.5
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• pp.69-74
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• 2010

In this paper, we proposed a compact arbitrary dual-band band-stop filter using CRLH transmission line. The proposed filter used CRLH transmission line as stub and it developed dual-band band-stop characteristics using non-linear phase response of CRLH transmission line. The size of proposed filter is compact. And it can control arbitrary dual stop band. In this paper, designed band-stop filter at GPS band and ISM band As result, the S(2,1) is about -30dB at GPS band and about -29dB at ISM band. The fabricated filter is very compact. Its dimension is 10mm*15mm.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.1
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• pp.25-30
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• 2017

In this paper, dual band patch antenna was designed using a CSRR structure with negative values permeability which inserted into the ground plane. We propose an antenna that can be used in dual band f1(1.53GHz) and f2(1.63GHz) for satellite communications by using the CSRR placed on the backside of feeding line, which is a negative shape of SRR. The proposed antenna can be arrayed using microstrip line and can be made smaller than conventional patch antenna. The fabricated antenna has the input reflection coefficient of -12.5dB and -14.5dB at f1 and f2, and the gain of 2dB and -0.8dB, respectively. and it was confirmed that the performance was sufficient in the dual-band.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.5
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• pp.943-948
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• 2018

In this paper, SSPA Module for X-band radar was designed and fabricated by using GaN MMIC. For the purpose of configuring the high power SSPA module, the drive steamers are composed of 2-layers of GaN MMIC with considering Gain Loss. In addition, the power divider and power combiner used a 4way approach by designing a 4-stage power amplifier. The power divider has a loss of -3.0dB or more, and the I/O has a loss of -0.2dB in the power combiner and the phase difference between the ports are good at $2^{\circ}$ on average. The fabricated SSPA module got the measurement results that satisfy a Gain 48dB, P(sat)=88.3W(49.46 dBm), PAE=30.3% or more efficiency in condition of frequency range 9~10GHz. The fabricated X-Band SSPA module can be applied in RF performance improvement for SSPA module whit improvement of power divider/combiner.

• Journal of electromagnetic engineering and science
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• v.15 no.1
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• pp.6-13
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• 2015

In this paper, a novel monopole antenna for WLAN/WiMAX application is presented. The proposed antenna consists of two arc-shaped strips, a vertical strip, and a slot in the ground plane. In this study, a prototype of the proposed triple-band antenna was designed, fabricated, and tested. The quantitative and experimental results demonstrate that the proposed antenna satisfy the -10 dB impedance bandwidth requirement of 440 MHz for 2.4/2.5 GHz bands (from 2.26 to 2.70 GHz), 970 MHz for 3.5 GHz bands (from 3.27 to 4.24 GHz), and 870 MHz for the GHz bands (from 5.08 to 5.95 GHz), while simultaneously covering the WLAN and WiMAX bands. In addition, the presented triple-band antenna has an omnidirectional radiation pattern at all three frequency bands with an antenna gain of 4.45 dBi for the lowest band, 2.04 dBi for the middle band, and 3.98 dBi for the highest band.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.4 s.119
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• pp.358-363
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• 2007

The multi-band and wide-band antenna for a portable broadcasting terminal is proposed. The proposed antenna consists of two radiators with a parallel structure. The antenna has an enough wide impedance bandwidth for the DVB-H(Digital Video Broadcasting-Handheld) service band since two radiators have adjacent resonance frequencies and operates in the DAB(Digital Audio Broadcasting) service band using the third harmonic of the radiator 1. The fabricated antenna has VSWR characteristics of less than 2:1 in the frequency band $470{\sim}740\;MHz$ for DVB-H and $1,450{\sim}1,480\;MHz$ for DAB. The measured peak gain of the antenna is $1.97{\sim}4.10\;dBi$ in the DVB-H band and $1.98{\sim}2.04\;dBi$ in the DAB band.

• Ceramist
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• v.22 no.4
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• pp.350-356
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• 2019

Recently, transition metal dichalcogenide (TMDC) monolayers have been the subject of research exploring the physical phenomenon generated by low dimensionality and high symmetry. One of the keys to understanding new physical observations is the electronic band structure of 2D TMDCs. Angle-resolved photoelectron spectroscopy (ARPES) is, to this point, the best technique for obtaining information on the electronic structure of 2D TMDCs. However, through ARPES research, obtaining the long-range well-ordered single crystal samples always proves a challenging and obstacle presenting issue, which has been limiting towards measuring the electronic band structures of samples. This is particularly true in general 2D TMDCs cases. Here, we introduce the approach, with a mathematical framework, to overcome such ARPES limitations by employing the high level of symmetry of 2D TMDCs. Their high symmetry enables measurement of the clear and sharp electronic band dispersion, which is dominated by the band dispersion of single-crystal TMDCs along the two high symmetry directions Γ-K and Γ-M. In addition, we present two important studies and observations for the direct measuring of the exciton binding energy and charge transfer of 2D TMDCs, both being established by the above novel approach.