• 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.

• ETRI Journal
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• v.40 no.2
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• pp.188-196
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• 2018

This paper presents a pulse radar system to detect drones based on a target fluctuation model, specifically the Swerling target model. Because drones are small atypical objects and are mainly composed of non-conducting materials, their radar cross-section value is low and fluctuating. Therefore, determining the target fluctuation model and applying a proper integration method are important. The proposed system is herein experimentally verified and the results are discussed. A prototype design of the pulse radar system is based on radar equations. It adopts three different pulse modes and a coherent pulse integration to ensure a high signal-to-noise ratio. Outdoor measurements are performed with a prototype radar system to detect Doppler frequencies from both the drone frame and blades. The results indicate that the drone frame and blades are detected within an instrumental maximum range. Additionally, the results show that the drone's frame and blades are close to the Swerling 3 and 4 target models, respectively. By the analysis of the Swerling target models, proper integration methods for detecting drones are verified and can thus contribute to increasing in detectability.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.9
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• pp.25-30
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• 2004

In this Paper, the 0.1 w InGaAs/InAlAs/GaAs Metamorphic HEMT, which is applicable to MIMIC, and a 100 GHz MIMIC amplifier were designed and fabricated. The DC characteristics of MHEMT are 640 mA/mm of drain current density, 653 mS/mm of maximum transconductance. The current gain cut-off frequency(fT) is 173 GHz and the maximum oscillation frequency(fmax) is 271 GHz. A 100 GHz amplifier was designed using 0.1${\mu}{\textrm}{m}$ MHEMT and CPW technology. The measured results from the 100 GHz MIMIC amplifiers show good S21 gain of 10.1 dB and 12.74 dB at 100 GHz and 97.8 GHz, respectively.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.12
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• pp.25-35
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• 2001

In order to analyze the electrical characteristics of complicated thin film transistor-liquid crystal display (TFT-LCD) array circuits, it is indispensible to use simulation programs such as PSPICE and AIM-SPICE. In this paper, we present a systematic method of extracting the input parameters of poly-Si TFT for SPICE simulations. This method was applied to two different types of poly-Si TFTs, fabricated by excimer laser annealing and silicide mediated crystallization methods, and yielded good fitting results to experimental data. Among the SPICE simulators, PSPICE has the graphic user interface feature making the composition of complicated circuits easier. We added successfully a poly-Si TFT device model to the PSPICE simulator, and analyzed easily the electrical characteristics of pixels considering the line RC delay. The results of this work would contribute to efficient simulations of poly-Si TFT-LCD arrays.

• JSTS:Journal of Semiconductor Technology and Science
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• v.4 no.3
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• pp.189-195
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• 2004

A 10 Gb/s limiting amplifier IC with the emitter area of $1.5{\times}10{\mu}m^2$ for optical transmission system was designed and fabricated with a AIGaAs/GaAs HBTs technology. In this stud)', we evaluated fine pitch bump using WL-CSP (Wafer Level-Chip Scale Packaging) instead of conventional wire bonding for interconnection. For this we developed WL-CSP process and formed fine pitch solder bump with the $40{\mu}m$ diameter and $100{\mu}m$ pitch on bonding pad. To study the effect of WL-CSP, electrical performance was measured and analyzed in wafer and package module using WL-CSP. In a package module, clear and wide eye diagram openings were observed and the riselfall times were about 100ps, and the output" oltage swing was limited to $600mV_{p-p}$ with input voltage ranging from 50 to 500m V. The Small signal gains in wafer and package module were 15.56dB and 14.99dB respectively. It was found that the difference of small signal gain in wafer and package module was less then 0.57dB up to 10GHz and the characteristics of return loss was improved by 5dB in package module. This is due to the short interconnection length by WL-CSP. So, WL-CSP process can be used for millimeter wave GaAs MMIC with the fine pitch pad.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.583-586
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• 2005

In this paper, millimeter-wave monolithic integrated circuit (MIMIC) low noise amplifier (LNA) for V-band, which is applicable to 58 GHz, we designed and fabricated. We fabricated the module using the fabricated LNA chips. The V-band MIMIC LNA was fabricated using the high performance $0.1\;{\mu}\;m$ ${\Gamma}-gate$ pseudomorphic high electron mobility transistor (PHEMT). The MIMIC LNA was designed using active and passive device library, which is composed $0.1\;{\mu}\;m$ ${\Gamma}-gate$ PHEMT and coplanar waveguide (CPW) technology. The designed V-band MIMIC LNA was fabricated using integrated unit processes of active and passive device. Also we fabricated CPW-to-waveguide fin-line transition of WR-15 type for module. The Transmission Line was fabricated using RT Duroid 5880 substrate. The measured results of V-band MIMIC LNA and Module are shown $S_{21}$ gain of 13.1 dB and 8.3 dB at 58 GHz, respectively. The fabricated LNA chip and Module in this work show a good noise figure of 3.6 dB and 5.6 dB at 58 GHz, respectively.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.4
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• pp.185-190
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• 2015

In this paper we characterized and designed the waveguide antipodal finline transition at 57-65GHz frequency band in V-band for 5G mobile communication systems. Especially, we proposed the design method of spline taper for finline tapers by means of increasing curvature from linear taper. We could perform optimization more effectively by excluding improper regions for optimal performance from optimization using the method. Return losses and insertion losses of antipodal finline transitions were mainly affected by the taper shape of the finline. The resonances in the structure of the finline transition were the strongest enemies who deteriorate the performance of the transition. And we alleviated the resonances using semicircle shaped patch. The designed antipodal finline transition showed good performance as it showed less than -24.2dB of return loss and -0.24dB of insertion loss in the band(57-65GHz) which we suppose to use.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.6
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• pp.401-406
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• 2018

In this paper, we present E-band bond-wire modeling and a matching network to compensate for the effect of the bond-wire. The impedance of the bond-wires is extracted using three-dimensional electromagnetic simulation. The matching network was designed using a simple structure. The implemented matching network was verified with a commercial 71~81 GHz LNA IC and an interconnection based on the WR-12 waveguide. The matching network increases the transmission coefficient of the system by up to 4.5 dB, power gain by up to 3.12 dB, $P_{1dB}$ by up to 2.2 dB, and improves the gain flatness by ${\pm}1.07dB$.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.1
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• pp.11-17
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• 2017

In this paper, an 8-direction switched beamforming antenna system at 28GHz frequency band is described for 5th generation wireless communication. This system is composed of an $8{\times}8$ Butler matrix and an 8-element patch array antenna. The antenna system switches beams in 8-direction in the wide range of ${\pm}40^{\circ}$. The antenna spacing is $0.65{\lambda}$ to achieve ${\pm}40^{\circ}$ steering range. Designed results show that the 8-direction beams are placed at ${\pm}6^{\circ}$, ${\pm}17^{\circ}$, ${\pm}28^{\circ}$, ${\pm}40^{\circ}$ offset from the center. Parasitic radiation effect from the large dimension Butler matrix need to be suppressed by employing a stripline structure.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.9
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• pp.1699-1709
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• 2015

Moving terminals like high-speed-train undergo high Doppler frequency shift, and this leads to carrier frequency offsets that have to be compensated to avoid degradation of communication performance. In multiple access mechanism like OFDMA, base-stations need complex hardware to compensate the uplink frequency offset. In this paper, we propose a method, which can reduce burden of the base-station and makes frequency offset estimation and compensation simple. This method contains transmitting new synchronization signal, estimating frequency offsets in base-station, transmitting feedback information to terminal, and compensating the offset in uplink transmission. Simulation results show the proposed method operates well in high Doppler frequency shift conditions of 500 km/h which is the requirements of 5G mobile communication.