• Journal of Navigation and Port Research
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• v.27 no.1
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• pp.81-86
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• 2003

In the paper, the power amplifier using active biasing for LDMOS MRF-21060 is designed and fabricated. Driving amplifier using AH1 and parallel power amplifier AH11 is made to drive the LDMOS MRF 21060 power amplifier. The variation of current consumption in the fabricated 5 Watt power amplifier has an excellent characteristics of less than 0.1A, whereas passive biasing circuit dissipate more than 0.5A. The implemented power amplifier has the gain over 12 dB, the gain flatness of less than $\pm$0.09dB and input and output return loss of less than -19dB over the frequency range 2.11~2.17GHz. The DC operation point of this power amplifier at temperature variation from $0^{\circ}C$ to $60^{\circ}C$ is fixed by active circuit.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.9
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• pp.673-684
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• 2003

A degenerated differential pair has been widely used as a standard topology for digitally programmable CMOS VGAs. A variable degeneration resistor has been implemented using a resistor string or R-2R ladder with MOSFET switches. However, in the VGAs using these conventional methods, low-voltage and high-speed operation is very hard to achieve due to the dc voltage drop over the degeneration resistor. To overcome this problem a new variable degeneration resistor is proposed where the dc voltage drop is almost removed. Using the proposed gain control scheme, a low-voltage and high-speed CMOS VGA is designed. HSPICE simulation results using a 0.25${\mu}{\textrm}{m}$ CMOS process parameters show that the designed VGA provides a 3dB bandwidth of 360MHz and a 80dB gain control range in 2dB step. Gain errors are less than 0.4dB at 200MHz and less than l.4dB at 300MHz. The designed circuit consumes 10.8mA from a 2.5V supply and its die area is 1190${\mu}{\textrm}{m}$${\times}$360${\mu}{\textrm}{m}$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.175-175
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• 2009

양자점 (quantum dot) 기반의 반도체 레이저 다이오드(laser diode)는 낮은 문턱전류와 높은 미분 이득 및 높은 특성온도 등과 같은 장점을 갖는다. 이러한 레이저 다이오드의 특성은 양자점 활성층 품질에 의해 큰 영향을 받기 때문에 고품위 양자점 성장에 관한 연구가 활발히 진행되고 있다. 양자점 구조 성장시 발생하는 변형 (strain)은 레이저 다이오드의 문턱전류, 발진 파장, 내부양자효율 등과 같은 특성에 영향을 미치는 중요한 요소이다. 특히, 레이저 다이오드의 고출력 동작을 위해서는 양자점 적층 기술이 중요한데, 이때 양자점 활성층 영역에 많은 변형이 발생한다. 따라서, 양자점 성장후 변형을 감소하기 위한 변형 완화층(strain released layer)에 관한 연구가 활발히 진행되고 있다. 본 논문에서는 변형 완화층 연구의 일환으로 비대칭 변형 완화층의 조성 및 두께 변화에 따른 양자점 파장 변화에 대한 연구를 수행하였다.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.1
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• pp.35-46
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• 2004

In comparison with edge-emitting lasers(EELs), predicting the output power and slope efficiency of Vertical-Cavity Surface-Emitting Lasers(VCSELs) is very difficult due to the absorption loss in DBR layers. However, by using transfer matrix method(TMM), we've made possible to calculate such parameters of multi-layer structures like VCSELs. In this paper, we've calculated the threshold gain, threshold current and slope efficiency through the methodology based on TMM. Also TMM is the way of customizing the VCSEL structure for the desired threshold current and slope efficiency by changing the number of DBR mirror layers.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.4
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• pp.386-392
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• 2002

This paper presents a basic characteristics of 4-element circular array dipole antennas for 4-sector beam steering. The coupled integral equations for the unknown current distributions on dipole elements are derived and solved by applying Galerkin's method of moments. The parasitic elements have been used to increase the directional gain and the beam is steered electronically either by sswitching between the parasitic elements or switching the position of the active element. The parasitic elements are switched short-circuited or open-circuited as required to steer a directional beam. In order to verify the theoretical analysis, the radiation pattern was compared with experiments.

• Korean Journal of Optics and Photonics
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• v.7 no.4
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• pp.440-444
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• 1996

In this paper, we report an InGaAs/InAlAs multi-quantum well (MQW) avalanche photodiode (APD) showing a performance suitable for 10 Gbps lightwave communications. In designing the device, emphasis is given on the effect of indiffusion of Be dopant from the highly doped field layer into the MQW multiplication region. It is found that a small amount of diffusion can alter the dark current and gain characteristics of the device significantly. A spacer used to restrain such indiffusion is shown effective in reducing dark current (500 nA at a gain of 10) while maintaining a high bandwidth (10 GHz at a gain of 10) devices grown by molecular beam epitaxy.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.1
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• pp.16-21
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• 2007

A Dual-Path Voltage Multiplier for passive RFID Tags was proposed and fabricated by using a 0.25um CMOS process with additional steps for schottky diodes. The proposed circuit needs only 4 additional diodes, and the area increment compared to conventional one is negligible in multi-stage voltage multipliers. The simulation and measurement results show that the output power capability of proposed multiplier are about two times larger than the conventional half-wave multiplier.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.5
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• pp.1-10
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• 1999

A low power concumption 2.4 GHz one-chip transceiver MMIC was designed and fabricated using $1.0\mu\textrm{m}$ ion-implantation MESFET process and packaged on a 24 lead SSOP. In the transmitter mode, it revealed conversion gain of 7.5 dB, output IP3 of -3.5 dBm, and noise figure of 3.9 dB at 2.44 GHz with 3.9 mA current consumption. In the receiver mode, it revealed voltage sensitivity of 6.5 mV/$\mu\$W with 2 .0 mA current consumption. Comparing the fabricated MMIC with the results of MMICs reported elsewhere, it was shown that the fabricated MMIC had good performance. The low power consumption 2.4 GHz transceiver MMIC is expected to be used for various applications such as wireless local area networks, wireless local loops and RFID tags in ISM-band.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.442-445
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• 2003

In this study, we developed the 40 J-class MPC(magnetic pulse compression) system for exciting excimer laser and investigated the optimal conditions of each stage of MPC circuit. This system consists of a DC power supply, a pulse transformer and four saturable inductors. The number of turns of saturable inductors at each stage of MPC circuit are 140, 25, 5, 1 and the optimal storage capacitance of each stage are 34 nF, 28.9 nF, 22.1 nF, respectively. In the improvement MPC system, we have obtained an output voltage of 43 kV, a current of 8.25 kA and a pulse duration of 360 ns. Also, the maximum pulse compression ratio of 77.7 and the current gain of 71.7 were obtained.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.3
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• pp.226-234
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• 2010

This paper proposes an improved feed-forward controller that calculates the gain value by estimating the changed boost inductance in practical operating condition of transformer. The boost inductance is estimated by the measurement of input current and voltage. The estimated boost inductance is optimized by the least square method. The proposed feed-forward controller can be achieved the robust control through the gain value calculating the estimated boost inductance despite of the changed condition of transformer and can minimize the interference phenomenon by reducing the harmonics of input current. The validity of proposed technique is verified through the simulation and experiment.