• Proceedings of the KSR Conference
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• 1998.05a
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• pp.442-449
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• 1998

Since it is essential for traction motors to reduce size and weight to achieve given traction effort, they need high input voltage. But the lack of input voltage occurs periodically due to the characteristics of train system. Therefore traction inverters use over-modulation PWM to maximize inverter's voltage gain. On the other hand, IGBT inverters can use higher frequency twice than GTO ones, which resulted in the need for novel optimal synchronous PWM strategy. This paper suggests that linearly-compensated overmodulation/optimal synchronous PWM strategy and also the simulation results of the method for a real traction motor-intertia model are presented.

• Proceedings of the KIPE Conference
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• 2008.10a
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• pp.112-114
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• 2008

This paper proposes a new two-stage Z-source converter (TSZC). The purpose of the proposed system is to obtain the ac voltage with a maximum boost voltage for fuel cell applications as a renewable energy source. In order to provide a continuous current path, a switching strategy for the dc-ac ZSI and ac-ac ZSC of the proposed system was used. The operation principle, analysis and simulation results of 1.2 kW fuel cell stack were also presented.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.232.1-232.1
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• 2013

본 연구에서는 asymmetric과 symmetric 구조의 n채널 MOSFET 소자의 성능 평가에 관한 실험을 진행하였다. 소자의 성능 평가에 있어 아날로그 회로에서의 DC 이득은 중요한 파라미터 중 하나 이다. 따라서 본 연구에서는 gm/ID 측정법을 이용하여 각 소자의 DC 이득 특성을 분석하였다. 게이트 전압에 따른 드레인 전류-드레인 전압 특성 곡선으로부터 early voltage 값을 추출하였다. 이후 최종적으로 수치적 계산을 통해 DC 이득 값을 추출하였다. 실험 결과 asymmetric과 symmetric 소자의 경우 early voltage 값이 각각 -34 V와 -15 V였으며 따라서 DC 이득 특성 또한 asymmetric 소자의 경우가 우수한 것을 확인하였다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.1
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• pp.23-30
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• 2016

Wake effects cause wind turbine generators (WTGs) within a wind power plant (WPP) to produce different levels of active power and subsequent reactive power capabilities. Further, the impedance between a WTG and the point of interconnection (POI)-which depends on the distance between them-impacts the WPP's reactive power injection capability at the POI. This paper proposes a voltage control scheme for a WPP based on the available reactive current of the doubly-fed induction generators (DFIGs) and its impacts on the POI to improve the reactive power injection capability of the WPP. In this paper, a design strategy for modifying the gain of DFIG controller is suggested and the comprehensive properties of these control gains are investigated. In the proposed scheme, the WPP controller, which operates in a voltage control mode, sends the command signal to the DFIGs based on the voltage difference at the POI. The DFIG controllers, which operate in a voltage control mode, employ a proportional controller with a limiter. The gain of the proportional controller is adjusted depending on the available reactive current of the DFIG and the series impedance between the DFIG and the POI. The performance of the proposed scheme is validated for various disturbances such as a reactive load connection and grid fault using an EMTP-RV simulator. Simulation results demonstrate that the proposed scheme promptly recovers the POI voltage by injecting more reactive power after a disturbance than the conventional scheme.

• Journal of Korea Multimedia Society
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• v.6 no.1
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• pp.161-166
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• 2003

This paper presents a high gain LNA for a bluetooth application using 0.25$\mu\textrm{m}$ CMOS technology. The conventional one stage LNA has a low power gain. The presented one stage LNA using a cascode inverter LNA with a voltage reference and without a choke inductor has an improved Power gain. Simulation results of the 2.4GHz designed LNA shows a high power gain of 21dB, a noise figure of 2.2dB, and the power consumption of 255mW at 2.5V power supply.

• JSTS:Journal of Semiconductor Technology and Science
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• v.11 no.4
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• pp.309-317
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• 2011

This paper describes a baseband analog (BBA) chain for wireless local area network (WLAN) applications. For the given specifications of the receiver BBA chain, the optimum allocation of the gain and filter rejection of each block in a BBA chain is achieved to maximize the SFDR. The fully integrated BBA chain is fabricated in 0.13 ${\mu}m$ CMOS technology. An input-referred third-order intercept point (IIP3) of 22.9 dBm at a gain of 0.5 dB and an input-referred noise voltage (IRN) of 32.2 nV/${\surd}$Hz at a gain of 63.3 dB are obtained. By optimizing the allocation of the gain and filter rejection using the proposed design methodology, an excellent SFDR performance of 63.9 dB is achieved with a power consumption of 12 mW.

• ETRI Journal
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• v.28 no.3
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• pp.386-388
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• 2006

Monolithic SiGe heterojunction bipolar transistor (HBT) variable gain amplifiers (VGAs) with a feedforward configuration have been newly developed for 5 GHz applications. Two types of the feedforward VGAs have been made: one using a coupled-emitter resistor and the other using an HBT-based current source. At 5.2 GHz, both of the VGAs achieve a dynamic gain-control range of 23 dB with a control-voltage range from 0.4 to 2.6 V. The gain-tuning sensitivity is 90 mV/dB. At $V_{CTRL}$= 2.4 V, the 1 dB compression output power, $P_{1-dB}$, and dc bias current are 0 dBm and 59 mA in a VGA with an emitter resistor and -1.8 dBm and 71mA in a VGA with a constant current source, respectively.

• Journal of electromagnetic engineering and science
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• v.10 no.1
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• pp.25-27
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• 2010

This paper presents a gain and phase mismatch calibration technique for an image-reject RF receiver. The gain mismatch is calibrated by directly measuring the output signal amplitudes of two signal paths. The phase mismatch is calibrated by measuring the output amplitude of the final IF output at the image band. The calibration of the gain and phase mismatch is performed at power-up, and the normal operation of the RF receiver does not interfere with the mismatch calibration circuit. To verify the proposed technique, a 2.4-GHz Weaver image-reject receiver with the gain and phase mismatch calibration circuit is implemented in a 0.18-${\mu}m$ CMOS technology. The overall receiver achieves a voltage gain of 45 dB and a noise figure of 4.8 dB. The image rejection ratio(IRR) is improved from 31 dB to 59.76 dB even with 1 dB and $5^{\circ}$ mismatch in gain and phase, respectively.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.12
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• pp.90-95
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• 2014

This paper presents a VHF/UHF-band variable gain low noise amplifier for multi-standard mobile TV tuners. A proposed VHF-band variable gain amplifier is composed of a resistive shunt-feedback low noise amplifier to remove external matching components, a single-to-differential amplifier with input PMOS transcoductors to improve low frequency noise performance, a variable shunt-feedback resistor and an attenuator to control variable gain range. A proposed UHF-band variable gain amplifier consists of a narrowband low noise amplifier with capacitive tuning to improve noise performance and interference rejection performance, a single-to-differential with gm gain control and an attenuator to adjust gain control range. The proposed VHF-band and UHF-band variable gain amplifier were designed in a $0.18{\mu}m$ RF CMOS technology and draws 22 mA and 17 mA from a 1.8 V supply voltage, respectively. The designed VHF-band and UHF-band variable gain amplifier show a voltage gain of 27 dB and 27 dB, a noise figure of 1.6-1.7 dB and 1.3-1.7 dB, OIP3 of 13.5 dBm and 16 dBm, respectively.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.4
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• pp.349-356
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• 1999

This paper presents an instantaneous voltage control scheme of au킹liary power supply system for the electric railway v vehicles, The resonance problem of the LC filter and the existing steady state error are more serious as the use of l instantaneous voltage control techniques for the fast transient response at the nonlinear load, A filter capacitor current f feedback loop is considered to increase the damping ratio of the voltage transfer function for the suppression of the resonance problem of the LC inverter output filter. To eliminate the steady state en‘or existing in case of the AC l instantaneous voltage control. the high gain transfer function is added to the conventional PI controller. The theoretical a analysis is well described with the simulation results. The validity of the proposed schemes is well verified through the s simulation and expelimental results for the 5 kVA prototype.