• ETRI Journal
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• v.19 no.2
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• pp.35-47
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• 1997

A power amplifier operating at 3.3 V has been developed for CDMA/AMPS dual-mode cellular phones. It consists of linear GaAs power MESFET's, a new gate bias control circuit, and an output matching circuit which prevents the drain terminal of the second MESF from generating the harmonics. The relationship between the intermodulation distortion and the spectral regrowth of the power amplifier has been investigated with gate bias by using the two-tone test method and the adjacent channel leakage power ratio (ACPR) method of CDMA signals. The dissipation power of the power amplifier with a gate bias control circuit is minimized to below 1000 mW in the range of the low power levels while satisfying the ACPR of less than -26 dBc for CDMA mode. The ACPR of the power amplifier is measured to be -33 dBc at a high output power of 26 dBm.

• Journal of Sensor Science and Technology
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• v.14 no.1
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• pp.28-32
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• 2005

In this paper, a CMOS integrated detection circuit for capacitive type fingerprint sensor signal processing is described. We designed a detection circuit of charge-sharing sensing scheme. The proposed detection circuit increases the voltage difference between a ridge and valley. The test chip is composed of $160{\times}192$ array sensing cells (12 by $12.7{\;}mm^{2}$). The chip was fabricated on a 0.35 m standard CMOS process. Measured difference voltage between a ridge and valley was 0.95 V.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2003.09a
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• pp.58-61
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• 2003

This paper proposes e-Learning environments far digital circuit experiment. The e-Learning environments are implemented as a WBT system that includes the circuits monitoring system and the students management system. In the WBT client-server system, the instructor represents the server and students represent clients. The client computers are equipped with a digital circuit training board and connected to the server on the World Wide Web. The training board consists of a Programmable Logic Device (PLD) and measuring instruments. The instructor can reconfigure the PLD with various circuit designs from the server so that students can investigate signals from the training board. The instructor can monitor the progress of the students using Joint Test Action Grouo(JTAG) technology. We implement the WBT system and a courseware fo digital circuits and evaluation the environments.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.5
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• pp.1068-1073
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• 2004

5 V/500 mA transless type power module was designed by using a semiconductor switching technique for a small-sized electric power source. It used voltage drop type chopper method, and is composed of switching circuit, control circuit, voltage detect circuit, and constant voltage circuit. The switching power module which is designed in this study, showed load regulation of 0.2 V, line regulation of 0.1 V, output ripple of 85 mVp-p, switching frequency of 64.7 kHz, maximum power efficiency of 58 %, and satisfied its reliability and EMC test.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.466-467
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• 2006

Several synthetic testing methods have widely been used for the performance evaluation of ultra high-voltage circuit breaker. Among these synthetic method, in the paper, capacitance switching testing method which can meet the test requirements and increase the testing capacity has been proposed. This method is made up of two separated sources of short-circuit generator for current source and L-C resonance circuit for voltage source. By using this method, KERI will perform the performance evaluation of capacitive current switching performance for the 800kV GCB(Gas Circuit Breaker).

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2002.05a
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• pp.147-152
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• 2002

This paper was studied on corrosion of heat exchanger tube for absorption refrigeration machine. In the 62 % lithium bromide solution at $60^{\circ}C$, polarization test of Cu, Al-brass, 10 % cupro nickel(90-10 % Cu-Ni) and 30 % cupronickel(70-30 % Cu-Ni) tube was carried out. And polarization behavior, polarization resistance characteristics, open circuit potential, anodic polarization of heat exchanger tube for absorption refrigeration machine were considered. The main results are as following: The open circuit potential of Al-brass tube becomes less noble than that of Cu tube, corrosion current density of that becomes lower than Cu tube. The open circuit potential of cupronickel tube is more noble than that of Cu tube, corrosion current density of that is controlled than Cu tube. The passivation critical current of 30 % Cu-Ni tube is lower than that of 10 % Cu-Ni tube, potential of passive region of that is more wide than 10 % Cu-Ni tube.

• Journal of Electrical Engineering and Technology
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• v.9 no.1
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• pp.178-183
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• 2014

This paper presents a motor characteristics analysis method using an equivalent circuit. Motor characteristics analysis via equivalent circuit is very important for designing a high efficiency single phase induction motor. The accuracy of the motor characteristics depends on the accuracy of the parameters, especially saturation factor, which determines the cyclical relationship in the analysis process. Therefore, using the proposed method, the saturation factor was calculated using the iteration routine and numerical technique. The proposed method was verified by comparing the finite element method results and the dynamo test results of manufactured prototype model.

• Proceedings of the KIEE Conference
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• 2002.04a
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• pp.64-67
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• 2002

To increase the short-circuit testing capacity of distribution transformers, testing facility has been installed for KEPCO in Vi-wang. The power supply of testing facility is directly supplied from the network substation located closely. Testing can be performed up to 300 kVA for single-phase transformers, 500 kVA for three-phase transformers. Operating with this facility, the distribution company is able to maintain the reliable supply of electricity. Also the critical quality of transformers from manufacturers can be verified by short-circuit testing. This paper describes the design concept and specification of newly developed equipment and the procedure of short-circuit test.

• ETRI Journal
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• v.28 no.3
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• pp.347-354
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• 2006

The characteristic variation of 3-dimensional (3-D) solenoid-type embedded inductors is investigated. Four different structures of a 3-D inductor are fabricated by using a low-temperature co-fired ceramic (LTCC) process, and their s-parameters are measured between 50 MHz and 5 GHz. The circuit model parameters of each building block are optimized and extracted using the partial element equivalent circuit method and an HSPICE circuit simulator. Based on the model parameters, the characteristics of the test structures such as self-resonant frequency, inductance, and quality (Q) factor are analyzed, and predictive modeling is applied to the structures composed of a combination of the modeled building blocks. In addition, characteristic variations of the 3-D inductors with different structures using extracted building blocks are also investigated. This approach can provide a characteristic estimation of 3-D solenoid embedded inductors for structural variations.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.154-157
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• 2004

With the need of high-speed and mass data transmission, optical communication system requires the growth of optical components. Waveguide photodiodes(WGPDs) are introduced and circuit models of WGPD and submodule are required for the optical receiver application. In this paper, the circuit models of WGPD and submodule are investigated and modeling results are derived by PEEC methodology. The s-parameters are measured for the test structures of WGPD and submodule and the equivalent circuit models are examined. The modeling results agreed well with the measured data and can present a reasonable physical representation.