• Journal of Advanced Marine Engineering and Technology
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• v.29 no.6
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• pp.618-627
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• 2005

In this paper, we have compared and analyzed the performance of high amplifier using Doherty technique to improve linearity and efficiency of base station and repeater Power amplifier for WCDMA. This Doherty amplifier implements with 3dB branch line coupler and $90^{\circ}C$ transmission line The phase offset line is designed to maintain the high linearity and efficiency at the low efficiency Period of the power amplifier CW 1-tone experimental results at the WCDMA frequency $2.11{\sim}2.17GHz$ shows that Doherty amplifier which achieves power add efficiency(PAE) of 50% at 6dB back off the point from maximum output power 52.3 dBm, obtains higher efficiency of 13.3% than class AB Finding optimum bias Point after adjusted gate voltage, Doherty amplifier shows that $IMD_3$ improves 4dB.

• International journal of advanced smart convergence
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• v.8 no.4
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• pp.34-39
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• 2019

Millimeter-wave (mmWave) and Non-orthogonal multiple access (NOMA) are expected to be the major techniques that lead to the next generation wireless communication. NOMA provides a high spectrum efficiency by sharing of spatial resources among users in the same frequency band. Meanwhile, millimeter-wave gives a huge underutilized bandwidth at extremely high frequency band (EHF) which covers 30GHz to 300GHz. These techniques have been proven in several recent literatures to achieve high data rates. The combination of NOMA and millimeter-wave techniques further improves average sum capacities, as well as reduces the interference compared to conventional wireless communication systems. In this paper, we focus on hybrid NOMA system working in millimeter-wave frequency. We propose a clustering algorithm used for a hybrid NOMA scheme to optimize the usage of wireless resources. The proposed clustering algorithm adds several conditions in grouping users and defining clusters to increase the probability of the successful superposition decoding process. The performance of the proposed clustering algorithm is investigated in hybrid NOMA system and compared with the conventional orthogonal multiple access (OMA) scheme.

• Journal of the Semiconductor & Display Technology
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• v.11 no.2
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• pp.7-11
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• 2012

SiNx films have been wildly used as anti-reflection coatings and passivation for crystalline silicon solar cells. In this study, the SiNx films were deposited by using high frequency (13.56MHz) PECVD and optical & passivation properties were investigated. The RF power was changed in a certain range for the film deposition. Then, the refractive index, etch rate, minority carrier lifetime and cell efficiency were measured to study the properties of the film respectively. The optimal deposition conditions for application to crystalline silicon solar cells were proposed as results of the study. Finally, the best cell efficiency of 16.98% was obtained from the solar cell with the SiNx films deposited by RF power of 550W.

• Proceedings of the KIEE Conference
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• 1998.11a
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• pp.125-127
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• 1998

The widely used power supply (Switched Mode Power Supply : SMPS) as a source in order to stabilize direct current for electronics or communication systems has merits, when it is compared to the existing source for stability, such as high efficiency, small size, light weight by means of switching process of the semiconductor device which controls the flow of power. However, due to existence of inductors and capacitors used for charging energy, the source part in electronic or communication systems hasn't reached the speed, that is supposed to get, for achieving smaller size and lighter weight. In order to got smallness in size, it is necessary to increase switching frequency. And that makes devices for measuring energy smaller. Nevertheless, the rise switching frequency brings increases in switching loss, inductor loss, and power loss. Also, the occurrence of surge and noise caused by high frequency switching is setting higher. The resonant converter has been considered as one of methods that give solutions for the problems of SMPS and that method has been paid attention as a source technology in electronics and communication.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.4
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• pp.588-591
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• 2009

We had experimental studies of microwave output generator. We experimented with a corrugate-shped K-band slow wave guide in the backward wave oscillator. It generated output 표 interaction between electron beam's generation and magnetic field. We estimated oscillation frequency at 24GHz by changing propagation velocity and group velocity. We identified movement by second harmonic of Cherencov interaction and slow cyclotron mode. In our study we achieved oscillation stabilization, generation of long pulse, improvement of oscillation efficiency and output.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.595-598
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• 1999

A new of the automotive High Intensity Discharge(HID) lamp ballast systems is proposed. Proposed scheme is consisted of the high frequency DC-DC converter and low frequency DC-AC inverter as same as conventional HID ballast system. But this system separates ignition voltage from dc link voltage, which results to used the lower voltage rating power devices for HID lamp ballast system compared with conventional system. As a result, proposed system has a lower cost and higher efficiency.

• Proceedings of the KIEE Conference
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• 1993.11a
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• pp.94-96
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• 1993

At an operating point of the induction motor, there are many sets of stator frequency and voltage. This paper presents an algorithm to determine the stator frequency and voltage which maximizes the power factor without any informations of motor parameters. Improvement of efficiency us also expected due to high-power-factor operation.

• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.2145-2147
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• 1998

This paper presents a Class-D type switched mode audio power amplifier employing ZVT(Zero-Voltage-Transition) soft switching technique. In order to obtain a wide bandwidth and lower distortion for an audio amplifier a high switching frequency is essential. The ZVT switching scheme enables a high frequency switching without sacrificing the efficiency much as in a hard switching. A prototype amplifier is built to demonstrate the feasibility of this technique for the audio power amplifier.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.34 no.4
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• pp.153-153
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• 1985

A method of computer aided design (C.A.D.) is proposed to analize a load circuit of a high frequency induction heating. Various formulas are derived from the properity of the heating load, which is useful for the design of heating materials. A load circuit which is designed by the proposed C.A.D. is realized and tested. The experimental results show in good agreement with the theoritical analysies. Especially the result reveal that the power transfer efficiency increases as the Q and coupling coefficient of the work coil increase.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.7-8
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• 2008

It is well-known that one of the most serious problems of Orthogonal Frequency Divison Multiplexing (OFDM) is its high Peak-to-Average Power Ratio (PAPR) which seriously limits the power efficiency of High Power Amplifier (HPA). This paper introduces various methodologies to cope with this problem.