• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
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• pp.326-329
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• 2003

In this paper, we designed and implemented a high power amplifier(HPA) to achieve the high Power Added Efficiency(PAE) over 40% at the 90W output power for the ISM-band(fo=2.45GHz). HPA presented in this paper has 3-stage drive amplifier and 1-stage final amplifier. In the final amplifier, we utilized balanced amplifier configuration with GaAs FET and each of two amplifiers has the push-pull configuration to increase PAE. From the measurement results, we obtained PAE of 42.95% at the 90.57W output power.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 ITC-CSCC -2
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• pp.941-944
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• 2000

This paper proposes, for the first time, the design of class I pull-push power amplifier. With the new design, the output power is increased by four times when compared to conventional single-end class I connection amplifier with the same supply voltage. The performance of the proposed amplifier is verified by with a 100-kHz power amplifier constructed using general-purpose NPN transistors.

• Journal of Power Electronics
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• 제14권3호
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• pp.444-457
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• 2014

This paper presents the design and realization of a digital PV simulator with a Push-Pull Forward (PPF) circuit based on the principle of modular hardware and configurable software. A PPF circuit is chosen as the main circuit to restrain the magnetic biasing of the core for a DC-DC converter and to reduce the spike of the turn-off voltage across every switch. Control and I/O interface based on a personal computer (PC) and multifunction data acquisition card, can conveniently achieve the data acquisition and configuration of the control algorithm and interface due to the abundant software resources of computers. In addition, the control program developed in Matlab/Simulink can conveniently construct and adjust both the models and parameters. It can also run in real-time under the external mode of Simulink by loading the modules of the Real-Time Windows Target. The mathematic models of the Push-Pull Forward circuit and the digital PV simulator are established in this paper by the state-space averaging method. The pole-zero cancellation technique is employed and then its controller parameters are systematically designed based on the performance analysis of the root loci of the closed current loop with $k_i$ and $R_L$ as variables. A fuzzy PI controller based on the Takagi-Sugeno fuzzy model is applied to regulate the controller parameters self-adaptively according to the change of $R_L$ and the operating point of the PV simulator to match the controller parameters with $R_L$. The stationary and dynamic performances of the PV simulator are tested by experiments, and the experimental results show that the PV simulator has the merits of a wide effective working range, high steady-state accuracy and good dynamic performances.

• 전력전자학회논문지
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• 제12권3호
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• pp.199-204
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• 2007

본 논문에서는 멀티램프 구동이 유리하여 인버터 개수를 줄일 수 있는 장점을 가지고 있는 EEFL을 사용하였으며, 변압기의 자체 손실을 줄이고 소형화가 가능하며, 높은 승압비를 갖는 압전 변압기를 병렬로 연결하여 멀티램프 구동이 가능하도록 하였다. 최적의 EEFL 구동회로를 구성하기 위해서 Push-Pull 타입의 압전 인버터를 설계하였으며, 설계된 인버터 회로에 대한 시뮬레이션 분석을 통하여 타당성을 검증하였다. 향후 본 논문에서 제안하는 구동 방식을 대화면 LCD 백라이트에 적용할 수 있을 것으로 기대된다.

• 한국전자파학회논문지
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• 제21권2호
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• pp.121-128
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• 2010

본 논문에서는 부궤환 회로, 푸쉬풀 구조, 광대역 RF choke, 전송 선로 트랜스포머를 이용하여 30~512 MHz의 초광대역에서 동작하는 100 W 고효율 전력 증폭기를 설계하였다. 출력 전력을 향상시키고자 전송 선로를 이용한 트랜스포머에 병렬로 커패시터를 삽입하여 적절하게 로드 임피던스를 정합하였다. 제작한 광대역 전력 증폭기는 동작 주파수 대역에서 100 W 이상의 출력 전력과 $18.34{\pm}0.9\;dB$의 높고 고른 이득 특성을 보였다. one-tone 측정에서 2차 고조파는 -34 dBc 이하, 3차 고조파는 -12 dBc 이하의 선형성 특성을 보였으며, 출력 전력 100 W에서 약 40% 이상의 고효율 특성을 보였다.

• Advances in concrete construction
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• 제1권4호
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• pp.273-288
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• 2013

The main objective of this research was to evaluate the potentials of self-compacting concrete (SCC) mixes to develop bond strength. The investigated mixes incorporated relatively high contents of dolomite powder replacing Portland cement. Either silica fume or fly ash was used along with the dolomite powder in some mixes. Seven mixes were proportioned and cast without vibration in long beams with 10 mm and 16 mm steel dowels fixed vertically along the flowing path. The beams were then broken into discrete test specimens. A push-put configuration was adopted for conducting the bond test. The variation of the ultimate bond strength along the flowing path for the different mixes was evaluated. The steel-concrete bond adequacy was evaluated based on normalized bond strength. The results showed that the bond strength was reduced due to Portland cement replacement with dolomite powder. The addition of either silica fume or fly ash positively hindered further degradation as the dolomite powder content increased. However, all SCC mixes containing up to 30% dolomite powder still yielded bond strengths that were adequate for design purpose. The test results demonstrated inconsistent normalized bond strength in the case of the larger diameter compared to the smaller one.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.101-104
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• 2007

Efficient Query processing and optimization are critical for reducing network traffic and decreasing latency of query when accessing and manipulating sensor data of large-scale sensor networks. Currently it has been studied in sensor database projects. These works have mainly focused on in-network query processing for sensor networks and assumes homogeneous sensor networks, where each sensor network has same hardware and software configuration. In this paper, we present a framework for efficient query processing over heterogeneous sensor networks. Our proposed framework introduces query processing paradigm considering two heterogeneous characteristics of sensor networks: (1) data dissemination approach such as push, pull, and hybrid; (2) query processing capability of sensor networks if they may support in-network aggregation, spatial, periodic and conditional operators. Additionally, we propose multi-query optimization strategies supporting cross-translation between data acquisition query and data stream query to minimize total cost of multiple queries. It has been implemented in WSN middleware, COSMOS, developed by ETRI.

• Journal of Electrical Engineering and Technology
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• 제12권4호
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• pp.1484-1494
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• 2017

We present a two-stage inverter with high step-up conversion ratio engaging modified finite-set Model Predictive Control (MPC) for utility-integrated photovoltaic (PV) applications. The anticipated arrangement is fit for low power PV uses, the calculated efficiency at 150 W input power and 19 times boosting ratio was around 94%. The suggested high-gain dc-dc converter based on Cockcroft-Walton multiplier constitutes the first-stage of the offered structure, due to its high step-up ability. It can boost the input voltage up to 20 times. The 3S current-source inverter constitutes the second-stage. The 3S current-source inverter hires three semiconductor switches, in which one is functioning at high-frequency and the others are operating at fundamental-frequency. The high-switching pulses are varied in the procedure of unidirectional sine-wave to engender a current coordinated with the utility-voltage. The unidirectional current is shaped into alternating current by the synchronized push-pull configuration. The MPC process are intended to control the scheme and achieve the subsequent tasks, take out the Maximum Power (MP) from the PV, step-up the PV voltage, and introduces low current with low Total Harmonic Distortion (THD) and with unity power factor with the grid voltage.

• Journal of Power Electronics
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• 제18권2호
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• pp.407-417
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• 2018

A novel family of Buck mode three-level direct ac converters with a high frequency link is proposed. These converters can transfer an unsteady high ac voltage with distortion into a regulated sinusoidal voltage with a low THD at the same frequency. The circuit configuration is constituted of a three-level converter, high frequency transformer, cycloconverter, as well as input and output filters. The topological family includes forward, push-pull, half-bridge, and full-bridge modes. In order to achieve a reliable three-level ac-ac conversion, and to overcome the surge voltage and surge current of the cycloconverter, a phase-shifted control strategy is introduced in this paper. A prototype is presented with experimental results to demonstrate that the proposed converters have five advantages including high frequency electrical isolation, lower voltage stress of the power switches, bi-directional power flow, low THD of the output voltage, and a higher input power factor.

• 한국항공우주학회지
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• 제33권10호
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• pp.60-67
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• 2005

현대의 고성능 전투기는 한계받음각 내에서 적절한 조종성(Controllability) 및 안정성(Stability)을 확보하고 있어야 한다. 고받음각에서 항공기가 이탈에 진입할 수 있는 한계값은 항공기 형상설계에 직결되는 문제이다. 하지만 현대의 고성능 전투기는 전기식 비행제어계통(Digital Fly-By-Wire Flight Control System)을 사용하여 고받음각 제어법칙을 설계함으로써 한계값 내에서 항공기의 안정성을 보장하고 있다. 현재, T-50 세로축 고받음각 제어법칙에는 (+)한계받음각 이상으로의 비행을 제한하는 받음각 제한기(Angle of Attack Limiter)가 설계되어 있다. 그러나 (-)한계받음각 이상으로 비행을 제한하는 받음각 제한기는 설계되어 있지 않아, 조종사의 과도한 (-)세로축 기동에 대해 항공기가 이탈에 진입할 수 있다. 그리고 T-50 비행시험에서 PA에서 과도한 (+)세로축 기동 시, 받음각(Angle of Attack)이 현재 설계되어 있는 한계받음각을 초과하는 문제점이 발생하였다. 본 논문에서는 고받음각 제어법칙을 일부 수정하여 한계받음각 내에서 항공기의 세로축 조종성능을 향상시키고, 항공기 안정성을 확보할 수 있는 제어법칙에 관한 연구를 수행하였다.