• 대한기계학회논문집A
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• 제33권4호
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• pp.380-387
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• 2009

The reliability concerns of solder interconnections in flip chip PBGA packages are produced mainly by the mismatch of coefficient of thermal expansion(CTE) between the module and PCB. Finite element analysis has been employed extensively to simulate thermal loading for solder joint reliability and deformation of packages in electronic packages. The objective of this paper is to study the thermo-mechanical behavior of FC-PBGA package assemblies subjected to temperature change, with an emphasis on the effect of the finite element model, material models and temperature conditions. Numerical results are compared with the experimental results by using $moir{\acute{e}}$ interferometry. Result shows that the bending displacements of the chip calculated by the finite element analysis with viscoplastic material model is in good agreement with those by $moir{\acute{e}}$ inteferometry.

• Journal of Power Electronics
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• 제18권3호
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• pp.826-840
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• 2018

This paper presents a distributed maximum power point tracking (DMPPT) algorithm based on the reference voltage perturbation (RVP) method for the PV modules of a series PV string. The proposed RVP-DMPPT algorithm is developed to accurately track the maximum power point (MPP) for each PV module operating under all atmospheric conditions with a reduced hardware overhead. To study the influence of parameters such as the controller reference voltage ($V_{ref}$) and PV current ($I_{pv}$) on the PV string voltage, a small signal model of a unidirectional differential power processing (DPP) based PV-Bus architecture is developed. The steady state and dynamic performances of the proposed RVP DMPPT algorithm and small signal model of the unidirectional DPP based PV-Bus architecture are demonstrated with simulations and experimental results. The accuracy of the RVP DMPPT algorithm is demonstrated by obtaining a tracking efficiency of 99.4% from the experiment.

• 반도체디스플레이기술학회지
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• 제22권2호
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• pp.64-71
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• 2023

If an impedance mismatch occurs between the source and load in a Radio Frequency transmission system, reflected power is generated. This results in incomplete power transmission and the generation of Reflected Power, which returns to the Radio Frequency generator. To minimize this Reflected Power, Impedance matching is performed. Fast and efficient Impedance matching, along with converging reflected power towards zero, is advantageous for achieving desired plasma characteristics in semiconductor processes. This paper explores Impedance matching by adjusting the Vacuum Variable Capacitor of an L-type Matching Module based on the trends observed in the voltage of the Phase Sensor and Electromotive Force voltage. After assessing the impedance matching characteristics, the findings are described.

• Current Photovoltaic Research
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• 제10권3호
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• pp.77-83
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• 2022

Renewable energy is receiving attention again as a way to realize carbon neutrality to overcome the climate change crisis. Among renewable energy sources, the installation of Photovoltaic is continuously increasing, and as of 2020, the global cumulative installation amount is about 590 GW and the domestic cumulative installation amount is about 17 GW. Accordingly, O&M technology that can analyze the power generation and fault diagnose about PV plants the is required. In this paper, a study was conducted to diagnose fault using I-V curves of PV strings and deep learning. In order to collect the fault I-V curves for learning in the deep learning, faults were simulated. It is partial shade and voltage mismatch, and I-V curves were measured on a sunny day. A two-step data pre-processing technique was applied to minimize variations depending on PV string capacity, irradiance, and PV module temperature, and this was used for learning and validation of deep learning. From the results of the study, it was confirmed that the PV fault diagnosis using I-V curves and deep learning is possible.

• 한국전자파학회논문지
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• 제17권3호
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• pp.239-248
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• 2006

본 논문에서는 pHEMT(pseudo-morphic High Electron Mobility Transistor)로 구성된 저잡음 증폭기 MMIC(Monolithic Microwave Integrated Circuit)를 이용하여 극저온에서 동작하는 전파 망원경 수신기 전단부용 22 GH2 대역 저잡음 증폭기 모듈을 설계, 제작하였다. pHEMT MMIC 선정에는, 극저온에서의 동작이 입증된 pHEMT 공정을 사용하여 제작된 저잡음 증폭기 MMIC를 선택하였다. 선정된 2개의 MMIC는 박막(thin film) 세라믹 기판에 장착하여 모듈화 하였다. 모듈화 시 하우징(housing)과 캐리어(carrier) 사이의 간극을 제거하고 전파 흡수체를 사용하여 불필요한 구조에 의한 발진을 제거하였다. 또한 커넥터와 기판 사이의 부정합으로 나타나는 잡음 및 이득의 열화를 리본 조정을 통해 개선시켜 상온에서 최적의 성능을 가지도록 했다. 제작된 증폭기 모듈은 상온에서 $21.5{\sim}23.5GHz$ 대역 내 이득 $35dB{\pm}1dB$, 잡음지수 $2.37{\sim}2.57dB$를 보였다. 제작된 증폭기는 헬륨 냉각기를 이용하여 $15^{\circ}K$로 냉각 후 측정 결과, 대역 내에서 이득 35 dB 이상, 잡음온도 $28{\sim}37^{\circ}K$를 얻었다.

• 대한전자공학회논문지SD
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• 제47권4호
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• pp.7-12
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• 2010

열전소자의 SPICE 모델을 유도하였고, Harman method를 이용하여 전기적인 측정과 열전 소자 양단면의 온도 측정값 만으로 모델 파라미터를 추출하기 위한 방법을 제시하였다. 본 논문에서 제시된 SPICE 모델 파라미터 추출방식은 열전도 측정 데이터를 사용하지 않고, 모델 파라미터를 추출할 수 있으며, 기존의 열전도 측정에 의한 값과 비교하였을 때 오차가 크지 않아서 실제로 열전 모듈을 제작하였을 때 유용하게 사용할 수 있는 방법이 될 수 있음을 보였다. 제시된 SPICE 모델은 열전모듈을 이용한 냉각 장치와 열전 발전 장치의 열적 시뮬레이션과 전기적인 시뮬레이션에 모두 적용이 가능하다.

• 한국태양에너지학회 논문집
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• 제29권2호
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• pp.8-13
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• 2009

In this paper, two configurations of PV array are analyzed and tested under shading condition, where two configurations are series-parallel and total-crass-tied configuration. Each photovoltaic module is emulated by two 5 inch po1y-crystalline cells in series and an array is constructed by connecting 24 of the modules to compare a generated maximum power of the two configurations. Pspice and Sun simulator. PASAN IIIb, are used for simulation and experiment to test the array under various partial shading conditions. Test results show the total-cross-tied configuration generates 7.63% higher maximum power than the series-parallel configuration, and it is well matched to the analysis and simulations of the two configurations.

• 한국전자파학회논문지
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• 제23권5호
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• pp.606-612
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• 2012

W-CDMA 단말기에 적용 가능한 고효율 다중 모드 balanced 전력증폭기 구조를 제안하였다. 제안된 전력증폭기는 2단 증폭기로 구성되었고, 낮은 전력 영역 및 중간 전력 영역에서 효율을 증가시키기 위해 stage-bypass 기법과 부하 임피던스 스위칭 기법이 적용되었다. 이를 통해 4가지의 고효율 전력 모드를 구현하였으며, 제안된 구조를 실험적으로 검증하기 위해 GaAs HBT 전력증폭기를 설계 및 제작하였고, 측정하였다.

• Current Photovoltaic Research
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• 제10권4호
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• pp.133-137
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• 2022

The economic feasibility of a photovoltaic (PV) system is greatly influenced by the initial investment cost for system installation. Also, electricity generation by PV system is highly important. The profits competitiveness of PV system will be maximized through intelligent operation and maintenance (O&M). Here, we developed a microconverter which can maximize electricity generation from PV modules by tracking the maximum power point of PV modules, and help efficient O&M. Also, the microconverter mitigates current mismatch caused by shading, hence maximize power generation. The microconverters were installed PV modules and demonstrated through the field tests. Power outputs such as voltage, string current were measured with variuos weather environments and partial shadings. We found that PV modules with the microconvertors shows 12.05% higher power generation compared to the reference PV modules.

• Journal of electromagnetic engineering and science
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• 제18권3호
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• pp.188-198
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• 2018

In this study, we propose an approach for the design and satisfy the requirements of the fabrication of a small, lightweight, reliable, and stable ultra-wideband receiver for millimeter-wave bands and the contents of the approach. In this paper, we designed and fabricated a stable receiver with having low noise figure, flat gain characteristics, and low noise characteristics, suitable for millimeter-wave bands. The method uses the chip-and-wire process for the assembly and operation of a bare MMIC device. In order to compensate for the mismatch between the components used in the receiver, an amplifier, mixer, multiplier, and filter suitable for wideband frequency characteristics were designed and applied to the receiver. To improve the low frequency and narrow bandwidth of existing products, mathematical modeling of the wideband receiver was performed and based on this spurious signals generated from complex local oscillation signals were designed so as not to affect the RF path. In the ultra-wideband receiver, the gain was between 22.2 dB and 28.5 dB at Band A (input frequency, 18-26 GHz) with a flatness of approximately 6.3 dB, while the gain was between 21.9 dB and 26.0 dB at Band B (input frequency, 26-40 GHz) with a flatness of approximately 4.1 dB. The measured value of the noise figure at Band A was 7.92 dB and the maximum value of noise figure, measured at Band B was 8.58 dB. The leakage signal of the local oscillator (LO) was -97.3 dBm and -90 dBm at the 33 GHz and 44 GHz path, respectively. Measurement was made at the 15 GHz IF output of band A (LO, 33 GHz) and the suppression characteristic obtained through the measurement was approximately 30 dBc.