• Current Photovoltaic Research
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• 제4권3호
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• pp.87-92
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• 2016

The effects of selenization pressure on the structural, optical and electrical properties of the CIGS thin films prepared by RF magnetron sputtering using a single quaternary target were investigated. At selenization pressures lower than atmospheric pressure, CIGS thin films formed non-stoichiometric compounds due to deficiencies of Se vapor. In contrast, when selenization process was conducted at above atmospheric pressure, the residence time of Se vapor inside the tube increased so that the Se element could be incorporated within vacant sites of the CIGS structure, resulting in the formation of stoichiometric CIGS thin films. High quality CIGS thin films could be obtained when the selenization process was performed at pressures greater than atmospheric and $550^{\circ}C$.

• Journal of Astronomy and Space Sciences
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• 제15권2호
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• pp.509-523
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• 1998

군 통신위성 탑재 체의 개념모델(payload Concept Model; PCM) 연구는 실제 위성의 설계 및 제작 이전에 탑재 체를 지상에서 상용부품으로 구성하고 실제 위성과 가까운 통신전파 조건에서 시험하여 그 특성과 성능을 미리 파악하고자 하는 것이다. 본 논문에서는 이러한 통신 탑재 체 개념 모델을 구현하기 위한 기계구조물의 설계와 제작 과정을 기술하고 있다. 제작된 개념모델의 설계 조건의 만족여부를 검증하기 위하여 기본 RF 특성 시험을 실시하였으며 시스템이 양호한 통신품질을 제공함과 정상적으로 작동됨이 확인되었다.

• 전자공학회논문지D
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• 제34D권10호
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• pp.24-31
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• 1997

A new design method of stable RF power amplifier using 3dB coupled line is proposed in this thiesis. The proposed method of broadband matching consist of resistive matching circuits at low frequency and lossless matching circuits at microwave band. This design method increase the stability of an amplifier and is suitable for interstage matching. When high power amplifier is designed using this method for PCS base transceiver station, the measured resutls show thst the gain of 18.5dB, and 9W (39.5dBm) output power. We use motorola's MRF6401 for medium power and MRF 6402 for large power and cascaded them.

• JSTS:Journal of Semiconductor Technology and Science
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• 제8권4호
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• pp.283-288
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• 2008

A post-linearization technique for the differrential CMOS LNA is presented. The proposed method uses an additional cross-coupled common-source FET pair to cancel out the third-order intermodulation ($IM_3$) current of the main differential amplifier. This technique is applied to enhance the linearity of CMOS LNA using $0.18-{\mu}m$ technology. The LNA achieved +10.2 dBm IIP3 with 13.7 dB gain and 1.68 dB NF at 2 GHz consuming 11.8 mA from a 1.8-V supply. It shows IIP3 improvement by 6.6 dB over the conventional cascode LNA without the linearizing circuit.

• Journal of Astronomy and Space Sciences
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• 제17권2호
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• pp.257-266
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• 2000

A satellite RF communication link is analyzed based on a simple fundamental equations by systematic approach in this paper. The number of variables related to a design and analysis of satellite RF link is often a dozen or more, thus it is a tedious and time-consuming task. With the given input data, the important parameters are calculated step by step and three communication characteristics such as communication channel capacity, carrier-to-noise ratio(CNR) at the satellite and ground station are analyzed. It gives very useful information to the system engineers for designing and analyzing the overall satellite communication system in the conceptual design phase.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.317-318
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• 2006

A transfer loading system for 21' RF band assembly box was developed in the present study. The weight of a box is approximately 60kgf End total weight of one day job per person is about $4,000kg_f$. For an efficient design and manufacturing process, three dimensional design and engineering technique were applied to the presented system. Motion analysis for a popup unit and structural analysis for belt part subjected to the load of box weight were performed, respectively. It was found that the evasion of duty and labor intensity is reduced after appling the developed system to manufacturing field of small and midium business.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2004년도 한국우주과학회보 제13권2호
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• pp.360-363
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• 2004

This review is concerned with the MP (multipactor) phenomena of the diplexer for RFDU DM of next generation satellite. The MP discharge is serious problems to design RF components in space applications such ase damage of physical structure, performance degradation, and mission failure of the satellite. In this work, we employed the 3D finite element method (FEM) to calculate the critical gap points and adopted ESTEC curve, MP susceptibility zone, to analyze the maximum handling RF power in the diplexer. And this work also recommends that one should design the tx filter of the diplexer which is more wider bandwidth upto the points to escape the ears of the group delay especially the cavity type of RF components in space applications.

• 전기학회논문지
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• 제62권1호
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• pp.127-132
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• 2013

In this paper, we design the physical layer of Guardian modem for wireless public networks. The physical layer is composed of a dual-band RF (Radio Frequency) transceiver and a baseband-processor with quasi-orthogonal codes. The 2.4/5GHz dual-band RF transceiver can overcome the communication difficulty of dense 2.4GHz band for wireless public environment. Also the quasi-orthogonal code can reduce the required ASIC (Application Specific Integrated Circuit) design area. Finally, we analyze the performance of the developed system in viewpoint of data rate, BER (Bit Error Rate), PER (Packet Error Rate). Moreover we verify the performance of the dual-band RF communication.

• Journal of Positioning, Navigation, and Timing
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• 제11권2호
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• pp.127-134
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• 2022

In this paper, a low-cost, flexible GPS simulator based on USRP is designed as a general-purpose software wireless front-end. The simulator consists of a software GPS signal generator and a USRP-based RF transmitter. The simulator supports various scenarios including specified reception time, quantization bit level, I/Q data types, IF frequency, sampling frequency, SNR, ionospheric delay and user dynamics. The generated GPS RF signal is verified using the spectrum analyzer and off-the-shelf GNSS receivers such as U-blox M8T. The experimental results shows that the difference between generated and real live signal is ignorable. It is expected that designed GPS simulator can be used to GNSS signal design, receiver design and signal processing algorithms such as anti-jamming.

• 한국정보전자통신기술학회논문지
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• 제9권6호
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• pp.534-538
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• 2016

This paper discusses the characteristics and effects of dielectric inner-supports on discone antenna for broadband RF test chamber, and the verification has been performed by simulation. Several design parameters such as the thickness of the gap support, the position of the side support, and the thickness of the side support has been analyzed. The thickness of the gap support affected the reflection coefficient. An effect of the offset of the side support from the center was slight below 3 GHz and significant above 3 GHz. The thickness of the side support did not affect the reflection coefficient or the gain much. The performance of the fabricated discone antenna was in good agreement with the simulated results. This investigation of a dielectric support effects could be used to design a commercial discone antenna for broadband RF test chamber, focusing on electrical performance and mechanical stability.