• Journal of Astronomy and Space Sciences
• /
• v.32 no.3
• /
• pp.209-219
• /
• 2015

The Accurate Ranging System for Geodetic Observation - Mobile (ARGO-M) was successfully developed as the first Korean mobile Satellite Laser Ranging (SLR) system in 2012, and has joined in the International Laser Ranging Service (ILRS) tracking network, DAEdeoK (DAEK) station. The DAEK SLR station was approved as a validated station in April 2014, through the ILRS station "data validation" process. The ARGO-M system is designed to enable 2 kHz laser ranging with millimeter-level precision for geodetic, remote sensing, navigation, and experimental satellites equipped with Laser Retro-reflector Arrays (LRAs). In this paper, we present the design and development of a next generation high-repetition-rate SLR system for ARGO-M. The laser ranging rate up to 10 kHz is becoming an important issue in the SLR community to improve ranging precision. To implement high-repetition-rate SLR system, the High-repetition-rate SLR operation system (HSLR-10) was designed and developed using ARGO-M Range Gate Generator (A-RGG), so as to enable laser ranging from 50 Hz to 10 kHz. HSLR-10 includes both hardware controlling software and data post-processing software. This paper shows the design and development of key technologies of high-repetition-rate SLR system. The developed system was tested successfully at DAEK station and then moved to Sejong station, a new Korean SLR station, on July 1, 2015. HSLR-10 will begin normal operations at Sejong station in the near future.

• Korean Journal of Optics and Photonics
• /
• v.31 no.6
• /
• pp.334-343
• /
• 2020

In this paper, a study of the design of a lighting optical system to form indirect light was conducted, to reduce the glare caused by the hot spot of the LED. In the case of using an LED for indoor lighting, glare is caused because of the high luminance and non-uniform luminance distribution. In particular, LED stands are located close to the user's eyes and are used for a long time, so research to reduce glare is essential. Therefore, in this paper an optical system structural study and the design of an LED stand for glare reduction were conducted. Afterward, the luminance analysis and comparison to an existing LED stand product confirmed that the reflective LED stand proposed in this paper had better performance in terms of glare.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.41 no.1
• /
• pp.35-46
• /
• 2004

In comparison with edge-emitting lasers(EELs), predicting the output power and slope efficiency of Vertical-Cavity Surface-Emitting Lasers(VCSELs) is very difficult due to the absorption loss in DBR layers. However, by using transfer matrix method(TMM), we've made possible to calculate such parameters of multi-layer structures like VCSELs. In this paper, we've calculated the threshold gain, threshold current and slope efficiency through the methodology based on TMM. Also TMM is the way of customizing the VCSEL structure for the desired threshold current and slope efficiency by changing the number of DBR mirror layers.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.9 no.2
• /
• pp.41-50
• /
• 2010

In this paper, a multi-band antenna with novel structure for mobile communications is designed and fabricated. The proposed antenna has the Multi-band antenna characteristics by two common-grounded slots with different size and angle. In order to reduce size and to enhance the gain of the antenna, a reflector is consisted of chokes on the three sides. It is optimized by using the CST Microwave Studio commercial software based on the FIA(Finite Integration Algorithm) and PBA(Perfect Boundary Approximation), and then the fabricating and measuring is practiced. As a result of measurement, the reflection coefficient is less than -11 dB(VSWR < 1.8) and the gain of antenna is more than 6dBi at 824~894MHz and 1885-2500MHz.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.2 no.1
• /
• pp.65-72
• /
• 2009

For the evaluation of far-field performance by using the near-field probing on the base station dipole array antenna, the effects of mutual coupling depending on the heights between the array antenna with reflector and the probe were analyzed. When the height is varied in the near-field region, S parameters on the input ports of antenna and probe are measured and analyzed to decide the height for the minimum mutual coupling effect and the maximum probing efficiency. This height will be applicable to the near-field probing system design to achieve the precision far-field performance of a base station array antenna system.

• Publications of The Korean Astronomical Society
• /
• v.28 no.3
• /
• pp.75-82
• /
• 2013

An optical grism for education is fabricated and tested. It is composed of a transmission grating as dispersion element and a prism as diffraction angle compensation device. The transmission grating is Edmundoptics #49-584(spatial frequency 600 lines/mm, dimension $50mm{\times}50mm$). The prism is the fused silica type with angles ($41.3^{\circ}$, $-48.7^{\circ}$, $-90^{\circ}$). The grism device is fabricated by bonding the transmission grating and the prism with an optical adhesive. The zig for assembling the grism, telescope and camera is composed of an aluminum tube, an aluminum disk ring and a T-ring camera adaptor. The fabricated optical grism spectrograph is tested in laboratory using Halogen lamp and Neon lamp with DSLR camera. And the grism assembled with reflector telescope is tested in a field using stellar light. The results show good agreements with design parameters. The wavelength coverage range of the grism is 250 nm at the un-deviated wavelength of 506 nm. The wavelength resolution is 0.11 nm/pixel.

• 한국신재생에너지학회:학술대회논문집
• /
• 2008.05a
• /
• pp.182-185
• /
• 2008

The thermal performance of air receiver with a change of flow direction for dish solar collector. This system is installed and operated in Incheon, Korea. The thermal capacity of the system is about 5 kW thermal. The aperture diameter of the cylindrical-shape receiver which is made of stainless steel is 100 mm, and the height is 210 mm. Experiments are being carried out to investigate the thermal performance variation of the receivers with several design parameters such as the shape of the receiver, the flow directions and the flow rate of air. First, air flows into the upper part of the receiver, which is the opposite side of the aperture. After the air flows through the inside receiver, that goes out of the receiver through 3 exits which are located near the aperture. Second, air flows into the backside of the receiver, Which is the forward side of the aperture. After the air flows through the inside receiver, that goes out of the receiver through 1 exit. The results show that the system efficiency and receiver efficiency increase as the volume flow rate increases as expected.

• Journal of information and communication convergence engineering
• /
• v.18 no.3
• /
• pp.162-166
• /
• 2020

The present paper presents an array antenna of a microstrip patch for 5G applications. Four rectangular microstrip patch elements are arranged in parallel and series to form an array antenna. Two insets are made on both sides of each patch element to achieve a wide frequency bandwidth of 23.97-31.60 GHz. To attain a high gain and wider bandwidth, the microstrip patch antenna is fed using series and corporate feeding networks. Further, three director elements on top of the top-most patch elements, and one reflector element at the open end of each patch element, are added. The addition of the Yagi elements improved the overall gain and acquired a higher radiation efficiency throughout the operating frequency bandwidth, with the array antenna achieving a maximum peak gain of 8.7 dB. The proposed antenna is built on a low-loss and low-cost substrate of FR4-eproxy. The proposed antenna design with a simple structure is suitable for Internet of Things and 5G applications.

• 전자공학회논문지 IE
• /
• v.45 no.2
• /
• pp.6-12
• /
• 2008

In this study, because of the importance of asphalt content, the target is to develop a asphalt content detector that the influence of the jurisdiction and usage of radioisotopes are limited of 100[${\mu}Ci$] or less. For development of a asphalt content detector, it is divided into three parts that is affected the change of asphalt content due to the position of neutron source. First part is to decrease the distance between asphalt mixture and neutron source, second is to install the reflector, and last is to change the history number. It performed to analysis by computer simulation and satisfactory results of error range can use to design data for development of a asphalt content detector.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.27 no.5
• /
• pp.471-481
• /
• 2016

We introduce the design technique and test results of a millimeter-wave compact antenna test range. Physical optics is employed for the analysis of the plane wave collimated by an electrical large parabolic reflector of the compact range in the test zone. The performance of the manufactured compact range is verified with the field probing test on the quiet zone and the measurement of high gain antenna. A millimeter-wave compact range designed in the frequency range of 75~110 GHz with a diameter of the test zone of 50 cm shows the magnitude variation of less than 0.75 dB.