• 제목/요약/키워드: communications

검색결과 30,803건 처리시간 0.061초

Communications Link Design and Analysis of the NEXTSat-1 for SoH File and Mission Data Using CAN Bus, UART and SerDesLVDS

  • Shin, Goo-Hwan;Chae, Jang-Soo;Min, Kyung-Wook;Sohn, Jong-Dae;Jeong, Woong-Seob;Lee, Dae-Hee
    • Journal of Astronomy and Space Sciences
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    • 제31권3호
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    • pp.235-240
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    • 2014

  • The communications link in a space program is a crucial point for upgrading its performance by handling data between spacecraft bus and payloads, because spacecraft's missions are related to the data handling mechanism using communications ports such as a controlled area network bus (CAN Bus) and a universal asynchronous receiver and transmitter (UART). The NEXTSat-1 has a lot of communications ports for performing science and technology missions. However, the top level system requirements for the NEXTSat-1 are mass and volume limitations. Normally, the communications for units shall be conducted by using point to point link which require more mass and volume to interconnect. Thus, our approach for the novel communications link in the NEXTSat-1 program is to use CAN and serializer and deserializer low voltage differential signal (SerDesLVDS) to meet the system requirements of mass and volume. The CAN Bus and SerDesLVDS were confirmed by using already defined communications link for our missions in the NEXTSat-1 program and the analysis results were reported in this study in view of data flow and size analysis.

  • https://doi.org/10.5140/JASS.2014.31.3.235 인용 PDF KSCI

NVIS 통신을 활용한 HF 도약지대 극복가능성 검증 (Verification of the Possibility for Overcoming HF Skip Zone through NVIS communications)

  • 이명노;유재영;이종명
    • 한국통신학회논문지
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    • 제36권5A호
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    • pp.529-535
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    • 2011

  • HF 통신은 별도의 중계 없이 근거리 및 장거리 통신이 가능한 방법으로 해외에서는 주/부 통신수단으로 활용되고 있으나, 국내에서는 도약지대 극복 문제와 전리층 변화에 따라 사용가능한 주파수가 변한다는 이유로 사용자 기피 현상이 심화된 상태였다. NVIS 통신은 일반적인 전리층 반사 통신에 비해 잡음이 적고 도약지대를 포함한 근거리내에서도 통신이 가능한 방법으로써, 이번 연구를 통해 HF 통신의 기존 단점들을 극복하고 HF 통신의 활성화를 위해 외국의 NVIS 통신방법에 대해서 실험을 통해 검증해 보았다. 본 논문에서는 NVIS 통신의 개념을 설명하고, 실제 국내의 HF 통신운용 현황을 확인하였다. 이를 바탕으로 NVIS 통신의 도약지대 극복가능성을 검증하였으며, 효율적인 HF 통신을 위한 예측프로그램의 적용가능성도 판단해보았다.

  • https://doi.org/10.7840/KICS.2011.36A.5.529 인용 PDF KSCI

Report of the Oblique Ionospheric Sounding Results from Korea to Japan

  • Bae, Seok-Hee;Park, Chung-Rim;Wee, Kyu-Jin;Akira Ohtani;Mikitoshi Nagayama;Kiyoshi Igarashi
    • International Union of Geodesy and Geophysics Korean Journal of Geophysical Research
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    • 제22권1호
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    • pp.1.2-5
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    • 1994

  • Ionospheric sounding experiments have been conducted at RRL (Radio Research Laboratory), Ministry of Communications, using Digisonde 256 since its installation in 1990. Routine observations of the vertical sounding are carried out 48 times (or 39 times) a day, at every 24 hour. In addition, we also made oblique sounding experiments to obtain the real time data of Maximum Usable Frequency (MUF) and detect the anomalous HF propagation, as a part of the joint study between RRL and CRL (Communications Research Laboratory) of Japan. The two stations involved in the study were Anyang (RRL, Korea) and Kokubunji (CRL, Japan). The ionosondes used in both stations were Digisonde 256, developed by ULCAR (University of Lowell, Center for Atmospheric Research), U. S. A. , and the synchronization of time was accomplished with the help of GPS receiver. During most part of the experiments RRL transmitted non-modulated pulses, and CRL received them. The experiment was scheduled from October 25 through October 29, 1993. However, the ionosphere was not developed well enough to conduct the experiment with pre-set operation parameters. The experiment became successful (from 0500 UT to 0800 UT, October 29) only after the operation parameters had been changed, and the continuous ionograms were obtained by CRL at 0718 UT and 0733 UT in October 29, 1993. We believe this type of experiment will ensure the qualitative enhancement of solar-terrestrial physics research and a routine observation of the oblique ionospheric sounding. In this report, we present the results of the fore-mentioned oblique sounding as well as the vertical sounding results obtained by Digisonde 256 at Anyang station of RRL.

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Improved Breakdown Voltage Characteristics of $In_{0.5}Ga_{0.5}P/In_{0.22}Ga_{0.78}As/GaAs$ p-HEMT with an Oxidized GaAs Gate

  • I-H. Kang;Lee, J-W.;S-J. Kang;S-J. Jo;S-K. In;H-J. Song;Kim, J-H.;J-I. Song
    • JSTS:Journal of Semiconductor Technology and Science
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    • 제3권2호
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    • pp.63-68
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    • 2003

  • The DC and RF characteristics of $In_{0.5}Ga_{0.5}P/In_{0.22}Ga_{0.78}As/GaAs$ p-HEMTs with a gate oxide layer of various thicknesses ($50{\;}{\AA},{\;}300{\;}{\AA}$) were investigated and compared with those of a Schottky-gate p-HEMT without the gate oxide layer. A prominent improvement in the breakdown voltage characteristics were observed for a p-HEMT having a gate oxide layer, which was implemented by using a liquid phase oxidation technique. The on-state breakdown voltage of the p-HEMT having the oxide layer of $50{\;}{\AA}$was ~2.3 times greater than that of a Schottky-gate p-HEMT. However, the p-HEMT having the gate oxide layer of $300{\;}{\AA}$ suffered from a poor gate-control capability due to the drain induced barrier lowering (DIBL) resulting from the thick gate oxide inspite of the lower gate leakage current and the higher on-state breakdown voltage. The results for a primitive p-HEMT having the gate oxide layer without any optimization of the structure and the process indicate the potential of p-HEMT having the gate oxide layer for high-power applications.

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