• Title/Summary/Keyword: Daejeon correlator

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Analysis and solution to the phase concentration and DC-like component of correlation result in Daejeon correlator (대전 상관기의 상관 결과에 나타난 유사 DC 성분과 위상 집중 현상에 대한 원인 분석과 해결 방법)

  • Roh, Duk-Gyoo;Oh, Se-Jin;Yeom, Jae-Hwan;Oh, Chung-Sik;Jung, Jin-Seung;Chung, Dong-Kyu;Yun, Young-Joo;Oyama, Tomoaki;Ozeki, Kensuke;Onuki, Hirofumi
    • Journal of the Institute of Convergence Signal Processing
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    • v.14 no.3
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    • pp.191-204
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    • 2013
  • In this paper, we investigated the correlation outputs of Daejeon correlator at the viewpoints of the buffer memory setting related to the fine delay tracking and the under/overflow issue in FFT modules, in order to eliminate DC-like component and phase concentration to 0 degree. As the ring buffer memory is being used for the fine delay tracking, the DC-like component in correlation outputs is generated by improper setting of data read/write address, and then that address setting method is modified to exclude a polluted FFT segment in correlation processing when crossing the port/stream boundary. The phase concentration to 0 degree at beginning of bandpass is caused by inadequate scaling factors, which may be the origins of under/overflow occurred at internal computation of FFT stage. With the revised method of the ring buffer memory setting and the scaling factors in FFT, we could obtain higher signal-to-noise ratio and flux density, compared to the previous method, through the correlation processing of true observational data.

Development of Transmission Algorithm of VLBI Observation Data and Transmission Experiment Between Server and RVDB (VLBI 관측 데이터의 전송 알고리즘 개발과 서버와 RVDB 사이의 전송 시험)

  • Yeom, Jae-Hwan;Oh, Se-Jin;Roh, Duk-Gyoo;Jung, Dong-Kyu;Oh, Chung-Sik;Yun, Youngjoo;Kim, Hyo-Ryoung
    • Journal of the Institute of Convergence Signal Processing
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    • v.15 no.4
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    • pp.183-191
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    • 2014
  • This paper describes the development of the observational data transmission algorithm for high-speed network in radio astronomy. For the preprocessing of VLBI data observed by radio telescope, data transmission algorithm uses the VDIF specification, VDIFCP, and UDP protocol by transferring VLBI data stored in a massive storage server with one-to-one correspondence between the server and the RVDB of Daejeon correlator. A transmission method is proposed, which reads the recorded data in Mark5B VSI format and trnasmits 2048 Mbps VLBI data by software through UDP packet transmission, while RVDB system is waiting for the transmitting data from the server. In order to check the effectiveness of the proposed method, the data transmission between the massive storage server and RVDB is conducted and the transmitted data is correlated by Daejeon correlator for the accurate comparison concerning the data before and after. The transmitted data is shown to be completely the same as the original data without any data transmission loss. Henceforth, the developed data transmission algorithm in this research is expected to be applied effectively as e-VLBI for KaVA network.

File System Design and Software Development for Correlation Result Analysis (상관결과 분석을 위한 파일 시스템 설계 및 소프트웨어 개발)

  • Oh, Se-Jin;Kan-ya, Yukitoshi;Roh, Duk-Gyoo;Yeom, Jae-Hwan;Oh, Chung-Sik;Yun, Young-Joo;Jung, Jin-Seung;Jung, Dong-Kyu
    • Journal of the Institute of Convergence Signal Processing
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    • v.14 no.3
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    • pp.181-190
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    • 2013
  • In this paper, we designed file system in order to utilize data analysis by using correlation result from Daejeon correlator including related software development. Correlation results are consisted of visibility component (amplitude and phase) of radio source, but for data analysis of correlation result, various information such as weather, radio telescope position, observation time, radio source position, source type, and receiver noise temperature are needed. In this paper, we designed file system as a directory-structure for making use of these informations at Linux system for analyzing data and developed software to make file system. To verify the effectiveness of designed file system and developed software, file system generation experiment is conducted, and then astronomers accepted that there is no severe problem for scientific analysis using designed file system.

Design and development of VSI Optical Adapter for high speed transmission of VLBI observation data (VLBI 관측데이터 초고속 전송을 위한 VSI 광변환 송수신 장치의 설계 및 개발)

  • Oh, Se-Jin;Roh, Duk-Gyoo;Yeom, Jae-Hwan;Jung, Jin-Seung;Jung, Dong-Kyu;Oh, Chung-Sik;Ozeki, Kensuke;Onuki, Hirofumi;Harada, Keniichi
    • Journal of the Institute of Convergence Signal Processing
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    • v.14 no.4
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    • pp.261-269
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    • 2013
  • This paper describes the design and development of VSI (VLBI standard interface) optical adapter for transmitting VLBI(Very long baseline interferometry) observation data with optical signal. VSI cable comprised of 80-line is being used for observed data transmission with maximum length of 5-meter between playbacks (Mark5B, VERA2000) and raw VLBI data buffer (RVDB), RVDB and VLBI correlation subsystem (VCS) in Daejeon correlator. It has a plan to conduct the data processing for 16-stations and introduce the 14 RVDB systems in near future. And data loss frequently occurred because of trouble of VSI cable MDR80 connector. By considering the data loss by connector error of VSI cable, RVDB system extension plan, effective space usage and long distance data transmission(e-VLBI), the VSI optical adapter was proposed and developed for effectively transmitting and receiving VLBI data through optical signal. In order to confirming the performance of developed VSI optical adapter, the experiments for data transmission was conducted between playback and RVDB system, and confirmed that data transmission was clearly done without any data loss.