Journal of the Institute of Convergence Signal Processing (융합신호처리학회논문지)

The Korea Institute of Convergence Signal Processing (한국융합신호처리학회)
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A Study on the Test Results of 32 Gbps Observing System for Wideband VLBI Observation

광대역 VLBI 관측을 위한 32Gbps 관측장비의 시험결과 고찰

  • Oh, Se-Jin (Radio Astronomy Division, Korea Astronomy and Space Science Institute) ;
  • Yeom, Jae-Hwan (Radio Astronomy Division, Korea Astronomy and Space Science Institute) ;
  • Roh, Duk-Gyoo (Radio Astronomy Division, Korea Astronomy and Space Science Institute) ;
  • Jung, Dong-Kyu (Radio Astronomy Division, Korea Astronomy and Space Science Institute) ;
  • Harada, Kenichi (Radio Astronomy Division, Korea Astronomy and Space Science Institute) ;
  • Takezawa, Kosuke (Elecs Industry)
  • Received : 2017.05.12
  • Accepted : 2017.06.11
  • Published : 2017.06.30
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Abstract

In this paper, we evaluate the basic test results of the 32 Gbps observational equipment introduced as the back-end system for the wideband VLBI (Very Long Baseline Interferometry) observation of KVN (Korean VLBI Network). Radio astronomers want to make a large radio telescope that has excellent performance in order to observe the superfine structure of a celestial body, but a lot of money is needed. Therefore, in order to increase the sensitivity, the performance improvement of the receiving system and the method of observing the wide frequency bandwidth are introduced. To do this, we adopted a wideband sampling method for converting analog signals to digital with ultra-fast speeds and a wideband sampler for performing digital filtering in order to observe a wide observational frequency bandwidth. The wideband sampler (OCTAD-K) supports up to 16 Gsps-2bits sampling and supports a variety of observational bandwidth using digital filtering techniques. In particular, it is designed to support KVN's 4-frequency simultaneous observation system and VERA(VLBI Exploration of Radio Astrometry)'s 2-beam observation system. It can also support polKVN(Korean VLBI Network), KaVA(KVN and VERA Array), 32Gbps Direct Sampler, Digital Filter, Widebandarization observations and supports the standard VDIF(VLBI Data Interchange Format) format of observed data. In this paper, the performance of the system and the problem solving are described in detail after performing the factory inspection and field test before the system is introduced.

본 논문에서는 KVN의 광대역 VLBI 관측을 위한 백엔드 시스템으로써 도입한 32 Gbps 급 관측장비의 기본적인 시험결과에 대해 고찰한다. 천문학자들은 천체의 초미세 구조를 관측하고자 성능이 우수한 큰 전파망원경을 만들고 싶지만, 많은 돈이 소요된다. 따라서 민감도를 높이기 위해 수신시스템의 성능개선이나 넓은 주파수 대역폭을 관측하는 방법을 도입하고 있다. 이를 위해 본 연구에서는 넓은 관측 주파수 대역폭을 관측하기 위해서는 아날로그 신호를 초고속으로 변환하는 광대역 샘플링 방법과 디지털 필터링을 수행하는 광대역 샘플러를 도입하였다. 광대역 샘플러(OCTAD-K)는 최대 16Gsps-2bit 샘플링을 지원하며, 디지털필터링 기술을 이용하여 다양한 관측대역폭의 관측을 지원한다. 특히 KVN의 4주파수 동시관측시스템과 VERA의 2-beam 관측시스템을 지원할 수 있도록 설계되었다. 그리고 편파관측도 지원할 수 있으며, 관측데이터의 출력의 표준 VDIF 형식을 지원한다. 본 논문에서는 광대역 샘플러를 도입하기 전 수행한 공장검수와 현장시험을 수행한 후 시스템의 성능결과와 문제점 해결 등에 대해 자세히 기술한다.

Keywords

References

  1. Arthur Niell, Alan Whitney, and Bill Petrachenko et al., "VLBI2010: Current and Future Requirements for Geodetic VLBI Systems," VLBI2010 A vision for Geodetic VLBI, pp. 15-18, September 2005.
  2. Takahashi F., Kondo T., and Koyama Y., Very Long Baseline Interferometer, Ohmsha, 2000, pp. 35-55.
  3. Thompson, A. R., Moran, J. M., and Swenson, G. W.Jr., Interferometry and Synthesis in Radio Astronomy, 2nd Ed., (New York:John Wiley & Sons), 2001, pp. 289.
  4. Se-Jin Oh, Duk-Gyoo Roh, and Jae-Hwan Yeom et al.(2011, October), Performance Evaluation for VLBI Correlation Subsystem Main Product, Journal of The Institute of Signal Processing and Systems, 12(4), pp. 322-331.
  5. Se-Jin Oh, T. Oyama, and Jae-Hwan Yeom et al. (2016, December), A Study on the Test Results and Wideband Observing of the Korean VLBI Network, ournal of The Institute of Signal Processing and Systems, 17(2), pp. 83-92.
  6. Elecs Industry Co. Ltd., "RF Direct Sampler OCTAD Series," 2015.
  7. http://www.vlbi.org/vdif