• 융합신호처리학회논문지
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• 제12권4호
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• pp.322-332
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• 2011

본 논문에서는 한일공동VLBI상관기(Korea-Japan Joint VLBI Correlator, KJJVC)의 핵심 구성시스템인 VLBI상관서브 시스템(VLBI Correlation Subsystem, VCS) 본제품의 1차 성능시험에 대해 기술한다. VCS 본제품의 1차 성능시험의 주요 목적은 현장에 설치하기 전에 제작사에서 다양한 시험항목을 대상으로 시험을 수행하여 문제점을 확인 후 전체 시스템의 완성도를 높이는 것이다. 이번 성능시험에서는 VCS 시작품에서 발견된 FFT 재양자화의 유효비트 부족으로 인한 오버폴로어 문제점을 포함한 기능적인 시험을 수행하였다. 이번 VCS 본제품의 공장시험을 통하여 2008년 VCS 시작품의 성능시험에서 발견한 FFT 의 재양자화 문제점이 완전히 해결되었으며 VCS 본제품에 지연추적, 지연보상, 주파수 묶음 등의 중요 기능도 추가되었다. 그리고 실제 관측 데이터(광대역/협대역)를 이용한 상관처리 시험에서도 예측되는 상관결과가 출력되는 것을 확인하였다.

• 천문학논총
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• 제24권1호
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• pp.65-81
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• 2009

We present the performance test results of VLBI Correlation Subsystem (VCS) trial product which was being developed for 1 year from August 2007. It is a core component of Korea-Japan Joint VLBI Correlator (KJJVC). The aim for developing VCS trial product is to improve the performance of VCS main product to reduce the efforts and cost, and to solve the design problems by performing the preliminary test of the manufactured trial product. The function of VCS trial product is that it is able to process the 2 stations-1 baseline, 8 Gbps/station speed, 1.2 Gbps output speed with FX-type. VCS trial product consists of Read Data Control Board (RDC), Fourier Transform Board (FTB), and Correlation and Accumulation Board (CAB). Almost main functions are integrated in the FTB and CAB board. In order to confirm the performance of VCS trial product functions, the spectral analysis, delay compensation and correlation processing experiments were carried out by using simulation and real observation data. We found that the overflow problem of re-quantization after FFT processing was occurred in the delay compensation experiment. We confirmed that this problem was caused by valid bit-expression of the re-quantized data. To solve this problem, the novel method will be applied to VCS main product. The effectiveness of VCS trial product has been verified through the preliminary experimental results, but the overflow problem was occurred.

• 천문학논총
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• 제23권2호
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• pp.73-90
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• 2008

A software simulator is developed for verifying the VLBI Correlation Subsystem (VCS) trial product hardware. This software simulator includes the delay tracking, fringe rotation, bit-jump, FFT analysis, re-quantization, and auto/cross-correlation functions so as to confirm the function of the VCS trial product hardware. To verify the effectiveness of the developed software simulator, we carried out experiments using the simulation data which is a mixed signal with white noise and tone signal generated by software. We confirmed that the performance of this software simulator is similar as that of the hardware system. In case of spectral analysis and re-quantization experiment, a serious problem of the VCS hardware, which is not enough for expressing the data stream of FFT results specified in VCS hardware specification, was found by this software simulator. Through the experiments, the performance of software simulator was verified to be efficient. In future, we will improve and modify the function of software simulator to be used as a software correlator of Korea-Japan Joint VLBI Correlator (KJJVC).