• Title/Summary/Keyword: effective bit of FFT module

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A Study on Correlation Accuracy Improvement of the Daejeon Correlator using Expansion of Effective Bit-number (유효 비트수 확장을 이용한 대전상관기의 상관 정밀도 개선에 관한 연구)

  • Yeom, Jae-Hwan;Roh, Duk-Gyoo;Oh, Se-Jin;Oh, Chung-Sik;Jung, Jin-Seung;Chung, Dong-Kyu;Yun, Young-Joo;Ozeki, Kensuke;Onuki, Hirofumi;Kim, Yong-Hyun;Hwang, Cheol-Jun
    • Journal of the Institute of Convergence Signal Processing
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    • v.14 no.4
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    • pp.255-260
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    • 2013
  • In this paper, we propose the effective bit expansion of FFT module for improving the accuracy of correlation result of the Daejeon correlator. The Daejeon correlator based on FPGA was implemented in order to fast data processing with the fixed-point of FFT operation. In correlation result, however, the phenomenon of phase concentration to 0 degree was appeared in lower frequency area of bandwidth due to lack of operational bit. This phenomenon has an affect on the accuracy of correlation result by introducing the effect of data loss because of excluding phase concentration during analysis of observed radio source. In order to improving the accuracy of correlation result we carried out the simulation by expanding bit-number than 16-bit operation of previous FFT module within given resource limits of FPGA. Through the simulation results, the effective bit number for FFT module within used FPGA resource limits is able to expand, and we confirmed that the operational 20-bit of FFT module is effective for improving accuracy of correlation result by comparing with experimental result.

Performance Evaluation of VLBI Correlation Subsystem Main Product (VLBI 상관 서브시스템 본제품의 제작현장 성능시험)

  • Oh, Se-Jin;Roh, Duk-Gyoo;Yeom, Jae-Hwan;Oyama, Tomoaki;Park, Sun-Youp;Kang, Yong-Woo;Kawaguchi, Noriyuki;Kobayashi, Hideyuki;Kawakami, Kazuyuki
    • Journal of the Institute of Convergence Signal Processing
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    • v.12 no.4
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    • pp.322-332
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    • 2011
  • In this paper, we introduce the 1st performance evaluation of VLBI Correlation Subsystem (VCS) main product, which is core system of Korea-Japan Joint VLBI Correlator (KJJVC). The main goal of the 1st performance evaluation of VCS main product is that the perfection of overall system will be enhanced after checking the unsolved part by performing the experiments towards various test items at the manufacturer before installation of field. The functional test was performed by including the overflow problem occurred in the FFT re-quantization module due to the insufficient of effective bit at the VCS trial product in this performance test of VCS main product. Through the performance test for VCS main product in the factory, the problem such as FFT re-quantization discovered at performance test of VCS trial product in 2008 was clearly solved and the important functions such as delay tracking, daly compensation, and frequency bining were added in this VCS main product. We also confirmed that the predicted correlation results (fringe) was obtained in the correlation test by using real astronomical observed data(wideband/narrow band).