Journal of Xidian University

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Frequency signal control based on the characteristic of the phase difference group

JIA Zhaomin1,2,3;LI Zhiqi4;YANG Xuhai1,2;SUN Baoqi1,2;MIAO Miao4;DONG Shaofeng4   

  1. (1. National Time Service Centre, Chinese Academy of Sciences, Xi'an 710600, China;
    2. University of Chinese Academy of Sciences, Beijing 100049, China;
    3. Intelligence and Information Engineering College, Tangshan University, Tangshan 063020, China;
    4. School of Mechano-electronic Engineering, Xidian Univ., Xi'an 710071, China)
  • Received:2016-11-01 Online:2017-10-20 Published:2017-11-29

Abstract:

Based on thecontinuous character of the phase difference group between frequency signals of different nominal values, a method for direct digital phase lock between the different nominal value signals is proposed. The A/D converter is utilized to extract digital voltage value of the controlled frequency signal,whichreflects the phaseinformation. The switch point of the gate is generated by extracting the zero-crossing digital voltage value,then the frequency offset is obtained, on the basis of which the control voltage is obtained to control VCOCXO, and the frequency is locked. The experiment shows that the noise brought by the common complex circuit is reduced because of the simplified frequency transformation circuits, so that high precise locking is realized. The short term stability can reach the 10-12/s order of magnitude,and the phase noise index is good.

Key words: frequency control, phase difference group, phase locked loop, frequency stability