Chinese Journal of Quantum Electronics ›› 2025, Vol. 42 ›› Issue (4): 574-583.doi: 10.3969/j.issn.1007-5461.2025.04.013

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Microwave modulation method for CPT atomic clocks based on discrete sine wave frequency modulation

HUANG Pengxiang1 , LIAN Jiqing 2,3 , ZHU Chengyong4 , LI Limin1 , PAN Duo5*, CHEN Jingbiao5,6   

  1. 1 College of Electrical and Electronic Engineering, Wenzhou University, Wenzhou 325035, China; 2 Science and Technology on Vacuum Technology and Physics Laboratory, Lanzhou Institute of Physics, Lanzhou 730000, China; 3 School of Mechano-Electronic Engineering, Xidian University, Xi'an 710071, China; 4 School of Electrical & Electronics Engineering, Beijing University of Posts and Telecommunications, Beijing 100876, China; 5 School of Electronics, Peking University, Beijing 100871, China; 6 Hefei National Laboratory, Hefei 230088, China
  • Received:2024-11-06 Revised:2025-01-06 Published:2025-07-28 Online:2025-07-28

Abstract: In traditional binary frequency shift keying (2FSK) modulation, broad sidebands in the microwave signal indirectly impact alkali metal atom transitions at different optical frequencies, which will limit the accuracy of coherent population trapping (CPT) atomic clock. This paper proposes a microwave modulation method based on discrete sine wave frequency modulation (DSWFM), which uses direct digital modulation for dynamic carrier hopping, significantly narrowing the spectral sidebands. The measured results show that compared with the traditional 2FSK modulation, the frequency stabilities of CPT atomic clock at 1 s, 10 s, and 100 s intervals based on DSWFM modulation are improved by about 17%, 36% and 48%, respectively.

Key words: optoelectronics, frequency stability, discrete sine wave frequency modulation, coherent population trapping atomic clock, binary frequency-shift keying

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