Journal of Shandong University(Engineering Science) ›› 2017, Vol. 47 ›› Issue (5): 173-178.doi: 10.6040/j.issn.1672-3961.0.2017.296

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Dual-channel digital lock-in algorithm based on high-modulation frequency

ZHANG Xiaoli, QUAN Wei, LIU Gang   

  1. School of Instrument Science and Opto-Electronics Engineering, Beihang University, Beijing 100191, China
  • Received:2017-02-10 Online:2017-10-20 Published:2017-02-10

Abstract: In order to increase the maximum modulation frequency of digital lock-in amplifier and detect dual-frequency composite signal simultaneously, a fast digital lock-in algorithm based on square wave reference was proposed. There were four reference signals with frequencies of f and 2f respectively. Two modulation frequencies were set to (2a-1)f and ((4b-2)f respectively, and limited the length of the average filter to avoid interference between the channels. The results of the experiments showed that the proposed algorithm could detect the amplitude and phase of each frequency component of the input signal, and the errors of the amplitudes were less than 0.7% and the errors of the phase were less than 0.5%. It replaced the multiplication by additions and subtractions in the phase-sensitive detection improved the speed of the digital lock-in amplifier and effectively expanded the detection bandwidth of the lock-in amplifier.

Key words: digital lock-in amplifier, dual-channel, modulation frequency, weak signal detection, average filter

CLC Number: 

  • TP206
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