Journal of Shandong University(Engineering Science) ›› 2019, Vol. 49 ›› Issue (4): 24-28.doi: 10.6040/j.issn.1672-3961.0.2018.526

• Machine Learning & Data Mining • Previous Articles     Next Articles

Weak signal detector based on all-digital phase-shifting lock-in method

Lu WANG(),Hong WANG*(),Guoping CHEN   

  1. School of Optoelectronic Engineering, Chongqing University of Post and Telecommunications, Chonqging 400065, China
  • Received:2017-09-04 Online:2019-08-20 Published:2019-08-06
  • Contact: Hong WANG E-mail:luwang@cqupt.edu.cn;892086798@qq.com
  • Supported by:
    重庆市教委科学技术研究资助项目(KJ1600432);重庆市教委自然科学基金资助项目(KJ130507)

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Abstract:

In order to solve the problem of the uncontrollable phase difference in existing lock-in detection and the vulnerable to interference or high power consumption in analog phase-shifting circuit. The lock-in detection equipment based on all-digital phase-shifting method was designed, which the analog correlation signal was replaced by an all-digital reference signal with frequency traversal and co-frequency shift, then combined with the lock-in correlation detection to extract weak signals in low SNR. The reference signal and the weak signal to be tested were transmitted by direct memory access(DMA), the analog to digital converter(ADC) and digital to analog converter(DAC) were used to realize the transmission of synchronous frequency data with low power and faster transfer speed. The results showed that the lowest SNR detectable by this method was -46 dB with good stability and efficiency in a strong noise environment of 90 dB. It had great practical value for high-precision quality testing in high noise environment passive speaker equipment of the industrial plant.

Key words: weak signal detection, quality inspection, digital phase-shifting, lock-in amplifier, low SNR

CLC Number: 

  • TP206

Fig.1

System diagram"

Fig.2

Flow chart for generating 1 kHz sinusoidal excitation signa"

Fig.3

Flow chart for system code"

Fig.4

The refrence signal with co-frequency shift"

Fig.5

The 1 kHz sinusoidal excitation signal"

Fig.6

The detector prototype"

Fig.7

Detection results of 90 dB noise"

Fig.8

Detection results of pure noise"

Table 1

Test results of pure noise"

NOISE/V MAX PAPR
4.2 62 1.41
3.5 44 1.83
3.2 35 1.81
3.0 30 2.41
2.0 13 3.25

Table 2

Test results of 90 dB noise and the 1 kHz sine"

INPUT/V SNR/dB DC/mV MAX PAPR
4.20 0 0~600 74 1.68
2.00 -6 0~450 64 1.70
1.00 -13 0~340 61 1.69
0.50 -19 0~200 53 1.67
0.20 -26 0~100 52 1.62
0.10 -33 0~56 48 1.75
0.05 -40 0~30 40 1.68
0.03 -43 0~15 35 1.65
0.02 -46 0~6 16 1.64
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doi: 10.3390/s17112615
[1] ZHANG Xiaoli, QUAN Wei, LIU Gang. Dual-channel digital lock-in algorithm based on high-modulation frequency [J]. Journal of Shandong University(Engineering Science), 2017, 47(5): 173-178.
[2] MU Feng, CHANG Faliang, JIANG Qinyu. Signal filtering based on Improved Empirical Mode Decomposition [J]. JOURNAL OF SHANDONG UNIVERSITY (ENGINEERING SCIENCE), 2015, 45(3): 35-42.
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