Leilei Zhang, Zhensong Cao, Qing Zhong, Yinbo Huang, Zihao Yuan, Jun Huang, Gang Qi, Wenxue Pan, Xingji Lu. Digital lock-in amplifier controlled by FPGA for spectral measurement[J]. Infrared and Laser Engineering, 2023, 52(10): 20230023
- Infrared and Laser Engineering
- Vol. 52, Issue 10, 20230023 (2023)
Fig. 1. Block diagram of quadrature phase lock-in principle
Fig. 2. (a) Sine and cosine reference signal generated based on DDS principle; (b) Waveform changes with frequency
Fig. 3. (a) Amplitude frequency response of improved CIC filter with different integration length; (b) Relation between cut-off frequency of improved CIC filter and integration length
Fig. 4. FIR amplitude frequency response
Fig. 5. (a) JPL root of sum of squares; (b) JPL residual; (c) CORDIC root of sum of squares; (d) CORDIC residual
Fig. 6. Block diagram of digital lock-in amplifier
Fig. 7. Software interface
Fig. 8. Program flow chart
Fig. 9. Hardware circuit of digital lock-in amplifier
Fig. 10. (a) TDLAS system structure; (b) Experimental device of TDLAS system
Fig. 11. (a) Direct absorption signal; (b) 2f signal
Fig. 12. 2f signal peak value and CO2 concentration
Fig. 13. (a) Fluctuation of CO2 concentration; (b) Allan variance
Fig. 14. System response when CO2 concentration changes
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Table 1. Volume comparison of lock-in amplifier
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