Planar compact elliptic-function low-pass filter using high-permittivity ceramics substrate

✍ Scribed by Yuan-Bin Chen; Cheng-Liang Huang; Ching-Wen Lo

• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: English
• Weight: 145 KB
• Volume: 48
• Category: Article
• ISSN: 0895-2477
• DOI: 10.1002/mop.21637

✦ Synopsis

when just using the method of CDA. The result shows that the maximum strain variation is about 9.4 and the resolution is about 5.7 , which is better than the direct peak detection. In order to enhance the resolution of the system, two 201 st -order digital low-pass FIR filters with cutoff frequency of 10 Hz are applied on the detected scanning voltage and PD signal, respectively, to remove the high-frequency noise and improve the signalto-noise ratio (SNR). Then the CDA method, which has the effect of averaging, is used to determine the peak signal. The maximum strain variation is 2.2 and the resolution is 1.39 , which are better than just using the CDA method, are shown in Figure 3(c).

Comparing the results of Figures 3(a), 3(b), and 3(c), we can conclude that by combining the CDA and digital FIR filter, the resolution of the demodulation system is greatly enhanced. In order to verify the effectiveness of the technique, a series of stepped strains with step size of 36 and time interval of 2.5 s are applied on the FBG sensor. The experiment results are shown in Figures 4(a) and 4(b). It is clearly observed that with FIR and CDA, the measured strains are more resoluble than that of the method without FIR and CDA.

3. CONCLUSION

In conclusion, a fiber Bragg grating (FBG) strain-sensor demodulation system based on a wavelength-tunable fiber-ring laser has been developed. By using the digital FIR filter to improve the SNR and CDA peak-detection algorithm, the resolution of the strain system was greatly improved. An enhanced strain resolution of 1.39 was achieved, which is much better than the resolution (10.1 ) of the direct peak-detection method.