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Chen D.,Northwestern Polytechnical University | Chen D.,Xian University of Posts and Telecommunications | Liu S.-B.,Northwestern Polytechnical University | Yin S.-M.,Guilin University of Electronic Technology | And 3 more authors.
Guangxue Jingmi Gongcheng/Optics and Precision Engineering

Considering that the response signal of light addressable potentiometric sensor (LAPS) is quite week and the traditional method for extraction of fundamental component of frequency domain is easily impacted by signal drift and stochastic noise, a kind of two-step signal processing method based on the mean square root of component of frequency domain and Kalman filtering was proposed. Based on the theoretical model of devices of light addressable potentiometric sensor, the equivalent circuit model was established; the expression of output signal was deduced, and the causes of drifting and noise as well as inhibition methods were analyzed. Through tests, the solutes with different pH values were detected, and the photocurrent signal outputted by systems was collected. The mean square roots of breadth value of spectral line of fundamental component, second harmonic component and third harmonic component in the frequency domain after Fourier transformation were calculated. Then, the Kalman filtering was implemented for characteristic curve of normalized current-bias (I-V). The experimental results indicate that the two-step signal processing method based on the mean square root of component of frequency domain and Kalman filtering makes the mean square error (MSE) of testing result reduced by 97%, and the influences of signal drift and stochastic noise on testing result are obviously decreased compared to the simple method to extraction of fundamental component. © 2016, Science Press. All right reserved. Source

Hu F.,Guilin University of Electronic Technology | Hu F.,Guangxi Key Laboratory of Automatic Detection Technology and Instrument | Zhang L.,Guilin University of Electronic Technology | Zhang L.,Guangxi Key Laboratory of Automatic Detection Technology and Instrument | And 7 more authors.
Optical and Quantum Electronics

Based on the finite-integration-technology method, we calculate the high and low frequency resonant peaks of the split-ring-resonators (SRRs) which served as a terahertz sensor. An equivalent three-SRRs model is introduced to understand the SRR structure at the high frequency resonant absorption peak. At the same time, an equivalent circuit is set up to calculate the high frequency resonant peak. After that, we theoretically study the sensitivity of these two peaks. The results suggest that both of these two resonant peaks show redshift when the permittivity of surrounding medium increase, and the high frequency peak is more sensitive to this permittivity variation than the low one. The SRR sample is fabricated using a surface micromachining process and used to identify gasoline of 93# and 97#. The experiment results show that the redshift of the high frequency resonant peak is larger than that of the low one, and it is in good agreement with theory analysis. This study suggests that the SRR is a good sensor to identify the product oil, and its high frequency resonant peak is more sensitive to the variation of the permittivity than the low one. © 2015 Springer Science+Business Media New York Source

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