Implementation of the adaptive Wiener filtering algorithm in the problem of measuring the ¹³CO₂ content in expiratory air using the tunable diode laser absorption spectroscopy technique

Abstract

This paper reports on implementing the adaptive Wiener filtering algorithm for the processing of an experimental signal obtained by the tunable diode laser absorption spectroscopy technique near the wavelength of 2 µm using a tunable diode laser. It has been shown that applying this filter may improve the 13 CO 2 content measuring accuracy in a mixture with 12 CO 2 in expiratory air.

Application of adaptive filters to improve online detection sensitivity of 13CO2 in a mixture with 12CO2 in expiratory air

“…It is evident that minimum error values Δ are achieved while using the Kalman filter followed by applying other filters. It can be noted that the application of a Kalman filter [17] in earlier works [15,17,19] led to better results compared to using EMD [15] and Wiener filters [19].…”

“…A number of rotational absorption lines of 12 CO 2 molecules (vibrational band 20011-00001) and 13 CO 2 (vibrational band 20012-00001) [25] fall into the spectral generation range of the used TDL. As mentioned before, in [15,17,19], for the detection of 13 CO 2 in the present work, the absorption line P (12) of this molecule has been chosen, since in the TDL frequency tuning region, it is maximally removed from its neighbouring absorption lines R(32) and R(34) of the 12 CO 2 molecule.…”

“…To reduce the effect of noise, a number of methods are used, among which one of the most promising is the use of various adaptive filtering algorithms for an experimental signal. The empirical mode decomposition algorithm (EMD) [10][11][12][13][14][15][16], Kalman filters [17,18], and Wiener filters [18][19][20][21][22] are the most common of these filters. They have often been used over recent years in gas analysis problems as effective tools for increasing the signal-to-noise ratio.…”

“…They have often been used over recent years in gas analysis problems as effective tools for increasing the signal-to-noise ratio. We have also used these filters in [15,17,19] for processing experimental signals when measuring 13 CO 2 content in human expiratory air. These filters are applied to increase the sensitivity of measuring the 13 CO 2 content in a mixture with the 12 CO 2 in expiratory air.…”

Application of the least square method for processing the signal obtained by the tuneable diode laser absorption spectroscopy method in the range 4860–4880 cm−1for the problem of measuring13CO2content in exhaled air

“…The tuneable diode laser absorption spectroscopy (TDLAS) method, in which tuneable diode lasers (TDLs) are used as radiation sources, is widely used in various gas analysis problems [1][2][3][4][5]. In particular, this method has been successfully used to measure CO 2 content, including 13 CO 2 mixed with 12 CO 2 in exhaled air during respiratory tests in the noninvasive diagnosis of gastrointestinal cancer [6][7][8][9][10][11][12][13][14]. Thus one of the most promising spectral bands from the perspective of detection sensitivity is 13 CO 2 , and the measurement accuracy is in the 2 µm wavelength region.…”