Studies on adaptive filtering of analytical instrument signal based on wavelet theory

In this paper, a new type of adaptive filtering algorithm, which can adapti vely remove all kinds of noises from signals of analytical instruments unde r a variety of complex conditions, is proposed. At present, the popular fil tering algorithms which are widely applied to the data processing equipment for analytical instrument are low-pass filter or band-pass filter. The fun damental of those filters depends on the fact that the frequency characteri stics of real signals are different from those of noises. These filtering a lgorithms based on the different frequency distribution characteristics bet ween signals and noises have an obvious defect, that is, users have to pres et properly initial filter factors according to the width of peaks, which g reatly influences the objectivity and veracity of computational results in analytical procedures. In the light of the wavelet transform modulus maximu m theory proposed by Mallat, the characteristics of wavelet transform modul us maxima of real signals are distinctively different from those of noises in the practical signals of analytical instruments, such as chromatography. It is easy to identify them. Taking advantage of the different characteris tics between real signals and noises on different scales in wavelet transfo rmation domain, noises can be removed from the practical signals or analyti cal instruments while avoiding to distort the real signals. The adaptive fi ltering algorithm designed by this principle breaches the popular patterns of current filtering algorithms, and radically improves the filtering effec ts. A lot of tests using chromatography data prove that this algorithm has a serial of virtues, such as no requirement on artificially presetting filt er factors, excellent separation of signals and noises, holding the positio n and height of peaks, and so on. Its performance in the robustness, adapta bility and fidelity of peak completely satisfy the needs of signal processi ng for analytical instruments.