Adaptive Filtering for Impedance/Admittance Spectroscopy Noise Immunity Enhancement: Comparison with Fourier Transform

The time domain technique for impedance spectroscopy consists in computing excitation voltage and current response Fourier images by fast or discrete Fourier transform and calculating their relation. Here we propose an alternative method for excitation voltage and current response processing for deriving system impedance spectrum based on fast and flexible adaptive filtering method. We show the equivalence between the problem of adaptive filter learning and deriving system impedance spectrum. To be specific we express the impedance via the adaptive filter weight coefficients. The noise canceling property of adaptive filtering has been also justified. Using the RLC circuit as a model system we experimentally show that adaptive filtering yields correct admittance spectra and elements ratings in the high noise conditions when Fourier transform technique fails. Providing the additional sensitivity for impedance spectroscopy, adaptive filtering can be applied to otherwise impossible to interpret time-domain impedance data.