title: Selecting the optimal anti-aliasing filter for multichannel biosignal acquisition intended for inter-signal phase shift analysis.
abstract: The availability of microcomputer-based portable devices facilitates the high-volume multichannel biosignal acquisition and the analysis of their instantaneous oscillations and inter-signal temporal correlations. These new, non-invasively obtained parameters can have considerable prognostic or diagnostic roles. The present study investigates the inherent signal delay of the obligatory anti-aliasing filters. One cycle of each of the 8 electrocardiogram (ECG) and 4 photoplethysmogram signals from healthy volunteers or artificially synthesised series were passed through 100-80-60-40-20 Hz 2-4-6-8th order Bessel and Butterworth filters digitally synthesized by bilinear transformation, that resulted in a negligible error in signal delay compared to the mathematical model of the impulse- and step responses of the filters. The investigated filters have as diverse a signal delay as 2-46 ms depending on the filter parameters and the signal slew rate, which is difficult to predict in biological systems and thus difficult to compensate for. Its magnitude can be comparable to the examined phase shifts, deteriorating the accuracy of the measurement. As a conclusion, identical or very similar anti-aliasing filters with lower orders and higher corner frequencies, oversampling, and digital low pass filtering are recommended for biosignal acquisition intended for inter-signal phase shift analysis.
authors.affiliation: Heart Institute, Medical Faculty, University of Pécs, Medical Faculty, Ifjúság str. 13, Pécs, 7624, Hungary. Department of Automation, University of Pécs, Pollack Mihály Faculty of Engineering and Information Technology, Boszorkány str. 2, Pécs, 7624, Hungary. nemron tech Ltd., Felsővámház str 30, Pécs, 7626, Hungary (present affiliation.
authors.forename: Róbert
authors.initials: R
authors.lastname: Keresnyei
authors.forename: Péter
authors.initials: P
authors.lastname: Megyeri
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Zidarics
authors.forename: László
authors.initials: L
authors.lastname: Hejjel
mesh_terms: D003198:Computer Simulation; D004562:Electrocardiography / Q000295:instrumentation / Q000379:methods*; D008838:Microcomputers; D008962:Models, Theoretical; D017156:Photoplethysmography / Q000295:instrumentation / Q000379:methods*; D012815:Signal Processing, Computer-Assisted