Iliev, Ivo Tzvetanov; Илиев, Иво Цветанов; Tabakov, Serafim Dimitrov; Табаков, Серафим Димитров; Krasteva, Vеssela Tzvetanova; Кръстева, Весела Цветанова

Combined high-pass and power-line interference rejecter filter for ECG signal processing

2008

Proceedings of the Technical University – Sofia, 58(2), 2008, pp. 7-13

Технически университет - София

1311-0829 [issn]

Article

eng

Real-time ECG filtering, average filter, baseline drift, mains interference

In this study we introduce one alternative approach for ECG high-pass filtering and interference rejection based on the simple principle for averaging of samples N with a predefined distance between them D. FilterDxN has a comb frequency characteristic with high-pass cut-off defined by the number of samples N and zeros at the integer ratio of the sampling frequency fs divided by the number of samples D. For a predefined fs, FilterDxN is easily adjusted to different cut-off and zero frequencies only by changing D and N. In this work, we present the mathematical background for deriving the frequency response of FilterDxN, as well as one particular application of the filter, i.e. Filter10x19 designed for fs=250 Hz, high-pass at 1 Hz, zero at 50 Hz. Tests with both standardized and real ECG signals proved that Filter10x19 is capable to remove very intensive baseline wanderings, and to fully suppress 50 Hz interferences with minimal affect on the ECG waveform. FilterDxN would be preferable in ECG systems operating in real time because of its linear filter equation with integer coefficients that hasten the speed of computations.

Reviewer prof. Ivan Dotsinski. - Formulas, schemes, diagr. - References, pp. 12-13