Adaptive Combined High-Pass and Mains Interference Rejection Filter

The paper presents an alternative approach for high-pass filtering of ECG and simultaneous removal of mains interference.The approach is based on the summation of several filters having zeros for the mains and zero frequencies.A program is compiled that calculates the coefficients of the combined filter depending on the set cut-off frequency for the high-pass filtering, the sampling rate, and the frequency of the mains interference.The combined filter is adaptive to the mains interference's frequency deviation.The implementation of the filtering is carried out in three consecutive steps: ithe mains interference is subtracted from the ECG signal; iithe change in the mains frequency relative to its rated value is determined; iiithe coefficients of the combined filter are recalculated.The mathematical basis for synthesizing the combined filter is presented.Tests performed with artificial and real ECG signals and disturbances prove that the combined filter is able to remove very intense baseline drift and completely suppress mains interferences with minimal impact on the ECG signal shape.