Removing residual power-line interference using WHT adaptive filter

Power-line interference is a common phenomenom in low-frequency biophysical measurement. The usual way of solving this is the use of a fixed bandwidth in an analog or digital notch filter. However, these methods are not very suitable when the power-line interference frequency is non-stationary. In this paper, an effective adaptive filter (ADF) structure is proposed to minimize the residual power-line interference without loss of reality. In order to obtain a satisfactory and acceptable convergence performance, the Walsh-Hadamard (WHT) transform is used in the ADF. Throughout many clinical measurements, the result of this structure is effective in eliminating EMI/EMC interference. However, to overcome the continuous changing frequency of power-line interference and to obtain a better convergence rate, a transform domain adaptive filter (TDADF) is used. An ECG result is shown after removing the power-line interference and its FFT.