ECG Power line Interference Removal Using Combination of FFT and Adaptive Non-linear Noise Estimator

Modern ECG instruments have a very high common mode rejection ratio to reduce power-line interference noise as much as possible. Nevertheless, the residual power-line noiseshould be eliminated. Due to the fact that, the central frequency of power-line may alters about ±1Hz and the desired signalsaround the central frequency should not be attenuated, applying the ideal notch filter with a fixed frequency or a band stop filteris not practical. Benefitting from the powerful microcontroller STM32F4 in a new brand of Electrocardiograph instrument Araz630”, we present a low cost efficient method of powerlinenoise removal. This method includes an FFT-based algorithm to find the center frequency of power-line and thensubtracting the noise estimated by adaptive non-linear algorithm. In our implementation, we achieve between 30 to 35 dB of cancellation of the fundamental power-line noise component and the central frequency is obtained by the resolution of 0.1 Hz.

Keywords:

Adaptive noise estimation , power-line noise , STM32F4 , CMSIS DSP