Effects of extremely low frequency electromagnetic fields on electrocardiogram: Analysis with quadratic time-frequency distributions

Recently we have studied the effects of extremely low frequency pulsed electromagnetic fields (ELF-PEMF) on the human biosignals. Electrocardiogram (ECG) and electroencephalogram (EEG) of seventeen healthy volunteers before and after the electromagnetic (EMF) exposure were recorded and analyzed. The root mean square (RMS) values of the recoded data were considered as comparison criteria. EEG results were shown that there were small variations in the brain electrical activity before and after exposure. The ECG power level was increased up to 1% for most of the subjects. In this paper, we further investigate the effects of the ELF-PEMF on the ECG signal using the hyperbolic T-distributions (HTD). This distribution was shown to be suitable for efficient amplitude and instantaneous frequency (IF) estimation of mono- and multicomponent FM signals. In this work, we introduce this distribution to the analysis of ECG signals. The simulation results show that the HTD have a good performance in the analysis of the ECG signals comparing with the Choi-Williams distribution (CWD). Moreover, the results show that there are small shift in the frequency-domain signal before and after EMF exposure.