A novel quadrature interference subtraction technique in ECG noise reduction

A line-interference reduction technique is described. The technique employs acquired interference data and derives the quasi-quadtree interference signal, which is subsequently used to find the interference-signal amplitude and phase in ECGs through a minimum-least-squares procedure. The technique removes the necessity of estimating the frequency of interference and only considers amplitude fitting. The algorithm is fast and is integrated into the QRS detection algorithm. The reduction is very good, and the interference is entirely eliminated in the digital data, which consists of 500 samples/s/channel at 12-bit resolution