Performance Limitations Of A Single Frequency Adaptive Interference Canceller For Ecg Signals

A single-frequency adaptive noise canceller (SF-ANC) using the LMS algorithm can be used to remove power-line interference from electrocardiograms (ECG's) [l-21. The procedure is computationally rapid, provides a zero at the notch frequency and can often be carried out in close to real time. In this paper we study the performance of a SF-ANC and present some important but little understood experimental results which can be helpful in designing a real-time ANC. We show that an SF-ANC based on the LMS algorothim will not only attenuate signal components near the interference frequency but also amplify signal components far away from the interference frequency . We also demonstrate that the signal-to-noise-ratio(SNR) at the output is independent of the SNR at the input and that performance of an SF-ANC will be adversely affected by the arrival of a large magnitude signal such as the QRS complex in ECG's.