Second-Order N-path Notch Filter for Hum Noise Suppression

Hum noise activity such as power line noise is one of critical problems in biomedical signals processing. Various approaches utilizing both analog and digital techniques have been proposed. However, these approaches have some disadvantages. This paper proposes the use of N-path notch filter as a hum noise filter. The notch depth in a conventional N-path notch filter is limited by the number of path and off-resistance. A new N-path notch filter with second-order resistor equivalent switched capacitor is proposed. Simulation results show that with resistor equivalent switched capacitor circuit improves the notch depth by 63.67dB with an off-resistance of 200MΩ.