Time-varying IIR multi-notch filter based on all-pass filter prototype

In this paper a concept of infinite impulse response narrow multi-band-stop time-varying filter based on all-pass prototype filter is proposed. The IIR multi-notch filter is used for removing power-line interferences from biomedical sources such as ECG. In order to reduce the duration of the transient state of the proposed IIR multi-notch filter, the parameters of the all-pass prototype filter are temporarily varied in time. The proposed filter is tested using sinusoidal and ECG signals. Computer simulations and performance indexes demonstrate that the proposed time-varying IIR multi-notch filter based on the all-pass prototype filter possesses better properties than traditional time-invariant IIR multi-notch filter.