Improved algorithm for the lock-in-amplifier adaptive noise canceller

The algorithm of lock-in-amplifier adaptive noise canceller is a method of eliminating the power-line interference, which is based on the lock-in amplifier in the hardware circuits. It could be used to calculate the amplitude, frequency and phase of the interference signals accurately. And the de-noised signals will be obtained by subtracting the reconstructed interference signals from the original signals. The method could also be utilized to filter the power-line interference even when original signals have low signal-to-noise ratios (SNR). In this paper, the original method is improved by new algorithms. Firstly Hanning window processing is applied, which makes the connection of filtered segments smoother. And then the FIR filters are replaced by wavelet filters. Finally, the improved algorithm is tested by processing the actual ECG signals and a better result is attained.