A new interference-cancellation technique for instruments impacted by line-frequency signals

This paper introduces a new interference-cancellation technique for use in biomedical instruments and other devices impacted by line-frequency interference. This approach uses a Fourier decomposition to construct sinusoids that are subtracted from the corrupted input signal. The method has been implemented both in hardware and in software. Both systems have been designed using tools and techniques that have been successfully employed in power-system monitoring applications. Experimental results demonstrate the capabilities of both prototypes. The software-based approach uses a Kalman filter to drive a synchronization and resampling process that provides a simple and effective digital solution. Both systems are shown to be particularly useful in cases where the signal-to-noise ratio falls below unity.