A Method for Elimination of Alternative Noise by Digital Control of an Analog Laguerre Filter in Biopotential Measurements

摘要

The biological electrical signals measured on the surface of the body, such as electroencephalograms, elec-tromyograms, and electroretinograms, contain strong AC noise from the commercial power supply. Even if a differential amplifier with a high discrimination ratio is used, it is often difficult, depending on the measurement environment, to completely eliminate AC noise. This paper considers a method for AC noise elimination in which an analog Laguerre filter is inserted on the negative input side of the differential preamplifier, and digital control is applied to the filter. An algorithm is constructed in which the transfer function of the Laguerre filter is designed so that AC noise with the known frequency and its harmonic components are minimized, based only on the output power spectrum, without using the tap output of the filter. A system was constructed and its application to biological electrical signals such as electroencephalograms and electroretinograms was attempted.