Method and apparatus for interference reduction

摘要

A method of processing a periodic data-carrying signal (12) to reduce periodic interference at either of a first fundamental frequency or a second fundamental frequency, the second fundamental frequency being different from the first fundamental frequency, the periodic data-carrying signal (12) being derived from an excitation signal having an excitation frequency, the excitation frequency being a sub-multiple of the first fundamental frequency, the method comprising: subjecting the data-carrying signal (12) to both a comb filter operation to reject interference at the first fundamental frequency, and an averaging/integrating filter operation to reject interference at the second fundamental frequency; wherein the comb filter operation has a comb filter delay period related to the first fundamental frequency; and wherein the averaging/integrating filter operation averages or integrates over a period related to the second fundamental frequency. Also provided is apparatus for processing a periodic data-carrying signal (12) to reduce periodic interference at either of a first fundamental frequency or a second fundamental frequency, the second fundamental frequency being different from the first fundamental frequency, the periodic data-carrying signal (12) being derived from an excitation signal having an excitation frequency, the excitation frequency being a sub-multiple of the first fundamental frequency, the apparatus comprising: a comb filter (10) in series with an averaging/integrating filter (11), wherein the comb filter (10) is configured to reject interference at the first fundamental frequency from the data-carrying signal (12), and the averaging/integrating filter (11) is configured to reject interference at the second fundamental frequency from the data-carrying signal (12); wherein the comb filter (10) has a comb filter delay period related to the first fundamental frequency; and wherein the averaging/integrating filter (11) is configured to average or integrate over a period related to the second fundamental frequency.