Method and apparatus for interference reduction

The method as claimed in claim herein the excitation frequency is given by:

• (the first fundamental frequency)/n,
• where n is an integer.

A method of processing a periodic data-carrying signal 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 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 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.

Apparatus for processing a periodic data-carrying signal 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 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 in series with an averaging/integrating filter, wherein the comb filter is configured to reject interference at the first fundamental frequency from the data-carrying signal, and the averaging/integrating filter is configured to reject interference at the second fundamental frequency from the data-carrying signal.