Tracking Harmonic Notch Filter.
Patent, Filed 20 Mar 89, patented 3 Jul 90,
DEPARTMENT OF THE NAVY WASHINGTON DC
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An electronic filter for automatically tracking and removing harmonically related interfering electrical signals such as power line interference harmonics without attenuating other signals of interest even though the signals are frequency stable andor near the interference signal frequencies. The filter comprises a very narrow band electronic commutated capacitor-bank comb-notch filter driven by a counterdecoder circuit which is in turn driven by a phase locked loop. The filter also comprises two narrow band analog filters tuned to the two lowest harmonics of the interfering signal and drives the comb-notch at unit multiples of the fundamental of the interference frequency. This action is continuous such that center frequencies of the notches are automatically adjusted to compensate for small variations in the interference frequency. Patents. rrh
- Electricity and Magnetism