US 5,966,684 AGranted

Method and apparatus for cancelling periodic electrical interference

OwnerThomas L. Richardson, Robert F. Richardsoninventors

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Abstract

A system involving method and apparatus for cancelling a periodic electrical interference signal from a signal of interest is disclosed. The system of the invention creates an estimate of the periodic noise component in an electrical signal by sampling the electrical signal at intervals locked to the period of the source of the electrical interference signal. The system analyzes the sampled signal to isolate periodically repeating portions of the signal characteristic of noise. The system inverts the estimate of the noise component and constructs a continuous repeating waveform which is added to the electrical signal. The system does not eliminate transient features of the signal of interest, even when those transient features have frequency components which overlap with frequencies present in the electrical interference signal.

Claims20

Dependent claims

A method for cancelling electrical interference from an electrical signal, said method comprising the steps of:

a) providing an electrical signal comprising a signal of interest and a periodic interference signal having a period, said interference signal and said signal of interest both having components at one or more common frequencies;
b) cancelling said electrical interference signal from said electrical signal, without affecting said signal of interest at said common frequencies, by the steps of:
i) providing a timing signal having a period equal to said period of said interference signal;
ii) generating a sequence of digitized segments of said electrical signal by sampling and digitizing said electrical signal at times controlled by said timing signal, each digitized segment comprising a sequence of sampled values representing a segment of said electrical signal having a period equal to said period of said interference signal;
iii) generating an estimate of said interference signal from said digitized segments by extracting a stationery component from said digitized segments and periodically updating said estimate;
iv) generating a continuous, periodic anti-interference signal from said estimate;
and,
v) adding said anti-interference signal to said electrical signal to substantially cancel said electrical interference signal from said electrical signal.

5 more elements

A method for cancelling interference from a signal, said signal comprising a signal of interest mixed with a periodic interference signal having a period, said method comprising the step of adding an anti-interference signal to said signal to cancel said periodic interference signal from said signal, wherein said anti-interference signal is derived by the steps of:

a) in each of several sequential periods of said periodic interference signal, taking a plurality of m samples v(k), of said signal after said addition of said anti-noise signal, said samples taken at spaced apart phases of said interference signal, where k is an index representing said spaced apart phases with 1.ltoreq.k.ltoreq.m;
b) for each value of k, digitally integrating said sampled values v(k) and storing results of said integration in an integrator buffer;
c) performing a modified lateral filtering operation on said results in said integrator buffer and storing results of said modified lateral filtering operation as values in a replica buffer;
d) creating a continuous anti-interference signal having a waveform defined by said values in said replica buffer.

1 more element

Dependencies are inferred from the claim text.