Harmonic-series filter
First Claim
1. A filtering system comprising:
- a first input that receives a signal contaminated with noise;
a second input that receives a noise reference signal;
a set of M notch filters, wherein each of the M notch filters is responsive to a corresponding tuning coefficient so as to attenuate a corresponding noise frequency in the signal contaminated with noise;
a tuning parameter generator coupled to the second input, wherein the tuning parameter generator is arranged to generate a tuning parameter corresponding to a fundamental frequency of the noise based on the noise reference signal;
a filter coefficient generator coupled to the tuning parameter generator and to each of the M notch filters, wherein the filter coefficient generator is responsive to the tuning parameter so as to provide each of the M notch filters with the corresponding tuning coefficient; and
, a gain normalizer coupled to the M notch filters and to the first input, wherein the gain normalizer is arranged to adjust an overall gain of the M notch filters.
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Abstract
In a filtering system, a first input receives a signal contaminated with noise. A second input receives a noise reference signal. Each notch filter in a set of M notch filters is responsive to a corresponding tuning coefficient so as to attenuate a corresponding noise frequency in the signal contaminated with noise. A tuning parameter generator responds to the noise reference signal by generating a tuning parameter corresponding to a fundamental frequency of the noise and tracks that fundamental frequency. A filter coefficient generator responds to the tuning parameter by providing each of the M notch filters with the corresponding tuning coefficient. A gain normalizer adjusts the overall gain of the M notch filters.
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Citations
37 Claims
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1. A filtering system comprising:
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a first input that receives a signal contaminated with noise;
a second input that receives a noise reference signal;
a set of M notch filters, wherein each of the M notch filters is responsive to a corresponding tuning coefficient so as to attenuate a corresponding noise frequency in the signal contaminated with noise;
a tuning parameter generator coupled to the second input, wherein the tuning parameter generator is arranged to generate a tuning parameter corresponding to a fundamental frequency of the noise based on the noise reference signal;
a filter coefficient generator coupled to the tuning parameter generator and to each of the M notch filters, wherein the filter coefficient generator is responsive to the tuning parameter so as to provide each of the M notch filters with the corresponding tuning coefficient; and
,a gain normalizer coupled to the M notch filters and to the first input, wherein the gain normalizer is arranged to adjust an overall gain of the M notch filters. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A method comprising:
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generating a tuning parameter corresponding to a fundamental frequency of noise in a signal contaminated with the noise;
generating tuning coefficients β
1, β
2, β
3, . . . , β
M in response to the tuning parameter, wherein the tuning coefficients β
1, β
2, β
3, . . . , β
M correspond to the fundamental frequency and to harmonics of the fundamental frequency; and
,filtering the signal with notches positioned at frequencies determined by the tuning coefficients β
1, β
2, β
3, . . . , β
M that the noise is attenuated. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27)
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28. A notch filter comprising:
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an input that receives an input signal contaminated with noise, wherein the noise has a fundamental frequency;
an output that provides an output signal from the notch filter, wherein the output signal is substantially free of a harmonic of the fundamental frequency of the noise;
a first summer that sums the input signal with an output of a first delay, wherein the first summer has an output providing the output signal;
a first multiplier that multiplies the output signal by a gain coefficient;
a second summer that subtracts an output of the first multiplier from the input signal;
a third summer that subtracts an output of a second delay from an output of the second summer;
a second multiplier that multiplies an output of the third summer by a tuning coefficient related to the harmonic frequency;
a fourth summer that subtracts an output of the second multiplier from the output of the second summer, the fourth summer having an output coupled as an input to the second delay; and
,a fifth summer that subtracts the output of the second multiplier from the output of the second delay, wherein an output of the fifth summer is coupled as an input to the first delay. - View Dependent Claims (29, 30, 31, 32, 33)
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34. A notch filter that applies a transfer function F(z,n) to an input signal contaminated with noise in order to produce an output signal in which a harmonic of the noise is attenuated, wherein the transfer function F(z,n) is defined by the following equation:
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wherein n designates the harmonic, wherein β
n is a turning coefficient related to a center frequency of a bandwidth of the notch filter, wherein α
is a quantity related to the bandwidth of the notch filter, wherein z−
1 represents a first order delay, and wherein z−
1 represents a second order delay.- View Dependent Claims (35, 36, 37)
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Specification