Normalized frequency domain LMS adaptive filter
AssigneeHughes Aircraft Company
InventorPaul L. Feintuch
Life of this patent
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Abstract
A normalized frequency domain Least Means Square filter. The feedback coefficient for each frequency bin is adjusted separately in the filter by use of an input power estimate. The power estimate is incorporated directly into the filter algorithm as a data-dependent, time-varying stochastic feedback coefficient. The filter is particularly useful in applications in which the input signal has large spectral variations, which could lead to filter instabilities in some frequency bins if a single feedback coefficient were employed in all frequency bins.
Claims11
A method for determining the feedback coefficient in a frequency domain Least Mean Square adaptive filter, comprising the steps of:
- (i) fixing the value of a feedback constant;
- (ii) for each frequency bin of the input signal to the filter, adaptively determining an estimate of the spectral power of the input signal within the particular frequency bin;
- and
- (iii) for each frequency bin, normalizing the feedback constant as a function of the input spectral power within said frequency bin to provide individual feedback coefficients for each of the frequency bins.
A frequency domain Least Main Square adaptive filter, comprising:
- means for respectively transforming an input signal and a reference signal into the frequency domain;
- means for filtering the transformed input signal by an adaptive filter weight;
- means for comparing the filtered, transformed input signal and the transformed reference signal to provide an error signal;
- means for feeding said error signal back to said filtering means for adaptively adjusting said filter weight as a function of said error signal and a feedback coefficient;
- and
- means for determining said feedback coefficient, comprising:
- (i) means for fixing the value of a feedback constant;
- (ii) means for adaptively determining estimates of the spectral power of the input signal at each frequency bin of the transformed input signal;
- and
- (iii) means for normalizing said feedback constant by said power estimates within each frequency bin to provide individual feedback coefficients for each of the frequency bins.
Dependencies are inferred from the claim text.