Reduction of digital filter delay
AssigneeTelefonaktiebolaget L M Ericsson (publ)
InventorsDan Lusk, Tonu Trump
Life of this patent
Estimating the term…
Abstract
An apparatus for reducing a digital filter delay includes means for determining the magnitude response of a desired filter. Means form the real cepstrum of this magnitude response. Means transform the real cepstrum into a complex cepstrum of a corresponding minimum-phase filter having the same magnitude response as the desired filter. A filter applies a smoothly decaying shaping window to the complex cepstrum. Means transform the shaped complex cepstrum into an estimated minimum-phase filter.
Claims10
A method of reducing a digital filter delay, including the steps of
- determining a first finite sequence of coefficients representing a real cepstrum of a magnitude response of a desired digital filter,
- transforming said first sequence into a second sequence of coefficients representing a corresponding complex cepstrum,
- determining an estimate of a minimum-phase digital filter corresponding to said second sequence, where said transforming step includes shaping of coefficients to be included in said second sequence by applying a smoothly decaying window function.
An apparatus for reducing a digital filter delay, wherein said apparatus is configured to perform the following:
- determine a first finite sequence of coefficients representing a real cepstrum of a magnitude response of a desired digital filter,
- transform said first sequence into a second sequence of coefficients representing a corresponding complex cepstrum, and
- determine an estimate of a minimum-phase digital filter corresponding to said second sequence, where said apparatus is configured to transform said first sequence by applying a smoothly decaying window function to shape coefficients to be included in said second sequence.
An echo canceller for a telecommunication system, including a non-linear processor with a serially connected echo canceling digital filter, wherein said echo canceller comprises:
- an apparatus for reducing the delay of said filter, wherein said apparatus is configured to perform the following:
- determine a first finite sequence of coefficients representing a real cepstrum of a magnitude response of a desired digital filter,
- transform said first sequence into a second sequence of coefficients representing a corresponding complex cepstrum, and
- determine an estimate of a minimum-phase digital filter corresponding to said second sequence, where said apparatus is configured to transform said first sequence by applying a smoothly decaying window function to shape coefficients to be included in said second sequence.
A noise suppressor including a serially connected noise suppressing digital filter, said noise suppressor comprising:
- an apparatus for reducing the delay of said filter, wherein said apparatus is configured to perform the following:
- determine a first finite sequence of coefficients representing a real cepstrum of a magnitude response of a desired digital filter,
- transform said first sequence into a second sequence of coefficients representing a corresponding complex cepstrum, and
- determine an estimate of a minimum-phase digital filter corresponding to said second sequence, where said apparatus is configured to transform said first sequence by applying a smoothly decaying window function to shape coefficients to be included in said second sequence.
Dependencies are inferred from the claim text.