Partitioned block frequency domain adaptive filter device comprising adaptation modules and correction modules

A device for cancelling an echo signal of a time domain input signal, the device comprising a partitioned block frequency domain adaptive filter device, the partitioned block frequency domain adaptive filter device comprising:

• a frequency domain adaptive filter configured for filtering a frequency domain representation of the time domain input signal depending on a set of filter coefficients comprising a plurality of blocks of filter coefficients in order to produce a filtered signal;
• a frequency domain to time domain converter configured for converting the filtered signal into an estimated echo signal representing an estimation of the echo signal in time domain;
• a subtraction module for producing an output signal by subtracting the estimated echo signal from a signal-to-be-processed comprising the echo signal;
• a plurality of parallel arranged filter update blocks, each of the filter update blocks being configured for updating one of the blocks of filter coefficients based on an update signal gathered by a circular correlation of a block of the frequency domain representation signal and a frequency domain control signal comprising a representation of the filtered signal;
• wherein each of the filter update blocks comprises an adaptation module configured for executing an adaptation sequence comprising:
• calculating an approximation of a constrained gradient update for the filter coefficients of the respective block of filter coefficients by applying an approximated constraining matrix exhibiting a lesser complexity than a constraining matrix to an unconstrained gradient update for the filter coefficients of the respective block of filter coefficients, wherein the unconstrained gradient update is derived from the update signal, and
• calculating a cumulative error introduced on the unconstrained gradient by applying the approximated constraining matrix to the unconstrained gradient update;
• wherein each of the filter update blocks comprises a correction module configured for executing a correction sequence comprising:
• calculating a corrected constrained gradient update for the filter coefficients of the respective block of filter coefficients by applying the constraining matrix to a sum of the approximation of the constrained gradient update and the cumulative error.

An adaptive filtering method comprising:

• using a frequency domain adaptive filter for filtering a frequency domain representation of a time domain input signal depending on a set of filter coefficients comprising a plurality of blocks of filter coefficients in order to produce a filtered signal;
• using each filter update block of a plurality of parallel arranged filter update blocks for updating one of the blocks of filter coefficients based on an update signal gathered by a circular correlation of a block of the frequency domain representation signal and a frequency domain control signal comprising a representation of the filtered signal;
• executing an adaptation sequence for each of the filter update blocks by using an adaptation module of the respective filter update block, the adaptation sequence comprising:
• calculating an approximation of the constrained gradient update for the filter coefficients of the respective block of filter coefficients by applying an approximated constraining matrix exhibiting a lesser complexity than a constraining matrix to an unconstrained gradient update for the filter coefficients of the respective block of filter coefficients, wherein the unconstrained gradient update is derived from the update signal, and
• calculating a cumulative error introduced on the unconstrained gradient by applying the approximated constraining matrix to the unconstrained gradient update;
• executing a correction sequence for each of the filter update blocks by using a correction module of the respective filter update block, the correction sequence comprising:
• calculating a corrected constrained gradient update for the filter coefficients of the respective block of filter coefficients by applying the frequency domain constraining matrix to a sum of the approximation of the constrained gradient update and the cumulative error.

A non-transitory digital storage medium having a computer program stored thereon to perform the adaptive filtering method comprising:

• using a frequency domain adaptive filter for filtering a frequency domain representation of a time domain input signal depending on a set of filter coefficients comprising a plurality of blocks of filter coefficients in order to produce a filtered signal;
• using each filter update block of a plurality of parallel arranged filter update blocks for updating one of the blocks of filter coefficients based on an update signal gathered by a circular correlation of a block of the frequency domain representation signal and a frequency domain control signal comprising a representation of the filtered signal;
• executing an adaptation sequence for each of the filter update blocks by using an adaptation module of the respective filter update block, the adaptation sequence comprising:
• calculating an approximation of the constrained gradient update for the filter coefficients of the respective block of filter coefficients by applying an approximated constraining matrix exhibiting a lesser complexity than a constraining matrix to an unconstrained gradient update for the filter coefficients of the respective block of filter coefficients, wherein the unconstrained gradient update is derived from the update signal, and calculating a cumulative error introduced on the unconstrained gradient by applying the approximated constraining matrix to the unconstrained gradient update;
• executing a correction sequence for each of the filter update blocks by using a correction module of the respective filter update block, the correction sequence comprising:
• calculating a corrected constrained gradient update for the filter coefficients of the respective block of filter coefficients by applying the frequency domain constraining matrix to a sum of the approximation of the constrained gradient update and the cumulative error,
• when said computer program is run by a computer.