Method of and apparatus for identifying unknown system using adaptive filter
AssigneeNEC Corporation
InventorAkihiko Sugiyama
Life of this patent
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Abstract
A method of and an apparatus for identifying an unknown system using an adaptive filter wherein the step size is subsequently supplied to the adaptive filter so that the identification error may be decreased. Value of the step size is calculated by using a gradient of power of error signal according to the LMS or LIM (learning identification method) algorithm, and limited by the previous value of step size. Further, when a sudden change in the error signal is detected, the step size can be re-setted or the limitation to the step size can be released.
Claims93
A method of identifying an unknown system using an adaptive filter, which delays an input signal successively by one sample period to form a plurality of samples, calculates products between the samples and corresponding samples of a plurality of multiplicands provided correspondingly to the plurality of samples, and outputs the sum total of the products,
- wherein the unknown system is identified by adding to each of the multiplicands a product among a difference signal obtained by subtraction of an output of said adaptive filter from an output of the unknown system, the sample corresponding to the multiplicand and a parameter as an updated amount for unit updating to update the multiplicands so that the difference signal is decreased, characterized in that
- a value which increases in proportion to a gradient of the difference signal with respect to the parameter is added to the parameter to obtain a sum and the parameter is modified using a limited sum obtained by applying a limit to the sum, and a threshold value for applying the limit is determined using a previous limited sum or sums.
A method of identifying an unknown system using an adaptive filter, which delays an input signal successively by one sample period to form a plurality of samples, calculates products between the samples and corresponding samples of a plurality of multiplicands provided correspondingly to the plurality of samples, and outputs the sum total of the products,
- wherein the unknown system is identified by adding to each of the multiplicands a product among a difference signal obtained by subtraction of an output of said adaptive filter from an output of the unknown system, the sample corresponding to the multiplicand and a parameter as an updated amount for unit updating to update the multiplicands so that the difference signal is decreased, characterized in that
- a value which increases in proportion to a gradient of the difference signal with respect to the parameter is added to the parameter to obtain a sum and when a sudden change in the difference signal is detected, the sum is replaced with a predetermined constant, and the parameter is modified using a limited sum obtained by applying a limit to the sum, and further, a threshold value for applying the limit is determined using a previous limited sum or sums.
A method of identifying an unknown system using an adaptive filter, which delays an input signal successively by one sample period to form a plurality of samples, calculates products between the samples and corresponding samples of a plurality of multiplicands provided correspondingly to the plurality of samples, and outputs the sum total of the products,
- wherein the unknown system is identified by adding to each of the multiplicands a product among a difference signal obtained by subtraction of an output of said adaptive filter from an output of the unknown system, the sample corresponding to the multiplicand and a parameter as an updated amount for unit updating to update the multiplicands so that the difference signal is decreased, characterized in that
- a value which increases in proportion to a gradient of the difference signal with respect to the parameter is added to the parameter to obtain a sum and a limited sum is calculated by applying a limit to the sum, and when a sudden change in the difference signal is detected, the limited sum is replaced with a predetermined constant, and then the parameter is modified using the thus replaced limited sum and a threshold value for applying the limit is determined using a previous limited sum or sums.
An identifying apparatus for identifying a characteristic of an unknown system using an adaptive filter, characterized in that said apparatus comprises:
- a subtracter for subtracting an output of said adaptive filter from an output signal of the unknown system to obtain a difference signal;
- a step size controller for receiving the difference signal and an input signal to said adaptive filter and successively calculating a step size for use for the updating of coefficients of said adaptive filter;
- a limiter for receiving an output of said step size controller and limiting the received output;
- a first delay element for feeding back an output of said limiter to said limiter and said step size controller;
- and
- a first multiplier for multiplying the output of said limiter by the difference signal;
- and in that
- an output of said first multiplier is used as the step size for the updating of coefficients of said adaptive filter.
An identifying apparatus for identifying a characteristic of an unknown system using an adaptive filter, characterized in that said apparatus comprises:
- a subtracter for subtracting an output of said adaptive filter from an output signal of the unknown system to obtain a difference signal;
- an error change detecting circuit for receiving the difference signal and detecting a sudden change of the received difference signal;
- a step size controller for receiving the difference signal and an input signal to said adaptive filter and successively calculating a step size for use for the updating of coefficients of said adaptive filter;
- a limiter for receiving an output of said step size controller and limiting the received output;
- a first selector for receiving an output of said limiter and a predetermined constant and selectively outputting one of the two received signals in response to an output of said error change detecting circuit;
- a second delay element for feeding back an output of said first selector to said limiter and said step size controller;
- and
- a first multiplier for multiplying the output of said limiter by the difference signal;
- and in that
- an output of said first multiplier is used as the step size for the updating of coefficients of said adaptive filter.
A method of identifying an unknown system using an adaptive filter, which delays an input signal successively by one sample period to form a plurality of samples, calculates products between the samples and corresponding samples of a plurality of multiplicands provided correspondingly to the plurality of samples, and outputs the sum total of the products,
- wherein the unknown system is identified by adding to each of the multiplicands a product among a difference signal obtained by subtraction of an output of said adaptive filter from an output of the unknown system, the sample corresponding to the multiplicand and a parameter as an updated amount for unit updating to update the multiplicands so that the difference signal is decreased, characterized in that
- a value which increases in proportion to a gradient of the difference signal with respect to the parameter is added to the parameter to obtain a sum and a limit is applied to the sum to obtain a limited sum, and when a sudden change in the difference signal is detected, the sum is regarded as the limited sum only for a period of time of a number of clocks equal to a predetermined first constant, and then the parameter is modified using the limited sum, and a threshold value for applying the limit is determined using a previous limited sum or sums.
An identifying apparatus for identifying a characteristic of an unknown system using an adaptive filter, characterized in that said apparatus:
- a subtracter for subtracting an output of said adaptive filter from an output signal of the unknown system to obtain a difference signal;
- a first delay element;
- an error change detecting circuit for receiving the difference signal and detecting a sudden change of the received difference signal;
- a counter for receiving an output of said error change detecting circuit and counting clocks;
- a first selector for receiving an output of said error change detecting circuit and an output of said first delay element and selectively outputting one of the two received outputs in response to an output of said counter;
- a step size controller for receiving the difference signal and an input signal to said adaptive filter and successively calculating a step size for use for the updating of coefficients of said adaptive filter;
- a limiter for receiving an output of said step size controller and limiting the received output;
- a second selector for receiving an output of said limiter and the output of said step size controller and selectively outputting one of the two received outputs in response to an output of said first selector;
- a second delay element for feeding back an output of said second selector to said limiter;
- and
- a first multiplier for multiplying the output of said second selector by the difference signal;
- and that
- said first delay element delays the output of said first selector and feeds back the delayed output to an input of said first selector;
- and
- an output of said first multiplier is used as a step size for the updating of coefficients of said adaptive filter.
A method of identifying an unknown system using an adaptive filter, which delays an input signal successively by one sample period to form a plurality of samples, calculates products between the samples and corresponding samples of a plurality of multiplicands provided correspondingly to the plurality of samples, and outputs the sum total of the products,
- wherein the unknown system is identified by adding to each of the multiplicands a product among a difference signal obtained by subtraction of an output of said adaptive filter from an output of the unknown system, the sample corresponding to the multiplicand and a parameter as an updated amount for unit updating to update the multiplicands so that the difference signal is decreased, characterized in that
- a value which increases in proportion to a gradient of the difference signal with respect to the parameter is added to the parameter to obtain a sum and a limit is applied to the sum to obtain a limited sum, and then, an average value of these limited sums is calculated and is determined as the parameter for calculation of the updated amount.
An identifying apparatus for identifying a characteristic of an unknown system using an adaptive filter, characterized in that said apparatus:
- a subtracter for subtracting an output of said adaptive filter from an output signal of the unknown system to obtain a difference signal;
- a step size controller for receiving the difference signal and an input signal to said adaptive filter and successively calculating a step size for use for the updating of coefficients of said adaptive filter;
- a limiter for receiving an output of said step size controller and limiting the received output;
- and
- an averaging circuit for receiving an output of said limiter and calculating an average value from the received output;
- and in that
- an output of said averaging circuit is used as a step size for the updating of coefficients of said adaptive filter.
An identifying apparatus for identifying a characteristic of an unknown system using an adaptive filter, characterized in that said apparatus:
- a subtracter for subtracting an output of said adaptive filter from an output signal of the unknown system to obtain a difference signal;
- an error change detecting circuit for receiving the difference signal and detecting a sudden change of the received difference signal;
- a counter for receiving an output of said error change detecting circuit and counting clocks;
- a first delay element;
- a first selector for receiving an output of said error change detecting circuit and an output of said first delay element and selectively outputting one of the two received outputs in response to an output of said counter;
- a step size controller for receiving the difference signal and an input signal to said adaptive filter and successively calculating a step size for use for the updating of coefficients of said adaptive filter;
- a limiter for receiving an output of said step size controller and limiting the received output;
- an averaging circuit for receiving an output of said limiter and calculating an average value from the received output;
- and
- a second selector for receiving an output of said averaging circuit and a predetermined constant and selectively outputting one of the two received signals in response to an output of said first selector;
- and that
- said first delay element delays the output of said first selector and feeds back the delayed output to an input of said first selector;
- and in that
- an output of said averaging circuit is used as a step size for the updating of coefficients of said adaptive filter.
A method of identifying an unknown system using an adaptive filter, which delays an input signal successively by one sample period to form a plurality of samples, calculates products between the samples and corresponding samples of a plurality of multiplicands provided correspondingly to the plurality of samples, and outputs the sum total of the products,
- wherein the unknown system is identified by adding to each of the multiplicands a normalized value of a product among a difference signal obtained by subtraction of an output of said adaptive filter from an output of the unknown system, the sample corresponding to the multiplicand and a parameter as an updated amount for unit updating to update the multiplicands so that the difference signal is decreased, said normalized value being obtained by normalization of the product with a value of input power to said adaptive filter, characterized in that
- a value which increases in proportion to a gradient of the difference signal normalized with the value of input power to said filter with respect to the parameter is added to the parameter to obtain a sum, and the parameter is modified using the sum.
A method of identifying an unknown system using an adaptive filter, which delays an input signal successively by one sample period to form a plurality of samples, calculates products between the samples and corresponding samples of a plurality of multiplicands provided correspondingly to the plurality of samples, and outputs the sum total of the products,
- wherein the unknown system is identified by adding to each of the multiplicands a normalized value of a product among a difference signal obtained by subtraction of an output of said adaptive filter from an output of the unknown system, the sample corresponding to the multiplicand and a parameter as an updated amount for unit updating to update the multiplicands so that the difference signal is decreased, said normalized value being obtained by normalization of the product with a value of input power to said adaptive filter, characterized in that
- a value which increases in proportion to a gradient of the difference signal normalized with the value of input power to said filter with respect to the parameter is added to the parameter to obtain a sum and the parameter is modified using a limited sum obtained by applying a limit to the sum, and a threshold value for applying the limit is calculated using a previous limited sum or sums.
An identifying apparatus for identifying a characteristic of an unknown system using an adaptive filter, characterized in that said apparatus:
- a subtracter for subtracting an output of said adaptive filter from an output signal of the unknown system to obtain a difference signal;
- a correlation calculating circuit for receiving an input signal to said adaptive filter and calculating and outputting a power value and a correlation of the input signal;
- a first delay element for receiving the power value and delaying the received power value by one sample period;
- a second delay element;
- a step size controller for receiving the difference signal, the correlation value, an output of said first delay element and an output of said second delay element and successively calculating a step size for use for the updating of coefficients of said adaptive filter;
- a limiter for receiving an output of said step size controller and limiting the received output;
- a first multiplier for multiplying an output of said limiter by the difference signal;
- and
- a first normalizing circuit for normalizing an output of said first multiplier with the power value;
- and in that
- said second delay element delays the output of said limiter by one sample period and feeds back the thus delayed output to said step size controller;
- and
- an output of said first normalizing circuit is used as a step size for the updating of coefficients of said adaptive filter.
An identifying apparatus for identifying a characteristic of an unknown system using an adaptive filter, characterized in that said apparatus comprises:
- a subtracter for subtracting an output of said adaptive filter from an output signal of the unknown system to obtain a difference signal;
- an error change detecting circuit for receiving the difference signal and detecting a sudden change of an identification error of said adaptive filter included in the received difference signal;
- a correlation calculating circuit for receiving an input signal to said adaptive filter and calculating and outputting a power value and a correlation of the input signal;
- a first delay element for receiving the power value and delaying the received power value by one sample period;
- a second delay element;
- a step size controller for receiving the difference signal, the correlation value, an output of said first delay element and an output of said second delay element and successively calculating a step size for use for the updating of coefficients of said adaptive filter;
- a limiter for receiving an output of said step size controller and limiting the received output;
- a selector for receiving an output of said limiter and a predetermined first constant and selectively outputting one of the two received signals in response to an output of said error change detecting circuit;
- a first multiplier for multiplying an output of said selector by the difference signal;
- and
- a first normalizing circuit for normalizing an output of said first multiplier with the power value;
- and in that
- said second delay element delays the output of said limiter by one sample period and feeds back the thus delayed output to said step size controller and said limiter;
- and
- an output of said first normalizing circuit is used as a step size for the updating of coefficients of said adaptive filter.
An identifying apparatus for identifying a characteristic of an unknown system using an adaptive filter, characterized in that said apparatus:
- a subtracter for subtracting an output of said adaptive filter from an output signal of the unknown system to obtain a difference signal;
- an error change detecting circuit for receiving the difference signal and detecting a sudden change of an identification error of said adaptive filter included in the received difference signal;
- a holding circuit for holding an output of said error change detecting circuit for a fixed period of time;
- a correlation calculating circuit for receiving an input signal to said adaptive filter and calculating and outputting a power value and a correlation of the input signal;
- a first delay element for receiving the power value and delaying the received power value by one sample period;
- a second delay element;
- a step size controller for receiving the difference signal, the correlation value, an output of said first delay element and an output of said second delay element and successively calculating a step size for use for the updating of coefficients of said adaptive filter;
- a limiter for receiving an output of said step size controller and limiting the received output;
- a selector for receiving an output of said limiter and the output of said step size controller and selectively outputting one of the two received signals in response to an output of said holding circuit;
- a first multiplier for multiplying an output of said selector by the difference signal;
- and
- a first normalizing circuit for normalizing an output of said first multiplier with the power value;
- and in that
- said second delay element delays the output of said limiter by one sample period and feeds back the thus delayed output to said step size controller and said limiter;
- and
- an output of said first normalizing circuit is used as a step size for the updating of coefficients of said adaptive filter.
Dependencies are inferred from the claim text.