Self adaptive filter and control circuit therefor

Claim 3

A method as claimed in claim 1, wherein said step of generating and storing, in an error function store, comprises the steps of sampling a difference signal at time-spaced intervals over a predetermined period to produce first difference signal samples, said difference signal being the difference between said another signal and said output signal, and storing said first difference signal samples, said first difference signal samples comprising said set of first error function co-efficients and each said set of modified error function co-efficients comprising a separate set of modified difference signal samples and said step of generating and storing, in a control function store, comprises the steps of sampling said input signal at time-spaced intervals over a period substantially corresponding to said predetermined period to produce input signal samples, and storing said input signal samples in said control function store, whereby said input signal samples comprise said control function coefficients.

Claim 4

A method as claimed in claim 2, wherein said first set of changes id determined by a. computing partial derivatives of said error function with respect to said co-efficients of impulse response in accordance with the following equation:

Claim 5

A method as claimed in claim 3, wherein said step of modifying the last preceding co-efficients stored in said error function store comprises the step of subtracting said modifications from said last preceding coefficients, said modifications being coefficients of the matrix product X. Delta R where X is the matrix of said input signal samples and Delta R is the matrix of the last-determined set of changes to said impulse response co-efficients.

Claim 6

A method as claimed in claim 1, wherein said step of generating and storing, in an error function store, comprises the steps of generating electrical signals representing coefficients of crosscorrelation between said input signal and a difference signal, said difference signal being the difference between said another signal and said output signal, sampling said electrical signals to provide a first set of cross-correlation coefficient samples, and storing this first set of cross-correlation samples in said error function store whereby said first set of cross-correlation samples comprise said set of first error function coefficients and each said set of modified error function coefficients comprise a set of modifiEd cross-correlation coefficients, and wherein said step of generating and storing in a control function store comprises the step of generating electrical signals representing coefficients of auto-correlation of said input signal, sampling the last-mentioned signals to provide auto-correlation samples, and storing the auto-correlation samples in said control function store, whereby said auto-correlation samples comprise said control function coefficients.

Claim 7

A method as claimed in claim 5, wherein said first set of changes is determined by the step of reading the signs of cross-correlation samples of said first set thereof and each said further set of changes is determined by reading the signs of the last computed set of modified cross-correlation samples.

Claim 8

A method as claimed in claim 6, wherein said step of modifying the last preceding coefficients stored in said error function store comprises the step of subtracting said modifications to said last preceding coefficients, said modifications being computed as coefficients of the matrix product A. Delta R where A is the matrix of said auto-correlation samples and Delta R is the matrix of the last determined set of changes to said impulse response coefficients.

Claim 9

Apparatus including a control circuit for altering the output signal from a filter network, resulting from an input signal thereto by altering the impulse response of said filter network and so as to conform to another signal, in which said control circuit comprises: first shiftable storage means for receiving samples of at least one first signal at least related to said input signal; second shiftable storage means for receiving samples of at least one second signal at least related to said output signal; third shiftable storage means for storing values of adjustments of said impulse response; modification means coupling said third storage means to the output of at least said second storage means for repetitively modifying said impulse response adjustment values; updating means including multiplier means and aggregating means, said updating means being connected from said first and third storage means to said second storage means and repetitively, and in alternation to said repetitive modification of said impulse response adjustment values, applying outputs of said first and third storage means to said multiplier means and aggregating means for producing an aggregation of multiplicands of said first signal samples and stored values of adjustments in said third storage means, said updating means further including difference means connected to the output of said aggregating means and to said second storage means for updating of said second storage means to provide repetitively, and in alternation to said modifying of said impulse response adjustment values, revised values of said second signal samples to provide iterative revision of said impulse response adjustment values before a new set of samples are applied to said first and second storage means whereby, in response to repetitively modified impulse response adjustment values from said third storage means, said output signal of said filter network can be adjusted to conform to said another signal.

Claim 10

Apparatus including a control circuit for altering the output signal from a filter network, resulting from an input signal thereto by altering the impulse response of said filter network and so as to conform to another signal, in which said control circuit comprises: first shiftable storage means for receiving samples of at least one first signal at least related to said input signal; second shiftable storage means for receiving samples of at least one second signal at least related to said output signal; third shiftable storage means for storing values of adjustments of said impulse response; modification means coupling said third storage means to the output of at least said second storage means for repetitively modifying said impulse response adjustment values; updating means including multiplier means and aggregating means, said updating means being connected from said first and third storage means to said second storage means and repetitively, and in alternation to said repetitive modification of said impulse response adjustment values, applying outputs of said first and third storage means to said multiplier means and aggregating means for producing an aggregation of multiplicands of said first signal samples and stored values of adjustments in said third storage means, said updating means further including difference means connected to the output of said aggregating means and to said second storage means for updating of said second storage means to provide repetitively, and in alternation to said modifying of said impulse response adjustment values, revised values of said second signal samples to provide iterative revision of said impulse response adjustment values before a new set of samples are applied to said first and second storage means whereby, in response to repetitively modified impulse response adjustment values from said third storage means, said output signal of said filter network can be adjusted to conform to said another signal.

Claim 11

A self-adaptive filter including a filter network, a control circuit for altering the output signal from the filter network, resulting from an input signal thereto, difference means for generating from said output signal and said another signal a difference signal at least representing the difference between said another signal and said output signal, and sampling means for sampling said difference signal and for sampling said input signal to produce difference signal samples and input signal samples, said control circuit comprising: first shiftable storage means for receiving said input signal samples; second shiftable storage means for receiving said difference signal samples; third shiftable storage means for storing values of adjustments of said impulse responSe; modification means coupling said third storage means to the output of at least said second storage means for repetitively modifying said impulse response adjustment values; updating means associated with said second storage means, said updating means including multiplier means and aggregating means and means repetitively, and in alternation to said repetitive modification of said impulse response adjustment values, connecting outputs of said first and third storage means to said multiplier means and aggregating means for producing an aggregation of multiplicands of said first samples and stored values of adjustments in said third storage means, said updating means further including difference means connected to the output of said aggregating means and to said second storage means for updating of said second storage means to provide repetitively, and in alternation to said modifying of said impulse response adjustment values, revised values of said difference signal samples to provide iterative revision of said impulse response adjustment values before a new set of samples are applied to said first and second storage means, whereby, in response to repetitively modified impulse response adjustment values from said third storage means, said output signal of said filter network can be adjusted to conform to said another signal.

Claim 12

A self-adaptive filter including a filter network, a control circuit for altering the output signal from the filter network, resulting from an input signal thereto, difference means for generating from said output signal and said another signal a difference signal at least representing the difference between said another signal and said output signal, and sampling means for sampling said difference signal and for sampling said input signal to produce difference signal samples and input signal samples, said control circuit comprising: first shiftable storage means for receiving said input signal samples; second shiftable storage means for receiving said difference signal samples; third shiftable storage means for storing values of adjustments of said impulse responSe; modification means coupling said third storage means to the output of at least said second storage means for repetitively modifying said impulse response adjustment values; updating means associated with said second storage means, said updating means including multiplier means and aggregating means and means repetitively, and in alternation to said repetitive modification of said impulse response adjustment values, connecting outputs of said first and third storage means to said multiplier means and aggregating means for producing an aggregation of multiplicands of said first samples and stored values of adjustments in said third storage means, said updating means further including difference means connected to the output of said aggregating means and to said second storage means for updating of said second storage means to provide repetitively, and in alternation to said modifying of said impulse response adjustment values, revised values of said difference signal samples to provide iterative revision of said impulse response adjustment values before a new set of samples are applied to said first and second storage means, whereby, in response to repetitively modified impulse response adjustment values from said third storage means, said output signal of said filter network can be adjusted to conform to said another signal.

Claim 13

A self-adaptive filter as claimed in claim 9, wherein said modification means couples said third storage means to outputs of said first and second storage means and includes means connecting said last-mentioned outputs to said multiplier and aggregating means for computing partial derivatives in accordance with the following equation:

Claim 14

A self-adaptive filter as claimed in claim 10, wherein said multiplicands are components of co-efficients of the matrix X. Delta R where X is the matrix of said input signal samples and Delta R is the matrix of the last stored impulse response values in said third storage means, said accumulator accumulating components of each co-efficient.

Claim 15

A self-adaptive filter including a filter network, a control circuit for altering the output signal from the filter network, resulting from an input signal thereto by altering the impulse response of said filter network and so as to conform to another signal; difference means for generating, from said another signal and said output signal, a signal at least representing the difference between said another signal and said output signal; auto-correlation generating means for generating a plurality of first signals representing coefficients of auto-correlation of said input signal, and first sampling means for sampling said second signals to provide a set of auto-correlation samples; cross-correlation generating means for generating a plurality of second signals representing coefficients of cross-correlation between said difference signal and said input signal, second sampling means for sampling said second signals to provide a set of cross-correlation samples; said control circuit comprising: first shiftable storage means for receiving said auto-correlation samples; second shiftable storage means for receiving said cross-correlation samples; third shiftable storage means for storing values of adjustments of said impulse response; modification means coupling said third storage means to the output of at least said second storage means for repetitively modifying said impulse response adjustment values; updating means for said second storage means, said updating means including multiplier means and aggregating means repetitively, and in alternaTion to said repetitive modification of said impulse response adjustment values, connecting outputs of said first and third storage means to said multiplier means for producing an aggregation of multiplicands of said auto-correlation samples and stored values of adjustments in said third storage means; said updating means further including difference means connected to the output of said aggregating means and to said output of said second storage means for updating of said second storage means to provide repetitively, and in alternation to said modifying of said impulse response adjustment values revised values of said auto-correlation samples to provide iterative revision of said impulse response adjustment values before a new set of samples are applied to said first and second storage means whereby, in response to repetitively modified impulse response adjustment values from said third storage means, said output signal of said filter network can be adjusted to conform to said another signal.

Claim 16

A self-adaptive filter including a filter network, a control circuit for altering the output signal from the filter network, resulting from an input signal thereto by altering the impulse response of said filter network and so as to conform to another signal; difference means for generating, from said another signal and said output signal, a signal at least representing the difference between said another signal and said output signal; auto-correlation generating means for generating a plurality of first signals representing coefficients of auto-correlation of said input signal, and first sampling means for sampling said second signals to provide a set of auto-correlation samples; cross-correlation generating means for generating a plurality of second signals representing coefficients of cross-correlation between said difference signal and said input signal, second sampling means for sampling said second signals to provide a set of cross-correlation samples; said control circuit comprising: first shiftable storage means for receiving said auto-correlation samples; second shiftable storage means for receiving said cross-correlation samples; third shiftable storage means for storing values of adjustments of said impulse response; modification means coupling said third storage means to the output of at least said second storage means for repetitively modifying said impulse response adjustment values; updating means for said second storage means, said updating means including multiplier means and aggregating means repetitively, and in alternaTion to said repetitive modification of said impulse response adjustment values, connecting outputs of said first and third storage means to said multiplier means for producing an aggregation of multiplicands of said auto-correlation samples and stored values of adjustments in said third storage means; said updating means further including difference means connected to the output of said aggregating means and to said output of said second storage means for updating of said second storage means to provide repetitively, and in alternation to said modifying of said impulse response adjustment values revised values of said auto-correlation samples to provide iterative revision of said impulse response adjustment values before a new set of samples are applied to said first and second storage means whereby, in response to repetitively modified impulse response adjustment values from said third storage means, said output signal of said filter network can be adjusted to conform to said another signal.

Claim 17

A self-adaptive filter as claimed in claim 12, wherein said multiplicands are components of co-efficients of the matrix product A. Delta R where A is the matrix of said auto-correlation samples and Delta R is the matrix of the last stored impulse response adjustment values in said third store and said components being accumulated in said aggregating means.

Claim 18

A self-adaptive filter as claimed in claim 13, wherein said modification means comprises means for determining the signs of samples in said second storage means whereby said repetitive modification to said impulse response adjustment values is in accordance with said signs.

Claim 19

A self-adaptive filter including a filter network having a plurality of impulse response coefficient establishing means, a control circuit for computing an alteration to the filter network impulse response, the alteration being an alteration of the filter network impulse response coefficients to alter an output signal of the filter network, resulting from application of an input signal thereto, in a manner tending to conform the output signal to another signal and difference means for generating an electrical difference signal representing the difference between said output signal and said another signal; said control circuit comprising: sampling means for providing a series of time-spaced electrical signal first samples representing said input signal, and a set of time-spaced electrical signal second samples representing said difference signal; first storage means coupled to said sampling means for storing said first samples; second storage means coupled to said sampling means for receiving and storing said set of second samples and for receiving and storing subsequent sets of modified second samples; first output means associated with the first storage means for repeatedly delivering, from said first storage means, first storage output signals corresponding to said first samples; second output means associated with said second storage means for repeatedly delivering, from said second storage means, second storage output signals corresponding to samples of that one of said set of second samples and sets of modified second samples then stored therein; first computing means connected to said first and second storage means and responsive to output signals of said first and second storage means for computing successive sets of gradient signals comprising a first set of gradient signals representing partial derivatives of said coefficients of impulse response with respect to said difference signal, and successive further sets representing partial derivatives of said coefficients of impulse response with respect to successive modified difference signals represented by successive ones of said sets of modified second samples; increment means coupled to said first computing means for obtaining from each set of gradient signals, a separate set of increment signals determined at least in accordance with the signs of corResponding ones of that set of gradient signals; third storage means for sequentially storing said sets of increment signals; first coupling means coupling said third storage means and increment means for passing said sets of increment signals to said third storage means, for storage; second coupling means associated with said third storage means and coupled to said impulse response coefficient establishing means and operable to increment the coefficients of impulse response in accordance with each successive set of increment signals whereby successive incrementations of said impulse response coefficients comprise said alteration; and third output means coupled to said third storage means for repeatedly delivering, from said third storage means, third storage output signals corresponding to signals of that one of said set of increment signals then stored in said third storage means; second computing means connected to said second and third storage means and responsive to output signals thereof for computing sets of electrical difference signal modification signals comprising a first set representing estimated modifications of said difference signal samples occurring as a result of incrementing of said impulse response coefficients in accordance with the first of said sets of increment signals and successive further sets each representing estimated modifications of the last stored set of modified difference signal samples occurring as a result of incrementing of said impulse response coefficients in accordance with a last stored set of increment signals in said third storage means; second sample modification means coupled between said second computing means and said second storage means to modify said second samples in said second storage means in accordance with said first set of difference signal modification signals and to modify each successively stored set of modified difference signal samples in said second storage means in accordance with a corresponding one of said further sets of difference signal modification signals.

Claim 20

A self-adaptive filter including a filter network having a plurality of impulse response coefficient establishing means, a control circuit for computing an alteration to the filter network impulse response, the alteration being an alteration of the filter network impulse response coefficients to alter an output signal of the filter network, resulting from application of an input signal thereto, in a manner tending to conform the output signal to another signal and difference means for generating an electrical difference signal representing the difference between said output signal and said another signal; said control circuit comprising: sampling means for providing a series of time-spaced electrical signal first samples representing said input signal, and a set of time-spaced electrical signal second samples representing said difference signal; first storage means coupled to said sampling means for storing said first samples; second storage means coupled to said sampling means for receiving and storing said set of second samples and for receiving and storing subsequent sets of modified second samples; first output means associated with the first storage means for repeatedly delivering, from said first storage means, first storage output signals corresponding to said first samples; second output means associated with said second storage means for repeatedly delivering, from said second storage means, second storage output signals corresponding to samples of that one of said set of second samples and sets of modified second samples then stored therein; first computing means connected to said first and second storage means and responsive to output signals of said first and second storage means for computing successive sets of gradient signals comprising a first set of gradient signals representing partial derivatives of said coefficients of impulse response with respect to said difference signal, and successive further sets representing partial derivatives of said coefficients of impulse response with respect to successive modified difference signals represented by successive ones of said sets of modified second samples; increment means coupled to said first computing means for obtaining from each set of gradient signals, a separate set of increment signals determined at least in accordance with the signs of corResponding ones of that set of gradient signals; third storage means for sequentially storing said sets of increment signals; first coupling means coupling said third storage means and increment means for passing said sets of increment signals to said third storage means, for storage; second coupling means associated with said third storage means and coupled to said impulse response coefficient establishing means and operable to increment the coefficients of impulse response in accordance with each successive set of increment signals whereby successive incrementations of said impulse response coefficients comprise said alteration; and third output means coupled to said third storage means for repeatedly delivering, from said third storage means, third storage output signals corresponding to signals of that one of said set of increment signals then stored in said third storage means; second computing means connected to said second and third storage means and responsive to output signals thereof for computing sets of electrical difference signal modification signals comprising a first set representing estimated modifications of said difference signal samples occurring as a result of incrementing of said impulse response coefficients in accordance with the first of said sets of increment signals and successive further sets each representing estimated modifications of the last stored set of modified difference signal samples occurring as a result of incrementing of said impulse response coefficients in accordance with a last stored set of increment signals in said third storage means; second sample modification means coupled between said second computing means and said second storage means to modify said second samples in said second storage means in accordance with said first set of difference signal modification signals and to modify each successively stored set of modified difference signal samples in said second storage means in accordance with a corresponding one of said further sets of difference signal modification signals.

Claim 21

A self-adaptive filter as claimed in claim 15, wherein said plurality of impulse response coefficient establishing means comprises fourth storage means for storing said impulse response coefficients as impulse response coefficient signals, said fourth storage means having coupled thereto fourth output means operable to repeatedly deliver, from said fourth storage means, fourth storage output signals corresponding to said impulse response coefficient signals, said second coupling means being connected to said third and fourth output means to receive said third and fourth storage output signals and comprising additive circuit means operable to successively modify said impulse response coefficients signals in accordance with corresponding ones of increment signals of each said set of increment signals, and to pass these to the fourth storage means to replace the impulse response coefficient signals previously stored.

Claim 22

A self-adaptive filter as claimed in claim 16, wherein said filter network further comprises fifth storage means; input means associated with said fifth storage means and operable to pass, into said fifth storage means, said first samples; fifth output means associated with said fifth storage means and operable to repeatedly deliver, from said fifth storage means, electrical signals corresponding to said first samples; third coupling means coupling said fourth and fifth output means to third computing means; said third computing means including multiplier and accumulator means operable to generate electrical signals, representing said output signal.

Claim 23

A self-adaptive filter as claimed in claim 15, wherein said first computing means comprises multiplier means and accumulator means operable to compute each said set of gradient signals in accordance with the following equation:

Claim 24

A self-adaptive filter as claimed in claim 17, wherein said second computing means comprises multiplier means and accumulator means operable to generate each said difference signal modification signal as a product x. Delta r where x is the matrix of said first samples and Delta r is the matrix consisting of the last stored set of increment signals in said third storage means.

Claim 25

A self-adaptive filter as claimed in claim 19, wherein said second sample modification means comprises a subtractor.

Claim 26

A self-adaptive filter as claimed in claim 19, wherein said first and second computing means include a common multiplier and and accumulator and further include switch means for selective coupling thereto of the first and second storage output signals or the first and third storage output signals.

Claim 27

A self-adaptive filter including a filter network having a plurality of impulse response coefficient establishing means; a control circuit for computing an alteration to the filter network impulse response, the alteration being an alteration of the filter network impulse response coefficients to alter an output signal of the filter network, resulting from application of an input signal thereto, in a manner tending to conform the output signal to another signal and difference means for generating an electrical difference signal representing the difference between said output signal and said another signal; said control circuit comprising: auto-correlation generating means for computing coefficients of auto-correlation of said input signal; first sampling means for providing a series of time-spaced electrical signal first samples representing said auto-correlation coefficients; first storage means coupled to said first sampling means for receiving and storing said first samples; cross-correlation coefficient generating means for computing coefficients of cross-correlation between said another signal and said difference signal; second sampling means for providing a set of time-spaced electrical signal second samples of said cross-correlation coefficients; second storage means coupled to said second sampling means for receiving and storing said set of second samples, and for receiving and storing subsequent sets of modified second samples; third storage means; second storage output and coupling means coupling said second storage means to said third storage means to store in said third storage means sets of increment signals comprising a first set determined in accordance with the signs of corresponding ones of said second samples and further sets each determined in accordance with the signs of corresponding ones of modified second samples of a separate one of said subsequent sets; first coupling means coupling said third storage means to said filter network and operable to increment the impulse response coefficient establishing means in accordance with said increment signals of each said set of increment signals whereby successive incrementations comprise said alteration; first storage output means associated with the first storage means for repeatedly delivering from said first storage means first storage output signals corresponding to said first samples; third storage output means associated with the said third storage means for repeatedly delivering, from said third storage means, third storage output signals corresponding to signals of that one of said sets of increment signals then stored in said third storage means; third coupling means operable to couple said first and third storage output means and to deliver said first and third storage output signals; computing means connected to said third coupling means and responsive to said first and third storage output signals to compute sets of second sAmple modification signals comprising a first set representing estimated modifications to said set of second samples occurring as a result of said incrementation of impulse response coefficients in accordance with said first set of increment signals and subsequent sets each representing estimated modifications to the last stored set of modified second samples stored in said second storage means occurring as a result of an incrementation of impulse response coefficients in accordance with a corresponding last determined one of said further sets of increment signals; second sample modification means coupled between said computing means and said second storage means and operable to modify said set of second samples in said second storage means in accordance with the second sample modification signals and to modify each said further set of modified second samples in accordance with the last computed one of said subsequent sets of second sample modification signals.

Claim 28

A self-adaptive filter including a filter network having a plurality of impulse response coefficient establishing means; a control circuit for computing an alteration to the filter network impulse response, the alteration being an alteration of the filter network impulse response coefficients to alter an output signal of the filter network, resulting from application of an input signal thereto, in a manner tending to conform the output signal to another signal and difference means for generating an electrical difference signal representing the difference between said output signal and said another signal; said control circuit comprising: auto-correlation generating means for computing coefficients of auto-correlation of said input signal; first sampling means for providing a series of time-spaced electrical signal first samples representing said auto-correlation coefficients; first storage means coupled to said first sampling means for receiving and storing said first samples; cross-correlation coefficient generating means for computing coefficients of cross-correlation between said another signal and said difference signal; second sampling means for providing a set of time-spaced electrical signal second samples of said cross-correlation coefficients; second storage means coupled to said second sampling means for receiving and storing said set of second samples, and for receiving and storing subsequent sets of modified second samples; third storage means; second storage output and coupling means coupling said second storage means to said third storage means to store in said third storage means sets of increment signals comprising a first set determined in accordance with the signs of corresponding ones of said second samples and further sets each determined in accordance with the signs of corresponding ones of modified second samples of a separate one of said subsequent sets; first coupling means coupling said third storage means to said filter network and operable to increment the impulse response coefficient establishing means in accordance with said increment signals of each said set of increment signals whereby successive incrementations comprise said alteration; first storage output means associated with the first storage means for repeatedly delivering from said first storage means first storage output signals corresponding to said first samples; third storage output means associated with the said third storage means for repeatedly delivering, from said third storage means, third storage output signals corresponding to signals of that one of said sets of increment signals then stored in said third storage means; third coupling means operable to couple said first and third storage output means and to deliver said first and third storage output signals; computing means connected to said third coupling means and responsive to said first and third storage output signals to compute sets of second sAmple modification signals comprising a first set representing estimated modifications to said set of second samples occurring as a result of said incrementation of impulse response coefficients in accordance with said first set of increment signals and subsequent sets each representing estimated modifications to the last stored set of modified second samples stored in said second storage means occurring as a result of an incrementation of impulse response coefficients in accordance with a corresponding last determined one of said further sets of increment signals; second sample modification means coupled between said computing means and said second storage means and operable to modify said set of second samples in said second storage means in accordance with the second sample modification signals and to modify each said further set of modified second samples in accordance with the last computed one of said subsequent sets of second sample modification signals.

Claim 29

A self-adaptive filter as claimed in claim 22, wherein said computing means comprises a multiplier and an accumulator operable to generate each said set of second sample modification signals as the product A. Delta R where A is the matrix of first samples and Delta R is the matrix of the last determined set of increment signals, said second sample modification means comprising a subtractive network.

Claim 30

A self-adaptive filter as claimed in claim 23, wherein said filter network includes a delay line operable to generate from said input signal a plurality of time-spaced delay line signals corresponding thereto, said impulse response coefficient establishing means comprising a plurality of multipliers coupled to said delay line, and operable to multiply respective ones of said delay line signals by signals held therein representing the impulse response coefficients, the filter network further including summation means coupled to said multipliers to sum the outputs thereof to provide said output signal.

Claim 31

A self-adaptive filter as claimed in claim 24, wherein said auto-correlation computing means and said cross-correlation computing means are each coupled to said delay line to receive said delay line signals.