US 6,856,790 B1 · Receiver with dual D.C. noise cancellation circuits

Abstract

A circuit employing dual adaptive D.C. noise cancellation loops to eliminate D.C. noise from a signal received from a communication channel. The circuit employing the two adaptive D.C. noise cancellation loops is constructed such that the two adaptive D.C. noise cancellation loops are decoupled to insured stability of the circuit while eliminating the D.C. noise components from a signal received from a communication channel. A first D.C. noise canceler generates a first D.C. noise cancellation signal that is a product of an error signal that is an estimate of noise within the signal and a first D.C. gain constant. The first D.C. Noise is connected within the receiver to an input of a decision circuit that subtractively combines the first D.C. noise cancellation signal with the signal to remove a first portion of the D.C. noise components. A second D.C. noise canceler additively restores the first D.C. noise cancellation signal to the error signal and multiplies the restored error signal with the first D.C. noise cancellation signal by a second D.C. gain constant. The second D.C. noise canceler is connected to the input of the receiver to subtractively combine the received signal acquired from the communication channel with the second D.C. noise cancellation signal to remove a second portion of the D.C. noise components.

Claims44

Dependent claims

A noise canceling circuit for removing D.C. noise from an input signal received by a receiver having an error circuit which generates an error signal, said noise canceling circuit comprising:

a first D.C. noise canceler to generate a first D.C. noise cancellation signal in response to the error signal from the error circuit,
wherein the first DC noise cancellation signal is input to the error circuit;
and
a second D.C. noise canceler responsive to the error signal from the error circuit and the first D.C. noise cancellation signal from said first D.C. noise canceler to provide a second D.C. noise cancellation signal.

1 more element

A receiver comprising:

an input circuit to receive an input signal;
a feedforward/feedback equalizer responsive to the input circuit;
an error circuit to provide an error signal;
a first D.C. noise canceler to generate a first D.C. noise cancellation signal in response to the error signal from said error circuit,
wherein said error circuit is responsive to the first DC noise cancellation signal;
a first adder to subtract the first D.C. noise cancellation signal from said first D.C. noise canceler from an output of said feedforward/feedback equalizer;
a decision circuit that determines an estimate of input signal in response to an output of said first adder,
wherein said error circuit comprises:
a second adder to subtract an output of said decision circuit from the error signal output by said first adder;
wherein said first D.C. noise canceler comprises:
a first multiplication circuit to multiply an output of said second adder by a first gain constant to produce a first product;
a third adder;
and
a first delay circuit responsive to an output from said third adder to generate the first DC noise cancellation signal,
wherein said third adder adds an output from a first multiplication circuit to the first D.C. noise cancellation signal;
and
a second D.C. noise canceler responsive to the error signal from the error circuit and the first D.C. noise cancellation signal from said first D.C. noise canceler to provide a second D.C. noise cancellation signal,
wherein said input circuit is responsive to said second D.C. noise canceler,
wherein said second D.C. noise canceler comprises:
a fourth adder to add an output of said second adder to the first DC noise cancellation signal;
a second multiplication circuit to multiply an output of said fourth adder by a second gain constant;
a fifth adder;
and
a second delay circuit responsive to an output of said fifth adder to provide the second D.C. noise cancellation signal,
wherein said fifth adder adds the second D.C. noise cancellation signal to an output of said second multiplier,
wherein said input circuit comprises a sixth adder to subtract the second D.C. noise cancellation signal from the input signal.

23 more elements

A receiver comprising:

an input circuit to receive an input signal;
a feedforward/feedback equalizer responsive to the input circuit;
an error circuit to provide an error signal;
a first D.C. noise canceler to generate a first D.C. noise cancellation signal in response to the error signal from said error circuit,
wherein said error circuit is responsive to the first DC noise cancellation signal;
a first adder to subtract the first D.C. noise cancellation signal from said first D.C. noise canceler from an output of said feedforward/feedback equalizer;
a decision circuit that determines an estimate of input signal in response to an output of said first adder,
wherein said error circuit comprises:
a second adder to subtract an output of said decision circuit from the error signal output by said first adder;
wherein said first D.C. noise canceler comprises:
a first multiplication circuit to multiply an output of said second adder by a first gain constant to produce a first product;
a third adder;
and
a first delay circuit responsive to an output from said third adder to generate the first DC noise cancellation signal,
wherein said third adder adds an output from a first multiplication circuit to the first D.C. noise cancellation signal,
wherein the first D.C. noise cancellation signal is formed as a function of the error signal according to the formula:
DC1n+1=DC1n+μdc1×εk
wherein:
DC1n is the first D.C. noise cancellation signal for the current sampling time of the input signal,
DC1n+1 is the first D.C. noise cancellation signal for the next sampling time of the input signal,
μdc1 is the first gain constant, and
εk is the error signal determined by the formula:
εk=fknc−âi
where:
âi is the estimated value of the transmitted encoded signal from said decision circuit, and
fknc is an equalized, noise cancelled received signal of the current sampling from said first adder;
and
a second D.C. noise canceler responsive to the error signal from the error circuit and the first D.C. noise cancellation signal from said first D.C. noise canceler to provide a second D.C. noise cancellation signal,
wherein said input circuit is responsive to said second D.C. noise canceler.

26 more elements

A receiver comprising:

an input circuit to receive an input signal;
a feedforward/feedback equalizer responsive to the input circuit;
an error circuit to provide an error signal;
a first D.C. noise canceler to generate a first D.C. noise cancellation signal in response to the error signal from said error circuit,
wherein said error circuit is responsive to the first DC noise cancellation signal;
a first adder to subtract the first D.C. noise cancellation signal from said first D.C. noise canceler from an output of said feedforward/feedback equalizer;
a decision circuit that determines an estimate of input signal in response to an output of said first adder,
wherein said error circuit comprises:
a second adder to subtract an output of said decision circuit from the error signal output by said first adder;
wherein said first D.C. noise canceler comprises:
a first multiplication circuit to multiply an output of said second adder by a first gain constant to produce a first product;
a third adder;
and
a first delay circuit responsive to an output from said third adder to generate the first DC noise cancellation signal,
wherein said third adder adds an output from a first multiplication circuit to the first D.C. noise cancellation signal;
and
a second D.C. noise canceler responsive to the error signal from the error circuit and the first D.C. noise cancellation signal from said first D.C. noise canceler to provide a second D.C. noise cancellation signal,
wherein said input circuit is responsive to said second D.C. noise canceler,
wherein said second D.C. noise canceler comprises:
a fourth adder to add an output of said second adder to the first DC noise cancellation signal;
a second multiplication circuit to multiply an output of said fourth adder by a second gain constant;
a fifth adder;
and
a second delay circuit responsive to an output of said fifth adder to provide the second D.C. noise cancellation signal,
wherein said fifth adder adds the second D.C. noise cancellation signal to an output of said second multiplier,
wherein said input circuit comprises a sixth adder to subtract the second D.C. noise cancellation signal from the input signal,
wherein the second D.C. noise cancellation signal is formed as a function of the error signal and the first D.C. noise cancellation signal according to the formula:
DC2n+1=DC2n+μdc2×(εk+DC1n)
wherein:
DC2n is the second D.C. noise cancellation signal for the current sampling time of the input signal,
DC2n+1 is the second D.C. noise cancellation signal for the next sampling time of the input signal,
μdc2 is the second gain constant,
εk is the error signal determined by the formula:
εk=fknc−âi
where:
âi is the estimated value of the transmitted encoded signal from said decision circuit,
fknc is an equalized, noise cancelled received signal of the current sampling from said first adder, and
DC1n is the first D.C. noise cancellation signal for the current sampling time of the input signal.

35 more elements

A method to remove D.C. noise components from an input signal received from a communication channel comprising the steps of:

(a) generating an error signal as an estimate of noise within the input signal, wherein step (a) comprises the steps of:
(a1) feedforward/feedback equalizing the input signal;
(a2) subtracting the first D.C. noise cancellation signal from the input signal equalized in step (a1);
(a3) determining an estimate of the input signal in response to step (a2);
and
(a4) subtracting the estimate from step (a3) from the subtracted signal from step (a2);
(b) generating a first D.C. noise cancellation signal in accordance with the error signal, wherein in step (a) the error signal is generated in accordance with the first D.C. noise signal, wherein step (b) comprises the steps of:
(b1) multiplying the subtracted signal from step (a4) by a first gain constant;
(b2) delaying the signal multiplied in step (b1);
and
(b3) adding the delayed signal of step (b2) to the signal multiplied in step (b1);
(c) generating a second D.C. noise cancellation signal in accordance with the error signal and the first D.C. noise cancellation signal, wherein step (c) comprises the steps of:
(c1) adding the delayed signal from step (b2) to the subtracted signal of step (a4);
(c2) multiplying the added signal of step (c1) by a second gain constant;
(c3) delaying the signal multiplied in step (c2);
and
(c4) adding the delayed signal of step (c3) to the signal multiplied in step (c2),
wherein generating the second D.C. noise cancellation signal is formed as a function of the error signal and the first D.C. noise cancellation signal according to the formula:
DC1n+1=DC2n+μdc2×(εk+DC1n)
wherein:
DC2n is the second D.C. noise cancellation signal for the current sampling time of the input signal,
DC2n+1 is the second D.C. noise cancellation signal for the next sampling time of the input signal,
μdc2 is the second gain constant,
εk is the error signal determined by the formula:
εk=fknc−âi
where:
âi is the estimated value from step (a3),
fknc is an equalized, noise cancelled received signal from step (a2), and
DC1n is the first D.C. noise cancellation signal from step (b2);
and
(d) subtracting the second D.C. noise cancellation signal from the input signal.

28 more elements

A receiver comprising:

input means for receiving an input signal;
feedforward/feed back equalizer means for equalizing an output of the input means;
error means for providing an error signal;
first D.C. noise canceling means for generating a first D.C. noise cancellation signal in response to the error signal from said error means,
wherein said error means is responsive to the first DC noise cancellation signal;
first adding means for subtracting the first D.C. noise cancellation signal from said first D.C. noise canceling means from an output of said feedforward/feedback equalizer means;
decision means for determining an estimate of input signal in response to an output of said first adding means,
wherein said error means comprises:
second adding means for subtracting an output of said decision means from the error signal output by said first adding means,
wherein said first D.C. noise canceling means comprises:
first multiplying means for multiplying an output of said second adding means by a first gain constant to produce a first product;
third adding means;
and
first delay means to responsive to an output from said third adding means for generating the first DC noise cancellation signal,
wherein said third adding means adds an output from a first multiplying means to the first D.C. noise cancellation signal;
and
second D.C. noise canceling means responsive to the error signal from the error means and the first D.C. noise cancellation signal from said first D.C. noise canceling means for providing a second D.C. noise cancellation signal,
wherein said input means is responsive to said second D.C. noise canceling means,
wherein the second D.C. noise canceling means comprises:
fourth adding means for adding an output of said second adding means to the first DC noise cancellation signal;
second multiplying means for multiplying an output of said fourth adding means by a second gain constant;
fifth adding means;
and
second delay means responsive to an output of said fifth adding means for providing the second D.C. noise cancellation signal,
wherein said fifth adding means adds the second D.C. noise cancellation signal to an output of said second multiplier,
wherein said input means comprises a sixth adding means for subtracting the second D.C. noise cancellation signal from the input signal.

23 more elements

A receiver comprising:

input means for receiving an input signal;
feedforward/feed back equalizer means for equalizing an output of the input means;
error means for providing an error signal;
first D.C. noise canceling means for generating a first D.C. noise cancellation signal in response to the error signal from said error means,
wherein said error means is responsive to the first DC noise cancellation signal;
first adding means for subtracting the first D.C. noise cancellation signal from said first D.C. noise canceling means from an output of said feedforward/feedback equalizer means;
decision means for determining an estimate of input signal in response to an output of said first adding means,
wherein said error means comprises:
second adding means for subtracting an output of said decision means from the error signal output by said first adding means
wherein said first D.C. noise canceling means comprises:
first multiplying means for multiplying an output of said second adding means by a first gain constant to produce a first product;
third adding means;
and
first delay means to responsive to an output from said third adding means for generating the first DC noise cancellation signal,
wherein said third adding means adds an output from a first multiplying means to the first D.C. noise cancellation signal
wherein the first D.C. noise cancellation signal is formed as a function of the error signal according to the formula:
DC1n+1=DC1n+μdc1×εk
wherein:
DC1n is the first D.C. noise cancellation signal for the current sampling time of the input signal,
DC1n+1 is the first D.C. noise cancellation signal for the next sampling time of the input signal,
μdc1 is the first gain constant, and
εk is the error signal determined by the formula:
εk=fknc−âi
where:
âi is the estimated value of the transmitted encoded signal from said decision means, and
fknc is an equalized, noise cancelled received signal of the current sampling from said first adding means;
and
second D.C. noise canceling means responsive to the error signal from the error means and the first D.C. noise cancellation signal from said first D.C. noise canceling means for providing a second D.C. noise cancellation signal,
wherein said input means is responsive to said second D.C. noise canceling means.

26 more elements

A receiver comprising:

input means for receiving an input signal;
feedforward/feed back equalizer means for equalizing an output of the input means;
error means for providing an error signal;
first D.C. noise canceling means for generating a first D.C. noise cancellation signal in response to the error signal from said error means,
wherein said error means is responsive to the first DC noise cancellation signal;
first adding means for subtracting the first D.C. noise cancellation signal from said first D.C. noise canceling means from an output of said feedforward/feedback equalizer means;
decision means for determining an estimate of input signal in response to an output of said first adding means,
wherein said error means comprises:
second adding means for subtracting an output of said decision means from the error signal output by said first adding means,
wherein said first D.C. noise canceling means comprises:
first multiplying means for multiplying an output of said second adding means by a first gain constant to produce a first product;
third adding means;
and
first delay means to responsive to an output from said third adding means for generating the first DC noise cancellation signal,
wherein said third adding means adds an output from a first multiplying means to the first D.C. noise cancellation signal;
and
second D.C. noise canceling means responsive to the error signal from the error means and the first D.C. noise cancellation signal from said first D.C. noise canceling means for providing a second D.C. noise cancellation signal,
wherein said input means is responsive to said second D.C. noise canceling means,
wherein the second D.C. noise canceling means comprises:
fourth adding means for adding an output of said second adding means to the first DC noise cancellation signal;
second multiplying means for multiplying an output of said fourth adding means by a second gain constant;
fifth adding means;
and
second delay means responsive to an output of said fifth adding means for providing the second D.C. noise cancellation signal,
wherein said fifth adding means adds the second D.C. noise cancellation signal to an output of said second multiplier,
wherein said input means comprises a sixth adding means for subtracting the second D.C. noise cancellation signal from the input signal;
wherein the second D.C. noise cancellation signal is formed as a function of the error signal and the first D.C. noise cancellation signal according to the formula:
DC2n+1=DC2n+μdc2×(εk+DC1n)
wherein:
DC2n is the second D.C. noise cancellation signal for the current sampling time of the input signal,
DC2n+1 is the second D.C. noise cancellation signal for the next sampling time of the input signal,
μdc2 is the second gain constant,
εk is the error signal determined by the formula:
εk=fknc−âi
where:
âi is the estimated value of the transmitted encoded signal from said decision means,
fknc is an equalized, noise cancelled received signal of the current sampling from said first adding means, and
DC1n is the first D.C. noise cancellation signal for the current sampling time of the input signal.

35 more elements

A computer medium for obtaining program code to remove D.C. noise components from an input signal received from a communication channel for execution on a processor, the program code comprising the steps of:

(a) generating an error signal as an estimate of noise within the input signal;
wherein step (a) comprises the steps of:
(a1) feedforward/feedback equalizing the input signal;
(a2) subtracting the first D.C. noise cancellation signal from the input signal equalized in step (a1);
(a3) determining an estimate of the input signal in response to step (a2);
and
(a4) subtracting the estimate from step (a3) from the subtracted signal from step (a2);
(b) generating a first D.C. noise cancellation signal in accordance with the error signal, wherein in step (a) the error signal is generated in accordance with the first D.C. noise signal;
wherein step (b) comprises the steps of:
(b1) multiplying the subtracted signal from step (a4) by a first gain constant;
(b2) delaying the signal multiplied in step (b1);
and
(b3) adding the delayed signal of step (b2) to the signal multiplied in step (b1);
(c) generating a second D.C. noise cancellation signal in accordance with the error signal and the first D.C. noise cancellation signal
wherein step (c) comprises the steps of:
(c1) adding the delayed signal from step (b2) to the subtracted signal of step (a4);
(c2) multiplying the added signal of step (c1) by a second gain constant;
(c3) delaying the signal multiplied in step (c2);
and
(c4) adding the delayed signal of step (c3) to the signal multiplied in step (c2),
wherein generating the second D.C. noise cancellation signal is formed as a function of the error signal and the first D.C. noise cancellation signal according to the formula:
DC2n+1=DC2n+μdc2×(εk+DC1n)
wherein:
DC2n is the second D.C. noise cancellation signal for the current sampling time of the input signal,
DC2n+1 is the second D.C. noise cancellation signal for the next sampling time of the input signal,
μdc2 is the second gain constant,
εk is the error signal determined by the formula:
εk=fknc−âi
where:
âi is the estimated value from step (a3),
fknc is an equalized, noise cancelled received signal from step (a2), and
DC1n is the first D.C. noise cancellation signal from step (b2);
and
(d) subtracting the second D.C. noise cancellation signal from the input signal.

31 more elements

Dependencies are inferred from the claim text.

Receiver with dual D.C. noise cancellation circuits

Life of this patent

Receiver with dual D.C. noise cancellation circuits

Life of this patent

Abstract

Claims44