Method and apparatus for removing DC from the output of a precoder in a transmitter of a data communication system
AssigneeAdtran, Inc.
InventorRichard L. Goodson
Life of this patent
Estimating the term…
Abstract
A method and apparatus for driving the DC output of a precoder in the transmitter of a data communication system to zero after the end of a scheduled transmission of data include the use of a DC canceling circuit in a feedback arrangement with the precoder to drive the DC output of the precoder and of the transmitter circuits associated therewith to zero.
Claims16
A precoding apparatus in a transmitter of a data communication system, said precoding apparatus having a data symbol sequence as an input and having a precoded data symbol sequence as an output, said precoding apparatus comprising:
- a modulo device for receiving an adjusted data symbol sequence that is based on said input data symbol sequence and for generating a modulo signal;
- and
- a circuit coupled to said modulo device for driving the DC output of said precoding apparatus to zero at a predetermined time, said circuit comprising:
- a compensator summer for adding said modulo signal and a compensation signal thereby obtaining an adjusted modulo signal;
- a compensator means for generating said compensation signal, said compensator means incorporating an integrator for obtaining a running sum of said adjusted modulo signal;
- and
- an insertion switch programmed to selectively set the output of said precoding apparatus to be said adjusted modulo signal prior to said predetermined time and, at said predetermined time, to set said output of the precoding apparatus to be the negative value of said running sum.
A precoding apparatus in a transmitter of a data communication system, said precoding apparatus having a data symbol sequence as an input and having a precoded data symbol sequence as an output, said precoding apparatus comprising:
- a feedback filter and a filter summer for subtracting the output of said feedback filter from said input data symbol sequence thereby obtaining an adjusted data symbol sequence;
- a level shifter responsive to said adjusted data symbol sequence for generating a level shifting signal;
- a modulo summer for adding said level shifting signal to said adjusted data symbol sequence thereby outputting a modulo signal;
- and
- a circuit coupled to said modulo summer for driving the DC output of said precoding apparatus to zero at a predetermined time, said circuit comprising:
- a compensator summer for adding the output of said modulo summer and a compensation signal thereby obtaining an adjusted modulo signal;
- a compensator means for generating said compensation signal, said compensator means incorporating an integrator for obtaining a running sum of said adjusted modulo signal;
- and
- an insertion switch programmed to selectively set the output of said precoding apparatus to be said adjusted modulo signal prior to said predetermined time and, at said predetermined time, to set said output of the precoding apparatus to be the negative value of said running sum.
A method for driving the DC output of a precoding apparatus in a transmitter of a data communication system to zero at a predetermined time after a scheduled transmission, said precoding apparatus having a data symbol sequence as an input and having a precoded data symbol sequence as an output, said method comprising the steps of:
- a. subtracting the output of a precoder feedback filter from said data symbol sequence, thereby generating an adjusted data symbol sequence;
- b. generating a level shifting signal in response to said adjusted data symbol sequence and in accordance with a predetermined algorithm;
- c. adding said level shifting signal to said adjusted data symbol sequence, thereby obtaining a level shifted data symbol sequence;
- d. adding a DC compensation signal to said level shifted data symbol sequence thereby obtaining an adjusted modulo signal;
- e. determining a running sum of said adjusted modulo signal;
- f. terminating said scheduled transmission prior to said predetermined time;
- g. selectively setting the output of said precoding apparatus to be said adjusted modulo signal for all time prior to said predetermined time and, at said predetermined time, setting said output of the precoding apparatus to be the negative value of said running sum;
- h. updating said running sum;
- i. updating the value of said compensation signal;
- j. updating the value of said feedback filter output;
- and
- k. returning to step a upon the initiation of the next scheduled transmission of a data symbol sequence.
A method for driving the DC output of a precoding apparatus in a transmitter of a data communication system to zero at a predetermined time after a scheduled transmission, said precoding apparatus having a data symbol sequence as an input and having a precoded data symbol sequence as an output, said method comprising the steps of:
- a. performing a modulo operation upon said input data symbol sequence;
- b. adding a DC compensation signal to the data symbol sequence resulting from said modulo operation thereby obtaining an adjusted modulo signal;
- c. determining a running sum of said adjusted modulo signal;
- d. terminating said scheduled transmission prior to said predetermined time;
- and thereafter
- e. selectively setting the output of said precoding apparatus to be said adjusted modulo signal for all time prior to said predetermined time and, at said predetermined time, setting said output of said precoding apparatus to be the negative value of said running sum;
- f. updating said running sum;
- g. updating the value of said compensation signal;
- and
- h. returning to step a upon the initiation of the next scheduled transmission of a data symbol sequence.
In a time division duplex data communication system, a method for driving the DC output of a precoding apparatus to zero at a predetermined time after a scheduled transmission, said precoding apparatus having a data symbol sequence as an input and having a precoded data symbol sequence as an output, said method characterized by the steps of:
- a. performing a modulo operation upon said input data symbol sequence;
- b. adding a DC compensation signal to the data symbol sequence resulting from said modulo operation thereby obtaining an adjusted modulo signal;
- c. determining a running sum of said adjusted modulo signal;
- d. terminating said scheduled transmission prior to said predetermined time;
- and thereafter
- e. selectively setting the output of said precoding apparatus to be said adjusted modulo signal for all time prior to said predetermined time and, at said predetermined time, setting said output of said precoding apparatus to be the negative value of said running sum;
- .
- f. updating said running sum;
- g. updating the value of said compensation signal, and
- h. returning to step a upon the initiation of the next scheduled transmission of a data symbol sequence.
In a precoding apparatus in a transmitter of a time division duplex data communication system, said precoding apparatus having a data symbol sequence as an input and having a precoded data symbol sequence as an output, said precoding apparatus comprising a modulo device for receiving an adjusted data symbol sequence that is based on said input data symbol sequence and for generating a modulo signal, the improvement characterized by a circuit for driving the DC output of said precoding apparatus to zero at a predetermined time, said circuit comprising:
- a compensator summer for adding said modulo signal and a compensation signal thereby obtaining an adjusted modulo signal;
- a compensator means for generating said compensation signal, said compensator means incorporating an integrator for obtaining a running sum of said adjusted modulo signal;
- and
- an insertion switch programmed to selectively set the output of said precoding apparatus to be said adjusted modulo signal prior to said predetermined time and, at said predetermined time, to set said output of the precoding apparatus to be the negative value of said running sum.
In a precoding apparatus in a transmitter of a time division duplex data communication system, said precoding apparatus having a data symbol sequence as an input and having a precoded data symbol sequence as an output, said precoding apparatus comprising a feedback filter and a filter summer for subtracting the output of said feedback filter from said input data symbol sequence thereby obtaining an adjusted data symbol sequence;
- a level shifter responsive to said adjusted data symbol sequence for generating a level shifting signal;
- and a modulo summer for adding said level shifting signal to said adjusted data symbol sequence thereby obtaining a level shifted data symbol sequence;
- the improvement characterized by a circuit for driving the DC output of said precoding apparatus to zero at a predetermined time, said circuit comprising:
- a compensator summer for adding said level shifted data symbol sequence and a compensation signal thereby obtaining an adjusted modulo signal;
- a compensator means for generating said compensation signal, said compensator means incorporating an integrator for obtaining a running sum of said adjusted modulo signal;
- and
- an insertion switch programmed to selectively set the output of said precoding apparatus to be said adjusted modulo signal prior to said predetermined time and, at said predetermined time, to set said output of the precoding apparatus to be the negative value of said running sum.
A method for driving the DC output of a precoding apparatus in a data communication system to zero at a predetermined time after a scheduled transmission of data, the method comprising the steps of:
- a. generating a data symbol sequence d(n);
- b. subtracting the output f(n) of a precoder filter from the data symbol sequence d(n) to form an adjusted data symbol sequence a(n);
- c. adding a level shifting signal r(n) to the adjusted data symbol a(n) to form a level shifted (modulo) data symbol sequence b(n);
- d. adding a DC compensation signal q(n) to the level shifted data symbol sequence b(n) to obtain an adjusted modulo signal m(n);
- e. determining a running sun s(n) of the adjusted modulo signal m(n);
- f. setting the value of an output signal p(n) to the value of the adjusted modulo signal m(n) until said predetermined time;
- and
- g. setting the value of the output signal p(n) to the negative value of the running sum s(n−1) at said predetermined time.
Dependencies are inferred from the claim text.