Method and apparatus for settling and maintaining a DC offset
AssigneeMotorola, Inc.
InventorsKeith A. Tilley, Raul Salvi, Enrique Ferrer, Atif A. Meraj, David J. Graham
Life of this patent
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Abstract
A DC offset correction loop (200) utilizes a sign bit generator (204), binary search stage (206), and a digital-to-analog converter (208) in its feedback path to correct for DC offsets at the input of a gain stage (202). When a correction value is obtained, it is applied and held (524) to compensate for the DC offset. When a programming event occurs (534), such as detecting an increase in DC offset beyond a threshold, detecting a significant temperature change, or passage of time, a new DC offset correction cycle is initiated.
Claims20
A method of correcting a DC offset in a radio receiver, comprising:
- disabling a front end of the radio receiver to disrupt receipt of radio signals;
- performing a DC offset correction process to determine a DC compensation value;
- holding the DC compensation value to compensate for the receiver's DC offset;
- enabling the receiver's front end;
- determining that a programming event has occurred;
- and
- repeating the disabling, performing, holding and enabling to update the DC compensation value.
A DC offset correction system, comprising:
- a gain stage having an input with a DC offset and an output having an amplified DC offset;
- a feedback loop coupled between the input and the output of the gain stage, the feedback loop including a source of DC offset correction voltage which can be set to a correction value and held at that correction value;
- and
- a controller which instructs the source of DC offset correction voltage to set and hold a correction value, and the controller monitors a programming event and initiates an offset correction cycle to set a new correction value when the programming event occurs.
A method of correcting DC offset, comprising:
- performing an initial DC offset correction by determining a DC correction value and holding the DC correction value;
- determining that a programming event has occurred suggesting that the DC correction value is no longer adequately correcting DC offset;
- and
- responsive to the determining, repeating the performing to obtain a revised DC correction value and holding the DC correction value.
Dependencies are inferred from the claim text.