DC offset removal using digital feedback
AssigneeQuintic Holdings
InventorsMark Magdaleno, John B. Groe
Life of this patent
Estimating the term…
Abstract
Apparatus and methods for removing dc offsets in feedback loops such as may be used in communication circuits are disclosed. A comparator may be used to sample the output of the feedback loop, with the comparator output applied to a DSP module. The DSP module is configured to determine a dc offset in the output signal and generate an offset correction signal, which may then be applied to the input of the feedback loop to adjust the de offset.
Claims18
An apparatus for removing a dc offset in a feedback loop, comprising:
- a comparator operative to sample a feedback loop output signal and provide a comparator output signal;
- a digital signal processing (DSP) module configured to receive the comparator output signal and, at least in part in response to the comparator output signal, determine a dc offset level in the feedback loop output signal;
- a digital to analog (D/A) converter coupled to the DSP module to provide an offset compensation signal based on the dc offset level;
- a moving average filter (MAF) coupled to an output of the comparator;
- an up/down (U/D) counter having a variable step size, the up/down counter being coupled to an output of the MAF;
- and
- control logic configured to:
- strobe the comparator;
- define a number of filter taps of the MAF;
- and
- set at least one of the step size and/or rate for the U/D counter.
Apparatus for removing a dc offset in a feedback loop, comprising:
- a comparator operative to sample a feedback loop output signal and provide a comparator output signal;
- a digital signal processing (DSP) module configured to receive the comparator output signal and, at least in part in response to the comparator output signal, determine a dc offset level in the feedback loop output signal;
- a digital to analog (D/A) converter coupled to the DSP module to provide an offset compensation signal based on the dc offset level;
- wherein the DSP module is configured to:
- selectively determine, during an inactive receive slot, the dc offset level;
- and
- generate, during a successive active receive slot, the offset compensation signal based at least in part on the selectively determined dc offset level.
A method for reducing a dc offset in a feedback loop, comprising:
- providing an output signal of the feedback loop to a comparator to generate a comparator output signal;
- providing the comparator output signal to a DSP module;
- determining, in the DSP module, a dc offset level in the output signal based at least in part on the comparator output signal;
- generating an offset compensation signal based on the dc offset level;
- strobing the comparator to generate a plurality of comparator output signal samples;
- accumulating, in a moving average filter (MAF), the plurality of comparator output signal samples;
- directing, in response to the accumulating, an up/down (U/D) counter;
- and
- providing an output of the U/D counter to a D/A converter to generate the offset compensation signal.
A method for reducing a dc offset in a feedback loop, comprising:
- providing an output signal of the feedback loop to a comparator to generate a comparator output signal;
- providing the comparator output signal to a DSP module;
- determining, in the DSP module, a dc offset level in the output signal based at least in part on the comparator output signal;
- generating an offset compensation signal based on the dc offset level;
- selectively determining, during an inactive receive slot, the dc offset level;
- and
- generating, during an active receive slot, the offset compensation signal based at least in part on the selectively determined dc offset level.
A method for reducing a dc offset in a feedback loop, comprising:
- generating a dither signal;
- combining the dither signal with an output signal of the feedback loop to generate a combined output signal;
- providing the combined output signal to a comparator to generate a comparator output signal;
- providing the comparator output signal to a DSP module;
- determining, in the DSP module, a dc offset level in the output signal based at least in part on the comparator output signal;
- and
- generating an offset compensation signal based on the dc offset level.
Dependencies are inferred from the claim text.