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US 7,116,721 B1Granted
Delta-sigma modulators with integral digital low-pass filtering
AssigneeCirrus Logic, Inc.
InventorsJohn Laurence Melanson, Heling Yi
Life of this patent
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Abstract
A feedback noise-shaper of an order of at least three implements a first pole set defining a signal transfer function of a selected corner frequency and a second pole set having at least one pole at a frequency at least twice the selected corner frequency defining a noise transfer function.
Claims28
A feedback noise-shaper comprising:
- a loop-filter having at least three stages for modulating an input signal;
- a quantizer for quantizing an output signal from the loop-filter;
- and
- feedback circuitry providing feedback from an output of the quantizer to the loop-filter stages, the feedback to the loop-filter stages weighted by a set of coefficients implementing a first pole set defining a signal transfer function of a selected corner frequency and a second pole set having at least one pole at a frequency at least twice the selected corner frequency defining a noise transfer function.
1 more element
A method of noise shaping comprising the steps of:
- selecting a first pole set defining a signal transfer function for generating a response of a selected corner frequency and a signal passband of a feedback noise-shaper of an order of at least three;
- and
- selecting a second pole set for improving a corresponding noise transfer function of the noise-shaper, wherein the second pole set comprises at least one pole at a frequency above the selected corner frequency for attenuating noise in the signal passband.
A delta-sigma modulator comprising:
- a loop-filer comprising a plurality of stages for modulating an input signal;
- a quantizer for quantizing a signal output from a loop-filter output;
- and
- a plurality of feedback paths for weights feedback to inputs of the stages of an output signal from said quantizer, said weights corresponding to a set of coefficients selected to implement a first pole set for defining a signal transfer function having a corner frequency and a second pole set with a pole at a frequency at least twice the corner frequency for defining a noise transfer function.
1 more element
A data converter for converting a digital input stream containing out-of-band noise to an analog output comprising:
- a delta-sigma modulator having noise and signal transfer functions, the signal transfer function producing a response having a corner frequency and signal passband and defined by a first set of poles and the noise transfer function producing a response improved by at least one additional pole at a frequency substantially greater than said corner frequency for attenuating noise in the signal passband;
- and
- a digital to analog converter for converting a filtered output from the delta-sigma modulator into analog form.
Dependencies are inferred from the claim text.