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US 6,888,484 B2Granted
Stable high-order delta-sigma error feedback modulators, and noise transfer functions for use in such modulators
AssigneeAgere Systems Inc.
InventorsPeter Kiss, Jesus Arias, Dandan Li
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Abstract
Stable, robust, and high-resolution delta-sigma error feedback modulators, such as those used in digital-to-analog converters and phase-locked loops, include an L-order noise transfer function that is provided with L+1 high-order bits from a truncation element. The stability of such delta-sigma error feedback modulators is independent of the input signal. Moreover, the out-of-band gain of the noise transfer function need not be limited, which improves the resolution and the signal-to-noise ratio of the in-band signal.
Claims34
Apparatus comprising:
- a) a first signal mixer having a first input for receiving an input signal, a second input, and an output;
- b) a truncation element having an input coupled with the output of the first signal mixer and an output for providing a number of higher order bits defining an output signal;
- c) means for providing bits of the output of the first signal mixer, other than those output by the truncation element, as lower order bits, the means for providing including an input coupled with the truncation element, and an output for providing the lower order bits;
- and
- d) a noise transfer function element having an input coupled with the output of the means for providing, and an output coupled with the second input of the first signal mixer, wherein the noise transfer function is an L-order transfer function, wherein L is at least 4, and wherein the number of higher order bits is L+1.
2 more elements
Apparatus comprising:
- a) a first signal mixer having a first input for receiving an input signal, a second input, and an output;
- b) a truncation element having an input coupled with the output of the first signal mixer and an output having a number of higher order bits defining an output signal;
- c) means for providing bits of the output of the first signal mixer, other than those output by the truncation element, as lower order bits, the means for providing including an input coupled with the truncation element, and an output for providing the lower order bits;
- and
- d) a noise transfer function element having an input coupled with the output of the means for providing, and an output coupled with the second input of the first signal mixer, wherein the noise transfer function is an L-order transfer function, wherein L is at least 1, wherein the number of higher order bits is L+1, and wherein a stability of the noise transfer function element is independent of the input signal.
2 more elements
A method comprising:
- a) accepting an input signal;
- b) mixing the input signal with a second signal to generate a third signal;
- c) truncating the third signal to generate a number of higher order bits defining an output signal;
- d) providing lower order bits of the third signal as a fourth signal;
- and
- e) applying the fourth signal to a noise transfer function to generate the second signal, wherein the noise transfer function is an L-order transfer function, wherein L is at least 4, and wherein the number of higher order bits is L+1.
3 more elements
Method comprising:
- a) accepting an input signal;
- b) mixing the input signal with a second signal to generate a third signal;
- c) truncating the third signal to generate a number of higher order bits defining an output signal;
- d) providing lower order bits of the third signal as a fourth signal;
- and
- e) applying the fourth signal to a noise transfer function to generate the second signal, wherein the noise transfer function is an L-order transfer function, wherein L is at least 1, wherein the number of higher order bits is L+1, and wherein a stability of the noise transfer function element is independent of the input signal.
3 more elements
Dependencies are inferred from the claim text.