Look-ahead delta sigma modulator with pruning of output candidate vectors using quantization error minimization pruning techniques
First Claim
1. A method of processing input signal data using a look-ahead delta sigma modulator of depth N using natural and pruned pattern loop filter responses, wherein N is greater than or equal to two, the method comprising:
- determining a set of pattern responses of a loop filter of the look-ahead delta sigma modulator for each output candidate vector by setting signal input data to the loop filter of the delta sigma modulator to at least approximately zero and filtering a set of output candidate vectors;
determining a natural response of the loop filter of the look-ahead delta sigma modulator by setting feedback data to the loop filter to at least approximately zero and filtering a set of input data signal samples;
pruning the set of pattern responses to determine a set of one or more pruned pattern responses; and
quantizing each input signal data sample by applying predetermined decision criteria to determine a best match between a member of the set of one or more pruned pattern responses and the natural response and selecting quantization output data from the output candidate vector associated with the pruned pattern response used to determine the best match.
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Abstract
A look-ahead delta sigma modulator utilizes pruning techniques to reduce the number of possible output candidate vectors used to determine quantization output values. The look-ahead delta-sigma modulators can also combine the pruning techniques with a reduction in the amount of processing by simplifying the computations used to generate quantizer output values. In one embodiment, the pruning techniques exploit application of superposition techniques to a loop filter response of the look-ahead delta sigma modulator. The set of possible pattern response vectors can be pruned to form a subset of P candidate pattern response vectors. If an element value of a pattern response vector proximally matches a value of the corresponding reference element of the natural response vector, a quantizer uses the proximally matching pattern response vector to determine a quantization output value.
52 Citations
38 Claims
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1. A method of processing input signal data using a look-ahead delta sigma modulator of depth N using natural and pruned pattern loop filter responses, wherein N is greater than or equal to two, the method comprising:
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determining a set of pattern responses of a loop filter of the look-ahead delta sigma modulator for each output candidate vector by setting signal input data to the loop filter of the delta sigma modulator to at least approximately zero and filtering a set of output candidate vectors; determining a natural response of the loop filter of the look-ahead delta sigma modulator by setting feedback data to the loop filter to at least approximately zero and filtering a set of input data signal samples; pruning the set of pattern responses to determine a set of one or more pruned pattern responses; and quantizing each input signal data sample by applying predetermined decision criteria to determine a best match between a member of the set of one or more pruned pattern responses and the natural response and selecting quantization output data from the output candidate vector associated with the pruned pattern response used to determine the best match. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A signal processing system comprising:
a look-ahead delta sigma modulator comprising; a loop filter; a pattern response generator coupled to the loop filter to determine a set of pattern responses by the loop filter obtained by setting signal input data to the loop filter to at least approximately zero and filtering a set of output candidate vectors; a natural response generator to determine a natural response of the loop filter by setting feedback data to the loop filter to at least approximately zero and filtering a set of input data signal samples; a pruning generator to determine a set of one or more pruned pattern responses; and a quantizer to receive output data from the loop filter and the set of pruned pattern responses, wherein the quantizer includes a function generator to quantize each input signal data sample by applying predetermined decision criteria to determine a best match between a member of the set of one or more pruned pattern responses and selecting output data from the output candidate vector associated with the pruned pattern response used to determine the best match. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32)
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33. An apparatus for processing input signal data using a look-ahead delta sigma modulator of depth N using natural and pattern loop filter responses, wherein N is greater than or equal to two (2), the apparatus comprising:
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means for determining a set of pattern responses of a loop filter of the look-ahead delta sigma modulator for each output candidate vector by setting signal input data to the loop filter of the delta sigma modulator to at least approximately zero and filtering a set of output candidate vectors; means for determining a natural response of the loop filter of the look-ahead delta sigma modulator by setting feedback data to the loop filter to at least approximately zero and filtering a set of input data signal samples; means for pruning the set of pattern responses to determine a set of one or more pruned pattern responses; and means for quantizing each input signal data sample by applying predetermined decision criteria to determine a best match between a member of the set of one or more pruned pattern responses and the natural response and selecting quantization output data from the output candidate vector associated with the pruned pattern response used to determine the best match. - View Dependent Claims (34)
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35. A method of processing an input signal using a look-ahead delta sigma modulator of depth N, wherein N is greater than or equal to two, the method comprising:
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pruning a set of candidate vectors by selecting a subset of the candidate vectors, wherein the subset of candidate vectors minimize quantization error of the look-ahead delta sigma modulator at a future time t+n, t is the current time, and n≧
2; andquantizing the input signal using the subset of candidate vectors. - View Dependent Claims (36, 37, 38)
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Specification