Overload protection and stability for high order 1-bit delta-sigma modulators
AssigneeCirrus Logic, Inc.
InventorsJohn L. Melanson, Kent B. Chambers
Life of this patent
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Abstract
A combination of low order and high order filters and a rule-based 1-bit quantizer with multiple feedback paths and separate quantization output provide stabilization to a delta-sigma modulator during quantizer overload conditions. The 1-bit delta-sigma modulator system combines the superior in-band noise shaping properties of a high order delta-sigma modulator with the stability of a low order delta-sigma modulator to obtain a high order delta-sigma modulator with overload stability. The 1-bit quantizer operates in accordance with a set of primary quantization rules that enables high and low order delta-sigma modulators to work together and remain stable during overload conditions while minimizing performance degradation.
Claims23
A delta-sigma modulation system comprising:
- an M-order filter to process input data, wherein M is greater than or equal to 3;
- an N-order filter that is stable during overload conditions;
- and
- a quantizer system coupled to the M-order and N-order filters to receive input data from the M-order and N-order filters, provide quantized feedback data, qM, to the M-order filter, provide quantized feedback data, qN, to the N-order filter, and provide two state quantization output data q, wherein q=qM+qN.
A digital signal processing system having a delta-sigma modulator with stability protection during quantizer overload conditions, the system comprising:
- an M-order loop filter to process a sum of input data and feedback data, qM, wherein M is more than two;
- an N-order loop filter to process feedback data, qN, wherein N is selected from the group consisting of one and two;
- a rules based 1-bit quantizer to process output data from the N-order loop filter and M-order filter and to provide qM, qN, and 1-bit quantized output data, q, wherein q=qM+qN, and qMmax is greater than the maximum value of q and qMmin is less than the minimum value of q to maintain stability of the M-order loop filter during overload conditions.
A digital signal processing system comprising:
- an M-order filter to process input data, wherein M is greater than 2;
- an N-order filter that is stable during overload conditions;
- and
- a quantizer system coupled to the M-order and N-order filters to receive input data from the M-order and N-order filters, provide quantized feedback data to the M-order filter, provide quantized feedback data to the N-order filter, and provide two state quantization output data, wherein the quantization output data approximately equals the feedback data to the M-order filter plus the feedback data to the N-order filter.
A method of maintaining stability of a 1-bit delta-sigma modulation system under overload conditions, the method comprising:
- providing quantized output data using output data of an M-order filter and output data of an N-order filter, wherein M is greater than or equal to 3 and the N-order filter is stable under overload conditions;
- providing feedback data, qM, to the M-order filter;
- providing feedback data qN to the N-order filter;
- and
- providing 1-bit quantization output data, q, wherein q equals qN+qM.
A method of maintaining stability of a 1-bit delta-sigma modulator during overload conditions, wherein the 1-bit delta-sigma modulator comprises a quantizer, an M-order loop filter, and an N-order loop filter, the method comprising:
- providing 1-bit output data, q, based on input data from an M-order loop filter and an N-order loop filter, wherein M is greater than or equal to three and N is selected to provide stability to the delta-sigma modulator during overload conditions;
- detecting an overload condition of a quantizer;
- providing appropriate feedback data, qM, for the M-order loop filter to enable the M-order loop filter to remain stable during the overload conditions, wherein a maximum value of feedback data qM is greater than the maximum value of output data q;
- and
- providing compensating feedback data, qN, for the N-order loop filter to maintain an acceptable gain level of the quantizer.
Dependencies are inferred from the claim text.