System and method for encoding an input data stream by utilizing a predictive, look-ahead feature

• US 20020126027A1
• Filed: 01/08/2001
• Published: 09/12/2002
• Est. Priority Date: 01/08/2001
• Status: Active Grant

• Current Assignee: Broadcom International Pte Ltd. (Broadcom, Inc.)
• Original Assignee: Agilent Technologies, Inc.
• Inventors: Walker, Richard C.
• Granted Patent: US 6,501,404 B2
• Time in Patent Office: Days
• US Class Current: 341/76
• CPC Class Codes: H03M 7/3015 Structural details of digital delta-sigma modulators
• CPC Class Codes: H03M 7/3051 adaptive, e.g. adaptive delta modulation [ADM]

Abstract

In accordance with one aspect of the invention, a method operates to compare an input value of the input signal stream with an output value of an integration function of a previous binary value to generate a new binary value based upon the comparison. The method then stores a plurality of successive binary values from the comparing step, and simulates an integration function for a plurality of possible bit sequences of the plurality of successive binary values. Finally, the method determines which sequence results in the smallest error between the input signal stream and the output value of the integration function, and uses the most significant bit of the determined sequence to adjust the integration function. In accordance with another aspect of the invention, an encoder is provided for encoding an input signal stream. The encoder includes a comparator configured to compare an input value of the input signal stream with an output value of an integration function of a previous binary value to generate a new binary value based upon the comparison. The encoder further includes a memory configured to store a plurality of successive binary values from the comparator, and means for simulating an integration function for a plurality of possible bit sequences of the plurality of successive binary values. The comparator further includes means for determining which sequence results in the smallest error between the input signal stream and the output value of the integration function, and means for adjusting the integration function based upon the most significant bit of the determined sequence.

Claims

1. A method for encoding an input signal stream comprising the steps of:

comparing an input value of the input signal stream with an output value of an integration function of a previous binary value to generate a new binary value based upon the comparison;

storing a plurality of successive binary values from the comparing step;

simulating an integration function for a plurality of possible bit sequences of the plurality of successive binary values;

determining which sequence results in the smallest error between the input signal stream and the output value of the integration function; and

using the most significant bit of the determined sequence to adjust the integration function.

2. The method as defined in claim 1, wherein the step of simulating an integration function for a plurality of possible bit sequences includes simulating an integration function for all possible bit sequences.

3. The method as defined in claim 1, wherein the step of determining which sequence results in the smallest error further includes the step of calculating a root mean square (RMS) error value of the output value of the integration function and the input value.

4. The method as defined in claim 1, wherein the step of using the most significant bit of the determined sequence further includes adaptively adjusting a step size of the integration function based upon the most significant bit of the determined sequence.

5. The method as defined in claim 4, further including the step of adaptively adjusting the step size of the integration function based upon successive values of the most significant bit of the determined sequence.

6. The method as defined in claim 1, wherein the step of storing a plurality of successive binary values includes storing eight successive binary values.

7. The method as defined in claim 1, wherein the method modulates the input signal stream in accordance with a delta encoding algorithm.

8. The method as defined in claim 1, wherein the method modulates the input signal stream in accordance with a sigma delta encoding algorithm.

9. In an encoder having a comparator for comparing an input value of an input signal stream with an output value of an integration function, wherein the integration function operates on a binary value previously output from the comparator, a method for adjusting the integration function to encode the input signal stream, the improvement comprising the step of looking ahead to future binary values to the integration function and adjusting the integration function accordingly.

10. The method as defined in claim 9, wherein the step of looking ahead includes the step of simulating an integration function for a plurality of possible bit sequences of the plurality of successive binary values.

11. The method as defined in claim 10, wherein the step of simulating an integration function for a plurality of possible bit sequences includes simulating an integration function for all possible bit sequences.

12. The method as defined in claim 10, further including the step of determining which sequence results in the smallest error between the input signal stream and the output value of the integration function.

13. The method as defined in claim 12, further including the step of using the most significant bit of the determined sequence to adjust the integration function.

14. The method as defined in claim 9, wherein the comparator and the integration function are configured as a delta encoder.

15. The method as defined in claim 9, wherein the comparator and the integration function are configured as a sigma delta encoder.

17. The encoder as defined in claim 16, wherein the encoder is implemented in hardware.

18. The encoder as defined in claim 16, wherein the encoder is implemented in software.

19. A computer readable storage medium containing program code to implement the encoder as defined in claim 18.

20. The encoder as defined in claim 16, wherein the comparator and the integration function are configured as a delta encoder.

16. An encoder for encoding an input signal stream comprising:

a comparator configured to compare an input value of the input signal stream with an output value of an integration function of a previous binary value to generate a new binary value based upon the comparison;

memory configured to store a plurality of successive binary values from the comparator;

means for simulating an integration function for a plurality of possible bit sequences of the plurality of successive binary values;

means for determining which sequence results in the smallest error between the input signal stream and the output value of the integration function; and

means for adjusting the integration function based upon the most significant bit of the determined sequence.