Signal averaging circuit and method for sample averaging

• US 20070143383A1
• Filed: 12/16/2005
• Published: 06/21/2007
• Est. Priority Date: 12/16/2005
• Status: Active Grant

• Current Assignee: Monterey Research, LLC (Vector Capital Corporation)
• Original Assignee: Silicon Light Machines Corporation (SCREEN Holdings Co., Ltd.)
• Inventors: Xu, Yansun, Krishnan, Gopalakrishnan
• Granted Patent: US 7,765,251 B2
• Time in Patent Office: Days
• US Class Current: 708/200
• CPC Class Codes: G01D 1/02 giving mean values, e.g. root means square values measuring root mean square values of currents or voltages G01R19/02

Abstract

An averaging circuit and method are provided to compute a running average over a number of samples without the need for maintaining a large sample queue or register. Generally, the method includes the steps of (i) receiving and accumulating data samples in a plurality of sample-accumulators while counting the number of samples received in a sample-counter; (ii) alternately selecting the sum of the samples accumulated in each of the sample-accumulators; (iii) dividing the sum of the samples accumulated in a selected sample-accumulator by the number of samples received to provide an average of the samples accumulated therein; and (iv) interleaving selection of the plurality of sample-accumulators and alternating reset of each to provide a running average over a number of samples.

Claims

1. A method of computing a running average of samples of data over a number of samples, the method comprising steps of:

receiving and accumulating data samples in a plurality of sample-accumulators while counting the number of samples received in a sample-counter;

alternately selecting an average of the samples accumulated in each of the plurality of sample-accumulators by dividing the sum of the samples accumulated in each of the plurality of sample-accumulators by the number of samples accumulated therein; and

alternately resetting each of the sample-accumulators after a number (N) of samples have been received,

whereby a running average is provided over ((M−

1)·

N) samples where M is the number of sample accumulators.

2. A method according to claim 1, wherein the step of alternately selecting an average of the samples accumulated in each of the plurality of sample-accumulators comprises the steps of:

dividing the sum of the samples accumulated in each of the plurality of sample-accumulators by the number of samples received in each of the plurality of sample-accumulators to provide from each of the plurality of sample-accumulators an average of the samples accumulated therein; and

interleaving selection of the average of the samples accumulated from each of the plurality of sample-accumulators.

3. A method according to claim 1, wherein the step of alternately selecting an average of the samples accumulated in each of the plurality of sample-accumulators comprises the steps of:

alternately selecting the sum of the samples accumulated in each of the plurality of sample-accumulators; and

dividing the sum of the samples accumulated in a selected sample-accumulator by the number of samples received to provide an average of the samples accumulated therein.

4. A method according to claim 3, further comprising the step of resetting the sample-counter following N of cycles.

5. A method according to claim 4, wherein the step of dividing the sum of the samples comprises the step of dividing the sum of the samples accumulated in a selected sample-accumulator by the sum of ((M−

1)·

N) and the number of samples received after the last sample counter reset where M is number of sample accumulators.

6. A method according to claim 5, wherein the step of receiving and accumulating samples comprises the step of receiving and accumulating samples in a first and a second sample-accumulator.

7. A method according to claim 6, wherein the step of interleaving selection of the average and alternating reset of each of the sample-accumulators comprises the steps of:

after N samples have been received resetting the second sample-accumulator while resetting the sample counter after the reset selecting as the running average the average of the samples accumulated in the first sample-accumulator;

after 2N samples have been received resetting the first sample-accumulator while resetting the sample-counter after the reset selecting as the running average the average of the samples accumulated in the second sample-accumulator; and

repeating the above steps.

8. A method according to claim 1, further comprising an initial step of selecting the number (N) of samples over which the running average is to be provided.

9. A signal averaging circuit for computing a running average over a number of samples of data, the circuit comprising:

a plurality of sample-accumulators to receive and accumulate samples;

a sample-counter to count the number of samples received up to a predetermined number (N);

a selection circuit to alternately select a sum of the samples accumulated in each of the plurality of sample-accumulators;

a divider to divide the sum of the samples accumulated in the selected sample-accumulator by the sum of ((M−

1)·

N) and the number of samples received after the last sample counter reset to provide from the selected sample-accumulator an average of the samples accumulated therein; and

a reset circuit to alternately reset each of the sample-accumulators after N samples have been received,

whereby, a running average is provided over ((M−

1)·

N) samples where M is number of sample accumulators.

10. A circuit according to claim 9, wherein the reset circuit is configured to reset the sample-counter following N of cycles.

11. A circuit according to claim 10, wherein the plurality of sample-accumulators comprises a first sample-accumulator and a second sample-accumulator.

12. A circuit according to claim 11, wherein the selection circuit is adapted to select the sum of the samples accumulated in the first sample-accumulator to compute the running average after N samples (and subsequent odd sets of N samples) have been received, and to select the sum of the samples accumulated in the second sample-accumulator to compute the running average after 2N samples (and subsequent even sets of N samples) have been received.

13. A circuit according to claim 12, wherein the reset circuit is adapted to reset the second sample-accumulator after N samples (and subsequent odd sets of N samples) have been received while the average of the samples accumulated in the first sample-accumulator is selected as the running average, and to reset the first sample-accumulator after 2N samples (and subsequent even sets of N samples) have been received while the average of the samples accumulated in the second sample-accumulator is selected as the running average.

14. A circuit according to claim 13, wherein the sample-counter is a n-bit forward counter where N=2ⁿ, and wherein the sample-counter is configured to roll over to zero after each set of N samples has been received

15. A signal averaging circuit for computing a running average over a number of samples of data, the circuit comprising:

a plurality of sample-accumulating means for receiving and accumulating digital samples of a signal;

counting means for counting the number of samples received in the plurality of sample-accumulating means;

selection means for alternately selecting from an output of each of the plurality of accumulating means a sum of the samples accumulated therein;

dividing means for dividing the sum of the samples accumulated in the selected sample-accumulating means by the number of samples received in the selected sample-accumulating means to provide average of the samples accumulated therein; and

reset means for alternately resetting the plurality of sample-accumulating means at regular intervals offset with respect to each other by N samples,

whereby, a running average is provided.

16. A circuit according to claim 15, wherein the reset means is further adapted to reset the sample counter when it reaches N.

17. A circuit according to claim 16, wherein the plurality of sample-accumulating means comprises a first sample-accumulator and a second sample-accumulator.

18. A circuit according to claim 17, wherein the selection means is adapted to select the sum of the samples accumulated in the first sample-accumulator to compute the running average after N samples (and subsequent odd sets of N samples) have been received, and to select the sum of the samples accumulated in the second sample-accumulator to compute the running average after 2N samples (and subsequent even sets of N samples) have been received.

19. A circuit according to claim 18, wherein the reset means is adapted to reset the second sample-accumulator after N samples (and subsequent odd sets of N samples) have been received while the average of the samples accumulated in the first sample-accumulator is selected as the running average, and to reset the first sample-accumulator after 2N samples (and subsequent even sets of N samples) have been received while the average of the samples accumulated in the second sample-accumulator is selected as the running average.

20. A circuit according to claim 19, wherein the counting means is a n-bit forward counter where N=2ⁿ, and wherein the sample-counter is configured to roll over to zero after each set of N samples has been received.