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Differing frequency sine wave generation from a look-up table

  • US 5,363,443 A
  • Filed: 12/08/1993
  • Issued: 11/08/1994
  • Est. Priority Date: 12/08/1993
  • Status: Expired due to Term
First Claim
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1. A method for generating at least two different frequency sine waves for transmission at a first frequency from a look-up table having entries including samples taken at a second sampling frequency which is not an integral multiple of said first frequency, said method comprising the steps of:

  • selecting a fundamental table frequency such that the frequencies of said different frequency sine waves to be generated are each an integral multiple of said fundamental table frequency;

    determining a fractional correction factor by;

    placing said second sampling frequency over said first frequency to form a fraction; and

    reducing said fraction;

    forming a look-up table for a sine wave of said fundamental table frequency by taking samples at a rate equal to said second sampling frequency times a denominator of said fractional correction factor;

    accessing said look-up table using at least two different table steps corresponding to said at least two different frequency sine waves to be generated; and

    taking first and second fractional portions of two different table steps for transitions between corresponding first and second frequency sine waves, said first and second fractional portions summing to one.

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