Differing frequency sine wave generation from a look-up table

Details Differing frequency sine wave generation from a look-up table Differing frequency sine wave generation from a look-up table

1993-12-08

1994-11-08

Dwyer, James L.

Telephonic communications

Call signal generating

379361, 379355, 379 97, 379 98, 84600, 84605, 84607, 84615, H04M 300

Patent

active

053634438

ABSTRACT:
Sine waves are generated by a port circuit processor of a telephone switching office by accessing a look-up table stored in a memory associated with the port circuit processor. Entries in the look-up table are accessed by using table steps or .DELTA.'s which correspond to the frequencies of the sine waves to be generated. The table steps or .DELTA.'s are changed for different sine wave frequencies and may be changed each bit period. Whether changed or not, a first fractional portion of the table step or .DELTA. for the previous frequency is combined with a second fractional portion of the table step or .DELTA. for the current frequency with the first and second fractional portions adding up to one. In this way, an X sample per second data stream, X equaling the base sample rate of the look-up table, that precisely matches a Y bits per second rate, Y equaling the transmission rate of the data stream, is generated.

REFERENCES:
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patent: 5086475 (1992-02-01), Kutaragi et al.
patent: 5208852 (1993-05-01), Tamura et al.
Bresenham Line Drawing Algorithm, Newman and Sproull, Principles of Literature Computer Graphics, McGraw Hill, 2nd Edition, 1979.
Computer Music Journal, J. Gold 1975 vol. I, No. 2. pp. 4-7 CA, 94025 Apr. 1975.

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