TRIGONOMETRIC WAVE GENERATION CIRCUIT, DTMF SIGNAL GENERATING CIRCUIT USING THE SAME, SOUND SIGNAL GENERATING CIRCUIT, AND COMMUNICATION DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a technology for reducing a circuit scale which generates a trigonometric wave.

SOLUTION: A DTMF signal generating circuit 12 of the present invention is provided with a frequency designating unit 30 which designates frequencies to form a DTMF signal, a sinusoidal wave computing unit 32 which computes sinusoidal waves by referring to frequencies designated by the frequency designating unit 30, and a sinusoidal wave synthesizing unit 34 which synthesizes two sinusoidal waves computed by the sinusoidal wave computing unit 32. The sinusoidal wave computing unit 32 is provided with operators such as an adder-subtracter and a multiplier and generates a sinusoidal wave by determining terms of a Taylor expansion of a sinusoidal function by arithmetic operation.

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