| 摘要 |
PROBLEM TO BE SOLVED: To provide a DDS system modulation signal generating device which freely sets the amplitude and modulation degree of an external signal and maximally utilizes resolution in the AD conversion of the external signal. SOLUTION: A frequency register 1, a cumulative adder 2 and a cumulative addition register 3 generate modulated wave signal. A modulation memory 13 stores a table for converting AD conversion data into modulation data, modulation data is read from a conversion table in response to AD conversion data which is obtained by AD-converting the external signal SE by an AD converter 13 and a modulation wave signal is outputted by a modulation wave register 11. A digital comparator 7 compares the modulated wave signal with a modulation wave so that a PWM modulated signal SPWM is obtained. Modulation data of the conversion table is previously and optionally re-written from a CPU, etc. The modulation wave signal by modulation data of the conversion table is used for phase modulation or frequency modulation through the use of the external signal SE.
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