| 摘要 |
<p>An A/D converter 1 converts analog modulation signals, such as video signals and audio signals, into digital modulation signals. A center frequency data setting circuit 6 outputs center frequency data for setting the center frequency of an FM wave. An operation unit 5 outputs such addition data, on the basis of the center frequency data and average frequency data from a counter circuit 4, as will make the average frequency of the FM wave substantially identical with the center frequency that has been set. An adder 2 adds the digital modulation signals and the addition data, and outputs addition digital signals. A DDS 3 accumulates an addition digital signal in every sampling period supplied from a reference oscillator 7. In the ROM 32 of the DDS 3 are stored sine wave data and the ROM 32, having the accumulated signals as its address input, outputs the sine wave data. The counter circuit 4 figures out the average frequency of the FM wave from the DDS 3, and supplies average frequency data to the operation unit 5.</p> |
