| 摘要 |
PURPOSE:To generate an optional low frequency signal by forming a digital low pass filter having 2nd degree of attenuation characteristic or over whose break frequency is (f), and supplying the output signal of a digital signal generating means whose fundamental frequency is (f). CONSTITUTION:When a frequency f8a desired to be generated is designated externally, a frequency division ratio calculation means 8 calculates a frequency division ratio N8b from the relation between frequencies F and f8a of the output 2a of an original oscillator 2 to obtain a signal 3a whose frequency is (f) from a frequency divider 3. This signal is a rectangular wave signal 4a whose fundamental frequency is (f) via an A/D converter 4. When the signal 4a passes through a digital filter means 5 whose break frequency is (f) having a 2nd-degree of low pass characteristic or over, a sinusoidal wave digital signal 5a whose fundamental frequency is (f) is extracted. When the signal 5a passes through a D/A converter 6 and an integration device 7, a correct signal 7a from which a loopback frequency component is eliminated is extracted. |
