| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a frequency adjustment circuit capable of realizing the adjustment of the center frequency of a current controlled oscillator in a modulation-demodulation circuit of a high fidelity VTR, with high accuracy. <P>SOLUTION: The frequency adjustment circuit of this invention is used for a frequency modulation system wherein a current superimposing circuit 3 superimposes a signal current converted from a modulated voltage signal to be given to a signal current controlled oscillator 4 by a voltage/current conversion circuit 2 on a DC current outputted from an adjustment current generating circuit 7 to control the center frequency of the signal current controlled oscillator 4. The frequency adjustment circuit comprises: a timing generating circuit 11 for receiving a reference signal to generate a timing signal for specifying a prescribed period; a counter 9 for counting an output of an adjustment current controlled oscillator 12 receiving an adjustment current being the same value of that of the signal current controlled oscillator 4 within the prescribed period; and a DAC control circuit 8 for controlling the adjustment current of a DAC 6 until the count of the counter 9 matches a target count. <P>COPYRIGHT: (C)2003,JPO |
