| 摘要 |
PROBLEM TO BE SOLVED: To suppress fluctuation in gain characteristics at a voltage controlled oscillator.SOLUTION: The voltage controlled oscillator 11 includes an inductor 100, a fine tuning capacitor 101p, and a rough tuning capacitor 102p, and generates an oscillation clock CKout. A frequency divider 12 divides the oscillation clock CKout to generate a frequency divided clock CKdiv. In the rough tuning mode, a DC voltage supply circuit 13 supplies a DC voltage V13 to a control node Ni and changes the voltage value of the DC voltage V13 according to a DC value of an oscillation voltage VP. In the rough tuning mode, a frequency band selection circuit 14 switches the capacitance value of the rough tuning capacitor 102p so as to set the oscillation frequency band of the voltage controlled oscillator 11 to an oscillation frequency band corresponding to a target frequency based on frequency difference between a reference clock and the frequency divided clock. In the fine adjustment mode, an oscillation control circuit 15 increases or decreases a control voltage VT according to a phase difference between the reference clock and the frequency divided clock. |
