| 摘要 |
PURPOSE:To prevent high frequency oscillation by controlling a gain of an oscillating circuit according to a level change in an output signal of a phase shift circuit connected to the oscillation circuit. CONSTITUTION:A peak of an output vi of an oscillation circuit comprising a variable amplifier 24, a resonator 21, a phase shift circuit 22, a phase detector 25 and a synthesis ratio control circuit 33 is detected by a peak detector 26 and after the output vi is shifted by a phase shift circuit 27, the peak is detected by a peak detector 28 and the level of both the peak detection circuits is compared by a threshold value circuit 29. Since the phase shift amount of the phase shift 27 is a function of a frequency of the output vi, an output (level difference) of the threshold value circuit 29 represents the oscillation frequency. The output of the threshold value circuit 29 is inputted to a gain control circuit 31 and the gain of the variable amplifier 24 is controlled thereby preventing the high frequency oscillation. |
