| 摘要 |
PURPOSE:To stabilize a voltage controlled oscillating frequency corresponding to the set numeral externally, by counting an output of the voltage controlled oscillator intermittently, comparing this counting value with the set numeral from the outside, converting this compared output into an analog signal and supplying it to the voltage controlled oscillator. CONSTITUTION:An output signal of a voltage controlled oscillator 11 is supplied to one input terminal of an inhibition gate 12. A reference pulse signal Ps is fed to another input terminal of the gate 12, and the output signal of the voltage controlled oscillator 11 can intermittently be picked up at the on-period of the pulse signal Ps. Further, this output signal is frequency-divided to 1/N a counter 13, and this frequency-divided output is fed to a subtractor 14 together with the set numeral M externally supplied at the next on-period of the reference pulse signal Ps to perform the subtraction. As the result of this subtraction, the error signal is fed to a D/A converter 17 at the on-period of the reference pulse signal Ps, and the output of the converter 17 is fed to the voltage controlled oscillator as a control voltage via an LPF18. |
