| 摘要 |
PURPOSE:To avoid the change in noise band width when the frequency dividing ratio and the output frequency are changed, by using a voltage controlled oscillator having the characteristics increasing the voltage-frequency conversion gain. CONSTITUTION:An oscillation angular frequency omegan when the specific oscillation number of an oscillator of PLL constitution is assumed to be continuously oscillated, is expressed as omegan=(k0 kd/tau1N)<1/2>, (wherein kd is the conversion gain of a phase comparator, k0 is voltage-frequency conversion gain of VCO, tau1 is a value relating to the low pass filter element, and CR1, N are frequency dividing ratio). The kd, tau1 are kept constant and k0 is changed with the frequency dividing ratio N. In this case, by changing the voltage-frequency characteristic of the voltage controlled oscillator VCO as indicated in the Figure, the change in noise band width can be avoided, when the output frequency is changed through the change in the frequency dividing ratio in the oscillator of PLL constitution. |
