| 摘要 |
PROBLEM TO BE SOLVED: To generate highly precise voltage controlled oscillator(VCO) control voltage with a simple circuit without using a digital/analog converter by generating control voltage from carry output with an up/down counter and an adder. SOLUTION: The output of an up/down counter is inputted to an adder, the carry output pulse of the operation of feed-back is averaged and VCO control voltage is generated. In this circuit, the up/down counter 4 inputs an up signal s106 and a down signal s107, counts up or counts down the counter of N bits in accordance with inputs and output the count value s109 of N bits. A full adder 5 inputs the count value s109, and adds the count value s109 of N bits and the addition output s110 of N bits with the period of not more than the reciprocal of N-th power of 2 on a period when the count value is updated. The highest carry s111 of an addition result is outputted. |
