| 摘要 |
PROBLEM TO BE SOLVED: To avoid a cycle strange sound generated by relation between an integrated value with carry and a fractional setting value, in a fractional N frequency synthesizer.SOLUTION: A calculation unit 11 calculates a remainder of a division in which a dividend is a minimum value with carry of a &Dgr;&Sgr; modulator 2 and a divisor is a fractional setting value, and calculates a quotient and a remainder of a division in which a dividend is a divisor of a previous division and a divisor is a value of a remainder calculated by the previous division, until a value of the remainder becomes zero. A strange sound determination unit 12, in a case where there is a quotient, which is calculated by the calculation unit 11 for the fractional setting value that is set to the &Dgr;&Sgr; modulator 2, larger than a threshold, determines that a cycle strange sound is generated at the fractional setting value. A fractional setting unit 1, in a case where the strange sound determination unit 12 determines that no cycle strange sound is generated with respect to the fractional setting value changed in a range that an output frequency of a VCO 4 is not larger than a predetermined value, sets the changed fractional setting value to the &Dgr;&Sgr; modulator 2. |
