| 摘要 |
An inexpensive and low power consumption frequency synthesizer in which sufficient frequency switching characteristics and spurious characteristics can be obtained without substantially raising the phase comparison frequency. A variable frequency divider divides the oscillation signal of a VCO while switching the frequency dividing ratio in accordance with an integral frequency dividing ratiogenerated by frequency dividing ratio generating means, and controls VCO with anoutput of a loop filter, and frequency dividing ratio generating means comprises multiple integrators connected in cascade and differentiators which differentiate the carry-out signals of the integrators, so that a phase error generated at the variable frequency divider is obtained from an output of an adder included in the final stage integrator of frequency dividing ratio generating means, and a phase error compensation value is output, and further a pulse width of a signal to be used for compensating for phase error is varied in accordance with the phase error compensation value to perform compensation for the phase error.
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