| 摘要 |
PURPOSE: A fractional-N frequency synthesizer and a signal-delta modulator thereof are provided to reduce an usable input range and increase an output level by forming one-bit modulator with a multi-bit modulator. CONSTITUTION: A fractional-N frequency synthesizer includes a phase detector, a VCO, a divider, and a signal-delta modulator. The phase detector(10) is used for detecting a phase difference between a reference signal and a feedback signal. The VCO(12) is used for receiving a phase difference signal from the phase detector and oscillating a signal of a desired frequency. The divider(13) is used for selecting one integer from plural integers, dividing a frequency of an output signal of the VCO by using the selected integer, and outputting the feedback signal to the phase detector. The signal-delta modulator(14) is used for adding an input value to a feedback value, performing continuously the adding process and quantizing the added value to plural levels.
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