| 摘要 |
A loop system capable of auto-calibrating an oscillating frequency range includes a frequency error detector, a voltage controlled oscillator (VCO), a voltage input unit, and a switch. The frequency error detector includes a rotational frequency detector, a state machine, and an up-down counter. The rotational frequency detector is used for comparing the reference frequency and the feedback frequency. The state machine is used for determining an auto-calibration state. The up-down counter is used for generating the second control signal or the coarse-lock-state signal. The VCO is used for selecting to operate at one of a plurality of frequency operating curves so as to generate an oscillating signal. The voltage input unit is used for providing a fixed voltage to the VCO. The switch is used for switching the VCO to couple to the voltage input unit or to couple to a fine frequency tuner.
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