Patent ID: 7486146

Claim:
A loop system capable of auto-calibrating an oscillating frequency range comprising: a frequency error detector for generating a second control signal or a coarse-lock-state signal and performing coarse tuning in accordance with a reference frequency and a feedback frequency, the frequency error detector comprising: a rotational frequency detector for comparing the reference frequency and the feedback frequency so as to generate a first control signal; a state machine coupled to the rotational frequency detector for determining an auto-calibration state in accordance with a polarity of the first control signal and a time-counting signal; and an up-down counter coupled to the state machine, for generating the second control signal or the coarse-lock-state signal in accordance with the auto-calibration state; a voltage controlled oscillator (VCO) coupled to the frequency error detector for selecting to operate at one of a plurality of frequency operating curves in accordance with the second control signal so as to generate an oscillating signal; a voltage input unit for providing a fixed voltage to the VCO; and a switch for switching the VCO to couple to the voltage input unit or to couple to a fine frequency tuner in accordance with the coarse-lock-state signal.