Patent ID: 7453962

Claim:
An adaptive frequency control apparatus, which is in a device for controlling the frequency of a received radio frequency signal in a digital communication system, the adaptive frequency control apparatus comprising: a frequency downstreamer for converting the frequency of the radio frequency signal to a frequency of a predetermined band according to an input reference signal; a frequency error measurer for measuring a frequency error between a frequency of the output signal of the frequency downstreamer and a predetermined frequency; a loop filter for filtering the frequency error output from the frequency error measurer based on a plurality of operational parameters, the operational parameters being changeable; a numerically controlled oscillator for controlling a numeral of the output signal based on the output of the loop filter; a frequency error compensator for compensating for the frequency of the output signal of the frequency downstreamer according to the output signal of the numerically controlled oscillator, and transmitting the compensated frequency to the frequency error measurer; a frequency sweeping processor for determining whether to perform frequency sweeping and determining a sweeping range based on the output signal of the frequency error measurer, and outputting a corresponding control signal; a differential amplifier for converting the control signal to a sweeping control signal; and a voltage-controlled oscillator for changing a frequency of the reference signal according to the sweeping control signal of the differential amplifier, wherein one of the plurality of operational parameters is variable in software according to different system standards, and wherein a frequency error range controlled by the numerically controlled oscillator is smaller than a frequency error control range controlled by the voltage controlled oscillator.