Patent ID: 6853255

Claim:
An AFC circuit for compensating for an error of the oscillation frequency of a detecting oscillator based on a detection signal from a detector circuit, said detector circuit generating said detection signal upon detecting an amplitude of a received signal at a timing tied to the oscillation frequency of said detecting oscillator, said AFC circuit comprising: a frequency error determining circuit for converting the detection signal amplitude to a frequency error value; a reference oscillator; a frequency error/control voltage conversion circuit connected to receive the frequency error value from said frequency error determining circuit and connected to feed a control voltage signal to said reference oscillator; a PLL (phase lock loop) circuit; a detecting frequency computing circuit connected to receive the frequency error value from said frequency error determining circuit and connected to feed a detection oscillation frequency control value to said PLL circuit; said reference oscillator connected to provide an oscillator input to said PLL; said PLL connected to provide a control voltage to said detecting oscillator, said detecting oscillator responsive to said control voltage for controlling the oscillation frequency thereof; wherein said AFC circuit controls the oscillation frequency of the detecting oscillator based on the frequency error value so as to vary the oscillation frequency used as a sampling frequency of the detector circuit.