A data-pattern feedback mechanism is introduced into the peak detection process
of an automatic frequency compensation system in a Gaussian Frequency Shift Keying
(GFSK) modulated system, providing fast and accurate fine-stage automatic frequency
compensation (AFC). Maximum positive and negative peak registers are updated with
new values as necessary based on detection during a sequence of identical binary
bit values (e.g., during a "00" for detection of maximum negative peak frequency,
or during a "11" for detection of maximum positive peak frequency), in a particular
data frame. As soon as an initial value is determined for both the maximum positive
and negative peak frequencies (e.g., after the first occurrence of a "11" and a
"00", in any order), fine-stage automatic frequency compensation can be initiated.
Subsequent adjustments to the VCO of the local oscillator will further refine the
frequency offset towards the ideal of zero. Quick determination of the maximum
positive and negative peak frequencies is made based on data pattern feedback in
accordance with the principles of the present invention, allowing for a fast and
accurate fine-stage automatic frequency compensation adjustment of a local oscillation
clock signal.