A frequency synchronizer system is based on the maximum likelihood criterion
from
estimation theory and that can achieve both frequency acquisition and frequency
tracking without requiring knowledge at the receiver of the carrier's phase angle,
baud timing, or a preamble consisting of known signal symbols. The synchronizer
includes a processor for executing the following sequence of operations: a) initializing
an estimated frequency correction factor; b) determining a corrected frequency
offset value from a first product of a sample signal and the estimated frequency
correction factor; c) filtering a first sample of the corrected frequency offset
value to obtain a filtered corrected frequency offset value; d) imparting a delay
to a second sample of the corrected frequency offset value to obtain a delayed
corrected frequency offset value; e) determining a conjugate product value from
a second product of the filtered corrected frequency offset value and a conjugate
of the filtered corrected frequency offset value; f) determining a delay conjugate
value from a third product of the delayed corrected frequency offset value and
the conjugate product value; g) determining an error signal from the delay conjugate
value; h) determining a frequency offset value from the error signal; and i) determining
an updated value of the estimated frequency correction factor from the frequency
offset value.