Automatic frequency control (AFC) system and method using an adaptive threshold to improve accuracy of the direct current (DC) component calculation for a received signal

摘要

A radio device requires a tunable transceiver such that the transceiver can be accurately set to a desired frequency. When a signal with known frequency accuracy is being received, an offset detector can determine the frequency offset generated by the transceiver due to improper tuning. An automatic frequency control (AFC) system ( 100 ) is comprised of a tunable transceiver, an adaptive detector ( 102 ) for comparing an incoming sample from the tunable transceiver to an adaptive maximum deviation threshold for determining if a sample from the tunable transceiver should be used for the direct current (DC) component of the AFC, an offset detector ( 103 ) and an AFC control processor ( 105 ) for utilizing information from the offset detector to reduce the inaccuracy in frequency by tuning the transceiver towards the received signal frequency. The AFC control processor ( 105 ) utilizes one of more threshold levels for defining a maximum correction threshold ( 311 ) based upon the desired maximum offset correction.