Automatic frequency control system using multiple threshold levels and method of using same

A radio transceiver having a detector and at least one processor for controlling an automatic frequency control (AFC) tuning of the radio transceiver, the at least one processor utilizing a method comprising the steps of:

• determining if a frequency offset between the transceiver operating frequency and a received signal is larger than a first threshold limit, where the first threshold limit is determined by a predetermined absolute frequency offset;
• determining if a frequency offset between the transceiver operating frequency and a received signal is larger than a second threshold limit, where the second threshold limit is determined by a predetermined frequency specification of the radio transceiver;
• determining if a frequency offset between the transceiver operating frequency and the received signal is within a third threshold limit, where the third threshold limit is a predetermined maximum frequency correction;
• and
• wherein the first threshold limit, second threshold limit and third threshold limit are used by the at least one processor to ensure stable operation of AFC.

A method for use by at least one control processor for adjusting an automatic frequency control (AFC) in a radio transceiver receiving signals at a transceiver operating frequency comprising the steps of:

• determining a frequency difference between the transceiver operating frequency and an incoming signal frequency;
• comparing the frequency difference with a predetermined accuracy limit defined by a predetermined maximum frequency offset of the transceiver operating frequency from an actual receive frequency;
• comparing the frequency difference with a predetermined hardware tuning threshold defined by a predetermined radio transceiver specification;
• comparing the frequency difference with a predetermined maximum correction threshold defined by a predetermined maximum correction from the transceiver operating frequency;
• and
• processing at least one of the comparing steps in a microprocessor to provide correction information to stabilize the automatic frequency control to provide stable operation of the radio transceiver.