Automatic Frequency Control: Theory and Simulation

The theory and simulation of a base line Automatic Frequency Control, AFC, are proposed in this paper. The AFC is used to track the Voltage Controlled Temperature Compensated Crystal Oscillator (VCTCXO) drift. It is required to lock on to a valid signal at some frequency offset of a predetermined range. This method of producing a frequency estimate that is computationally more expensive is introduced which involves the Arctangent. Despite the increased complexity, the Arctangent implementation is more robust. The estimate is independent of amplitude effects and also increases the pull-in range of the AFC. Further, the AFC simulation performance was shown to be good and there was minimal degradation compared to the baseline system without the AFC.