Hysteresis nonlinear state machine with overlapping thresholds for automatic frequency control

An apparatus for providing hysteresis non-linear frequency tracking of a control loop in a frequency generator of a wireless mobile device having a voltage controlled oscillator (VCO) and an adaptive loop filter, the apparatus comprising:

• a memory;
• a processor coupled to the memory, the memory containing instructions for providing coefficients to an adaptive loop filter from a plurality of coefficients, each of the plurality of coefficients associated with an operating state of the frequency generator wherein the operating state is determined by:
• determining a channel metric based upon one or more channel quality indicators determined for a received radio frequency channel and is a function of one or more channel quality indicators selected from a signal-to-noise ratio of the received channel, bit-error rate of the received channel, a received signal strength measurements, and carrier-to-interference-plus-noise ratios (C/I+N) wherein each of the one or more channel quality indicators has an associated weighting in determining the channel metric;
• determining a state metric associated with the control loop based on the operating state of the control loop wherein the state metric comprises a function of a frequency error between the frequency of the received radio frequency channel and an output frequency of the VCO and at least one of:
• a weighted function of the current channel metric;
• and
• one or more previous operating state metrics weighted by a time parameter, wherein the time parameter decreases the weighting of the previous operating state metric;
• determining one or more state metric threshold values associated with the determined channel metric from a table stored in the memory, the one or more state metric threshold values selected from a plurality of state metric threshold values each associated with a transition to a possible operating state of the control loop from the current operating state;
• determining if one of the one or more state metric threshold values has been exceeded based upon the determined state metric, wherein the state metric threshold is defined for each transition between each of operating states;
• and
• transitioning from the current operating state to the operating state associated with the exceeded state metric threshold value;
• wherein the state metric threshold values associated with the operating states provide overlapping region between common operating states to provide hysteresis for operating state transitions.