Method and apparatus for precise open loop tuning of reference frequency within a wireless device

A method for correcting errors in a reference frequency signal for a communications subsystem, the method comprising:

• storing values for a reference frequency adjustment signal according to an operating temperature of the subsystem, wherein values are stored according to a range of operating temperatures;
• generating the reference frequency adjustment signal for correcting the reference frequency signal by using a closed loop reference frequency correction module when the communications subsystem operates in a closed loop mode and based on the operating temperature of the subsystem;
• sampling at least two values of the reference frequency adjustment signal during the closed loop mode;
• providing a frequency correction signal based on the reference frequency adjustment signal when the subsystem operates in closed loop mode and providing the frequency correction signal based on a correction value derived from at least two of the sampled values;
• and
• correcting the reference frequency signal using the frequency correction signal.

A wireless device having a communications subsystem for correcting errors in a reference frequency signal, the communications subsystem comprising:

• a frequency generator for generating the reference frequency signal;
• a closed loop reference frequency correction module connected to the frequency generator for generating a reference frequency adjustment signal to correct the reference frequency signal when the communications subsystem operates in closed loop mode;
• and
• an open loop frequency correction subsystem connected to the closed loop reference frequency correction module and the frequency generator, the open loop frequency correction subsystem being configured to sample values of the reference frequency adjustment signal during the closed loop mode and to generate a frequency correction signal to correct the reference frequency signal when the communications subsystem operates in another mode other than closed loop mode;
• and
• a plurality of storage modules configured to store values for the reference frequency adjustment signal, wherein each storage module is indexed by operating temperature,
• wherein the communications subsystem is further configured to sample operating temperature and generate the reference frequency signal based on stored values corresponding to the sampled operating temperature.

A non-transitory computer-readable storage medium having program instructions stored thereon for execution by a processor of a wireless device, wherein the program instructions when executed by the processor causes the wireless device to perform a method for correcting errors in a reference frequency signal for a communications subsystem, the method comprising:

• storing values for a reference frequency adjustment signal according to an operating temperature of the subsystem, wherein values are stored for a range of operating temperatures;
• generating the reference frequency adjustment signal for correcting the reference frequency signal by using a closed loop reference frequency correction module when the communications subsystem operates in a closed loop mode and based on the operating temperature of the subsystem;
• sampling at least two values of the reference frequency adjustment signal during the closed loop mode;
• providing a frequency correction signal based on the reference frequency adjustment signal when the subsystem operates in closed loop mode and providing the frequency correction signal based on a correction value derived from at least two of the sampled values;
• and
• correcting the reference frequency signal using the frequency correction signal.