Reference oscillator

A correction circuit for a receiver, comprising:

• a mixer configured to receive a transmitted signal and a local oscillator signal, the mixer configured to output an IF signal;
• processing circuitry configured to receive the IF signal and to output a demodulated signal;
• a low pass filter configured to receive the demodulated signal and output a filtered signal;
• a non-volatile memory configured to store frequency correction information;
• a summing circuit configured to receive the filtered signal and a correction factor signal, the summing circuit configured to output a correction signal;
• a reference oscillator configured to receive the correction signal, the reference oscillator configured to generate a reference signal that is used to generate the local oscillator signal;
• a computational device configured to receive a temperature signal and the filtered signal, the computation device performing the steps of:
• retrieving frequency correction information from the non-volatile memory responsive to the temperature signal;
• generating the correction factor signal using the retrieved frequency correction information;
• generating updated frequency correction information responsive to the filtered signal;
• and
• storing data indicative of the updated frequency correction information in the nonvolatile memory.

A method of providing a reference frequency signal, comprising:

• storing discrete frequency correction factors for a reference oscillator;
• receiving current temperature data;
• determining a correction factor associated with the current temperature data by correlating the current temperature data with the discrete frequency correction factors;
• tuning a reference oscillator using the correction factor, the reference oscillator outputting the reference frequency signal;
• determining a frequency error in the reference frequency signal;
• generating updated frequency correction information using the frequency error;
• determining updated discrete frequency correction factors using the updated frequency correction information;
• and
• storing the updated discrete frequency correction factors.

A method of calibrating an oscillator in a communication device, comprising:

• determining initial frequency correction information for the oscillator;
• storing the initial frequency correction information in the communication device;
• correlating the initial frequency correction information with a current temperature to generate a current correction signal;
• tuning a reference oscillator in the communication device according to the current correction signal to generate a reference signal;
• transmitting a strong signal to the communication device,
• determining a frequency error in the reference signal according to the strong transmitted signal;
• calculating calibrated frequency correction information that compensates for the frequency error;
• and
• storing the calibrated frequency correction information in the communication device.

A method of maintaining frequency accuracy for an oscillator in a communication device, comprising:

• providing frequency correction information in the communication device;
• generating a correction signal indicative of a frequency error at a current temperature, the correction signal for tuning the oscillator;
• generating updated frequency correction information that compensates for the frequency error;
• and
• storing the updated frequency correction information in the wireless device.

A method for compensating a reference oscillator of a receiver, comprising:

• storing a plurality of predetermined temperature compensation factors, each temperature compensation factor being associated with a quality factor;
• correlating the receiver's temperature with a subset of temperature correction factors from the plurality to produce a current correction factor;
• compensating the reference oscillator according to the current correction factor, the reference oscillator thereby producing a reference signal;
• receiving a transmitted signal with the receiver tuned according to the reference signal to produce a received signal having a frequency offset;
• and
• adjusting the temperature compensation factors within the subset according to the frequency offset if the received signal's quality factor exceeds the quality factor associated with the subset.

A receiver, comprising:

• a reference oscillator;
• a automatic frequency control system coupled to the reference oscillator, wherein the automatic frequency control system controls the reference oscillator's frequency according to a frequency offset of a received signal;
• a computation engine coupled to a memory storing a plurality of predetermined temperature correction factors spanning a temperature range, wherein each temperature compensation factor is associated with a quality factor;
• and
• a temperature sensing device coupled to the computation engine for sensing the temperature of the receiver;
• wherein the computation engine is configured to correlate the temperature of the receiver with a subset of the temperature compensation factors to produce a current temperature compensation factor for adjusting the frequency of the reference oscillator, the computation engine being further configured to adjust the subset according to the frequency offset if the received signal's quality factor exceeds the quality factor associated with the subset.