Patent ID: 7242910
Filing Date: 2007-07-10
Classification: H03J

Abstract:
1. A radio configured to transmit a radio signal having a frequency based on a local oscillator, comprising: a local oscillator; a mixer coupled to receive a local oscillator signal from the local oscillator and a reference signal; an analog to digital converter coupled to receive an output of the mixer; a processor coupled to receive an output of the analog to digital converter, the processor configured to operate in a calibration mode to automatically calibrate the local oscillator by comparing the output of the analog to digital converter to a first threshold value, by integrating and averaging the output of the analog to digital converter, to determine a difference between a frequency of the local oscillator and the reference frequency, and adjusting the frequency of the local oscillator by an offset frequency that is a function of the difference, if the difference between the frequency of the local oscillator and the reference frequency is greater than the first threshold value; and a transmitter configured to transmit a radio signal having a local frequency; wherein the processor is further configured to permit selection between the calibration mode and a normal mode operable to transmit a radio signal, wherein the processor further stores tracking data indicative of the offset frequency determined during the calibration mode and wherein the stored tracking data is used in the normal mode to apply an offset correction voltage to the local oscillator so as to continuously adjust the local frequency by the offset frequency, and further wherein the processor updates the tracking data responsive to the difference between the frequency of the local oscillator and the reference frequency.