Frequency synthesizer correction using a temperature responsive divisor control

A selective call receiver comprising:

• a frequency reference element that produces a reference frequency;
• a frequency synthesizer having a temperature stabilized output frequency derived from the frequency reference element;
• a temperature sensor with substantial thermal coupling to the frequency reference element, the temperature sensor producing a temperature signal representative of an operating temperature associated with the frequency reference element;
• a receiver responsive to the output frequency of the frequency synthesizer, the receiver being capable of receiving an information signal to provide a received information signal;
• a demodulator for recovering a serial bit stream from the received information signal, the serial bit stream comprising an address signal, and
• a controller coupled to the frequency synthesizer, the temperature sensor, and the demodulator, the controller executing a microcode program that:
• controls operation of the selective call receiver;
• determines selection of the selective call receiver when the address signal substantially correlates with a predetermined address associated with the selective call receiver;
• decodes at least one selective call message from the serial bit stream and store the at least one selective call message in a message memory;
• and
• implements an automatic frequency control that generates a correction factor from an equation having at least one coefficient representing a previously measured temperature versus frequency characteristic of the frequency reference element, calculation of the correction factor being effected and having a range determined by a representation of the temperature signal as an independent variable, the correction factor serving to alter a divide factor that is programmed in a divider inside a closed frequency control loop in the frequency synthesizer, the divider operating to select a desired operating frequency that will eliminate any frequency error as measured between the temperature stabilized output frequency of the frequency synthesizer and the desired operating frequency.