| 摘要 |
An automatic frequency control is implemented in a selective call receiver (100) having a controllable frequency synthesizer (203). The output frequency of the synthesizer an is derived from a frequency reference element (205). A temperature sensor (206) with substantial thermal coupling to the frequency reference element (205) produces a temperature signal representative of an operating temperature associated with the frequency reference element. The temperature signal is coupled to a controller (105) that operates to execute a microcode program implementing the automatic frequency control. Responsive to the temperature signal and at least one set of parameters representing a predetermined temperature versus frequency characteristic of the frequency reference element, a correction factor is generated and programmed in the frequency synthesizer (203). The correction factor corrects the output frequency to reflect a frequency error of substantially zero parts per million with respect to a desired operating frequency.
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