Patent ID: 8742863
Filing Date: 2014-06-03
Classification: H03L

Abstract:
1. A wireless communication terminal, comprising: a crystal oscillator, which belongs to a specified type of crystal oscillators in which a dependence of an output frequency as a function of temperature has one or more temperature dependence coefficients that vary among the crystal oscillators belonging to the specified type; a transceiver, which is arranged to operate an Automatic Frequency Control (AFC) loop having a frequency accuracy requirement for initial AFC synchronization that is more stringent than an uncompensated frequency accuracy of the given crystal oscillator; and circuitry, which is arranged to determine one or more output frequencies of the crystal oscillator at one or more respective operating temperatures, to compute the one or more temperature dependence coefficients for the crystal oscillator based on both of the one or more determined output frequencies and the one or more operating temperatures, to correct a frequency error in the output frequency of the crystal oscillator using the dependence and the computed temperature dependence coefficients in an initial AFC synchronization stage in which the AFC loop is unlocked, to ascertain, before receiving a signal to be tracked by the AFC loop, that the corrected frequency error meets the frequency accuracy requirement of the AFC loop, and, in a subsequent tracking stage, to lock the AFC loop on the received signal and to correct a frequency of the received signal using the locked AFC loop.