Amelioration of frequency errors and their effects

摘要

A radio telephone contains a GPS receiver. The GPS includes a frequency down-converter and a non-crystal oscillator which controls the down-conversion. The output of the non-crystal oscillator is liable to discontinuous jumps, and is controlled intermittently in accordance with its value and that of a crystal oscillator. A filter is used to limit the rate of change of frequency that the control signal applied to the non-crystal oscillator demands such that the phase rotation of the output of the non-crystal oscillator is less than p over the period of time that it takes to despread a GPS signal. The crystal oscillator may also act as a controlling reference signal for the mobile phone. The cellular phone may provide control information to correct the crystal oscillator intermittently.