| 摘要 |
A mobile communication device 200 includes a receiver 210 for global navigation satellite system (GNSS) signals, and an RF receiver 210, e.g. a cellular radio receiver. The device 200 also includes a voltage controlled oscillator (VCO) 204 which supplies a signal to both the GNSS receiver and the RF receiver. The device 200 further includes a processor 202 which initialises and adjusts a model of the frequency behaviour of the VCO, and uses the model to track the GNSS signals when computing a location of the mobile device. The model of the VCO may be based on the operating temperature and the control voltage of the VCO. The processor may also adjust the model by comparing the oscillator signal to a reference frequency while varying a control voltage applied to the VCO. A reference signal may be supplied during manufacture to initialise the model. As long as the cellular modem 210 is not receiving cellular signals, the modelling procedure may be performed. The system allows the GNSS receiver accurately to track GNSS signals during operation of the cellular modem. |
