Temperature compensation in a telecommunications device

1. A communications device, comprising:

an oscillator, having a temperature-dependent frequency characteristic, for generating signals at a nominal frequency;

receiver circuitry, for receiving transmitted wireless signals using the signals generated by the oscillator;

at least one temperature sensor, having a known positional relationship to the oscillator;

an estimation device, for estimating a frequency of the signals generated by the oscillator, based on a measurement from the temperature sensor, and based on the temperature-dependent frequency characteristic of the oscillator;

at least one heat source wherein the temperature sensor and the oscillator are mounted on a printed circuit board (PCB) and co-located away from the heat source in a thermally isolated area surrounded by a thermal break, wherein the thermal break comprises one or more gaps in one or more layers of the PCB; and

a prediction device, for predicting a change in temperature of the oscillator, based on a state of the heat source, and further based on a model of the thermal properties of the communications device, and hence for predicting a change in the frequency of the signals generated by the oscillator, based on the temperature-dependent frequency characteristic of the oscillator,

wherein the receiver circuitry uses the estimated frequency of the signals generated by the oscillator, and the predicted change in the frequency of the signals generated by the oscillator, in receiving the transmitted wireless signals.

2. The communications device as claimed in claim 1 , wherein the heat source is a component of the communications device, and the prediction device is adapted to predict an increase in temperature of the oscillator following activation of the component.

3. The communications device as claimed in claim 2 , wherein the heat source is a transceiver circuit of the communications device.

4. The communications device as claimed in claim 1 , wherein the prediction device is further adapted to predict a rate of change of a frequency of a signal generated by the oscillator, based on a model of the temperature-dependent frequency characteristic of the oscillator.

5. The communications device as claimed in claim 4 , wherein the prediction device is further adapted to update the model of the temperature-dependent frequency characteristic of the oscillator based on successfully received signals.

6. The communications device as claimed in claim 1 , wherein the receiver circuitry is adapted to receive frequency aiding updates at predetermined time intervals, and the prediction device is adapted to predict, for each of said predetermined time intervals, a change in the frequency of the signals generated by the oscillator over said time interval.

7. The communications device as claimed in claim 6 , wherein the predetermined time intervals are approximately one second.

8. The communications device as claimed in claim 6 , wherein the oscillator and the heat source are separated by a thermal resistance such that a change in the state of the heat source has no significant impact on the temperature of the oscillator within one predetermined time interval.

9. The communications receiver as claimed in claim 1 , wherein the receiver circuitry comprises a GNSS receiver.

10. The communications receiver as claimed in claim 9 , wherein the GNSS receiver circuitry comprises a downconversion mixer, for downconverting a frequency of a received signal based on an oscillator signal, and individual oscillators for tracking signals from respective satellite vehicles, and wherein the receiver circuitry uses the estimated frequency of the signals generated by the oscillator, and the predicted change in the frequency of the signals generated by the oscillator, in the downconversion mixer.

11. The communications receiver as claimed in claim 9 , wherein the estimation device estimates the frequency of the signals generated by the oscillator, based also on measurements from the GNSS receiver.

12. The communications receiver as claimed in claim 9 , further comprising cellular transceiver circuitry, for communicating in a cellular communications network, wherein the estimation device estimates the frequency of the signals generated by the oscillator, based also on measurements from the cellular transceiver.

13. A method of operation of a communications device, the communications device comprising:

an oscillator, having a temperature-dependent frequency characteristic, for generating signals at a nominal frequency;

receiver circuitry, for receiving transmitted wireless signals using the signals generated by the oscillator;

at least one temperature sensor, having a known positional relationship to the oscillator; and

at least one heat source wherein the temperature sensor and the oscillator are mounted on a printed circuit board (PCB) and co-located away from the heat source in a thermally isolated area surrounded by a thermal break, wherein the thermal break comprises one or more gaps in one or more layers of the PCB; the method comprising:

estimating a frequency of the signals generated by the oscillator, based on a measurement from the temperature sensor, and based on the temperature-dependent frequency characteristic of the oscillator;

predicting a change in temperature of the oscillator, based on a state of the heat source, and further based on a model of the thermal properties of the communications device, and hence predicting a change in the frequency of the signals generated by the oscillator, based on the temperature-dependent frequency characteristic of the oscillator, and

using the estimated frequency of the signals generated by the oscillator, and the predicted change in the frequency of the signals generated by the oscillator, in receiving the transmitted wireless signals in the receiver circuitry.

14. The method as claimed in claim 13 , wherein the heat source is a component of the communications device, comprising predicting an increase in temperature of the oscillator following activation of the component.

15. The method as claimed in claim 13 , comprising predicting a rate of change of a frequency of a signal generated by the oscillator, based on a model of the temperature-dependent frequency characteristic of the oscillator.

16. The method as claimed in claim 15 , comprising updating the model of the temperature-dependent frequency characteristic of the oscillator based on successfully received signals.

17. The method as claimed in claim 13 , comprising predicting, for each of a plurality of predetermined time intervals, a change in the frequency of the signals generated by the oscillator over said time interval, and using the predicted changes in the receiver circuitry during the predetermined time intervals.

18. The method as claimed in claim 13 , wherein the receiver circuitry comprises a GNSS receiver, and wherein the GNSS receiver circuitry comprises a downconversion mixer, for downconverting a frequency of a received signal based on an oscillator signal, and individual oscillators for tracking signals from respective satellite vehicles, and wherein the method comprises using the estimated frequency of the signals generated by the oscillator, and the predicted change in the frequency of the signals generated by the oscillator, in the downconversion mixer.

19. The method as claimed in claim 18 , comprising estimating the frequency of the signals generated by the oscillator, based also on measurements from the GNSS receiver.

20. The method as claimed in claim 18 , wherein the communications device further comprises cellular transceiver circuitry, for communicating in a cellular communications network, and the method comprises estimating the frequency of the signals generated by the oscillator, based also on measurements from the cellular transceiver.