Mobile communication apparatus

• US 20030017834A1
• Filed: 04/25/2002
• Published: 01/23/2003
• Est. Priority Date: 04/25/2001
• Status: Active Grant

• Current Assignee: ST-Ericcson SA (Telefonaktiebolaget LM Ericsson)
• Original Assignee: CEVA Ireland Ltd. (CEVA Incorporated)
• Inventors: Pratt, Anthony R.
• Granted Patent: US 6,901,265 B2
• Time in Patent Office: Days
• US Class Current: 455/456.1
• CPC Class Codes: G01S 19/235 Calibration of receiver components
• CPC Class Codes: G01S 19/29 carrier including Doppler, related G01S19/246 takes precedence
• CPC Class Codes: G01S 2205/008 using a mobile telephone network

Abstract

In a mobile unit housing a two-way communications subsystem and a satellite positioning system (SPS) receiver subsystem, the communications subsystem includes a training signal generator for generating a training signal mimicing a positioning signal transmitted by a remote SPS transmitter. The training signal is frequency-coupled to a reference frequency source contained within and used by the communications subsystem, which source is, itself, stabilized by means of communication with a remote station, e.g. a base station in a cellular telephone system. In a training sequence, the training signal is activated and coupled into the SPS receiver subsystem, and a replica signal generator for generating a carrier replica signal for position-fixing purposes is controlled so as to bring the carrier replica signal into aliment with the training signal. Information representative of the control setting of the replica signal generator corresponding to such alignment is stored. Subsequently in a searching sequence, the training signal is deactivated and the replica signal generator is set to a setting based on the stored information for acquisition and processing of positioning signals from remote SPS transmitters.

Claims

1. Mobile communication apparatus having a position-fixing capability, wherein the apparatus comprises:

a two-way communications subsystem having a first signal source for producing a signal having a precision reference frequency;

a training signal generator for generating a pilot signal at an output thereof, the training signal generator having an input coupled to an output of the first signal source so that the pilot signal is linked to the reference frequency; and

a satellite positioning system (SPS) receiver subsystem comprising;

at least one signal path;

a coupling between the signal path and the training signal generator output;

an antenna for applying to the signal path positioning signals received from SPS transmitters;

a carrier signal replica generator for generating a replica signal being a replica of a positioning signal received from an SPS transmitter; and

a control system operable to cause the carrier signal replica generator to bring the replica signal into alignment with the pilot signal when the pilot signal is received by the SPS receiver subsystem and to store information representative of a setting of the replica generator occurring at the time of said alignment;

the control system being further operable to cause the SPS receiver subsystem to search for positioning signals transmitted by a said SPS transmitter according to said setting information.

2. Mobile apparatus according to claim 1, in which the pilot signal is modulated with a modulation signal of a type modulated onto the positioning signals to be received by the SPS receiver subsystem, the modulation signal comprising at least one of data and a spreading code.

3. Mobile apparatus as claimed in claim 1, in which the training signal is a radio frequency signal at a frequency at least approximately equal to the frequency or frequencies of SPS positioning signals to be received by the SPS receiver subsystem.

4. Mobile apparatus as claimed in claim 1, wherein the SPS receiver subsystem includes a frequency down-converter for converting received positioning signals to an intermediate frequency and wherein the pilot signal is generated at a frequency at least approximately equal to said intermediate frequency.

5. Mobile apparatus as claimed in claim 3, in which the pilot signal includes a signal having a frequency offset from a transmission frequency of the SPS positioning signals by a predetermined amount.

6. Mobile apparatus as claimed in claim 4, in which the pilot signal includes a signal having a frequency offset from a typical frequency of the positioning signals after down-conversion to the intermediate frequency by a predetermined amount.

7. Mobile apparatus as claimed in claim 5, in which data representing the amount of the frequency offset is modulated onto the pilot signal.

8. Mobile apparatus according to claim 1, in which the control system of the SPS receiver subsystem comprises means to request the training signal generator to generate the pilot signal.

9. Mobile apparatus according to claim 8, in which the pilot signal is modulated with a modulation signal of a type modulated onto the positioning signals to be received by the SPS receiver subsystem, the modulation signal comprising at least one of data and a spreading code.

10. Mobile apparatus according to claim 8, in which the pilot signal is modulated with a signal of a type modulated onto the positioning signals to be received by the SPS receiver subsystem.

11. Mobile apparatus according to claim 8, in which the training signal is a radio frequency signal at a frequency at least approximately equal to the frequency or frequencies of SPS positioning signals to be received by the SPS receiver subsystem.

12. Mobile apparatus according to claim 8, wherein the SPS receiver subsystem includes a frequency down-converter for converting received positioning signals to an intermediate frequency and wherein the pilot signal is generated at a frequency at least approximately equal to said intermediate frequency.

14. A method as claimed in claim 13, further comprising modulating the pilot signal with a modulation signal of a type modulated onto positioning signals transmitted by the SPS transmitter, the modulation signal comprising at least one of data and a spreading code.

15. A method as claimed in claim 13, in which the pilot signal is deactivated during said searching for positioning signals transmitted by an SPS transmitter.

16. A method as claimed in claim 14, in which the pilot signal is deactivated during said searching for positioning signals transmitted by an SPS transmitter.

17. A method as claimed in claim 13, in which the step of using said signal source as a reference involves taking into account a predetermined frequency offset.

18. A method as claimed in claim 17, further comprising modulating the pilot signal with data indicative of the predetermined amount of offset.

19. A method according to claim 13, in which the pilot signal includes a radio frequency signal having a frequency at least approximately equal to the transmission frequency of said positioning signals.

20. A method according to claim 13, in which said positioning signals are down converted to an intermediate frequency and the carrier signal replica generator is so controlled that the replica signal is caused to become aligned with the down converted positioning signals, and in which the pilot signal includes at least a component having a frequency at least approximately equal to said intermediate frequency.

21. A method according to claim 19, in which the pilot signal includes a signal having a frequency offset from a transmission frequency of the SPS positioning signals by a predetermined amount.

22. A method according to claim 20, in which the pilot signal includes a signal having a frequency offset from a typical frequency of the positioning signals after down conversion to the intermediate frequency by a predetermined amount.

23. A method according to claim 13, wherein the step of using the carrier signal replica generator setting comprises using stored information representative of that setting to generate at least one new setting of the replica generator for searching for said positioning signals, which new setting is offset from the setting represented by the stored information.

24. A method according to claim 23, including computing the amount of the offset of the new setting.

25. A computer readable medium containing a computer program comprising instructions to perform the method of claim 13.

26. A communications system including mobile communication apparatus according to claim 1 and a remote station in wireless communication with the mobile apparatus, the remote station including a temperature controlled or temperature compensated precision reference frequency source.

28. A system according to claim 27, wherein the carrier signal replica generator is coupled to an oscillator, the replica signal being synthesised by a frequency synthesiser from an output signal from the oscillator, the synthesiser incorporating the setting produced by aligning the replica signal with the training signal.

29. A system according to claim 28, arranged such that the training signal is injected into a front end circuit of the SPS receiver.

30. A system according to claim 28, arranged such that the training signal is injected into an intermediate frequency stage of the SPS receiver.

31. A system according to claim 27. wherein the training signal is modulated with a modulation signal of a type modulated onto the positioning signals to be received by the SPS receiver, the modulation signal comprising at least one of data and a spreading code.

32. A system according to claim 27, wherein the control circuitry of the SPS receiver comprises means to request the training signal generator to generate the training signal.

33. A system according to claim 31, wherein the control circuitry of the SPS receiver comprises means to request the training signal generator to generate the training signal.

35. A storage medium according to claim 34, wherein the program means operate to initiate and terminate a training sequence which includes issuing a command causing the training signal to be activated and a command causing the training signal to be deactivated.

36. A storage medium according to claim 34, wherein the program means operate to alter the frequency of the training signal such that when it is no longer required for aligning the carrier replica signal it does not interfere with reception of the satellite positioning signals.

37. A storage medium according to claim 34, wherein the program means operate to alter the level of the training signal such that when it is no longer required for aligning the carrier replica signal it is reduced in level to an extent such that it does not interfere with reception of the satellite positioning signal.

38. A storage medium according to claim 34, wherein the program means operate to cause a frequency synthesiser setting to be stored in response to alignment of the replica signal with the training signal.

39. A storage medium according to claim 34, wherein the step of using the said setting of the carrier signal replica generator comprises using stored information representative of that setting to generate at least one new setting of the replica generator for searching the said positioning signals, which new setting is offset from said associated setting.

13. A method of searching for positioning signals transmitted by a satellite positioning system (SPS) transmitter, the method comprising:

using a signal source forming part of a two-way communications subsystem and having a precision reference frequency as a reference to generate a pilot signal;

generating a carrier replica signal in a carrier signal replica generator;

controlling the carrier signal replica generator to cause the replica signal to become aligned with the pilot signal;

using a setting of the carrier signal replica generator at a time when the replica signal was aligned with the training signal to search for positioning signals transmitted by an SPS transmitter; and

subsequently, controlling the carrier signal replica generator to cause the replica signal to become aligned with the positioning signals.

27. A communications and position-fixing system comprising a communications base station and a mobile station, each said station having a respective receiver and transmitter to provide a two-way radio communication link between the stations, wherein:

the base station has a precision frequency reference; and

the mobile station comprises a reference signal source, means for adjusting the reference signal source to cause it to produce a frequency reference signal calibrated by the precision frequency reference over the said link, a training signal generator arranged to generate an SPS training signal using the calibrated frequency reference signal as a frequency reference, and an SPS receiver arranged to receive SPS positioning signals and having a carrier signal replica generator for generating a replica signal which is a replica of a positioning signal which the SPS receiver is arranged to receive, the SPS receiver further having control circuitry arranged to set the carrier signal replica generator thereby to align the replica signal with the training signal, the SPS receiver being arranged to perform a search for satellite positioning signals using that setting of the replica generator.

34. A computer program storage medium for configuring a mobile station having a two-way communications subsystem, a position-fixing receiver subsystem, and a training signal generator for generating a pilot signal having the characteristics of an SPS signal, the storage medium storing program means which operate to feed the pilot signal to an SPS signal path in the receiver subsystem, to operate the receiver subsystem to pick up the pilot signal and to align a carrier replica signal generated in the receiver subsystem with the training signal, to store an associated setting of a carrier replica generator generating the replica signal, and to initiate a search by the receiver subsystem for satellite positioning signals using the said setting of the carrier replica generator.

40. A mobile transceiver comprising (i) a communications subsystem which is configured to receive a stabilising signal from a remote station and which includes a reference frequency source controllable in response to the stabilising signal, and (ii) a satellite positioning system (SPS) receiver subsystem for receiving and processing SPS positioning signals from remote transmitters forming part of an SPS, the SPS receiver subsystem including a replica signal generator for generating a carrier replica signal which is a replica of a said SPS positioning signal, a correlator stage for correlating said SPS positioning signals and the replica signal to determine the position of the transceiver, and a control system for controlling the replica signal generator;

wherein the communications subsystem includes a training signal generator for generating a training signal of a frequency such that the training signal can be received by the SPS receiver subsystem via coupling between said subsystems, the training signal generator being coupled to said reference frequency source in a manner such that the training signal frequency is linked to a frequency of the reference frequency source, and wherein the control system of the SPS receiver subsystem is operable in a training sequence to cause the carrier replica signal to be aligned with the training signal and to store information relating to a setting of the replica signal generator at which alignment was achieved, and in a search sequence to cause the SPS receiver subsystem to search for said SPS positioning signals using replica signal generator settings based on said stored information.