Methods and apparatus for obtaining GNSS time in a GNSS receiver

• US 7,936,303 B2
• Filed: 12/30/2008
• Issued: 05/03/2011
• Est. Priority Date: 09/06/2007
• Status: Active Grant

• Current Assignee: MediaTek, Inc.
• Original Assignee: MediaTek, Inc.
• Inventors: Chen, An-Bang, Liu, Hsien-Chang, Huang, Kung-Shuan
• Primary Examiner(s): Tarcza; Thomas H
• Assistant Examiner(s): LIU, HARRY K
• Application Number:
  US12/446,754
• Publication Number:
  US 20110050495A1
• Time in Patent Office: 854 Days
• Field of Search: 342/357.62, 342/357.73
• US Class Current: 342/357.62
• CPC Class Codes: G01S 19/23 Testing, monitoring, correcting or calibrating of receiver elements
• CPC Class Codes: G01S 19/39 the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
• CPC Class Codes: G04R 20/04 Tuning or receiving; Circuits therefor

Abstract

A method for obtaining GNSS time in a GNSS receiver includes: obtaining a time relationship between a first clock signal and the received GNSS time; obtaining a clock value B1 of a second clock signal and further obtaining an associated clock value A1 of the first clock signal to obtain a first pulse relationship at a first time point; calculating a GNSS time C1 corresponding to the clock value A1 according to the time relationship; obtaining a clock value B2 of the second clock signal and further obtaining an associated clock value A2 of the first clock signal to obtain a second pulse relationship at a second time point; and calculating a GNSS time C2 according to the GNSS time C1, the clock value B1, and the clock value B2. Exemplary values of A1, B1, C1, A2 B2, and C2 can be TTick1, FN1, TOW1, TTick2, FN2, and TOW2, respectively.

Claims

1. A method for obtaining Global Navigation Satellite System (GNSS) time in a GNSS receiver, the method comprising:

obtaining a time relationship between a first clock signal and the received GNSS time;

obtaining a clock value B1 of a second clock signal and further obtaining an associated clock value A1 of the first clock signal in order to obtain a first pulse relationship at a first time point;

calculating a GNSS time C1 corresponding to the clock value A1 according to the time relationship;

obtaining a clock value B2 of the second clock signal and further obtaining an associated clock value A2 of the first clock signal in order to obtain a second pulse relationship at a second time point; and

calculating a GNSS time C2 corresponding to the clock value A2 according to the GNSS time C1, the clock value B1, and the clock value B2.

2. The method of claim 1, further comprising:

controlling at least a portion of the GNSS receiver to enter a power saving mode during a time period between the first time point and the second time point.

3. The method of claim 1, further comprising:

storing at least the clock value B1 and the GNSS time C1 into a memory.

4. The method of claim 1, wherein the time relationship between the first clock signal and the GNSS time represents value mapping between the clock value of the first clock signal and the GNSS time.

5. The method of claim 1, further comprising:

performing synchronization measurement at the first time point to obtain the first pulse relationship; and

performing synchronization measurement at the second time point to obtain the second pulse relationship.

6. The method of claim 5, wherein the second clock signal is synchronized with a frame time clock of a cellular network;

the synchronization measurement performed at the first time point represents frame synchronization measurement, and the clock value B1 represents a frame number FN1; and

the synchronization measurement performed at the second time point represents frame synchronization measurement, and the clock value B2 represents a frame number FN2.

7. The method of claim 6, further comprising:

calculating the GNSS time C2 by the following equation;

C2=C1+(B2−

B1)*T_Frame*(1−

D_Frame);

wherein the T_Frame represents a length of a frame cycle of the frame time clock, and the D_Frame represents a frame time clock drift of the frame time clock.

8. The method of claim 6, further comprising:

calculating the GNSS time C2 according to a frame time clock drift of the frame time clock, the GNSS time C1, the frame number FN1, and the frame number FN2.

9. The method of claim 5, wherein the second clock signal is derived from a clock source representing a system clock;

the synchronization measurement performed at the first time point represents clock synchronization measurement; and

the synchronization measurement performed at the second time point represents clock synchronization measurement.

10. The method of claim 1, wherein the step of obtaining the clock value B1 of the second clock signal and further obtaining the associated clock value A1 of the first clock signal in order to obtain the first pulse relationship at the first time point further comprises:

utilizing the first clock signal to measure arrival time of a pulse corresponding to the clock value B1 in order to obtain the clock value A1;

wherein the step of obtaining the clock value B2 of the second clock signal and further obtaining the associated clock value A2 of the first clock signal in order to obtain the second pulse relationship at the second time point further comprises;

utilizing the first clock signal to measure arrival time of a pulse corresponding to clock value B2 in order to obtain the clock value A2.

11. An apparatus for obtaining Global Navigation Satellite System (GNSS) time in a GNSS receiver, the apparatus comprising:

a first clock source arranged to generate a first clock signal; and

at least one processing module arranged to obtain a time relationship between the first clock signal and the received GNSS time, wherein the processing module obtains a clock value B1 of a second clock signal and further obtains an associated clock value A1 of the first clock signal in order to obtain a first pulse relationship at a first time point, calculates a GNSS time C1 corresponding to the clock value A1 according to the time relationship, obtains a clock value B2 of the second clock signal and further obtains an associated clock value A2 of the first clock signal in order to obtain a second pulse relationship at a second time point, and calculates a GNSS time C2 corresponding to the clock value A2 according to the GNSS time C1, the clock value B1, and the clock value B2.

12. The apparatus of claim 11, wherein one of the at least one processing module controls at least a portion of the GNSS receiver to enter a power saving mode during a time period between the first time point and the second time point.

13. The apparatus of claim 11, wherein the apparatus further comprises a memory;

and the processing module stores at least the clock value B1 and the GNSS time C1 into the memory.

14. The apparatus of claim 11, wherein the time relationship between the first clock signal and the GNSS time represents value mapping between the clock value of the first clock signal and the GNSS time.

15. The apparatus of claim 11, wherein the processing module performs synchronization measurement at the first time point to obtain the first pulse relationship, and further performs synchronization measurement at the second time point to obtain the second pulse relationship.

16. The apparatus of claim 15, wherein the second clock signal is synchronized with a frame time clock of a cellular network;

the synchronization measurement performed at the first time point represents frame synchronization measurement, and the clock value B1 represents a frame number FN1; and

the synchronization measurement performed at the second time point represents frame synchronization measurement, and the clock value B2 represents a frame number FN2.

17. The apparatus of claim 16, wherein the processing module calculates the GNSS time C2 by the following equation:

C2=C1+(B2−

B1)*T_Frame*(1−

D_Frame);

wherein the T_Frame represents a length of a frame cycle of the frame time clock, and the D_Frame represents a frame time clock drift of the frame time clock.

18. The apparatus of claim 16, wherein the processing module calculates the GNSS time C2 according to a frame time clock drift of the frame time clock, the GNSS time C1, the frame number FN1, and the frame number FN2.

19. The apparatus of claim 15, wherein the second clock signal is derived from a clock source representing a system clock of the apparatus;

the synchronization measurement performed at the first time point represents clock synchronization measurement; and

the synchronization measurement performed at the second time point represents clock synchronization measurement.

20. The apparatus of claim 11, wherein the processing module utilizes the first clock signal to measure arrival time of a pulse corresponding to the clock value B1 in order to obtain the clock value A1;

and the processing module utilizes the first clock signal to measure arrival time of a pulse corresponding to the clock value B2 in order to obtain the clock value A2.