METHOD AND APPARATUS FOR SPREADING SIGNAL ACQUISITION AND TRACKING

• US 20080220736A1
• Filed: 03/07/2007
• Published: 09/11/2008
• Est. Priority Date: 03/07/2007
• Status: Active Grant

• Current Assignee: MediaTek, Inc.
• Original Assignee: MediaTek, Inc.
• Inventors: Yeh, Hsin-chung
• Granted Patent: US 8,090,002 B2
• Time in Patent Office: Days
• US Class Current: 455/296
• CPC Class Codes: G01S 19/29 carrier including Doppler, related G01S19/246 takes precedence
• CPC Class Codes: G01S 19/30 code related G01S19/246 takes precedence
• CPC Class Codes: H04B 1/70775 Multi-dwell schemes, i.e. multiple accumulation times
• CPC Class Codes: H04B 1/7085 using a code tracking loop, e.g. a delay-locked loop

Abstract

A spreading signal acquisition and tracking method and apparatus is proposed. In accordance with the present invention, coherent integrations are performed by segments and stored for a non-coherent integration. A better freedom of the non-coherent interval selection is provided. The window of the non-coherent integration is sequentially and gradually shifted to achieve better update rate to its detection circuit and to improve searching and tracking for a spreading signal. By using the present invention, rapid signal acquisition can be achieved even when intensity of the spreading signal is very weak, or even when deeper signal blocking or jamming occurs.

Claims

1. A spreading signal acquisition and tracking method, said method comprising steps of:

receiving a spreading signal;

coherently integrating the spreading signal to obtain coherent integration of each coherent integration interval;

accumulating a first predetermined number of the coherent integrations starting from a first time point as a non-coherent integration; and

accumulating the first predetermined number of the coherent integrations starting from a second time point as another non-coherent integration, said second time point being later than said first time point by a second predetermined number of the coherent integration intervals.

2. The method of claim 1, wherein said second predetermined number is less than said first predetermined number.

3. The method of claim 2, wherein said second predetermined number is one.

4. The method of claim 2, wherein said second predetermined number is variable.

5. The method of claim 1, wherein the coherent integration result is stored in a memory device and non-coherent integration can be calculated from that the coherent integration results stored in memory device.

6. A spreading signal acquisition and tracking method, said method comprising steps of:

receiving a spreading signal;

coherently integrating the spreading signal to obtain coherent integration of each coherent integration interval;

storing the coherent integration result to a memory device;

non-coherently accumulating the coherent integration results from the memory device to form a signal energy;

comparing the signal energy to a predetermined threshold;

executing a specific operation when said signal energy exceeds a threshold.

7. The method of claim 6, wherein the spreading signal is a global navigation satellite signal

8. The method of claim 6 further comprising suspending said specific operation whenever the signal energy drops below the threshold.

9. The method of claim 6, wherein said threshold is obtained from analysis of probability of false alarm.

10. A spreading signal acquisition and tracking apparatus comprising:

an antenna receiving a spreading signal;

an RF processing block for down converting, filtering and amplifying the received signal;

a correlator for coherently integrating the received signal to obtain coherent integration result for each coherent integration interval;

a memory device; and

a processor accumulating the coherent integrations to store a first predetermined number of the coherent integrations starting from a first time point into said memory device as a non-coherent integration and store the first predetermined number of the coherent integrations starting from a second time point into said memory device as another non-coherent integration, said second time point being later than said first time point by a second predetermined number of the coherent integrations.

11. The apparatus of claim 10, wherein said second predetermined number is less than said first predetermined number.

12. The apparatus of claim 11, wherein said second predetermined number is one.

13. The apparatus of claim 11, wherein said second predetermined number is variable.

14. The apparatus of claim 10, wherein old coherent integration is discarded to prevent the memory device from being saturated.

15. A spreading signal acquisition and tracking apparatus comprising:

an antenna receiving a spreading signal;

an RF processing block for down converting, filtering and amplifying the received signal;

a correlator for coherently integrating the received signal to obtain a coherent integration result for each coherent integration interval;

a memory device for storing the coherent integration result; and

a processor non-coherently accumulating from the coherent results stored in the memory device to form a signal energy, and instructing to execute a specific operation if the signal energy is greater than a predetermined threshold.

16. The apparatus of claim 15, wherein the processor requests to suspend said specific operation whenever the signal energy drops below the threshold.

17. The apparatus of claim 15, wherein said threshold is variably set according to different requirements.

18. The apparatus of claim 17, wherein the requirements comprise the trade off between signal searching or tracking ability and signal integrity.

19. The apparatus of claim 15, further comprising a negation block, said processor requests said negation block to execute signal tracking when the signal energy exceeds said threshold.

20. The apparatus of claim 19, wherein said processor request said negation block to suspend signal tracking when the signal energy drops below said threshold.